The Wonder Book of Volcanoes and Earthquakes
by Edwin J. Houston · English · Gutenberg #43320 · 605,942 chars · public domain (US)
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Title: The Wonder Book of Volcanoes and Earthquakes
Author: Edwin J. Houston
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*** START OF THE PROJECT GUTENBERG EBOOK THE WONDER BOOK OF VOLCANOES AND EARTHQUAKES ***
THE WONDER BOOK OF
VOLCANOES AND EARTHQUAKES
[Illustration: MOUNT VESUVIUS IN ERUPTION]
THE
WONDER BOOK
OF
VOLCANOES AND EARTHQUAKES
BY
Professor EDWIN J. HOUSTON, Ph.D.
NEW YORK
FREDERICK A. STOKES COMPANY
Publishers
Copyright, 1907, by
FREDERICK A. STOKES COMPANY
_All rights reserved_
_October, 1907_
ACKNOWLEDGMENTS
We take this opportunity of acknowledging the courtesy of the
following publishers, who have helped us in connection with the
illustrations of this book:--
Henry Holt and Company ("Physiography," by Rollin D. Salisbury).
D. Appleton and Company (Figs. 13, 35, 39, 40, 41, 42, 43, 44, 45 and
46, "Volcanoes: What They Are and What They Teach," by J. W. Judd;
Fig. 15, "Principles of Geology," by Sir C. Lyell).
The American Book Company ("Manual of Geology," by James Dwight Dana).
G. P. Putnam's Sons ("Earthquakes in the Light of the New Seismology,"
by C. E. Dutton).
The Clarendon Press ("Geology: Chemical, Physical, and
Stratigraphical," by Joseph Prestwich).
THE PUBLISHERS.
CONTENTS
CHAPTER PAGE
I. THE VOLCANIC ERUPTION OF KRAKATOA IN 1883 1
II. SOME EFFECTS OF THE ERUPTION OF KRAKATOA 12
III. THE VOLCANIC ISLAND OF HAWAII 26
IV. THE VOLCANIC ISLAND OF ICELAND 46
V. VESUVIUS 58
VI. OTHER VOLCANOES OF THE MEDITERRANEAN 73
VII. ORIZABA, POPOCATEPETL, IXTACCIHUATL, AND
OTHER VOLCANOES OF MEXICO 85
VIII. COSEGUINA AND OTHER VOLCANOES OF CENTRAL AMERICA 91
IX. THE VOLCANIC MOUNTAINS OF SOUTH AMERICA 97
X. VOLCANOES OF THE UNITED STATES 105
XI. THE CATASTROPHE OF MARTINIQUE AND THE VOLCANIC
ISLANDS OF THE LESSER ANTILLES 117
XII. SOME OTHER NOTED VOLCANIC MOUNTAINS 125
XIII. JORULLO, A YOUNG VOLCANIC MOUNTAIN 130
XIV. MID-OCEAN VOLCANIC ISLANDS 137
XV. SUBMARINE VOLCANOES 141
XVI. DISTRIBUTION OF THE EARTH'S VOLCANOES 148
XVII. VOLCANOES OF THE GEOLOGICAL PAST 153
XVIII. LAPLACE'S NEBULAR HYPOTHESIS 157
XIX. THE EARTH'S HEATED INTERIOR, THE CAUSE OF VOLCANOES 165
XX. SOME FORMS OF LAVA 178
XXI. MUD VOLCANOES AND HOT SPRINGS 193
XXII. THE VOLCANOES OF THE MOON 207
XXIII. EARTHQUAKES 219
XXIV. SOME OF THE PHENOMENA OF EARTHQUAKES 231
XXV. THE EARTHQUAKE OF CALABRIA IN 1783 245
XXVI. THE GREAT LISBON EARTHQUAKE OF 1755 252
XXVII. THE EARTHQUAKE OF CUTCH, INDIA, IN 1819 257
XXVIII. THE SAN FRANCISCO EARTHQUAKE OF APRIL 18, 1906 262
XXIX. SOME OTHER NOTABLE EARTHQUAKES 269
XXX. SODOM AND GOMORRAH AND THE CITIES OF THE PLAIN 281
XXXI. INSTRUMENTS FOR RECORDING AND MEASURING EARTHQUAKE
SHOCKS 290
XXXII. SEAQUAKES 296
XXXIII. THE DISTRIBUTION OF EARTHQUAKES 303
XXXIV. THE CAUSES OF EARTHQUAKES 308
XXXV. EARTHQUAKES OF THE GEOLOGICAL PAST--CATACLYSMS 319
XXXVI. THE KIMBERLY DIAMOND FIELDS AND THEIR VOLCANIC
ORIGIN 326
XXXVII. THE FABLED CONTINENT OF ATLANTIS 335
XXXVIII. PLATO'S ACCOUNT OF ATLANTIS 344
XXXIX. NATURE'S WARNING OF COMING EARTHQUAKES 364
FULL PAGE ILLUSTRATIONS
PAGE
MT. VESUVIUS IN ERUPTION Frontispiece
STONES AND LAVA THROWN UPWARDS--ERUPTION OF
MOKUAWEOWEO, HAWAII, JULY 4-21, 1899 fac. 36
COTOPAXI 102
THE LAVA FLOW OF THE CRATER OF KILAUEA, HAWAIIAN ISLANDS 184
A SAN FRANCISCO PAVEMENT TORN BY THE EARTHQUAKE 266
ILLUSTRATIONS IN TEXT
FIG. PAGE
1. THE SUNDA ISLANDS 3
2. KRAKATOA BEFORE THE ERUPTION 4
3. KRAKATOA AFTER THE ERUPTION 4
4. VOLCANIC DUST AS IT APPEARS UNDER THE MICROSCOPE 19
5. THE HAWAIIAN ISLANDS 27
6. HAWAII 29
7. PANORAMA OF MOKUAWEOWEO 35
8. VIEW OF THE CRATER OF KILAUEA FROM THE VOLCANO HOUSE 35
9. CRATER OF KILAUEA 40
10. SECTIONS OF KILAUEA AT DIFFERENT PERIODS 42
11. ICELAND 47
12. THE MEDITERRANEAN 59
13. THE VOLCANIC DISTRICT AROUND VESUVIUS 60
14. MT. ETNA 77
15. STROMBOLI, VIEWED FROM THE NORTHWEST, APRIL, 1874 79
16. MEXICO AND CENTRAL AMERICA 86
17. SOUTH AMERICA 98
18. THE UNITED STATES 106
19. PANORAMA FROM THE MESA AT THE EDGE OF MT. TAYLOR 110
20. VOLCANIC NECKS, EDGE OF MESA AT MT. TAYLOR 111
21. THE LESSER ANTILLES 118
22. GRAHAM'S ISLAND--A RECENT VOLCANIC ISLAND 143
23. ALEUTIAN ISLANDS 146
24. MAP OF THE WORLD, SHOWING LOCATION OF ACTIVE AND
RECENTLY EXTINCT VOLCANOES 150
25. VOLCANIC VESICLES 183
26. THREAD-LACE SCORIÆ FROM KILAUEA 185
27. THREAD-LACE SCORIÆ FROM KILAUEA 185
28. FROST-LIKE LAVA CRYSTALS 187
29. FROST-LIKE LAVA CRYSTALS 187
30. BASALTIC COLUMNS, ISLE OF CYCLOPS, ITALY 188
31. COLUMNAR AND NON-COLUMNAR BASALT 189
32, 33. DRIBLET CONES 190
34. LAVA STALACTITES 191
35. CRATER OF THE GREAT GEYSER OF ICELAND 202
36. GIANT GEYSER 203
37. BEE HIVE 203
38. BEE HIVE GEYSER OF ICELAND 205
39. HEAVY STONE OBELISKS TWISTED BY CALABRIAN EARTHQUAKE
OF 1783 229
40. CIRCULAR HOLLOW FORMED BY CALABRIAN EARTHQUAKE 239
41. SECTION OF CIRCULAR HOLLOW FORMED BY CALABRIAN
EARTHQUAKE 239
42. MAP OF THE CALABRIAN EARTHQUAKE OF 1783 246
43. FISSURES CAUSED BY THE CALABRIAN EARTHQUAKE 249
44. MAP SHOWING DISTRICT VISITED BY THE EARTHQUAKE OF
CUTCH OF 1819 258
45. SINDREE BEFORE THE EARTHQUAKE OF 1819 259
46. SINDREE AFTER THE EARTHQUAKE OF 1819 260
47. MAP OF WESTERN COAST OF CALIFORNIA SHOWING POSITION
OF SAN FRANCISCO 263
48. NEW ZEALAND 274
49. MAP SHOWING REGION AFFECTED BY THE CHARLESTON
EARTHQUAKE OF 1886 277
50. SYRIA 282
51. COMPLEX RECORD OF SEISMOGRAPH 293
52. LONG DISTANCE SEISMOGRAM 293
53. VICENTINI VERTICAL PENDULUM 294
54. VICENTINI PENDULUM AND RECORDER 295
55. DAVISON'S EARTHQUAKE MAP OF JAPAN 306
THE WONDER BOOK OF
VOLCANOES AND EARTHQUAKES
THE WONDER BOOK OF VOLCANOES
AND EARTHQUAKES
CHAPTER I
THE VOLCANIC ERUPTION OF KRAKATOA IN 1883
Krakatoa is a little island in the Straits of Sunda, about thirty
miles west of the island of Java, and nearly the same distance east
of the island of Sumatra. It is uninhabited and very small, measuring
about five miles in length and less than three miles in width. Its
total area is only thirteen square miles. This little piece of land
made itself famous by what took place on it during the month of
August, 1883.
Krakatoa is one of the many islands that form the large island chain
known as the Sunda Islands. The most important islands of this chain
are Sumatra, Java, Sumbawa, Flores, and Ceram. Between Sumatra and
Java, the largest two of these islands, there is a channel called the
Straits of Sunda that connects the waters of the Indian Ocean with
those of the Pacific Ocean. The Straits of Sunda is an important piece
of water that forms one of the great highways to the East. Shipping
is, therefore, always to be found in its waters.
As can be seen by the map, Krakatoa is not far from the Equator,
being situated in lat. 6° 7' S. and long. 105° 26' E. from Greenwich.
Since there are about sixty-nine miles in every degree of latitude,
Krakatoa is about 420 miles south of the Equator, and is about
twenty-five miles from Java. Java is part of the Dutch East Indies,
which includes Java, Celebes, the Spice Islands, and parts of Borneo
and Sumatra. Batavia, the principal seaport of Java, near the
northwest coast, is a great shipping centre, visited by vessels from
nearly all parts of the world. It has, however, no harbor, but is
approached from the ocean by means of a canal two miles in length, the
sides of which are provided with massive brick walls. Besides Batavia,
which is situated about one hundred English miles east of Krakatoa,
there are many smaller towns or villages, the most important of which
is Anjer, a thriving seaport town, where sailing vessels obtain their
supplies of food and fresh water. Before the eruption of Krakatoa,
Anjer was provided with a strong, stone lighthouse.
Java is especially noted for its production of coffee, in which it is
second only to Brazil. Its area is about the same as that of the State
of New York. Java is one of the most densely populated parts of the
world, containing nearly four times as many people as the whole State
of New York.
These facts about the situation and surroundings of Krakatoa are
necessary to an understanding of the wonderful thing that happened on
it during the month of August, 1883. In that month Krakatoa suffered a
most tremendous explosive volcanic eruption, for it is a volcano.
[Illustration: FIG. 1. THE SUNDA ISLANDS]
A volcano is a mountain or hill, generally conical in shape, having
at the top a nearly central opening, called a _crater_, from which
at times melted rock and lava, vapor and gases escape. The lava
either flows down the side of the mountain in a liquid condition, or
is thrown upwards into the air. If the distance the lava is thrown
upwards is sufficiently great the melted matter solidifies before it
falls to the earth. In such cases the largest fragments form what are
called _volcanic cinders_, the smaller pieces, _volcanic ashes_, and
the extremely small particles, _volcanic dust_. If, however, the lava
is thrown to a comparatively small height, it is still melted when it
falls, and is then known as _volcanic drops_ or _driblets_.
[Illustration: FIG. 2. KRAKATOA BEFORE THE ERUPTION]
It is not surprising that Krakatoa is a volcanic island, since it lies
in one of the most active belts of volcanic islands in the world, and
near the coasts of the most active of these islands; i. e., Java.
This belt, as shown in the map, includes, besides the Sunda Island
chain, parts of Gilolo, Celebes, Mindanao and the Philippine Islands.
These islands lie between Asia on the northwest and Australia on the
southeast.
[Illustration: FIG. 3. KRAKATOA AFTER THE ERUPTION]
There is no other part of the world with, perhaps, the single
exception of Japan, where so many active volcanoes are crowded in
so small a space. The island of Java, small as it is, has nearly
fifty volcanoes, of which at least twenty-eight are active. They are
situated in a lofty range running from east to west, some of the
peaks of which are more than 10,000 feet above the level of the sea.
Volcanic eruptions are so frequent that the island is seldom free from
them.
As will be seen from the map shown in Fig. 2, Krakatoa consists of
three groups of volcanic mountains, the southern group giving the name
of Krakatoa to the island. Strictly speaking, this mountain was called
_Rakata_, but as it is now generally known as Krakatoa, it would be
unwise to attempt to call it by any other name. The central mountain
or group of mountains is known as Danan, and consists largely of part
of an old crater. The group of mountains which lies near the northern
end of the island was known as Perboawatan. From the centre of this
latter group of mountains are several old lava streams consisting
of a variety of lava resembling a dark-colored glass, known to
mineralogists as _obsidian_, or _volcanic glass_.
Although Krakatoa was always a volcano, yet between the years 1680 and
1883, it was in the condition of a sleeping or extinct volcano. There
had been a severe explosive eruption in the year 1680, that caused
great loss of life and property, but ever since that time all activity
had ceased and it seemed that the volcano would never again burst out.
In other words, it was generally regarded as a trustworthy, sedate,
quiet, inoffensive and perfectly safe volcano, that had become extinct.
The long continued quiet of Krakatoa was broken on the 20th of May,
1883, when the inhabitants of Batavia on the island of Java were
terrified by noises like the firing of great guns, that were first
heard between ten and eleven o'clock in the morning. These noises
were accompanied by the shaking of the ground and buildings. The
sleeping volcano of Krakatoa was evidently growing restless, but no
great damage was done and soon all was again quiet. The disturbances
were merely the forerunner of the terrible eruption soon to follow,
and confidence was soon restored. But suddenly, on Sunday, August
26th, 1883, almost without any further warnings, Krakatoa burst into
terrible activity and began an explosive eruption that has never been
equalled in severity in the memory of man.
That memorable Sunday of August 26th, 1883, came during a season of
the year known as the _dry monsoon_, a name given the season of the
periodical winds from the Indian Ocean. Batavia, and the surrounding
country, greatly needed rain, for in this part of the world it seldom
rains from April to October, although the air is very moist and damp.
For this reason the beginning of the wet season is always welcomed.
When, therefore, the rumbling sounds of the approaching catastrophe of
Krakatoa were heard in Batavia, the people, believing that the noises
were due to peals of thunder, rejoiced, for all thought they heralded
an earlier setting in of the wet monsoon. But when the rumbling
sounds increased and reports were heard like heavy artillery, it was
clear that the sounds were the beginning of a volcanic eruption, a
phenomenon with which they were only too well acquainted, but, as
volcanic eruptions were far from being uncommon in Java, no one was
very greatly frightened.
But this time the noises increased to such an extent that the people
became alarmed. Throughout the night the appalling sounds continued
and were accompanied by shakings of the earth sufficiently strong to
shake the houses violently. Sleep was out of the question. Many of
the people left their houses and remained all night in the open air,
fearing the shocks would bring the houses down over their heads.
The morning instead of heralding the dawn of a beautiful tropical day,
with its bright, cheerful sunlight, brought with it skies covered
with gray clouds that completely hid the sun. The rumbling sounds,
however, had decreased, and the people were beginning to congratulate
themselves that the dangers were over, when suddenly, the sky grew
darker, and there began a shower of ashes that soon covered the
streets and houses of the city. About seven o'clock on the morning of
August 27th, a most tremendous crash was heard. The sky rapidly became
so dark that it was soon necessary to light the lamps in the houses
of Batavia, and some of the neighboring towns in the western part of
Java. In addition to this the air was filled with vapor, while every
now and then earthquake shocks were again felt. These shocks were
accompanied by terrific noises like those produced by the explosion of
heavy artillery. The noises rapidly increased in number and intensity
until they produced a nearly continuous roar, the nature of which it
is almost impossible to describe since it is probable that such sounds
had never been heard before by man. It is a curious fact, which, I
believe, has never been satisfactorily explained, that in most cases
the people in the immediate neighborhood of the volcano, as, for
example, those on board vessels in the Straits of Sunda, did not hear
the terrific noises at all. Possibly they were too loud and simply
gave a single inward impetus to the drum of the ear and then held it
in position.
Probably some of my readers may remember that witty description given
by Dr. Oliver Wendell Holmes of an alleged effort made by all the
people of the world to find out whether or not there is a man in the
moon. This wonderful plan was as follows:
Careful calculations were made to ascertain when it would be the same
time over all the earth so that all the people of the earth could
simultaneously shout at the top of their voices. In this way it was
hoped that the man in the moon, if there were such a person, would
notice the noise.
The story goes on to tell how when the time approached for the great
experiment, and all were ready to shout as loud as they could, that
each person reasoning to himself or herself, that amid so great a
noise no one could notice whether his or her voice was omitted,
determined to remain silent, so as to be able to hear the noise and
the better to observe what the man in the moon would do when the sound
reached him. The result was that every person on the earth remained
silent and simply listened, so that the earth was never so quiet
before.
Had Oliver Wendell Holmes, or any other person conceiving the witty
idea, lived during the time of the great explosive eruption of
Krakatoa, on that memorable August 27th, 1883, he might have taken
the opportunity of observing the man in the moon, had he not been
frightened by what was occurring, for certainly never before were
such tremendous or terrifying sounds produced, for these sounds, as
we shall see shortly, were actually heard for distances of more than
3,000 miles from the volcano.
There were two different kinds of waves produced in the air by the
tremendous forces at work in the eruption of Krakatoa; namely,
atmospheric waves and sound waves.
The atmospheric waves showed their presence in the air by means of
changes produced in the atmospheric pressure. Now, while these
changes cannot readily be felt by man, yet their presence can be
easily shown by the use of instruments called _barometers_.
There are in different parts of the world, buildings called
_meteorological observatories_, that are provided, among other
instruments, with recording barometers. These instruments caught
the great atmospheric waves that were produced by the eruption of
Krakatoa. In this manner, the astounding fact was learned that the
waves starting from the volcano travelled no less than seven times
around the world. When we say astounding, it must not be understood
that the formation of such waves was at all contrary to the known laws
of physics. On the contrary, provided the force of the eruption was
sufficiently great, such waves must have been produced in the great
ærial ocean. The astonishing, or wonderful thing, was that the force
setting up these waves was so great that it caused them to move seven
times around the globe.
The atmospheric waves were so powerful that it will be worth our while
to describe them in detail. Starting from the volcano of Krakatoa,
as a centre, these waves moved outwards in all directions, becoming
gradually larger and larger until they reached a point halfway round
the globe, or 180° from Krakatoa. The waves did not, however, stop
here, but continued moving onward, now growing smaller and smaller
until they reached a point in North America, immediately opposite
Krakatoa. Such a point on a globe is called an _antipodal point_.[1]
The waves did not stop at this point, but again advanced moving toward
Krakatoa, growing larger and larger until they again reached a point
halfway around the globe, or 180° from Krakatoa, when they again
continued moving but now continually growing smaller and smaller,
until they reached Krakatoa. Here they again began moving completely
around the globe, and this was continued for as many as seven times.
It must not be supposed that the waves ceased on the seventh time
around. On the contrary, they, probably, kept on moving for many
additional times, but they were then so feeble that even the sensitive
recording barometers were unable to detect their presence.
There was another kind of waves in the atmosphere that did not require
barometers for their detection. These were the sound waves, and can
readily be detected by the human ear.
Now, in the case of the great eruption of Krakatoa, the intensity of
the sounds was so great that the sounds could be heard distinctly at
distances of several thousand miles from Krakatoa.
The sound waves so closely resembled the explosion of artillery that
at Acheen, a port on the northern coast of Sumatra, 1,073 miles from
Krakatoa, the authorities, believing that an attack was being made on
the port, placed all their troops under arms to repel the invaders.
The sounds were also distinctly heard at Bangkok, in Siam, a distance
of 1,413 miles from the volcano. They were also heard at the Chagos
Islands, a group of islands situated in the Indian Ocean about 2,267
miles from Krakatoa.
Two steamers at Singapore, 522 miles distant, were despatched to find
the vessel that was believed to be firing guns as distress signals.
The sounds were distinctly heard in parts of South Australia, 2,100
miles distant, and in Western Australia, at 1,700 miles distance.
But it will be unnecessary to give any further details of the great
distances at which these sounds were actually heard. It will suffice
to say that they were heard as far off as about 3,000 miles.
It is difficult to picture to one's self such great distances.
Assuming the greatest distances to be in the neighborhood of 3,000
miles, it would be as if a sound produced, say, in Boston, New York,
or Philadelphia, was so loud that it could be heard in Amsterdam,
London, or Paris.
Some idea of the intensity of these sounds can be had from the fact
that in Batavia, when, in accordance with usage, a gun was fired from
one of the forts at eight o'clock in the morning, two hours before the
greatest intensity of the sounds had been reached, the sound of the
gun could scarcely be heard above the continuous roar.
While, of course, the principal reason the sound waves were carried
so far was the great force causing the eruption, yet these distances
were increased by the fact that the explosion occurred in a region
almost entirely surrounded by great bodies of water. The waves could,
therefore, be readily carried along the surface of the sea. Had there
been a high mountain wall, like the Andes of South America, on one
side of the volcano they would probably have been shut off in this
direction a short distance from where they were produced.
CHAPTER II
SOME EFFECTS OF THE ERUPTION OF KRAKATOA
Besides the sound waves in the air, there were waves in the waters of
the ocean. Suddenly, without any warning, the people of Batavia were
surprised by a huge wave that, crossing the Straits of Sunda, entered
the ship canal before referred to as connecting the city with the
ocean, and, rising above the brick wall, poured over the surrounding
country.
Although Batavia was 100 English miles from Krakatoa, yet after
travelling this distance the wave was sufficiently strong to enter
the city and flood its streets with water to a depth of several feet.
Fortunately, the loss of life was small in the city of Batavia, but
very great in the surrounding towns and villages.
The ocean waves varied in height at different times of the eruption.
The greatest were from fifty to eighty feet high. Just imagine the
effect of a wave twice the height of an ordinary house. The waves
caused great damage to the shipping in the neighborhood. In one
instance, a vessel was carried one and a half miles inland and left on
dry land thirty feet above the level of the sea.
The total loss of life by the waves has been estimated at 35,000
people; besides this, of course, there was a great amount of property
destroyed. The greatest loss was in the immediate neighborhood of
Krakatoa. Gigantic waves swept over the lowlands lying near the
shores of Sumatra and Java, where over areas several miles in width
nearly everything was destroyed, the houses, trees, and people being
swept away and the surface of the land greatly changed. The towns of
Karang and Anjer, as well as numerous smaller villages, were almost
completely destroyed.
The seaport town of Anjer, by far the most important of the above
towns, was almost completely swept away. The heavy stone lighthouse
was so completely obliterated that no traces of its heavy stone
foundations could afterwards be found. The Rev. Phillip Neale,
formerly a British chaplain at Batavia, from whose account of the
eruption of Krakatoa some of the above facts have been taken, tells
of the brave action of the keeper of the lighthouse at Anjer. Besides
his work as lighthouse keeper, to see that the light was constantly
burning during the night, he was charged with telegraphing to Batavia
the names of all passing vessels. On the fateful morning of the great
catastrophe, observing that the sun did not rise, he kept the light of
the lighthouse burning, and, notwithstanding the danger to which he
was exposed, continued at his post in order to send word to Batavia of
the passing of an English steamer. While doing this the lighthouse was
swept away and the brave man perished.
The following verbal account of the destruction of the port of Anjer
was given by a Dutch pilot stationed at Anjer. This description is
quoted by the Rev. Mr. Neale from an article prepared by him for
publication in "The Leisure Hour."
"I have lived in Anjer all my life, and little thought the
old town would have been destroyed in the way it has. I am
getting on in years, and quite expected to have laid my
bones in the little cemetery near the shore, but not even
that has escaped and some of the bodies have actually been
washed out of their graves and carried out to sea. The
whole town has been swept away, and I have lost everything
except my life. The wonder is that I escaped at all. I can
never be too thankful for such a miraculous escape as I had.
"The eruption began on the Sunday afternoon. We did
not take much notice at first, until the reports grew
very loud. Then we noticed that Krakatoa was completely
enveloped in smoke. Afterwards came on the thick darkness,
so black and intense that I could not see my hand before
my eyes. It was about this time that a message came
from Batavia inquiring as to explosive shocks, and the
last telegram sent off from us was telling you about
the darkness and smoke. Towards night everything became
worse. The reports became deafening, the natives cowered
down panic-stricken, and a red, fiery glare was visible
in the sky above the burning mountain. Although Krakatoa
was twenty-five miles away, the concussion and vibration
from the constantly repeated shocks were most terrifying.
Many of the houses shook so much that we feared every
minute would bring them down. There was little sleep for
any of us that dreadful night. Before daybreak on Monday,
on going out of doors, I found the shower of ashes had
commenced, and this gradually increased in force until at
length large pieces of pumice stone kept falling around.
About six A. M. I was walking along the beach.
There was no sign of the sun, as usual, and the sky had a
dull, depressing look. Some of the darkness of the previous
day had cleared off, but it was not very light even then.
Looking out to sea I noticed a dark, black object through
the gloom, travelling towards the shore.
"At first sight it seemed like a low range of hills rising
out of the water, but I knew there was nothing of the kind
in that part of the Sunda Strait. A second glance--and a
very hurried one it was--convinced me that it was a lofty
ridge of water many feet high, and worse still, that it
would soon break upon the coast near the town. There was
no time to give any warning, and so I turned and ran for
my life. My running days have long gone by, but you may
be sure that I did my best. In a few minutes I heard the
water with a loud roar break upon the shore. Everything
was engulfed. Another glance around showed the houses
being swept away and the trees thrown down on every side.
Breathless and exhausted I still pressed on. As I heard
the rushing waters behind me, I knew that it was a race
for life. Struggling on, a few yards more brought me to
some rising ground, and here the torrent of water overtook
me. I gave up all for lost, as I saw with dismay how high
the wave still was. I was soon taken off my feet and borne
inland by the force of the resistless mass. I remember
nothing more until a violent blow aroused me. Some hard,
firm substance seemed within my reach, and clutching it,
I found I had gained a place of safety. The waters swept
past, and I found myself clinging to a cocoanut palm-tree.
Most of the trees near the town were uprooted and thrown
down for miles, but this one fortunately had escaped and
myself with it.
"The huge wave rolled on, gradually decreasing in height
and strength until the mountain slopes at the back of
Anjer were reached, and then, its fury spent, the water
gradually receded and flowed back into the sea. The sight
of those receding waters haunts me still. As I clung to
the palm-tree, wet and exhausted, there floated past the
dead bodies of many a friend and neighbor. Only a mere
handful of the population escaped. Houses and streets were
completely destroyed, and scarcely a trace remains of where
the once busy, thriving town originally stood. Unless you
go yourself to see the ruin you will never believe how
completely the place has been swept away. Dead bodies,
fallen trees, wrecked houses, an immense muddy morass and
great pools of water, are all that is left of the town
where my life has been spent. My home and all my belongings
of course perished--even the clothes I am wearing are
borrowed--but I am thankful enough to have escaped with my
life and to be none the worse for all that I have passed
through."
As is common in cases of earthquake waves a great depression in the
level of the sea occurred at places great distances from Krakatoa. For
example, at the harbor of Ceylon, the water receded so far that for
about three minutes the boats were left high and dry, and then a huge
wave carried them with it as it rushed over the land.
Perhaps one of the best evidences of the immense power of ocean waves
is to be seen in the massive blocks of white coral rock that were
washed up by the waves, on parts of the coast of Java for distances of
from two to three miles from the ocean. Many of these blocks weighed
from twenty to thirty tons. Indeed, some of them reached the weight of
from forty to fifty tons.
It is probable that the island of Krakatoa and its neighboring smaller
islands formed portions of a huge cone about eight miles in diameter,
that has been broken up at some very remote but unknown time by,
perhaps, a greater catastrophe than that of August, 1883.
In the Straits of Sunda the water was raised fifty feet to eighty
feet above the ordinary level, and produced tremendous destruction
especially on the coasts of Java and Sumatra, sweeping away many
villages and drowning many thousands of people. The wave had a
velocity of progression of nearly 400 miles per hour, or eight times
faster than an ordinary express train.
When it is said that the _velocity of progression of the wave_ was
nearly 400 miles per hour, it is not meant that a body floating on
the ocean, such, for example, as a ship, would have been carried
forward at this high velocity, but would merely rise and fall in a
to-and-fro swing to about the height of the wave; that is, fifty to
eighty feet according to what may have been the height. As in the
case of the sound waves these motions of water covered or passed over
nearly all the waters of the earth. The waves progressing toward the
west, crossed the Indian Ocean reaching to the coast of Hindostan, and
Madagascar, and sweeping around the southern part of Africa, finally
reached the coasts of France and England, as well as the eastern part
of North and South America. Sweeping towards the east, they reached
the coasts of Australia, New Zealand, and crossing the vast Pacific
Ocean were felt at Alaska and the western coasts of North and South
America.
But besides the enormous waves caused by the eruption, there were
marked changes in the level of the land. Large portions of the coast
of Sumatra and Java were almost annihilated, much of the original
surface near the coast being submerged, and places that were formerly
dry land are now covered with water to a depth of from 600 to 900 feet.
The enormous amount of material thrown into the air by the forces
of the eruption is especially characteristic of this phenomenon.
Such quantities of pumice stone and ashes fell from the clouds that,
sinking in the water and collecting on the bed of the channel, they
changed the depth of the water, so as to render navigation dangerous.
Indeed, the Sebesi Channel, lying on the north of the island of
Krakatoa was completely blocked by a huge bank of volcanic material,
portions of which projected above the water, forming two smaller
islands. These, however, have since been washed away by the waves.
We will not attempt to give at present any explanations as to the
causes of this great volcanic eruption, since the different theories
as to the cause of volcanoes will be better understood when other
volcanic eruptions have been described. It is sufficient here to say
that if a large quantity of water should have suddenly reached a
great mass of molten rock, frightful explosive eruptions would have
occurred, and if the island was resting on a submerged crater its
sudden disappearance may be explained.
Another great wonder connected with the explosive eruption of Krakatoa
was the enormous heights to which the fine dust was thrown up into
the air. It has been asserted that during the most intense of these
eruptions the particles reached elevations of perhaps more than
twenty-five miles above the level of the sea. Carried by the winds,
the fine particles remained suspended in the air for many months,
and gave rise to magnificent sunlight effects, such as early dawn,
lengthened twilights, lurid skies, and gorgeous sunsets of a reddish
tint. There were also caused curious haloes, as well as green and blue
moons.
The fine dust particles consisted of minute crystals of feldspar and
other minerals, and when examined under the microscope presented the
appearance shown in Fig. 4.
These mineral substances permitted a portion of the light to pass
through them, thus producing wonderful optical effects in the
atmosphere either because they acted like minute prisms and so
produced rainbow colors, or because they turned the rays of light out
of their course as to produce what is called interference by color
effects of a nature similar to the colors seen in mother-of-pearl,
rainbow coal, or in the wing cases of many beetles. The explanations
of these phenomena are too difficult for a book of this character.
An explosive volcanic eruption is a very terrifying and wonderful
phenomenon. Frightful roaring sounds are suddenly heard, the earth
shakes for many miles around, when suddenly a vast quantity of molten
rock, and sometimes huge stones, are thrown out of the crater high up
into the air. So great is the force that throws these materials out
of the opening that heavy masses of rocks often are ejected very much
faster than the projectiles from the largest guns that are used in any
of the navies of the world.
[Illustration: FIG. 4. VOLCANIC DUST AS IT APPEARS UNDER THE
MICROSCOPE]
As the molten lava cools and falls in the form of prodigious clouds
of ashes, cinders and dust, for many miles around the volcano, even
the light of the sun is obscured, and one cannot see the hand before
the face. Some of the materials in these clouds are so light that they
remain suspended in the air for many hours, often indeed for many
days, and sometimes even for years. The heavier particles, however,
soon begin to fall, and before long the earth's surface both around
the volcano, and often at considerable distances from it, is covered
with a thick layer of ashes.
The sounds accompanying a volcanic eruption are often terrifying. Amid
shakings and tremblings of the earth's crust, known as earthquakes,
there are occasionally heard noises like the explosion of huge guns.
Sometimes these sounds follow one another so rapidly that they produce
an almost continuous roar. Through the roar of the explosion a
curious crackling noise can be heard, due to the fragments of stone
hurled out of the crater striking against one another, especially as
the stones which are thrown out of the crater and have commenced to
fall back again to the earth, are struck by others that are still
rising.
Immense quantities of ashes, stones, vapor and gases are thrown
upwards for great distances into the air, while, at the same time, a
lava stream pours over the lowest side of the crater. As the column
of ashes and cinders reaches its greatest height in the air, it
begins to spread outward on all sides, rapidly growing like a huge
dark mushroom. This soon shuts out the light of the sun, and from it
showers of red hot ashes and cinders fall to the earth.
It would be extremely dangerous to be on the side of the volcanic
mountain during an explosive eruption; for, even should you escape
falling into an opening in the side of the mountain, you might be
killed by the huge stones that are constantly falling on all sides
around the opening, or might be buried under the vast showers of red
hot ashes that are poured down from the dense clouds overhanging the
mountain, or suffocated by clouds of sulphur vapor that rush down its
sides.
When at a safe distance the sight is certainly magnificent. There is
no light from the sun. All would be in pitch darkness but for the
reddish glare thrown upwards by the red hot lava, by the glowing
showers of ashes that are being rained down on the sides of the
mountain, or by terrific lightning flashes, due to the discharge of
the immense quantities of electricity produced by the forces of the
eruption.
Naturally a great volcanic eruption can cause a considerable loss of
life and property. When a large lava stream begins to flow down the
sides of the mountain, it cannot be stopped, and should it flow toward
a village or town it is likely to destroy the town completely. Besides
this, the vegetation of the country for many miles around is destroyed
by the showers of red hot ashes that fall from the sky. The houses of
neighboring cities are similarly ruined by the great conflagrations
thus set up. Further destruction is also caused by large streams of
mud that rush down the slopes of the mountain, or by huge waves set
up in the ocean. If the volcano is situated, as most volcanoes are,
near the coast, the showers of ashes and falling stones may set fire
to vessels in the neighborhood, or the progress of such vessels may be
seriously retarded by layers of ashes or pumice stone that float on
the surface. Sometimes these layers are so thick as actually to bring
ships to a complete standstill.
It must not be supposed that volcanoes are in a constant state of
eruption. On the contrary, nearly all volcanoes, after an eruption,
become _quiet_ or _inactive_. The air soon clears by the ashes
settling, and the sunlight again appears. A crust forms over the
surface of the lava, which rapidly becomes hard enough to permit one
to walk over it safely. The vegetation, which has been destroyed by
the hot ashes, again springs up, and, if the volcano happens to be
situated within the tropics, where there is an abundance of moisture,
the land soon again becomes covered by a luxuriant vegetation. Most of
the people, who have escaped sudden death during the eruption, return
to the ruins of their houses; for it is a curious fact that no matter
how great has been a volcanic eruption, or how far-reaching the ruin,
the survivors, as a rule, do not appear to hesitate to return to their
old neighborhood. In a few years the fields are re-cultivated, the
villages are rebuilt, and the people apparently forget they are living
over a slumbering volcano, which may at any time again burst forth in
a dangerous eruption.
A volcano that throws out molten rock, vapor and gases is known as an
_active volcano_. An active volcano, however, is only correctly said
to be in a state of eruption when the quantity of the molten rock,
lava or vapor it throws out is greatly in excess of the ordinary
amount.
Sometimes the volcanic activity so greatly decreases that the molten
rock or lava no longer rises in the crater, but, on the contrary,
begins to sink, so that the top of the lava in the crater is often
at a considerable distance below its edges. The lava then begins to
harden on the surface, and, if the time is sufficient, the hardened
part extends for a considerable distance downward. In this way the
opening connecting the crater with the molten lava below becomes
gradually closed, the volcano being thus shut up, or corked, just as a
bottle is tightly closed by means of a cork driven into the opening at
its top so as to prevent the escape of the liquid it contains.
It may sound queer to say that a volcano has its crater so corked up
as to prevent the escape of the lava, but the idea is nevertheless
correct and helpful. To realize the size of these huge volcanic corks
one must remember that the craters of some volcanoes are several miles
across. A volcano thus choked or corked up is said to be _extinct_.
When we speak of an extinct volcano we do not mean that the volcano
will never again become active. A volcano does not cease to erupt
because there are no more molten materials in the earth to escape, but
simply because its cork or crust of hardened lava has been driven in
so tightly that the chances of its ever being loosened again seem to
be very small. But small as the chances may seem we must not forget
that the volcano may at any time become active, or go into its old
business of throwing out materials through its crater. A volcano in
an extinct condition is not unlike a steam boiler, the safety valve
of which has been firmly fixed in place. If the steam continues to be
generated in the boiler, it is only a matter of time when the boiler
will blow up, and the explosion will be all the greater because the
safety valve did not allow the steam to escape earlier.
Sometimes an intermediate class of volcanoes called _dormant_ is
introduced between active volcanoes on the one hand and extinct
volcanoes on the other. The name dormant volcano, or, as the word
means, _sleeping volcano_, is objectionable, since it might lead one
to think that an extinct volcano is not sleeping but dead, and this is
wrong.
Since the plug of hardened lava in the volcanic crater is generally at
a much lower level than the top of the crater, the crater will soon
become filled to a greater or less depth with water, produced either
by the rain, or by the melting of the snow that falls on the top of
the mountain. Crater lakes, often of very great depths, are common in
extinct volcanoes.
Of course, when an extinct volcano again becomes active, two things
must happen if the eruption is explosive. In the first place, the
force of the explosion must be sufficiently great to loosen the
stopper or plug of hardened lava which stops it. In doing this the
mass is broken into a number of fragments that are thrown forcibly
upwards into the air. After rising often for great heights they soon
fall again on the sides of the mountain.
But besides the breaking up of the stopper, the lake in the crater of
the volcano is thrown out along with the cinders or ashes, producing
very destructive flows of what are called aqueous lava or mud streams.
These streams flow down the sides of the mountain, carrying with them
immense quantities of both the ashes thrown out during the eruption,
or those that have collected around the sides of the crater during
previous eruptions. Very frequently, these streams of aqueous lava
produce greater destruction than the molten lava.
If you have ever watched common ants at work clearing out or enlarging
their underground homes, in a piece of smooth gravel walk in your
garden, you can form some idea why the mountain immediately around a
volcanic crater is conical in shape. If the colony of ants happens
to be fairly large, you can see an almost unbroken stream of these
industrious little animals, each bearing in its mandibles a small
grain of sand or gravel brought up from some place below the surface.
Carrying it a short distance from the opening, it throws it on the
ground, rapidly returning for another load. In this way there is
heaped up around all sides of the opening a pile of sand or gravel,
the outward slopes of which gives the pile a conical form. You have,
probably, noticed that the steepness of the slopes depends on the size
of the grains; for the larger these grains the sharper or steeper the
slopes, the very fine grains producing flat mounds or cones.
It is the same with a volcanic cone. The materials that are thrown
upwards into the air, falling again on the mountain, collect around
the crater on all sides, thus giving it the characteristic cone-like
shape of the volcanic mountain. Where nothing occurs to disturb
the formation of the cone its height above the level of the sea
will gradually increase. Very frequently, however, during explosive
eruptions, a large part of this cone will be blown away by the
force of the eruption only to be again built up during some later
eruption. Indeed, in the case of volcanic islands, the force of a
great volcanic eruption is sometimes so great that not only is a large
volcanic mountain blown entirely away, but a hole is left, where it
had been standing, that extends further downwards below the level
of the sea than the top of the mountain extended previously above
it. The above are some, but by no means all, the wonders attending
volcanic eruptions. We shall refer to others in subsequent chapters in
describing particular eruptions.
CHAPTER III
THE VOLCANIC ISLAND OF HAWAII
The volcanic island of Hawaii, the largest of the Sandwich Island
chain, is situated in the mid Pacific, south of the Tropic of
Cancer. As shown in Fig. 5, this island chain consists of Hawaii,
Maui, Molokai, Oahu, Kauai, Nihau, and about eight large islands,
together with numerous small islands, extending in a general northwest
direction from Hawaii to Nihau, a distance of about 400 miles. Like
most volcanic islands they lie in more or less straight lines,
probably along fissures, in this case in two nearly parallel lines.
The island of Nihau, however, is an exception, the direction of the
greatest length being almost straight across the two parallel lines.
The Sandwich Islands lie 2,000 miles from San Francisco in deep water,
between 2,000 and 3,000 fathoms, or between 12,000 and 18,000 feet in
depth. This island chain consists of great volcanic mountains, that
had, at one time, fifteen active volcanoes of the first class. These
are now all extinct but three, and all of these are on the island of
Hawaii.
In his report to the United States Geological Survey for 1882-83,
Dutton states that the summit of Mt. Haleakala on East Maui is 10,350
feet above the sea level. Oahu has peaks on its eastern side 2,900
feet high, and peaks on the western side 3,850 feet high. The summit
of Kauai is probably 6,200 feet above the sea.
[Illustration: FIG. 5. THE HAWAIIAN ISLANDS _From U. S.
Geological Survey_]
It can be shown by deep-sea soundings that all these volcanic piles
are the summits of a gigantic mountain mass that rises abruptly from
the bed of the Pacific. There are reasons for believing that this
submarine chain continues for many hundreds of miles in the same
direction beyond Kauai.
The extinct volcano, Haleakala, on East Maui appears to have been in
eruption at a much later day than Mt. Kea, which is also an extinct
volcano. But the natives have no traditions of any eruptions.
The volcanoes on the other islands have been extinct for a very long
time judging from the extent of their erosion. Dutton is of the
opinion that the western islands of the chain have been extinct for
much longer times than the remaining islands.
The Sandwich Islands, also known as the Hawaiian Islands, are one of
the colonial possessions of the United States. The island of Hawaii is
about 2,000 miles from San Francisco. Honolulu, on the island of Oahu,
the principal seaport of the chain, has a pleasant climate, and is an
important coaling station for warships, commercial vessels, whalers,
and trading ships generally.
The principal product of the island is sugar cane.
The island of Hawaii, as shown in map, Fig. 6, consists of five
volcanic mountains and some small coral reefs. These mountains are:
Mt. Kea, on the north, 13,805 feet in height; Mt. Haulalai, in the
west central part of the island, 8,273 feet in height; Mt. Loa, in the
south central part of the island, 13,675 feet in height; Mt. Kilauea,
twenty miles east of the crater of Loa, 4,040 feet high at the Volcano
House, and 4,158 feet on the highest point on the west, and Kohala,
5,505 feet in height, running through the northwestern part of the
island, and the Kohala mountains in the northwestern part.
[Illustration: FIG. 6. HAWAII _From Dana's Manual of
Geology_]
Of these mountains, Mt. Loa and Kilauea are the only active volcanoes,
and are in frequent eruption. Mt. Haulalai was in eruption during
1804. Mt. Kea has not been active during historical times, while Mt.
Kohala has been inactive for so long a time that its slopes are deeply
gullied wherever the rivers flow down them.
As you can see from the map, Hawaii is very large. It has a length of
ninety-three miles from north to south, and a breadth of eighty miles
from east to west, its area is about 6,500 square miles. With the
exception of small patches of coral reefs, Hawaii is formed entirely
of lava, and is the largest pile of lava in the world with the single
exception of Iceland.
Where the islands of the Hawaiian chain have coral reefs extending
off their coasts, excellent harbors are found in the deep waters
between the islands and the reefs. Hawaii, however, has no extended
reefs of this character, and, consequently, no first-class harbors.
Hilo, on the eastern coast, is the best harbor, and is, therefore, the
principal settlement.
A very brief examination of the map of Hawaii will show you that there
are no rivers on the island, except on the sides exposed to the wind,
that is, on the northern and northeastern slopes. Since the yearly
rainfall on Hawaii is large, being in the neighborhood of a hundred
inches, you will understand that considerable rain water falls on the
island. In those parts of the island where it does not run off the
surface it must drain downward through the loose piles of broken rocks
or cinders. A rainfall of one hundred inches a year means that if all
the rain which falls on each square foot of surface was collected
in a flat vessel one foot square with vertical sides it would fill
the vessel to the depth of one hundred inches, or over eight feet.
The drainage of the rainwater downwards through these parts of the
island, must, therefore, be large.
Another curious fact you can notice on the map, is that the lava
streams of the past fifty years from Mt. Loa indicated by heavy
dotted lines, in no cases begin at the crater, but start at fairly
considerable distances from it. Later on in this chapter we shall
explain the reason for this curious fact.
Since practically the whole of Hawaii has been formed from the streams
of lava that have flowed at one time or another, you can understand
how great these flows must have been. But to do this fully you must
not only take into consideration the portions of the island that
lie above the ocean and reach into the air at its greatest height
to 13,805 feet above its surface, you must also remember that this
mountain rises from a deep ocean, so that if all the water were
removed, you would see Hawaii towering up above the former level
of the sea to the height of about 31,000 feet, or higher than Mt.
Everest, the highest point on the earth above the present sea level.
This would be, approximately, five and eight-tenths miles. You can
understand, therefore, how great the flow of lava must have been.
We shall begin the description of Hawaii with the active volcano of
Mt. Loa, or, as it is sometimes called in Hawaii, "The White Mountain."
You will remember that the eruption of Krakatoa was of the explosive
type. Practically no melted rock or lava escaped from the crater.
Indeed, if it had escaped it would not have been seen; for, not only
the cone near the crater, but also much of the mountain itself was
blown completely out of sight and covered by the waters of the ocean.
The eruptions of Mt. Loa are of an entirely different type. In Loa
there are no explosions, the eruptions being what are called the
non-explosive or quiet volcanic eruption type. It will be necessary to
explain some of the peculiarities of this kind of eruptions.
There is a great difference in the liquidity or the ease with which
different kinds of lava flow. Some lava is very thick or viscid,
or is sticky like thick molasses or tar, and therefore flows very
sluggishly. Other lava is thin or mobile, more closely resembling
water in the ease with which it flows. Now, in the case of a volcanic
mountain of fairly considerable height, where the lava possesses
marked liquidity, the lava as it rises from great depths in the tube
of the volcano seldom flows over the top or rim of the crater. This is
not because the force that brings the lava up is unable to carry it
a few thousand feet higher, so that it can run over the brim of the
crater, but because the walls of the volcanic mountains are unable to
stand the great pressure which the mass of liquid lava exerts against
their sides.
It can be shown that a column of liquid lava 500 feet high, will exert
a pressure on the walls of the crater of about 625 pounds to the
square inch. Therefore, in very high volcanic mountains, long before
the lava can reach the edge of the crater and overflow, the pressure
becomes so great, that cracks or fissures are made in the sides of
the mountain, through which the lava is quietly discharged; when, of
course, the level of the lava in the crater falls considerably. In
volcanoes of the explosive type, no matter what may be the condition
of lava, should a large quantity of water suddenly find an entrance to
a large body of molten lava at some distance below the surface, the
lava would be suddenly thrown explosively into the air, where being
chilled, it would afterwards descend in showers of ashes, cinders, or
volcanic dust.
In some volcanic mountains such as Mt. Loa, the crater, instead
of being situated at the top of a conical pass of ashes or other
material, consists of a pit-like depression, generally occupying a
level tract or plain at the top of the mountain. This pit is known
as a _caldera_, or _caldron_, or what you might, perhaps, call a
huge kettle or boiler. The pit has more or less vertical sides that
extend downwards for unknown depths to the place from which the lava
comes. The vertical walls of the caldera are not, however, smooth, but
exhibit numerous horizontal ledges, that mark places where portions of
the floor of the caldera were situated at different times.
At the bottom of the large pit or caldera on the summit of Mt. Loa
can be seen the level floor formed of hardened lava. This floor is
surrounded by vertical walls on which can be seen the broken edges of
the old lake bed.
Captain Dutton, in a paper on Hawaiian volcanoes, prepared for the
United States Geological Survey, and published in its Fourth Annual
Report for 1882-83, thus describes the appearance at the great crater
as it was in 1882.
"The summit of Mauna Loa (Mt. Loa), is a broad and large
platform about five miles in length and four miles in
width, within which is sunken the great caldera called
Mokuaweoweo. The distance from the point where we first
reach the summit to the brink of the pit is about a mile
and a half. The surface of the platform is much more rugged
than the slopes just ascended. It is riven with cracks, and
small faults,[2] and piles of shattered rock are seen on
every hand. Nowhere is there to be seen the semblance of
a cinder cone. Doubtless many eruptions have broken forth
from the various fissures on this summit, but only here
and there can insignificant traces of such catastrophes
be definitely distinguished. The absence of fragmental
ejecta (broken rock that are thrown out) is extraordinary.
The shattered blocks, slabs, and spalls (chips) which
everywhere cumber the surface appear to have resulted from
the spontaneous shivering and shattering of the lava sheets
by their own internal tensions as they cooled.
Fig. 7, taken from Dutton's report, gives the general shape of this
great caldera. Dutton's description of the same is as follows:
"The length of the main caldera is a little less than
three miles and its width about a mile and three-quarters.
Its floor, viewed from above, appears to be composed of a
series of flat surfaces occupying two distinct levels, the
higher upon the surface of the black ledge, the lower lying
within the ledge. Upon the western side is a small cinder
cone standing close upon the border of the black ledge.
It is the only one visible, either within the caldera or
upon the surrounding summit. Its height is about 125 or 130
feet. It was seen in operation, throwing up steam, clots of
lava, and lapilli (some of the larger pieces of fragmentary
lava) in the year 1878. The only other diversifications of
the floor are many cracks which traverse it, the larger of
which are distinctly visible from above. Some of them are
considerably faulted. There is no difficulty in recognizing
the fact that the whole floor has been produced by the
sinkage of the lava beds which once continued over the
entire extent of the depression, their undersides having
been melted off most probably by the fires beneath. The
lava beds in the immediate vicinity of the brink upon the
summit platform wear the aspect of some antiquity. They
have become brown and carious by weathering, and, although
no soil is generated, little drifts of gravel are seen
here and there mixed with pumice. Since the caldera was
formed there is no indication that the lavas have anywhere
overflowed its rim. And yet it is a very strange fact that
within a half mile, and again within a mile to a mile and
a half, lavas have been repeatedly erupted within the last
forty years from the summit platform, and have outflowed
at points situated from 700 to 900 feet above the level of
the lava lake within. Traces may also be seen, at varying
distances back of the rim, of very many eruptions in which
the rocks betoken great recency, although no dates can be
assigned to their occurrence."
[Illustration: FIG. 7. PANORAMA OF MOKUAWEOWEO _From U. S.
Geological Survey_]
[Illustration: FIG. 8. VIEW OF THE CRATER OF KILAUEA FROM THE
VOLCANO HOUSE _From U. S. Geological Survey_]
During his visit to this great pit, Captain Dutton succeeded in
climbing down the almost vertical walls on the side of the crater,
and, reaching the surface of the hardened lake, walked over it. It
must have required no little courage to thus venture on the thin
floor of a lake which he knew was filled to great depths with red hot
boiling lava, for he was walking over the surface of a slumbering
volcano, that might at almost any moment awaken, and opening, swallow
him and his companions. Through enormous cracks in the floor, he could
feel the heat from the molten mass, while, through the same openings
came suggestive whiffs of sulphur vapor.
During the eruption of this mountain, on January 23d, 1859, the light
from the glowing lava streams was bright enough to read fine print at
Hilo, a distance of thirty-five miles.
During the eruption of 1852, a stream of white-hot lava was thrown up
into the air from one of the fissures to a height of from 300 to 400
feet.
[Illustration: STONES AND LAVA THROWN UPWARDS--ERUPTION OF
MOKUAWEOWEO, HAWAII, JULY 4-21, 1899 _From a Stereograph,
Copyright, by Underwood & Underwood_]
When an eruption takes place in Mt. Loa the column of lava slowly
rises in the crater, threatening to overflow its lowest edges, but
before this can take place the pressure becomes so great that some
portion of the mountain below the crater is fractured and the lava
quietly escapes.
During some conditions of the mountain every fifteen or twenty minutes
a column of highly glowing lava is shot upwards like a fountain to
a height of 500 feet and over, falling back into the lake in fiery
spray. Unusual heights of these streams are generally followed by an
eruption.
These curious jets of molten rock certainly cannot be due to the
pressure of higher columns of lava, since the crater itself is near
the top of a high plain. They are believed to be due to steam formed
by the penetration of the rain water that falls on this part of the
mountain.
You can now understand why the lava streams escaping from Mt. Loa as
shown on the map, in Fig. 6, do not begin at the level of the crater;
for the discharge of the lava does not take place over the rim of
the crater, but through the cracks or fissures formed further down
the sides of the mountains. It must not be supposed, however, that
the fissures are limited to the sides of the mountain where they can
be seen. They probably occur in many places below the surface of the
water on some part of the bed of the ocean.
The crevices that are formed in this manner in the sides of the
mountain vary greatly in size, some being so narrow that the lava
scarcely flows through them at all but simply fills up the crevice,
hardens on cooling, and mends the cracks in the mountains, in the way
that a crack is mended in a piece of china by the use of glue or in
a wall of masonry by mortar. Through the largest crevices or cracks,
however, large lava streams may continue to flow often for several
weeks, or even longer.
Sometimes, especially towards the close of the eruptive flow, the
lava may escape disruptively, so that small cones are formed along
the lines of the fissures. Cones of this character are called lateral
cones, and in the case of a volcanic island, where the lava flows out
below the level of the water, the lateral cones sometimes project
above the water and form volcanic islands or dangerous shoals that
impede navigation.
When the lava pours out of a crevice in the side of the mountain, a
river of molten rock rushes down the slopes, at first like a torrent,
but on reaching the more nearly level ground, it spreads out in great
lava lakes or fields, the surface of which takes on the characteristic
black appearance of basalt, a certain kind of glass, for the lavas of
Mt. Loa are generally basaltic. After an eruption the hardened floor
of lava in the caldera, being no longer supported by the liquid mass
formerly below it, falls in, leaving a large cavity with only the
edges of the old floor clinging to the sides of the pit.
It will be interesting to give a short account of some of the great
lava streams that have been poured out at different times from Mt. Loa.
In the great eruption of August 11th, 1855, the lava escaped through
fissures from two to thirty inches in width. Then, flowing in a
continuous stream, it did not stop until it was within five miles of
Hilo.
In the eruption of January 23d, 1859, the lava stream flowed towards
the northwest on the east side of Haulalai, reaching the sea in eight
days.
The eruption of March 27th, 1868, was characterized by severe
earthquake shocks, one of which, occurring on the second of April,
destroyed many houses and produced huge fissures in the earth. These
shocks produced great earthquake waves that reached distant coasts.
Mt. Kilauea, lies at a lower level towards the east. This crater is
situated at 4,040 feet above the level of the sea, and is nearly 6,000
feet below the caldera on the top of Mt. Loa.
Fig. 8, taken from the United States Geological Survey, Fourth
Annual Report, for 1882-83, shows a view of Kilauea from the Volcano
House. Dutton gives the following description of the appearance of
Halemaumau, the pit crater or caldera of Kilauea.
"In front of us and right beneath our feet, over the crest
of a nearly vertical wall, more than 700 feet below, is
outspread the broad floor of the far-famed Kilauea. It
is a pit about three and a half miles in length, and two
and a half miles in width, nearly elliptical in plan and
surrounded with cliffs, for the most part inaccessible to
human foot, and varying in altitude from a little more than
300 feet to a little more than 700 feet. The altitude of
the point on which we stand is about 4,200 feet above the
sea....
"The object upon which the attention is instantly fixed
is a large chaotic pile of rocks, situated in the centre
of the amphitheatre, rising to a height which by an
eye estimate appears to be about 350 to 400 feet. From
innumerable places in its mass volumes of steam are poured
forth and borne away to the leeward by the trade wind. The
color of the pile is intensely black....
"Around it spreads out the slightly undulated floor of the
amphitheatre, as black as midnight. To the left of the
steaming pile is an opening in the floor of the crater,
within which we behold the ruddy gleams of boiling lava.
From numerous points in the surrounding floor clouds of
steam issue forth and melt away in the steady flow of the
wind. The vapors issue most copiously from an area situated
to the right of the central pile, and in the southern
portion of the amphitheatre. Desolation and horror reign
supreme. The engirdling walls everywhere hedge it in. But
upon their summits, and upon the receiving platform beyond,
are all the wealth and luxuriance of tropical vegetation
heightening the contrast of the desolation below...."
[Illustration: FIG. 9. CRATER OF KILAUEA _From Dana's Manual
of Geology_]
Fig. 9 represents the pit-like crater of Kilauea as it appeared after
the eruption of 1886. Here, as will be seen, there are several lakes
of lava, the largest of which is known as Halemaumau. The eruption of
1886, like all the eruptions of Kilauea, consisted of the escape of
the lava from an opening on the side of the mountain below the crater,
and a sinking in of the hardened floor of the crater. The figure also
shows the position of the New Lake that lies east of Halemaumau. The
extent and appearance of each of these lakes are constantly changing,
both as to height and area.
Dutton gives the following description of the appearance of the lake
of lava, and some curious phenomena that occur on its surface. He is
describing the general appearance of the pool of molten lava covered
as it is with a hardened black crust:
"The surface of the lake is covered over with a black
solidified crust showing a rim of fire all around its edge.
At numerous points at the edge of the crust jets of fire
are seen spouting upwards, throwing up a spray of glowing
lava drops, and emitting a dull, simmering sound. The heat
for the time being is not intense. Now and then a fountain
breaks out in the middle of the lake and boils freely for a
few minutes. It then becomes quiet, but only to renew the
operation at some other point. Gradually the spurting and
fretting at the edges augment. A belch of lava is thrown
up here and there to the height of five or six feet, and
falls back upon the crust. Presently, near the edge, a
cake of the crust cracks off, and one edge of it bending
downwards descends beneath the lava, and the whole cake
disappears, disclosing a naked surface of liquid fire.
Again it coats over and turns black. This operation is
repeated edgewise at some other part of the lake. Suddenly
a network of cracks shoots through the entire crust. Piece
after piece of it turns its edge downwards and sinks with
a grand commotion, leaving the whole pool a single expanse
of liquid lava. The lake surges feebly for awhile, but soon
comes to rest. The heat is now insupportable, and for a
time it is necessary to withdraw from the immediate brink."
It is very curious to think of cakes of hardened lava floating on the
surface of molten lava, but, of course, this is just as natural as
cakes of ice floating on the surface of water; for a cake of hardened
lava is, as you will understand, only a cake of frozen lava, and,
being lighter than the molten lava, must, of course, float on its
surface.
The disappearance of these cakes of frozen lava and their remelting is
still more curious, and can be explained as follows: The frozen or
solidified mass of black basalt is a trifle lighter than the lava on
which it is floating only while its temperature is high, and therefore
expanded by heat. As soon as it cools, its density increases, and when
it becomes a little greater than that of the liquid lava, it begins to
sink and soon disappears.
[Illustration: FIG. 10. SECTIONS OF KILAUEA AT DIFFERENT
PERIODS _From Dana's Manual of Geology_]
Professor Dana, who has made a careful study of the phenomena of
Kilauea, shows in Fig. 10, a cross section of Kilauea at different
times. Before the eruption of 1823, the depth of the crater was from
800 to 1,000 feet. At the eruption the bottom 600 to 800 feet, making
the depth of Kilauea over this deeper central part about 1,500 feet.
The varying depths at different dates are clearly marked on the
drawing.
The eruptions of Kilauea generally occur as follows:
First there is a slow rising of the lava in the crater. This rising
continues until the pressure is so great that the mountain is ruptured
at some lower place. Next a discharge of the lava and a sinking to a
level in the conduit that will depend on the position of the crevice.
Then a gradual falling in of the hardened floor of the lake, a portion
of the horizontal walls remaining on the sides of the caldera.
The eruption of Kilauea, however, has not always been of the quiet
type. There was an eruption in the year 1789 that would appear to
have been of the explosive variety. The following account is given by
Dana as taken from a history of the Sandwich Islands by the Rev. I.
Dibble, published in 1843:
"The army of Keoua, a Hawaiian chief, being pursued by Kamehamoha,
were at the time near Kilauea. For two preceding nights there had
been eruptions, with ejections of stones and cinders. The army of
Keoua set out on their way in three different companies. The company
in advance had not proceeded far before the ground began to shake and
rock beneath their feet, and it became quite impossible to stand.
Soon a dense cloud of darkness was seen to rise out of the crater,
and, almost at the same instant, the thunder began to roar in the
heavens and the lightning to flash. It continued to ascend and spread
around until the whole region was enveloped, and the light of day
was entirely excluded. The darkness was the more terrific, being
made visible by an awful glare from streams of red and blue light,
variously combined through the action of the fires of the pit and the
flashes of lightning above. Soon followed an immense volume of sand
and cinders, which were thrown to a great height, and came down in a
destructive shower for many miles around. A few of the forward company
were burned to death by the sand, and all of them experienced a
suffocating sensation. The rear company, which was nearest the volcano
at the time, suffered little injury, and after the earthquake and
shower of sand had passed over, hastened on to greet their comrades
ahead on their escape from so imminent a peril. But what was their
surprise and consternation to find the centre company a collection
of corpses! Some were lying down, and others were sitting upright,
clasping with dying grasp their wives and children, and joining noses
(the mode of expressing affection) as in the act of taking leave. So
much like life they looked that at first they supposed them merely
at rest, and it was not until they had come up to them and handled
them that they could detect their mistake." Mr. Dibble adds: "A blast
of sulphurous gas, a shower of heated embers, or a volume of heated
steam would sufficiently account for this sudden death. Some of the
narrators who saw the corpses, affirm that though in no place deeply
burnt, yet they were thoroughly scorched." As you will see in Chapter
XI, this sudden and awful death due to highly heated air and dust
particles, caused even a greater loss of life in the catastrophic
eruption of Pelée, in Martinique on May 8, 1902.
By reason of its situation at a lower level on the slopes of Mt. Loa,
Kilauea was at one time thought to be one of the craters lower down
on the slopes of Loa. This was the opinion of Professor Dana when he
examined the district in 1840. Since this time the region has been
more carefully studied, and Mt. Loa and Kilauea, are now generally
regarded as separate and independent volcanoes, neither of which acts
as a safety valve for the other.
We shall not attempt in this chapter to say anything concerning the
sources or places from where these great supplies of lava have been
drawn. This will be left to some subsequent chapter, after we have
described still other volcanoes.
The outlines of mountains like Mt. Loa or Kilauea differ greatly from
mountains like Vesuvius; their slopes, like the slopes of all other
Hawaii volcanoes, have an inclination which does not exceed 10°.
The lava streams, therefore, as they flow down the mountains, move
more slowly than they would were the slopes more precipitous, as in
mountains like Vesuvius.
There have been many eruptions of Kilauea. That which occurred in the
year 1840, was of great magnitude (see map, Fig. 6), and began in a
fissure southwest of the crater. The principal eruption, however,
broke out about twelve miles from the sea coast, and about twenty-five
miles east of Kilauea. Here an enormous mass of lava forming a stream
nearly three miles wide reached the ocean at Nanawale.
When an eruption takes place on Mt. Loa through a fissure at the
height of 10,000 to 13,000 feet the length of the lava streams is
frequently as great as twenty-five to thirty miles. Often the lava
though hardening at the surface will continue to flow underneath
through huge tunnels, of which the top and sides are composed of
solidified parts of the same lava stream. After the flow has ceased
long hollow tunnels often remain. If the lower end of such a tunnel
containing molten lava is momentarily closed, the pressure of the
lava above may not only burst through the obstruction, but may even
throw the lava upwards in jets 300 to 700 feet high. Probably most of
you have seen illumined fountains where jets of water are beautifully
lighted up by different colored electric lights placed below them.
Such fountains, however, can but poorly compare either in beauty or
grandeur with these wonderful lava fountains, common on the slopes of
Mt. Loa during an eruption.
CHAPTER IV
THE VOLCANIC ISLAND OF ICELAND
The island of Iceland consists of a number of volcanic mountains some
of which are still active. As can be seen from the map, shown in
Fig. 11, Iceland lies in the North Atlantic Ocean, immediately below
the Arctic Circle, about 250 miles east of Greenland, and 600 miles
west of Norway. Its length from east to west is about 300 miles, and
its breadth about 200 miles, its total area, including the adjacent
islands, being more than 40,000 square miles.
Were all the water removed from the North Atlantic Ocean, it would be
seen that Iceland rests on the bed of the Atlantic, on a submarine
plateau or highland; for, in this part of the ocean the water is only
from 1,500 to 3,000 feet deep. This submarine plateau extends as far
as Norway on the east, Greenland on the north, and the island of Jan
Mayen on the northeast. Immediately north of the plateau the ocean
suddenly drops to a depth of 12,000 to 15,000 feet.
[Illustration: FIG. 11. ICELAND]
Toward the south the plateau extends with but few interruptions
through the middle of the ocean to a shoal known as the _Dolphin
Shoal_, as far as lat. 25° N. This part of the ocean, which can only
relatively be called a shoal, is not generally deeper than 9,600 feet,
although in some places the water is more than 12,000 feet deep. On
each side of the Dolphin Shoal the water is much deeper, being in
places 15,000 feet on the east, while on the west there are depths
as great as from 17,000 to 21,000 feet.
This sunken plateau, possibly including the shallower plateau on the
north, is believed by some to be the remains of the fabled continent
of _Atlantis_, to which we shall refer in another part of this book.
The coast line of Iceland is unbroken on the southeast, but the
remainder of the coast is deeply indented with bays or fiords in which
are many excellent harbors.
Iceland is liable to frequent earthquake shocks and volcanic
eruptions. From careful records that have been preserved in the
history of the island, we learn that since the beginning of the
twelfth century there have practically never been intervals longer
than forty years, and more generally not longer than twenty years,
in which there has not been a great earthquake or a great volcanic
eruption. These volcanic eruptions are often very protracted. For
example, one eruption of the volcano Hecla continued for six years
without ceasing. Sir Charles Lyell, the great English geologist,
writes as follows about Iceland:
"Earthquakes have often shaken the whole island at once,
causing great changes in the interior, such as the sinking
down of hills, the rending of mountains, the desertion of
rivers by their channels, and the appearance of new lakes.
New islands have often been thrown up near the coast, some
of which still exist, while others have disappeared, either
by subsidences or the action of the waves.
"In the interval between eruptions innumerable hot springs
afford vent to the subterranean heat, and solfataras
discharge copious streams of inflammable matter. The
volcanoes in different parts of the island are observed,
like those of the Phlegræan Fields, Italy, to be in
activity by turns, one vent often serving for a time as a
safety valve for the rest. Many cones are often thrown
up in one eruption and in this case they take a linear
direction, running generally from southeast to northwest."
The volcanic eruptions of Iceland belong for the greater part to the
fissure type. During a volcanic eruption in Iceland the ground is
split in fissures or cracks, generally parallel to each other, and
varying in width from a few inches to several yards. These fissures
extend for great distances across the country. The lava quietly wells
out along the fissures not unlike the way quiet spring waters flow
from their reservoirs.
According to Dr. Th. Thoroddsen, the Icelandic geologist, there are
two systems of fissures extending through Iceland, from southwest to
northeast in the southern part of the island, and from north to south
in the northern part. Where two lines of fissures cross each other the
points of intersection may be especially active.
Dr. Th. Thoroddsen arranges the volcanoes of Iceland under three
heads, i. e., _cone-shaped volcanoes_; _lava cones_; and _chains of
craters_, the last being the commonest. Out of 107 volcanoes examined
by him in Iceland, eight were of the Vesuvian type, or were built up
of layers of lava and volcanic ashes; sixteen were of the lava-cone
type, similar to Mt. Loa, of the Hawaiian Islands, and the remaining
eighty-three were of the type of crater chains.
The volcano of Snaefell Jökul, 4,710 feet above the level of the
ocean, is built up of alternate layers of lava and hardened volcanic
mud. It is not, however, a true cone-shaped mountain.
The largest volcano in Iceland, the Dyngjufköll, with its immense
crater of Askja, has an area of some twenty-five square miles. In its
form it resembles Snaefell.
Volcanoes of the lava-cone type have been built up entirely of lava
and have a slight angle of inclination. These volcanoes range in size
from small hillocks to the largest mountains on the island. Their
cones generally stand on a base of wide circumference and frequently
rise to great heights, the top being occupied by a caldera, or pit
crater like that on Mt. Loa or Kilauea.
Volcanoes of the type of chain-craters follow the natural fissures in
the crust. These craters are generally low, seldom being more than 350
feet high.
There are also seen in Iceland caldron-shaped depressions that have
been formed by explosive eruptions. One of the best instances of such
craters is Viti, on the side of Mt. Krafla. This crater was formed by
the sudden eruption of May 17th, 1724.
The lava sometimes quietly runs out of the entire length of the
fissure without forming any cone. This was the case of a great fissure
known as the Eldgja Chasm. Here three lava streams covered an area of
270 square miles.
As the lava comes out of the fissures, it generally produces long
ramparts of slags, and blocks of lava that are piled up on either side
of the fissure. Sometimes a line of low cones is built up. These cones
consist of heaps of slag, cinders, and blocks of lava. Their craters
are not rounded as in the case of volcanoes of the Vesuvian type, but
are oblong, or have their greatest diameter extending in a direction
of the fissure.
Icelandic lava as it escapes from the fissures is peculiar in that
it is very viscid or plastic and can be readily drawn out into long
threads that can be spun into ropes. When such lava runs down the
sides of a steep slope, it often splits on cooling into separate
blocks. Where it runs over flat, level ground, however, it spreads
uniformly on all sides, producing vast level lava deserts that are as
flat as the surface of a well built floor.
There are many rivers in the north and the west of Iceland. Now, as
the lava streams flow out of the fissures they enter the channels of
the rivers so that the streams of water must find new paths to the
sea, and this operation may be repeated again and again. Often the
time between eruptions is long enough to give the rivers opportunity
to cut deep channels or gorges in their new channels; but on the next
escape of the lava these gorges and valleys are again filled with the
molten rock, and the rivers must begin their channel cutting all over.
You will note the frequent use of the word Jökul, as Snaefell Jökul,
Skaptar Jökul, Orefa Jökul, etc. The name Jökul means a large mass of
ice, or a mountain that is continually covered with snow, for example,
Snaefell Jökul, is a beautifully shaped, snow-covered mountain
situated on a point of land on the western coast of the island,
extending out nearly fifty miles into the sea, between the Faxa Fiord
and the Briela Fiord. It is a very conspicuous object, being visible
to passing ships at considerable distances from the island. Orefa
Jökul is the highest mountain in Iceland. Skaptar Jökul is one of the
active volcanoes of Iceland.
There can be no doubt that Iceland has been formed entirely by lava
thrown up from the bottom of a submarine plateau, until it extended
above the surface of the waters. To make an island entirely of lava
with an area of 40,000 square miles, must, of course, have required
many cones or craters that continued to pour forth lava for periods of
time much longer than those during which man has lived on the earth.
The surface of Iceland is far from attractive. The interior is
practically a vast lava desert, covered with snow-clad mountains or
Jökuls. There is no plant life except in marshy lands near the coasts,
and even here scarcely enough grass is raised to feed the few cattle
and horses owned by the inhabitants. There is no agriculture, owing
to the very short summers, so that all grain is brought from Europe.
Every now and then the grass crop is destroyed by accumulation of
Polar ice on the northern and western coasts. Such failures are always
attended by great famines, when many of the people die.
Should you ever visit Iceland you would probably be surprised to hear
the people speaking about their forests. You might go over all the
coasts of the island without seeing anything larger than a birch bush,
not much higher than six feet. These are what the Icelanders like to
speak of as their forest trees, and I suppose there is no harm done,
if one only understands just what they mean by "trees."
While, however, Iceland has practically no trees, yet it has no
difficulty in obtaining a plentiful supply of timber, since in the
deep fiords or bays on the western and southern coasts there can
always be found much drift timber brought there by the ocean currents
from the forests of America.
The principal town or settlement in Iceland is Reykjavik, the capital
of the island, on the southwestern coast; this is the chief trading
place on the island. Thingvalla is also an important town.
The lavas that form the entire mass of Iceland were thrown out both
before and since the glacial age. It is the opinion of Geikie that
these outflows have continued uninterruptedly since that age to the
present time. It is known that the lavas of Iceland were thrown out
both before and after the glacial age, because during the glacial age,
deep cuttings or groovings were made on the surface of the earth by
the glaciers as they slowly moved over it. Now lava beds containing
the glacial scratches have been found and resting on them are other
lava streams. The scratched lavas must, therefore, have been thrown
out before the glacial age, and the second lavas after that age.
Let us now examine some of the more active volcanoes of Iceland and
their eruptions. We will begin with the well-known volcano of Skaptar
Jökul.
The following description of this volcano has been taken from a book
on Iceland by E. Henderson, published in Boston, 1831. Skaptar Jökul
lies in the south central part of Iceland about forty odd miles from
the coast. It takes its name from the Skaptar River, down whose
channel the lava flowed its entire distance of forty miles from the
ocean. Skaptar Jökul consists of about twenty conical hills lying
along one of the fissures that extends from northeast to southwest.
It appears from Henderson's account that people living in the
neighborhood of Skaptar Jökul were greatly alarmed by repeated
earthquakes that were felt at different times from the first to the
eighth of June, 1783. These earthquake shocks increased in number and
violence, so that the people left their homes and awaited in terror
the coming catastrophe. On the morning of the eighth a prodigious
cloud of dense smoke darkened the air, and the surrounding land soon
became covered with ashes, pumice, and brimstone. As is common with
eruptions in Iceland, that have been preceded by long periods of rest,
the heat produced by the escaping lava and the sulphurous gases,
melted such quantities of ice that great floods were produced in the
rivers.
On the 10th of June vast torrents of lava that had been escaping
from the craters entered the valley of the Skaptar River, and
commenced flowing through its channel. Immense quantities of steam
were produced, and, in less than twenty-four hours, the river was
completely dried up, for the lava had collected in the channel,
which in many places flows between high rocks from 400 to 600 feet
in height and nearly 200 feet in breadth, and had not only filled
the river to its brink, but had overflowed the adjacent fields to a
considerable extent, and flowing along the cultivated banks of the
river destroyed all the farms in its path.
On gaining the outlet, where the channel of the Skaptar emerged
into the plain, it might have been supposed that the burning flood
would have at once spread over the low fields, which lay immediately
before it, but, contrary to all expectations, this flow was for a
time stopped by an immense unfathomed abyss in the river's bed, into
which it emptied itself with great noise. When this chasm was at
last filled, the lava increased by fresh flows, rose to a prodigious
height, and breaking over the cooled mass, proceeded south towards the
plain.
In the meantime the thunder and lightning, together with subterranean
roars, continued with little or no intermission.
On the 18th of June, 1783, another dreadful eruption of red hot lava
came from the volcano. This flowed with great velocity and force over
the surface of the cooling stream that had been thrown out principally
on the tenth of the month. Floating islands consisting of masses of
flaming rock were seen on the surface of the lava stream, and the
water that had been banked up on both sides of the stream was thrown
into violent boiling.
In the meantime people living along the Hverfisfloit, the next largest
river to the east of the Skaptar, had not yet been visited by the
lava streams. It is true that their vegetation had been destroyed by
showers of red hot stone and ashes, and that both atmosphere and water
were filled with poisonous substances. The land had also been plunged
in utter darkness, so that it was scarcely possible at noonday to
distinguish a sheet of white paper held up at the window from the
blackness of the wall on either side. But the molten lava streams had
not yet reached the people of this valley and they hoped that the
eruption would soon be over, and that the lava flow would continue to
follow the Skaptar. On the 3d of August, however, they were alarmed by
seeing steam escaping from the River Hverfisfloit, and soon all its
water was dried up, and a fresh lava flow poured down upon them. As in
the case of the Skaptar, the melted rock completely filled the empty
channel to the brink, and then overflowing, covered the low grounds on
both sides, so that by the ninth of August it had reached the open and
level country near its mouth and in the course of a few hours spread
itself for a distance of nearly six miles across the plain. This flow
continued after the end of August, and, indeed, even as late as the
month of February, 1784, when a new eruption took place in this part
of the country.
Hecla, another well-known volcano in Iceland, situated about thirty
miles from the southern coast, consists of three peaks, the central of
which is the highest. Its craters form vast hollows on the sides of
these peaks, and at the time of the eruption in 1766 were covered with
snow. Hecla is believed to have been an active volcano long before
Iceland was inhabited. No less than twenty-three eruptions have been
recorded between A. D. 1004 and the great eruption of 1766-68.
Volcanic history frequently repeats itself. There had been no great
eruption of Hecla for a period of about twelve years, and the people
living in the neighborhood were congratulating themselves on the
belief that the mountain was becoming actually extinct, and that
therefore they need not trouble themselves about eruptions. Others,
however, more farseeing, pointed out the fact that the lakes and
rivers in the vicinity did not freeze, and that the amount of water
they contained was greatly decreased.
The following description of the great eruption of Hecla that was
remarkable both for its violence, as well as for the time during which
it continued, is taken from Symington's "Sketches of Faroe Islands and
Iceland":
"On the 4th of April, 1766, there were some slight shocks
of an earthquake, and early next morning a pillar of sand,
mingled with fire and red hot stones, burst with a loud
thundering noise from its summit. Masses of pumice, six
feet in circumference, were thrown to the distance of ten
or fifteen miles, together with heavy magnetic stones,
one of which, eight pounds weight, fell fourteen miles
off, and sank into ground still hardened by the frost. The
sand was carried towards the northwest, covering the land,
150 miles round, four inches deep, impeding the fishing
boats along the coast, and darkening the air, so that at
Thingore, 140 miles distant, it was impossible to know
whether a sheet of paper was white or black. At Holum, 155
miles to the north, some persons thought they saw the stars
shining through the sand-cloud. About mid-day, the wind
veering round to the southeast, conveyed the dust into the
central desert, and prevented it from totally destroying
the pastures. On the 9th of April, the lava first appeared,
spreading about five miles towards the southwest, and on
the 23d of May, a column of water was seen shooting up in
the midst of the sand. The last violent eruption was on the
5th of July, the mountains, in the interval, often ceasing
to eject any matter; and the large stones thrown into the
air were compared to a swarm of bees clustering around the
mountain-top; the noise was heard like loud thunder forty
miles distant, and the accompanying earthquakes were more
severe at Krisuvik, eighty miles westward, than at half the
distance on the opposite side. The eruptions are said to
be in general more violent during a north or west wind than
when it blows from the south or east, and on this occasion
more matter was thrown out in mild than in stormy weather.
Where the ashes were not too thick, it was observed that
they increased the fertility of the grass fields, and
some of them were carried even to the Orkney Islands, the
inhabitants of which were at first terrified by what they
considered showers of black snow."
The largest volcano in Iceland is Dyngjufjoll. This has on its summit
the gigantic crater of Askja, some twenty-five square miles in area.
This crater is of the intermediate form; the most general form of
volcanoes on the island consisting of a number of craters that closely
follow fissures.
Professor Johnstrup, in a report to the Danish Government, on this
volcano, states that the valley of Askja has been gradually filled
by repeated flows of lava from enormous craters on the edge of the
mountain. In many places the surface of the earth is covered with
bright red pumice stone that was thrown out during an eruption March
29th, 1875. Some of these craters are filled with steam that escapes
with an almost deafening roar. The surprising feature of this eruption
was the immense quantity of pumice stone that escaped.
The volcanoes in the Nyvatus Oraefi are entirely different. This
barren plain is thirty-five miles in length and thirteen miles in
breadth. Suddenly on the 18th of February, 1875, a volcano appeared in
the centre, and four other craters were formed at subsequent dates.
The mass of lava that was thrown out of these openings has been
estimated at 10,000,000,000,000 cubic feet, or eighteen times the
estimated mass of lava that has been emitted from Vesuvius between
1794 and 1855. This lava is basalt.
CHAPTER V
VESUVIUS
The old Greeks and Romans had but little knowledge of volcanoes. They
only knew the volcanic mountains in the Mediterranean Sea. Here there
are three volcanic regions:--one in the neighborhood of Naples; one
including Sicily and the neighboring islands, and the other that of
the Grecian Archipelago.
Some idea can be had of these three regions from a map of the
Mediterranean shown in Fig. 12. The principal volcanoes are Vesuvius,
Etna, Stromboli, and Vulcano, a mountain, by the way, that gave its
name to all volcanic mountains. In this chapter we will describe the
volcano of Vesuvius, the most active, though by no means the largest
of the volcanoes of the Mediterranean.
But, before doing this, it will be well first to describe briefly the
volcanic districts surrounding Vesuvius.
As shown in Fig. 13, this district includes Vesuvius, Procida, and
Ischia.
[Illustration: FIG. 12. THE MEDITERRANEAN]
Ischia is a small island measuring about five miles from east to west,
and three miles from north to south. There were such terrific volcanic
eruptions on this island long before the Christian Era, that several
Greek colonies were forced to abandon it. A colony established long
afterwards, about 380 B. C., by the king of Syracuse also
had to depart. Strabo, the Grecian geographer (born about 63 B.
C.), states that, according to tradition, terrific earthquakes
occurred on the island a little before his time, and its principal
mountain threw out large quantities of molten rock, which flowed into
the sea. At the time of this eruption there were earthquake waves in
the sea, the waters of which slowly receded, leaving large portions
of the bottom uncovered, and rushing, afterwards, violently over
the land, caused great destruction. It was during this disturbance,
so Strabo asserts, that the island of Procida was formed by being
violently torn from Ischia.
[Illustration: FIG. 13. THE VOLCANIC DISTRICT AROUND VESUVIUS]
The Phlegræan Fields was a name given by the ancients to some of the
lowlands in the neighborhood of Naples; they were believed to be under
the special protection of the Roman gods. When the frequent earthquake
shocks shook these fields, the Roman people believed that conflicts
were taking place between their gods and slumbering giants confined in
the regions below the surface.
It is more than probable that Mt. Vesuvius has always been the centre
of these volcanic disturbances. Long before the Christian Era,
however, Vesuvius, or Somma, the name given to the old crater that
then occupied the summit of the mountain, had been an extinct crater.
Indeed, it had been so quiet that the people who lived on its slopes
did not appear to know they were living on the slopes of a slumbering
volcano. Their knowledge of volcanic mountains must have been very
limited, for this mountain with the huge pit at its summit had all
the appearance of a volcanic crater. When they climbed to the top of
the mountain, which, of course, they frequently did to look after the
vineyards they were cultivating on the slopes, and looked down into
the deep pit from the rocks on its edge, they could see at the bottom
of a great central pit three miles in diameter, a lake, with room here
and there to enable one to walk along its borders. The walls of the
precipice were covered with luxuriant vines.
When we say that none of the people even suspected that Vesuvius had
ever been in a state of eruption, we must except some of their learned
men. For both Diodorus Siculus, a native of Sicily, who lived about
10 B. C., and wrote an Universal History, containing some
forty volumes, of which only about one-third remain, and Strabo, the
Geographer, pointed out in a general manner, that Vesuvius, and much
of the surrounding country, looked as if it had been eaten by fire.
Then, too, a Roman philosopher who lived between A. D. 1 and
A. D. 64, spoke of Vesuvius being "a channel for the eternal
fire!"
Let us now endeavor to obtain some idea of the appearance of this
region a short time before A. D. 79, when Vesuvius burst
forth in a terrific eruption. The slopes of the mountain were covered
with the rich vegetation that characterizes this part of Italy.
When most volcanic ashes and lava have been exposed for some time to
the atmosphere they make a very fertile soil. Now, this soil on the
slopes of Vesuvius made the vineyards that covered the mountain slopes
and the fields for miles around its base, bear very plentifully,
so that the people lived very comfortably. Here and there on the
slopes of the mountain large towns like Herculaneum and Pompeii had
long been established, while, in the distance, was the large city of
Naples. Besides these there were numerous populous towns and villages
scattered here and there over the plain or on the lower mountain slope.
You have all probably read of the Roman gladiator, Spartacus.
Spartacus was a Thracian by birth, and while a shepherd had been taken
prisoner by the Romans and sold to a trainer of gladiators at Capua.
Chaffing under the tyranny of the Romans, who forced him to fight in
the arena with men and beasts, he revolted against his masters, and
with a band of some seventy followers, fled to a mountain fastness in
the crater of Vesuvius. Proud Rome sent a few men to recapture him,
with scourges for his punishment, but they were beaten by Spartacus.
Every day dissatisfied men like himself escaped from the Romans and
joined his ranks. Rome sent a larger body of men against Spartacus,
but they also were beaten. At last, recognizing the gravity of the
position, the Roman Prætor, Clodius, was sent against Spartacus with
an army of some three thousand men. Clodius caught Spartacus in the
crater and guarded the only space by which it seemed possible for
Spartacus to escape. Using the vines that covered the precipitous
walls of the crater, Spartacus did escape, and falling unexpectedly
on the armies of Clodius, routed them. After this victory, Spartacus
with an army of over 100,000 men overran southern Italy, and sacked
many of the cities of the Roman Campania. During this time Spartacus
defeated one Roman army after another, until finally, in the year 71
B. C., Crassus was sent against him and vainly endeavored
to conquer him. Being unsuccessful, Crassus urged the Roman Senate
to recall Lucullis from Asia and Pompey from Spain, and finally poor
Spartacus was cut down in a fight he made against Crassus and Lucullis.
But let us come to the great eruption of Vesuvius in A. D.
79. The people living on the slopes of Vesuvius were not without
plenty of warnings of the dreadful catastrophe that was coming. As
early as A. D. 63 there was a great earthquake that shook the
country far beyond Naples. In Pompeii, then a flourishing city, the
Temple of Isis was so much damaged that it had to be rebuilt.
Even if the earthquake shocks had not foretold the coming eruption,
there were other signs. The height of water in the wells decreased.
Springs that had never before been known to fail, dried up completely.
These changes, as we well know, were due to the red hot lava being
slowly forced up from great depths into the tube connected with the
crater.
The earthquake shocks continued at irregular intervals for sixteen
years, until, on the 25th of August, A. D. 79, about one
o'clock in the afternoon, Vesuvius burst forth in the terrible
eruption that destroyed the towns of Pompeii and Herculaneum. Pompeii
was a seaport town situated near the mouth of the River Sarno,
about fifteen miles southeast of Naples. It was a beautiful place,
containing many splendid temples. Its people for the greater part
lived luxuriously, for Pompeii was the summer resort of the richer
people of Naples, some of whom lived there during the hottest months
of the year.
Herculaneum, the other town, was nearer Naples, only five miles from
the city. It was also, like Pompeii, a beautiful town, and contained
many splendid buildings. In each town there were magnificent baths and
a large theatre. The inhabitants spent so much of their time in the
open air, or in the baths, that it was not necessary for them to build
very large houses. The houses, however, were well built, and though
generally consisting of practically a single story, were provided with
all the luxuries that great wealth could command.
On August 25th, A. D. 79, severe earthquake shocks again
visited this part of the world and Vesuvius suddenly threw up from
its crater an immense column of black smoke, which, rising high in
the air, spread out in the form of a huge mushroom, or, perhaps, more
like the umbrella pine tree of the neighborhood. Rapidly spreading on
all sides, the smoke soon completely shut out the light of the sun,
and wrapped the earth in an inky darkness, except for a red glare from
columns of molten rock that rushed out of the crater.
From the dark cloud immense quantities of red hot stones, pumice, and
volcanic ashes descended on the earth. At the same time there fell
a deluge of rain, caused by the sudden condensation of the enormous
amount of water vapor that was thrown out from the crater during the
eruption. Fortunately, very few of the people were killed in either of
the cities of Pompeii and Herculaneum, although some bodies were found
in the ruins. Most of the people escaped through the darkness and
gloom, continuing to flee from the city for at least three days.
Both cities were covered so deep with ashes or mud that the tops of
the tallest buildings were no longer visible. Pompeii was buried by
showers of ashes or volcanic cinders, and Herculaneum mainly by vast
floods of aqueous lava.
So completely were these cities covered that their very existence was
at last forgotten. It is true that Titus, who was then Emperor of
Rome, endeavored to clear away the ashes and rebuild Pompeii, but the
task was so great that he finally abandoned it.
During the year 1592, the architect Fontana, while superintending the
building of an aqueduct, came across some ancient buildings. At a much
later date, in 1713, some workmen, while digging a well in the village
of Portici, uncovered three marvellously beautiful marble statues. In
the year 1738, the same well was dug deeper, when traces of the old
theatre of Herculaneum were discovered. Some effort was then made to
excavate the city and many of the public buildings and private houses
were uncovered, and statues, mosaics, wall paintings, and charred
manuscripts of papyrus were found. A few of these have been unrolled
and deciphered, but owing to the difficulty of doing this, without
destroying them, the greatest number still remain unread.
In 1860, the Italian Government began a systematic excavation of the
buried cities, and now both Pompeii and Herculaneum are thrown open to
the sunlight so that one can walk through the old streets, and look
into the houses, in which, before A. D. 79, the people lived
so happily.
Many interesting stories are told about the discoveries that were
made during the government excavations. The skeleton of one of the
inhabitants was found grasping a money bag. He might have escaped,
but had gone back to get his money. He got it, but remained with it.
In another place, the skeletons of a number of people were found in
an underground room or cellar of a house, where were also found some
mouldy bread and empty water flasks. Instead of leaving the city,
which they might have done, they had retreated to the underground
room for safety, but the fine volcanic dust drifted in and suffocated
them.
The younger Pliny, the historian, has given an excellent account of
some features of this great eruption. It appears that his uncle was
stationed with the Roman fleet, in the Bay of Naples, at the time of
the eruption. He describes the dark cloud of ashes that was formed
over Vesuvius. He refers to the rapidity with which it spread, and
to the showers of ashes, cinders, and stones that it rained down on
the earth. His uncle, the elder Pliny, landed on the coast, and was
afterwards killed by a cloud of sulphurous vapor that swept down the
side of the mountain.
The following letter from the younger Pliny, describing his flight
with his mother from Misenum, is quoted from Dana's "Characteristics
of Volcanoes."
"It was now seven o'clock [on the morning of August 25th],
but the light was still faint and doubtful. The surrounding
buildings had been badly shaken, and although we were in
an open spot [a little yard between his uncle's house and
the sea], the space was so small that the danger of a
catastrophe from falling walls was great and certain. Not
till then did we make up our minds to go from the town....
When we were free from the buildings we stopped. There we
saw many wonders and endured many terrors. The vehicles we
had ordered to be brought out kept running backward and
forward, though on level ground; and even when blocked
with stones they would not keep still. Besides this, we
saw the sea sucked down and, as it were, driven back by
the earthquake. There can be no doubt that the shore had
advanced on the sea, and many marine animals were left high
and dry. On the other side was a dark and dreadful cloud,
which was broken by zigzag and rapidly vibrating flashes of
fire, and yawning showed long shapes of flame. These were
like lightning, only of greater extent....
"Pretty soon the cloud began to descend over the earth
and cover the sea. It enfolded Capreæ and hid also the
promontory of Misenum." ... The flight was continued.
"Ashes now fell, yet still in small amount. I looked
back. A thick mist was close at our heels, which followed
us, spreading out over the country, like an inundation."
... Turning from the roar in order to avoid the fleeing,
terror-stricken throng, they rested. "Hardly had we sat
down when night was over us--not such a night as when there
is no moon and clouds cover the sky, but such darkness as
one finds in close-shut rooms. One heard the screams of
women, the fretting cries of babes, and shouts of men....
"Little by little it grew light again. We did not think
it the light of day, but a proof that the fire was coming
nearer. It was indeed fire, but it stopped afar off; and
then there was darkness again, and again a rain of ashes,
abundant and heavy, and again we rose and shook them off,
else we had been covered and even crushed by the weight....
At last the murky vapor rolled away, in disappearing smoke
or fog. Soon the real daylight appeared; the sun shone out,
of a lurid hue, to be sure, as in an eclipse. The whole
world which met our frightened eyes was transformed. It was
covered with ashes white as snow."
Young Pliny and his mother returned to Misenum, and survived the
perils to which they were exposed.
It was during this eruption that a large part of the old crater was
blown off the mountain by the tremendous force at work.
There have been many eruptions of Vesuvius since the great eruption
of A. D. 79. One of these occurred during the reign of Severus,
A. D. 203. It was during this eruption that an additional part of the
old crater of Somma was blown away.
Another great eruption occurred A. D. 472. Then great
quantities of volcanic dust were thrown up into the air, and falling,
covered practically all parts of Europe, producing darkening of the
sun and great fear as far as the city of Constantinople.
But what was perhaps a still greater eruption occurred during December
of 1631. This eruption spread great quantities of ashes over the
country for hundreds of miles around, and great streams of mud rushed
down the slopes of the mountain. Buccini gives the following account
of this eruption:
"The crater was five miles in circumference, and about
1,000 paces deep. Its sides were covered with brushwood,
and at the bottom there was a plain on which cattle grazed.
In the woody parts wild boars frequently harbored. In one
part of the plain, covered with ashes, were three small
pools, one filled with hot but bitter water; another with
water saltier than the sea, and a third with water that
was hot but tasteless. But at length these forests and
grassy plains were consumed, being suddenly blown into the
air and their ashes scattered to the winds. In December,
1631, seven streams of lava poured at once from the crater
and overflowed several villages, on its flanks, and at the
foot of the mountain. Reisna, partly built over the ancient
city of Herculaneum, was consumed by the fiery torrent.
Great floods of mud were as destructive as lava. This is
no unusual occurrence during these catastrophes for such
is the violence of the rains produced by the evolution of
aqueous vapors that torrents of water descend the cone and
become charged with impalpable volcanic dust, and rolling
among ashes, acquire sufficient consistency to deserve the
ordinary appellation of aqueous lava."
Of course, you will understand that we have given only a few of
the most notable of the eruptions of Mt. Vesuvius. Since the yea
A. D. 1500 there have been no less than fifty-six recorded
eruptions, that of the year 1857 being especially violent.
Omitting these eruptions we at last come to the great recent eruption
of 1872.
Fortunately, the eruption of 1872, as well as still more recent
eruptions that have occurred, have been more accurately described than
have most volcanic eruptions, for the Italian Government, recognizing
the value to the natives of Italy of a knowledge of what was going on
at the crater of Vesuvius, has maintained for the past thirty years
an observatory on the western part of the mountain. This observatory
has been placed in charge of Prof. Luigi Palmieri, a well-known
student of volcanoes and earthquakes. At this place records are kept
of the behavior of the volcano, of all earthquake disturbances, as
well as other phenomena. At the same time, by the use of photography,
excellent pictures have been obtained showing the appearance of the
sky during an eruption.
Vesuvius had been in a quiet state from November, 1848, to the year
1871, when small quantities of lava flowed continuously for several
months. Again, early in 1872, other quiet eruptions of lava continued
for weeks at a time. Finally, on April 26th, of that year, a violent
explosive eruption occurred. The following account has been taken from
Palmieri's report, entitled, "The Eruption of Vesuvius in 1872."
On April 23d the recording earthquake instruments, the seismographs,
were greatly affected. On the evening of the 24th lava streams flowed
down the cone in various directions. These streams were continued
on the 25th and the 26th, so that on the night of the 26th the
observatory lay between two streams of molten lava that threw out so
much heat that the glass windows in the observatory were cracked,
and a scorching smell was quite perceptible in the rooms. The cone
of the mountain was deeply fissured, lava escaping freely from all
the fissures, so that the molten rock appeared to ooze from over its
entire surface, or as Palmieri expressed it, "Vesuvius sweated fire."
This great cracking or fissuring of the cone was accompanied by the
opening of two large craters at the summit, that discharged, with a
great noise, immense clouds of steam, dust, lapilli, and volcanic
bombs. These latter are very curious and consist of masses of soft
lava that are thrown high into the air by the outrushing columns of
steam. Being rotated or spun, as they rise in the air, they assume a
spherical shape. Some of these volcanic bombs were thrown to a height
estimated by Palmieri to have been nearly 4,000 feet above the top of
the mountain. When the height of a projectile is known, the velocity
with which it left the opening from which it was projected or thrown
can be estimated, so that the volcanic bombs must have left the crater
at a velocity of about 600 feet per second.
On the 27th, in the evening, the lava streams ceased flowing, but the
dust and lapilli continued to fall during the 28th and the 29th. On
the 30th the detonations decreased and by the 1st of May the eruption
was entirely over.
Palmieri calculated that the quantity of molten rock thrown out during
this eruption was sufficient to cover an area of about 1.8 square
miles to an average depth of about thirteen feet.
As we can see from the above descriptions, the volcanic activity of
Vesuvius is characterized by long periods of rest followed by periods
of activity. The periods of rest are measured by years, and often by
centuries; the periods of activity by days or hours.
But Vesuvius was not to have a long period of rest after its eruption
of 1872. On the contrary, shortly after the great disaster of
Martinique in 1906, it again became active, and on the 5th of April,
1906, began throwing large blocks of lava out of its central cone, and
on the next day began to throw out large streams of lava, which, on
April 7th, destroyed a village in the neighborhood. At the same time
rumbling sounds were heard, and violent earthquake shocks shattered
the windows of the houses.
Professor Matteucci, the present director of the Vesuvius Observatory,
made the following report on April the 8th.
"The eruption of Vesuvius has assumed extraordinary
proportions. Yesterday and last night the activity of the
crater was terrific, and is increasing. The neighborhood
of the observatory is completely covered with lava.
Incandescent rocks are being thrown up by the thousands, to
a height of 2,400 feet or even 3,000 feet, and falling back
form a large cone. Another stream of lava has appeared....
The noise of the explosion and of the rocks striking
together is deafening. The ground is shaken by strong and
continuous seismic movements, and the seismic instruments
[instruments employed to record the time, direction, and
intensity of earthquake movements] threaten to break. It
will probably be necessary to abandon the observatory,
which is very much exposed to the shocks. The telegraph is
interrupted, and it is believed the Funicular railroad has
been destroyed."
On April 9th Matteucci made the following report:
"The explosive activity of Vesuvius, which was so great
yesterday, and was accompanied by very powerful electric
discharges, diminished yesterday afternoon. During the
night the expulsion of rocks ceased, but the emission of
sand increased, completely enveloping me and forming a
red mass from six to ten centimeters deep, which carried
desolation into these elevated regions. Masses of sand
gliding along the earth, created complete darkness until
seven o'clock. Several blocks of stone broke windows in the
observatory. Last night the earthquake shocks were stronger
and more frequent than yesterday, and displaced the seismic
apparatus. Yesterday afternoon and this morning, torrents
of sand fell."
On April 10th Matteucci sent the following report:
"Last night was calm, except for a few explosions of
considerable force from time to time. At four o'clock this
morning the explosions became more violent. The seismic
instruments recorded strong disturbances."
The eruption of Vesuvius of 1906 was especially noted for the great
quantities of sand and ashes thrown out of the crater. The amount
of sand that fell on the roof of the market house at Monti Olivetto
was so great that the roof fell in. In this eruption there were some
six lava streams that poured down the mountain. The most formidable
of these was that which descended towards Torre Annunziata. Here it
stopped just short of the wall of the cemetery outside of the town.
During this eruption of Vesuvius, as in previous eruptions, clouds of
volcanic dust collected in the air, shutting off the light of the sun.
Naples was in a state of semi-darkness. The roofs of the houses were
covered to a depth of several inches with an exceedingly fine reddish
dust. In some places this dust had drifted into heaps fully a yard in
depth.
CHAPTER VI
OTHER VOLCANOES OF THE MEDITERRANEAN
The relative positions of the other volcanic mountains of the
Mediterranean Sea; i. e., Etna, Stromboli, and the volcanoes of the
Santorin group of the Grecian Archipelago, are shown in the map, Fig.
12.
We will begin with the volcanic mountain of Etna, under which,
according to mythology, the angry gods had buried the rebellious
Typhoon.
Etna is situated on the island of Sicily, immediately southwest of
Italy. It is a much larger mountain than Vesuvius, rising, as it
does, from a circular base about eighty-seven miles around, to a
height of 10,840 feet above the level of the Mediterranean. It forms
a conspicuous object when seen either from the Mediterranean, or from
distant parts of Italy.
The height of Etna is so great that its slopes can be divided into
three distinct climatic zones or belts. The lowest of these lies
between the sea and a height of 2,500 feet. In this zone the mountain
slopes are covered with cultivated fields, olive groves, orchards,
and vineyards. The middle zone lies between 2,500 feet and 6,270
feet. This zone is covered with forests of chestnuts, oaks, beeches,
and cork trees. The third and highest zone includes the rest of the
mountain, and may be called the desert zone, since it is a sterile
region, covered with huge blocks of lava and scoriæ, and terminating,
in the higher portions, in a snow-covered plain, from which the
central cone rises.
Etna is continually sending up columns of steam and sulphur vapor.
Every now and then it starts in eruption, throwing out large
quantities of lava either from the crater on its summit, or from
some of the 200 smaller cones or craters that occupy portions of its
slopes. On account, probably, of its height the eruptions are most
frequently on the sides. Etna affords a magnificent example of a huge
volcanic pile of the Vesuvian type, which has been slowly built up
by the gradual accumulation of materials that have escaped from its
craters.
One of the most interesting features of the higher regions of Etna is
an immense chasm rent in a side of the cone near the summit, and known
as the Val del Bove. This chasm forms a vast amphitheater.
The great force that removed such an immense mass of matter from
the cone could not have been the eroding power of water, since the
materials of the cone are too porous to permit streams of any size to
rush down the slopes. The force is most probably to be found in some
explosive eruption of the mountain, when a portion of the crater was
suddenly blown off, just as was done in Vesuvius when a large part of
the old crater of Somma was blown away. What is especially interesting
about the Val del Bove is the opportunity it affords for studying the
interior structure of the mountain, for it practically enables one to
enter to almost the heart of this great volcano.
The Val del Bove has the shape of a great pit five miles in diameter.
It has almost vertical walls, the height of which varies with their
position. Those which reach highest up the mountain vary from 3,000 to
4,000 feet in height.
Like Vesuvius, Etna has been split or fissured into great crevices
that have been filled with lava during the many eruptions of its
central crater. On hardening, these lava streams form what are known
as dikes. As the sides of the mountain are worn away by erosion, the
dikes, being harder than the rest of the cone, project from its sides
like huge walls. An excellent opportunity for seeing them is afforded
in the walls of the Val del Bove.
Sir Charles Lyell, the English geologist, who has carefully studied
Mt. Etna, asserts that this mountain began to be formed during a
geological period known as the Tertiary Age, through a crater that
opened on the floor of the Mediterranean Sea. The material thus
thrown out, collected around the crater and produced a mountainous
pile that gradually emerged above the level of the sea, and on fresh
materials continuing to be thrown out, at length reached its present
height. It would appear that at some former time in its history, there
were two vents near the top of the mountain, the second crater being
formed immediately under the Val del Bove. Soon, however, the second
and lower crater was closed, the upper one alone remaining active.
The mountain, therefore, continued to be slowly raised in the air by
the materials brought out through this opening. Then came the great
explosive eruption during which the side of the mountain was blown off
to form the great chasm of the Val del Bove.
Because of its almost constant activity, Mt. Etna must have been
well known to the ancients, who described some of its most violent
eruptions. The following brief notes concerning these eruptions have
been taken from Lyell.
According to Diodorus Siculus, an eruption that occurred before the
Trojan war, caused the people living in districts near the mountain to
seek new homes. Thucididies, the Greek historian, states that in the
sixth year of the Peloponnesian war, which would be about the spring
of 425 B. C., a lava stream caused great destruction in the
neighborhood of Campania, this being the third eruption that had
occurred in Sicily since it had been settled by the Greeks.
Seneca, during the first century of the Christian Era, calls the
attention of Lucullus to the fact that during his time Mt. Etna had
lost so much of its height that it could no longer be seen by boatmen
from points at which it had before been readily visible.
But passing by these very early eruptions of Etna we come to the great
eruption of 1669. This eruption was preceded by an earthquake that
destroyed many houses in a town situated in the lower part of the
forest zone, about twenty-five miles below the summit of the mountain,
and ten miles from the sea at Catania. During this eruption two deep
fissures were opened near Catania. From these such quantities of sand
and scoriæ were thrown out, that, in the course of three or four
months, a double cone was formed 450 feet high, which is now known as
Monte Rosso. But what was most curious was the sudden opening, with
a loud crash, of a fissure six feet broad reaching down to unknown
depths that extended in a somewhat crooked course to within a mile
of the summit of Etna. This great fissure was twelve miles in length
and emitted a most vivid light. Five other parallel fissures of
considerable length opened, one after another, throwing out vapor,
and emitting bellowing sounds which were heard at a distance of forty
miles. These fissures were afterwards filled with molten rock, and in
this manner were formed the long dikes of porphyry and other rocks
that are seen to be passing through some of the older lavas of Mt.
Etna.
[Illustration: FIG. 14. MT. ETNA _From Map of State and
Government_]
The great lava streams which flowed down the side of the mountain
during this eruption, destroyed fourteen towns and villages, and
at length reached Catania. A great wall had been raised around this
city to prevent the lava from entering it. The molten rock, however,
accumulated, until it rose to the top of the wall, which was sixty
feet high, and then pouring over it in a fiery cascade, overwhelmed
part of the city. It is said that during the first part of its
journey, the lava streams moved over thirteen miles in twenty days,
or at the rate of 162 feet an hour. Beyond this, after the lava had
thickened by cooling, it had a velocity of only twenty-two feet per
hour.
Fig. 14 represents a plan of Mt. Etna reduced from a map by the
Italian Government. During the eruption of 1865, a rent was made in
the mountain extending from Mount Frumento (B in the preceding map)
for one and one-half miles, and six cones from 300 to 350 feet in
height were formed along the fissure.
During the eruption of 1874, great fissures three miles in length were
formed in the mountain.
There exists on the slopes of Mt. Etna vast subterranean grottoes
formed by the sudden conversion into steam of great quantities of
water that were overwhelmed by the molten mass. These immense volumes
of steam produced enormous bubbles in the molten lava. When the lava
hardened irregular grottoes were left. Lyell describes one of these as
follows:
"Near Nicolosi, not far from Monte Rosso, one of these
great openings may be seen, called the _Fossa della
Palomba_, 625 feet in circumference at its mouth and
seventy-eight deep. After reaching the bottom of this, we
enter another dark cavity, and then others in succession,
sometimes descending precipices by means of ladders. At
length, the vaults terminate in a great gallery ninety feet
long, and from fifteen to fifty broad, beyond which there
is still a passage, never yet explored, so that the extent
of these caverns remains unknown. The walls and roofs of
these great vaults are composed of rough bristling scoriæ
of the most fantastic forms."
Besides the eruptions mentioned there have been many others, such as
those of 1811, 1819, and 1852. The last of these was greater than any
eruption except that of 1669. It began in August, 1852, and continued
until May, 1853, and was remarkable for the immense quantity of lava
thrown out.
[Illustration: FIG. 15. STROMBOLI, VIEWED FROM THE NORTHWEST,
APRIL, 1874]
We come now to the volcano of Stromboli. Stromboli, one of the Lipari
islands, is situated about sixteen miles west of the Straits of
Messina. Its general appearance is shown in Fig. 15. The form of the
mountain is that of an irregular four-sided pyramid, which rises about
3,090 feet above the level of the Mediterranean, and stands on the
bottom of the sea in water about 3,000 feet deep.
If you carefully examine the appearance of Stromboli, as shown in the
preceding figure, you will notice that the flat cloud which hangs over
the island is made up of a number of globular masses of vapor, formed
during the peculiar action of the volcano.
When examined by night Stromboli presents a still more curious
appearance. Since the mountain stands alone, its height permits it to
be seen readily at sea for distances of at least a hundred miles. At
night a curious glow of red light may be seen on the lower surfaces of
the cloud. This light is not continuous, but increases in intensity
from a faint glow to a fairly bright red light, then gradually
decreases, and finally dies away completely. After awhile the light
again appears, again gradually decreases, and disappears, and this
continues until the rising sun prevents the red glow from being any
longer visible. Stromboli, therefore, acts not unlike the flashing
lighthouses so common on the sea coasts of all parts of the world.
Indeed, it is actually used by sailors in the Mediterranean for the
purpose of showing them their direction. For this reason Stromboli is
commonly called "The Lighthouse of the Mediterranean."
As Judd remarks, from whom much of the information concerning some of
the volcanic districts of the Mediterranean has been obtained, the
flashing light of Stromboli differs from that of the ordinary flashing
light in two important respects; viz., in the intervals that elapse
between the successive flashes, and in the intensity of the light
emitted. As you know, it is necessary that the different lighthouses
placed near one another on a coast must have their lights of such a
nature that they can be readily distinguished. In order to do this,
the flashing light has been devised. In flashing lighthouses, the
lights only appear at intervals, one lighthouse being distinguished
from another in its neighborhood by the intervals between successive
flashes, or, sometimes, indeed, by the color of some of the flashes.
Now, in the case of Stromboli, the intervals between the successive
glowings of the red lights are very irregular, varying between one and
twenty flashes per second. Moreover, the intensity of the light also
varies greatly from time to time.
You naturally inquire as to the cause of these flashes of light that
are emitted by Stromboli. If, as Judd suggests, you should climb to
the summit of the mountain, during the daytime, and look down the
inside of the crater, you could see its black slag bottom crossed by
many cracks and fissures. From most of the smaller fissures the vapor
of water is quietly escaping. This vapor rises in the air in which it
soon disappears. There are, however, larger cracks on the bottom of
the crater from which, at more or less regular intervals, masses of
steam are emitted with loud snorting puffs not unlike those produced
by a locomotive. From some of the openings molten matter is seen
slowly oozing out, collecting in parts of the crater and moving up and
down in a heaving motion. Every now and then a bubble is formed on
the surface of this liquid. The bubble swells to a gigantic size, and
suddenly bursts. The steam it contained escapes, carrying fragments of
scum which are thrown high into the air. The masses of steam, formed
below the surface of the sticky, boiling, lava, in endeavoring to
escape, force their way through the mass, blow huge bubbles, which,
on bursting, produce the roaring sounds that are heard, and throwing
great columns of vapor in the air, produce the rounded masses of
clouds you can see floating high up in the air over the mountain. At
the same time the scum is partially removed from the red hot surface,
its light illumines the lower surface of the overhanging cloud, which
flings it back again to the earth. With the bursting of each bubble,
and the clearing of the scum from the surface of the red hot mass,
the light begins, increases in intensity, and then as the scum again
begins to collect on the surface, decreases, and finally disappears,
and not until the bursting of the next bubble is it again visible.
But let us make a study of some of the peculiarities of Vulcano,
another of the Lipari islands, which lies north of Sicily.
Vulcano affords a curious example of a volcano that has been harnessed
by man, or made to do work for him. All volcanoes bring from inside
of the earth different kinds of chemical substances, in the form of
vapors, gases, or molten materials. Now, these materials acting on
one another, produce chemical substances some of which, such as sal
ammoniac, sulphur, and boracic acid, possess commercial value. This is
especially true in the case of Vulcano, and since the eruptions are
not generally violent, a chemical works has actually been erected by
a Scotch firm on the side of the mountain, where the materials are
collected from the crevices.
This effort to harness a volcano was for a time so successful that
the same people contemplated the building of great leaden chambers
over the principal fissure at the bottom of the crater, so that the
large volumes of ejected vapors might be condensed and collected. But
Vulcano, like all other volcanoes, could not be relied on continually
to keep the peace. One day it suddenly burst forth more fiercely than
usual, so that the workmen were compelled to abandon the factory and
fly down the mountain for their lives, but not, however, before some
of them were severely injured by the explosions.
Vulcano is an instance of a volcano in an almost exhausted or dormant
condition. It has had, however, many eruptions during the past few
centuries, some of which have been very violent, for example, that of
1783, and that of 1786.
There still remains to be considered the volcanic region of the
Santorin group of the Grecian Archipelago. The island of Santorin
or Thera, is the southernmost of the Cyclades. It is an exceedingly
curious island, being a submerged volcano, with most of the top of the
crater remaining above the waters, so that the entire island has the
shape of an irregular circle or crescent broken at several points.
Its formation is, probably, due to the gradual sinking of a volcanic
mountain until its crater has been almost completely submerged, only
the higher parts of the edges of the crater being left above the
surface of the waters. Suppose, for example, a mountain like Vesuvius
at the time the crater Somma existed, was sunk below the level of the
Mediterranean until only the highest parts of the crater remained
above the waters. If, now, one or more volcanic eruptions occurred,
producing craters or volcanic islands inside the submerged rim, you
would have a condition of affairs seen in the island of Santorin.
CHAPTER VII
ORIZABA, POPOCATEPETL, IXTACCIHUATL, AND OTHER VOLCANOES OF MEXICO
While some of the volcanoes of Mexico are still in an active
condition, most of them are either only slightly active or are dormant
or extinct. Humboldt, the celebrated traveller and geographer, states
that there are only four active volcanic mountains in Mexico; namely,
Popocatepetl, Tuxtula, Colima, and Jorullo. But there are many others,
among which may be mentioned Orizaba, Ixtaccihuatl, Xinantecatl,
Tuxtula, Cofre de Perote, and Colima.
Of course, you can understand that, since extinct volcanoes may at any
time become active, in parts of the world where communication with the
interior is not good, many volcanic mountains that have been regarded
as extinct may have broken out temporarily, during historical times,
without their eruptions having been recorded.
It was at one time thought that Popocatepetl was the highest mountain
in North America. More recent measurements, however, have shown that
there are at least three other mountains in this part of the world,
that are much higher. One of these is the active volcano of Orizaba
that we will now briefly describe.
[Illustration: FIG. 16. MEXICO AND CENTRAL AMERICA]
Orizaba is situated in the north central part of Mexico, about
seventy-five miles west of Vera Cruz. Its ancient Aztec name was
Cittaltepetl, or _Star Mountain_. The height of the mountain is
18,200 feet. Like all high tropical mountains whose summits are
snow-clad, one would pass through the same changes in climate, in
going from its base to its summit, as in going along the earth's
surface from the equator to the poles. Near the base of the mountain
will be found a tropical climate, above that a temperate climate,
while in still higher regions, the climate of the Arctic region.
According to Russell, from whose work on the volcanoes of North
America much of the information concerning the volcanoes of Mexico
and Central America has been condensed, Orizaba has three craters on
its summit. The last recorded eruption took place about the middle of
the Eighteenth Century. The mountain is now in a dormant or extinct
condition, as may be seen from the fact that its three craters are for
the greater part filled with snow.
Orizaba, like Etna, and many other volcanoes, has deep fissures
extending through its sides. Through these, lava streams have flowed
during times when it was active. There are also found on the slopes
of this mountain many cones of a type known as _parasitic cones_.
These cones are not caused by materials that have been brought to the
surface during an eruption, but have been formed by the steam passing
through lava streams that have come out of the crater during other
eruptions.
Popocatepetl, or, as the word means, _The Smoking Mountain_, is the
second highest mountain in Mexico. According to recent measurements
made by the Mexican Government, its height is 17,876 feet.
Popocatepetl is situated on the edge of the great plateau of Mexico,
forty miles southeast of the City of Mexico. It is a conical mountain,
and is a magnificent object when seen from the City of Mexico, rising,
as it does, fully 10,000 feet from the elevation of the city, while on
the east it towers for nearly 18,000 feet above the level of the sea.
This splendid mountain is poetically described by Russell:
"Seen from the basal plains, it sweeps up in one grand
curve to nearly its full height,--a collossus of three and
a quarter miles in elevation, white with everlasting frost
on its summit, and bathed in the green of palms, bananas,
oranges, and mangoes, at its base. Evergreen oaks and
pines encircle its middle height, and above them, before
the ice itself is reached, occur broad areas of loose sand
into which the lavas have been changed by weathering. Soft
wreaths of sulphurous vapor may at times be seen curling
over the crest of the summit crater,--gentle reminders that
the days of volcanic activity are not yet necessarily over."
Popocatepetl takes its name, _The Smoking Mountain_ from the fact that
gases and vapor are continually being emitted from its summit crater.
It has a conical peak with a depression or crater on its summit.
The bottom of the crater is crossed by fissures from which small
quantities of steam escape, not, however, sufficient to melt all the
snow which covers the slopes of the mountain to a depth of from eight
to ten feet. A small lake of hot water has collected in the crater
from the water derived from the melting snow. This water, sinking
through the porous materials in the cone, is the source of a great
number of large hot springs that occur around the base of the mountain.
Reclus states that the first to climb to the top of Popocatepetl was
one of Cortez' officers, 1519.
Another snow-capped volcano, which rising from the plain of Mexico is
in clear view of the city, is Ixtaccihuatl (Ets-tak'-se-wat-el), or as
the word means in the ancient Aztec, _The White Woman_. This mountain,
as measured by Heilprin, is 16,960 feet in height. Ixtaccihuatl is
now in so dormant a condition that many who have climbed to the top
assert that it is not a volcano at all, since they find no crater on
its summit. Nor are there any signs of volcanic heat, the summit being
snow clad during summer. The conical form of the mountain, however,
and the fact that the entire mountain is formed of volcanic rocks,
show beyond doubt that it is an extinct volcano, whose crater has most
probably been completely filled in by the washing away of its sides.
Xinantecatl is another extinct volcanic mountain situated about forty
miles southwest of the City of Mexico. It is about 16,500 feet high.
Its name means in the ancient Aztec language, _The Naked Lord_. It is
also sometimes known as the Nevado de Toluca, or _The Snow of Toluca_.
On the top of the peak are two craters filled with lakes of fresh
water. Russell states that the larger of these lakes is about thirty
feet in depth and contain a peculiar species of fish.
Tuxtula is another volcano of Mexico, situated on the western coast
of the Gulf of Mexico, about eighty miles southeast of Vera Cruz. It
was an active volcano in 1664, when it threw out molten lava. It then
became dormant until March, 1793, when its long rest was broken by one
of the grandest explosive eruptions of modern times. This eruption
rivalled in energy the great explosive eruption which blew off the
summit of Coseguina, in Central America, in 1835. As is common in the
case of explosive eruptions, volcanic dust and scoriæ were blown high
into the air, and, being carried by the winds, fell on the roofs of
houses and on the land at a distance of 150 miles.
There have been a number of less violent eruptions of Tuxtula since
1835. Tuxtula is a comparatively low mountain, being only 4,960 feet
high, because much of the mountain was blown away by the eruption of
1793.
As Russell points out, it is not safe to infer that because an eroded
mountain is not lofty it cannot be young or energetic, since the very
energy of some of its eruptions may, as in the case of Tuxtula, blow
away a large part of the mountain. A low mountain, with an unusually
large crater, generally means a mountain that has been visited by a
great explosive eruption.
Another extinct volcano known as the Cofre de Perote is situated on
the eastern coast of Mexico, east of Ixtaccihuatl, about thirty miles
north of Orizaba. It takes its name Cofre de Perote which means the
Coffin of Perote, from its peculiar box-like shape. It was called in
the Aztec language "Nauhcampatepetl," or the _Four-Ridged Mountain_.
Cofre de Perote is in a dormant or extinct condition.
We will conclude this brief description of the volcanoes of Mexico
with the volcano of Colima, a mountain about 5,500 feet high situated
on the western coast of Mexico.
Colima has been active of recent years, eruptions having occurred in
1869, 1872, 1873, and 1885. During these eruptions lava escaped from
lateral openings in the sides of the mountain, these openings being
termed by the natives the _Sons of Colima_.
CHAPTER VIII
COSEGUINA AND OTHER VOLCANOES OF CENTRAL AMERICA
Central America has a great number of volcanoes extending along nearly
all its western coast, or on the Pacific side of the country.
Central America consists of a high plain or table-land sloping gently
towards the northeast, but terminating abruptly on the southwest. In
the opinion of geologists this table-land consists of the surface of a
huge tilted block of the earth's crust, or, perhaps, more probably, of
a series of such blocks, that are limited on the southwest by a narrow
belt of intersecting fractures. It is in these fractures that scores
of volcanoes are situated, together with active craters, solfataras,
and hot springs. The volcanoes are mainly of the Vesuvian type. There
are so many volcanoes in this part of the world that it will be
possible to describe but a few of them.
We will begin with the volcano of Coseguina, situated on the Pacific
coast of Nicaragua. Its appearance is that of a conical mountain with
the top cut off, and suggests that it is most probably an explosive
volcano which has had the top blown away during some of its great
eruptions.
Coseguina is celebrated by reason of its tremendous eruption of 1835.
Before the still more tremendous explosive eruption of Krakatoa in
1883, described in the first two chapters of this book, Coseguina
shared with Sombawa, on the island of Sumatra, as being the foremost
of explosive volcanoes.
It had been estimated that before its eruption of 1835, Coseguina had
a height of perhaps 10,000 feet, but so much of it was blown away by
this eruption that it now is a little less than 4,000 feet.
The following description of the great eruption of Coseguina in 1835
has been condensed from an account prepared by Squier, published in
1850.
You will note in reading this brief account how closely many of the
phenomena resemble those that occurred during the eruption of Krakatoa
in 1833.
The eruption of Coseguina was heralded on the morning of January 20th,
1835, by several loud explosions that were heard for a distance of
some 300 miles around the crater of the volcano. Then followed an ink
black cloud formed directly over the mountain, which gradually spread
on all sides shutting off the light of the sun, except for a sickly
yellowish light. Fine sand was thrown from this cloud, which made it
both difficult and painful to breathe. For two whole days the cloud
continued to grow denser, the explosions louder and more frequent,
and the rain of sand thicker. On the third day the explosions were
strongest and the darkness greatest.
The amount of sand that fell from the cloud was so great that people
left their houses, fearing the roofs would be crushed in by the great
weight. This sand fell in large quantities over an area more than
1,500 miles in diameter, or, quoting the language of Squier:
"The noise of the explosions was heard nearly as far"
(1,500 miles). "And the Superintendent of Belize, eight
hundred miles distant, mustered his troops, under the
impression that there was a naval action off the harbor.
All nature seemed overawed; the birds deserted the
air, and the wild beasts their fastnesses, crouching,
terror-stricken and harmless, in the dwellings of men.
The people for a hundred leagues grouped, dumb with
terror, amidst the thick darkness, bearing crosses on
their shoulders and stones on their heads in penitential
abasement and dismay. Many believed that the day of doom
had come, and crowded in the tottering churches, where, in
the pauses of the explosions, the voices of the priests
were heard in solemn invocation to Heaven. The brightest
lights were invisible at the distance of a few feet; and
to heighten the terror of the scene, occasional lightnings
traversed the darkness, shedding a lurid glare over the
earth. This continued for forty-three hours, and then
gradually passed away."
It appears that the eruption of Coseguina was followed by violent
earthquake shocks and other evidences of volcanic energy over extended
regions. For example, there were fearful earthquakes along the Andes,
the worst of which occurred on February 20th, and continued at the
rate of three or four a day up to March 6th, and, less frequently,
to March 17th. It was during one of these earthquakes that the city
of Concepcion, Chile, was so completely destroyed, that but a single
house remained.
The same brilliant sunsets and sunrises occurred in different parts
of the world after the eruption of Coseguina, due to the presence of
large quantities of volcanic dust that followed the great eruption of
Krakatoa.
The cause of this great explosive eruption of Coseguina was most
probably the same as that which is believed to have caused the
eruption of Krakatoa, namely, a large volume of water suddenly gaining
access to a mass of liquid lava.
Volcán del Fuego is another of the many volcanoes of Central America.
It is situated as one of a group of volcanoes on the highest summit
of the Isthmus. This volcanic mountain has a regular cone with
regular slopes on all sides, except on the north, where a table-like
projection, about 1,000 feet below the summit, is all that remains of
a vast cone, the summit of which was blown away, according to Russell,
in prehistoric times, just as was the crater of Somma on Vesuvius.
There have been in Central America, since the time of the Spanish
conquest, some fifty volcanic eruptions sufficiently great to have
been recorded. Some idea of the activity of Fuego during this time
may be had from the fact that of all these eruptions some twenty were
those of Fuego. At the present time, however, the volcano is dormant
and apparently almost extinct.
The recorded eruptions of Fuego are nearly all of the explosive type.
Among the most violent were those that occurred during 1526, 1541,
and 1581. During 1582, 1585, and 1586, there were eruptions nearly
every month, the most terrible being near Christmas day in 1586. Other
memorable eruptions occurred in 1614, 1623, 1686, and 1705, and at
other dates down to August 17th, 1860, from which date to the present
time the volcano has been quiet.
We will conclude this brief description of the volcanoes of Central
America with that of Volcán de Agua, or, as the word means, _The Water
Volcano_. It is situated in Guatemala near the coast, and is one of
the mountains that occupies the plateau on which Fuego is situated.
The Volcán de Agua is one of the most remarkable volcanoes in Central
America, standing, as it does, nearly alone, and rising to an
elevation of 3,350 metres (10,988 ft.), above the level of the sea. It
has been extinct for a long time.
It has been supposed by some, from its name, that this is a volcano
that throws out water. Others believe that the name comes from the
water produced by the melting of the snow that is collected on the
sides of the mountain. Now there almost always escapes from the
craters of volcanoes during violent eruptions immense quantities of
water vapor, which, condensing, fall as vast showers of rain that
often deluge the surrounding country. In snow-clad mountains, the
escape of lava is often attended by floods caused by the rapid melting
of the snow. The water volcano did not, however, take its name from
either of these facts, but rather because at the time of the Spanish
invasion, the crater of the mountain was occupied by a large lake, and
that during an earthquake in 1541 the wall of the crater was broken,
when the lake was poured as an immense stream of water down the side
of the mountain, overwhelming a village which was situated on this
slope. That this was the correct origin of the same may be seen from
the fact that the crater at the present time still shows the remains
of its former lake basin, and that on the sides of the broken rim an
immense ravine can be seen through which the water poured down on the
village below.
Daubeny describes this volcano as follows:
"The Volcán de Agua (Water-Volcano) is of enormous height,
being covered with eternal snow, in the latitude of 14°.
Captain Basil Hall estimates it at more than 14,000 feet,
but a recent traveller states it at 12,600. It has the form
of a blunted cone clothed with perpetual verdure to its
summit. The crater is from forty to sixty yards in depth,
and about 150 in diameter,--the sides and bottom strewed
with masses of rock, apparently showing the effects of
boiling water or of fire.
"By a deluge of water from this volcano in 1527, the
original city of Guatemala was overwhelmed; and the next
built, called the Old City, _La Antiqua_, was ruined by an
earthquake in 1773. The present capital is situated at a
distance of eight leagues from the mountain."
Another volcano in this part of the country is described by Daubeny as
follows:
"Massaya, near the lake of that name, was one of the most
active vents at the time of the first discovery of the
country. Its flames were visible twenty-five miles off. Its
crater was only twenty or thirty paces in diameter; but
the melted lava 'seethed and rolled in waves as high as
towers.' A story is told of a Dominican who imagined the
fluid lava was melted gold, and descended into the crater
with an iron ladle to carry some away; but the ladle, it is
said, melted, and the monk escaped with difficulty."
CHAPTER IX
THE VOLCANIC MOUNTAINS OF SOUTH AMERICA
The volcanoes of South America are limited to the Andes Mountain
System that stretches like a huge wall along the entire western side
of the continent. The names of the more important of these volcanoes
are marked on the map of South America, shown in Fig. 17. As will be
seen, this huge mountain wall reaches from Patagonia on the south to
the Isthmus of Panama on the north. The arrangement of the volcanoes
in South America is of the linear type. The craters follow one another
in more or less straight lines, or are situated along the lines of
great fissures that lie near the ocean. You must not, however, suppose
that there is a continuous chain of active volcanic mountains from the
Isthmus of Panama to the southern part of the continent. According to
Lyell, from lat. 2° N., or from the north of Quito, to lat. 43° S. or
south of Chile, a total distance including 45° of latitude, there is a
succession of districts with active and extinct volcanoes, or at least
with volcanoes that have been quiet during the last three centuries.
[Illustration: FIG. 17. SOUTH AMERICA]
Lyell traces the volcanoes of South America as follows:
"The principal line of active vents which have been seen in
eruption in the Andes extends from lat. 43° 28' S., ... to
lat. 30° S.; to these thirteen degrees of latitude succeed
more than eight degrees, in which no recent volcanic
eruptions have been observed. We then come to the volcanoes
of Bolivia and Peru, extending six degrees from S. to N.,
or from lat. 21° S. to lat. 15° S. Between the Peruvian
volcanoes and those of Quito another space intervenes of no
less than fourteen degrees of latitude, in which there is
said to be but few active volcanoes as far as is yet known.
The volcanoes of Quito then succeed, beginning about 100
geographical miles south of the equator, and continuing
for about 150 miles north of it, when there occurs another
undisturbed region of more than six degrees of latitude,
after which we arrive at the volcanoes of Guatemala, or
Central America, north of the Isthmus of Panama."
Of course, you must not understand that there are no extinct volcanoes
in these gaps. On the contrary, according to Daubeny, we find,
beginning on the north in the United States of Colombia, the lofty
volcano of Tolima. According to Daubeny's book published in 1848,
Tolima was then constantly emitting steam and sulphur gases from its
summit. Tolima is situated in the easternmost of the three mountain
ranges that extend through this section of the country. It is,
therefore, at a comparatively great distance from the ocean. Tolima
was in eruption in 1595. It again burst out in 1826.
Coming now to Ecuador we find that this, the smallest of the South
American Republics, contains numerous great volcanic mountains.
Some of the principal volcanic mountains are Chimborazo, 20,498 feet
above the sea; Antisana, 18,880 feet; Cotopaxi, 19,660 feet; Pichincha
(17,644 feet in 1848, Daubeny), El Altar, 16,383 feet.
These all lie in South America on the plateau of Quito. As Baron
Alexander von Humboldt has pointed out, the volcanic mountains of
Quito are arranged in two parallel chains that extend side by side
for a distance of over 500 miles north into the State of Colombia,
including between them the high plateaus of Quito and Lacumbia.
According to Whymper, however, who has recently studied this part of
South America, there is a succession of basins between the mountains,
but there is no such thing as a single valley in the interior of
Ecuador. The extinct volcanoes of Cayamba, Antisana, and Chimborazo
are the most important. On all three mountains there are old lava
streams on their sides. Although no craters can be seen on their
summits, yet it is almost certain they once had craters. There is
plenty of room on the summit of Antisana for a cone as great as that
of Cotopaxi. Whymper is of the opinion that the snow domes that form
the summit of Chimborazo were at one time two of the highest points of
the rim of the old crater.
Nearly due south of Quito is the great volcanic cone of El Altar.
Like all the peaks of this high plateau, El Altar rises to a great
height above the sea, being at the present time 16,383 feet above the
sea. This mountain has an enormous crater that appears to be dormant
or extinct, and is covered with snow. According to the traditions of
Indians, El Altar, or, as they call it, _Capac Urcu_ or _The Chief_,
was the highest mountain near the equator, being much higher than
Chimborazo. But during a prodigious eruption that occurred before the
discovery of America, and continued uninterruptedly for eight years,
the height of the mountain was considerably reduced. According to
Boussingault, the fragments of the cone of this celebrated mountain
are now spread for great distances around the mountain on the
surrounding lowlands.
Pichincha in Ecuador, an extinct volcano, is situated almost
immediately on the equator. It has a height as measured by Whymper by
the barometer, of 15,918 feet above the Pacific. The summit is covered
by blocks of pumice. Several species of lichens are found at this
elevation. According to Daubeny, Pichincha was extinct prior to 1539,
when it became active. There were also eruptions in 1577, 1587, and
1668. It was also in activity during 1831.
Cayamba, another volcanic mountain of Ecuador, lies to the east of
Pichincha, a short distance north of the equator. Its height is 19,186
feet. It is nearly extinct.
Cotopaxi, 19,680 feet, is another volcanic mountain of the high
plateau of Quito. Cotopaxi is still active. Its slopes are covered
with snow down to a height of about 14,800 feet. Between the lower
edge of this snow line and the lower slopes of the mountain, there
lies a zone of naked rock.
According to Whymper, the eruption of Cotopaxi, in 1877, was preceded
by an unusual degree of activity in the earlier parts of the year.
This, however, did not cause any alarm until June 25th, 1877, when,
shortly after midday, an eruption, attended by tremendous subterranean
roars, began, and an immense black column shot up into the air for
about twice the height of the cone. This eruption was clearly visible
at Quito, for the wind blew the ashes towards the Pacific. At this
time the summit had not changed its appearance, but towards 6:30
A. M., on the next day, another enormous column of ashes
rose from the crater. The ashes and cinders were first carried due
north by the winds, and then, spreading out in all directions, were
subsequently distributed through the air all over the country. At
Quito, as early as 8 A. M., the sky assumed the appearance it
generally has at twilight, and the darkness increased until midday,
when it became as dark as at midnight. Indeed, it was so dark that one
could not see his hand before his face.
During this eruption, as is very common in the eruptions of the
snow-clad mountains of South America, a flood of water, due to the
rapid melting of the snow and ice on the summit, rushed down the
mountain slopes at 10 o'clock A. M., on the 26th of the
month, almost immediately after the appearance of a stream of lava
that began to flow down the mountain. In a few moments the mountain
was completely shut off from view by immense columns of steam and
smoke. At first, a low, moaning sound was heard, which rapidly
increased to a roar, when a deluge of mud, mingled with huge blocks of
ice and stones, swept down the mountain, leaving a desert in its path.
It is estimated that at some places this stream moved with a velocity
of fifty miles per hour.
The general appearance of Cotopaxi is shown in the accompanying
reproduction from the painting by Frederick E. Church in the Lenox
Library, New York.
According to Whymper, who made an ascent of Cotopaxi in 1880, the
crater on the summit has the form of an immense amphitheatre, 2,300
feet across from north to south, and 1,650 feet from east to west.
Its crest is irregular and notched. The crater is surrounded by
perpendicular cliffs. The western side of the volcano is irregular.
Barometric measurements gave the height of this volcano at 19,498
feet. Its height as taken by La Condamine, during the early parts of
the last century, was 19,605 feet, so that, according to Whymper,
assuming as would seem probable, that this difference in height has
not all been due to errors in measurements, the volcano has grown or
increased in height during the last century and a half.
Chimborazo, 20,498 feet, is another lofty mountain on the plateau of
Quito. This volcano is situated in lat. 1° 30' S., and is not at the
present time in an active condition. It is, however, formed entirely
of volcanic material. Its upper portions are covered with a layer of
snow to a level of some 2,600 feet below the summit.
[Illustration: COTOPAXI _From a Painting by Frederick E.
Church in the Lenox Collection of the New York Public Library. By
Permission_]
Chimborazo has an enormous volcanic summit, which, when seen from the
Pacific, when the air is especially clear after the long rains of
winter, is a most splendid sight. Whymper, who ascended the mountain,
says:
"When the transparency of the air is increased and its
enormous circular summit is seen projected upon the deep
azure of blue of the Equatorial sky, it represents a
magnificent sight. The great rarity of the air through
which the top of the Andes is seen adds much to the
splendor."
Whymper says, that as far as records are concerned, there have been no
eruptions of Chimborazo, which has apparently been an extinct volcano
for many years. Its crater has been completely buried by a thick cap
of ice on its summit, while what lava streams exist on the mountain
are either covered by large glaciers, or have been removed by erosion,
or hidden by vegetation.
Chimborazo possesses less of the conical outline than Cotopaxi. There
are steep cliffs towards the summit that have been named by Whymper
"the northern and southern walls." They seem to him to have been
formed by the violent upheavals of the explosive eruptions that have
blown away portions of the cone.
There are other volcanoes in this district, but the above are all we
have space for describing.
According to Lyell, the volcano of Rancagua, in Chile, lat. 34° 15'
S., is continually throwing up ashes and vapors like Stromboli.
Indeed, a year seldom passes in Chile without some earthquake shocks.
Of these shocks those which came from the side nearest the sea are
most violent. The town of Copiapo was laid waste by these shocks
during the years 1773, 1796, and 1819, in both instances after
intervals of twenty-three years.
Since the volcanic mountains of South America are snow-covered the
occurrences of volcanic eruptions are apt to be attended by great
floods caused by the rapid melting of the snow, as well as sometimes
by the breaking of huge subterranean cavities that are filled with
water.
According to Lyell, the volcanoes of Peru rise from a plateau from
17,000 to 20,000 feet above the sea. One of the principal volcanoes
of Peru is Arequipa, whose summit is 18,877 feet above the level of
the sea. The mountain takes its name from the city of Arequipa, which
is situated not far from its base. It is an active volcano. Another
volcano, Viejo, is found in lat. 16° 55' S.
According to Lyell, there are active vents extending through Chile to
the island of Chiloe to lat. 30° N.
Aconcagua, west of Valparaiso, in lat. 32° 39' S., 23,000 feet in
height, the highest mountain in South America, is still in an active
condition. According to Scrope, when the city of Mendoza was destroyed
by an earthquake, that killed 10,000 people, in March, 1861, it is
probable that Aconcagua was in eruption.
There are many other active volcanoes in Chile, extending as far south
as the volcanoes of Patagonia, north of the Straits of Magellan as
well as others of Tierra del Fuego.
CHAPTER X
VOLCANOES OF THE UNITED STATES
For some readers this may be a surprising chapter heading, for it is a
general impression that there are no volcanoes in the United States.
It is true that practically all of the volcanoes of this country are
dormant or extinct. They have, however, at one time been exceedingly
active, and, if reports are correct, some of them were active during
comparatively recent times.
Nearly all of the volcanoes of the United States lie west of the
meridian of Denver. These volcanoes belong to two distinct types,
either the Vesuvian type with built up cones, or the plateau or
fissure type already referred to.
The following brief description of the volcanoes of the United States
has been collated, for the greater part, from Wallace's excellent book
on the volcanoes of North America.
Crossing the United States on the Southern Pacific Railroad one's
attention is caught, in Arizona, by a magnificent group of mountains
known as the San Francisco Mountains. The highest peak of these
mountains reaches 12,562 feet above the level of the sea, and 5,700
feet above the surface of the plateau on which the mountains stand.
[Illustration: FIG. 18. THE UNITED STATES]
According to G. K. Gilbert, the San Francisco Mountain group is formed
of a variety of lava known as trachyte, that is of comparatively
recent ejection, possibly of a geological age called the Tertiary. The
lava forming the mountains escaped through a number of crater cones,
some of which can still be seen in the neighborhood. Some of these
craters are now in almost as perfect a condition as the day they were
formed. Indeed, to one looking at them from a neighboring elevation,
they appear so fresh, and so little affected by the climate, that one
might almost believe that the lava had just flowed out of the craters,
and has not yet hardened. Nevertheless, geologists are sure they have
been formed long before man appeared on the earth. In one of these
craters a lake of fresh water has collected.
Another extinct volcano of the United States is Mt. Taylor in New
Mexico, nearly east of the San Francisco Mountains. This mountain
rises from the surface of a high table-land, or, as it is called
in this part of the world, a _mesa_. The surface of the plateau is
covered with a thick lava stream from which Mt. Taylor rises to
a height of 11,390 feet above the level of the ocean. This mesa,
or table-land, is forty-seven miles in length from northwest to
southeast, and about twenty-three miles in breadth. Its general
elevation is about 8,200 feet. The plateau rises about 2,000 feet
above the surface of the level land that surrounds it. All these
2,000 feet have been removed by erosion. The table-land from which
Mt. Taylor rises has not been eroded by the action of the rain,
rivers, and other weathering agencies like the surface of the country
surrounding it, because of a covering of lava that has been spread
over its surface to a depth of about 300 feet.
Mt. Taylor is formed almost entirely of lava that has escaped through
a single opening and has built up a high cone around it. The volcano
is now quite extinct, so that the original form of the mountain has
been greatly changed by erosion.
You will remember, when we were discussing the general subject of
volcanoes, in the beginning of this book, that we spoke of volcanic
mountains being bottled up after an eruption, by the hardening of
the lava which remained in the crater and the tube that connects the
crater with the place from which the lava had been derived. We then
spoke of this hardened mass being known as a _volcanic plug_, or
stopper, explaining how the volcano could never again erupt through
its old crater unless it could develop sufficient force to blow out or
remove this stopper.
Now besides the crater at the top of Mt. Taylor there were several
others in the eroded region surrounding the mesa, or high table-land,
from which Mt. Taylor rises. When, therefore, the erosion which
removed the 2,000 feet of rocks on all portions of the old mesa that
were not protected by the coating of lava, these old mountain plugs
were too hard to be worn away or eroded, and were, therefore, left
projecting into the air like vast pyramids.
If you should ever visit Mt. Taylor and should go to the eastern
border of this mesa, and look over the eroded plain, you would see in
the lowlands a part of the places from which the 2,000 feet of matter
have been slowly eroded. Dutton describes the beautiful panorama that
is to be seen as follows:
"The edge of the mesa suddenly descends by a succession of
ledges and slopes, nearly 2,000 feet into the rugged and
highly diversified valley-plain below. The country beneath
is a medley of low cliffs and bluffs, showing the browns
and pale yellows of the Cretaceous sandstones and shales.
Out of this confused patchwork of bright colors rise
several objects of remarkable aspect. They are apparently
inaccessible eyries of black rock, and at a rough guess, by
comparison with the known altitudes of surrounding objects,
their heights above the mean level of the adjoining plain
may range from 800 to 1,500 feet. The blackness of their
shade may be exaggerated by contrast with the brilliant
colors of the rocks and soil out of which they rise, but
their forms are even more striking."
These black piles are the _necks_ or lava plugs of extinct volcanoes.
They rise above the level of the plain because, being harder than
the surrounding rocks, they have resisted erosion. In some cases
these necks or plugs have been converted by shrinkage, on cooling,
into beautiful columns, somewhat of the type of the basaltic columns
of the Giant's Causeway. It would be difficult to count the number
of volcanic necks that can be seen near the edge of the mesa. One's
attention is at once attracted to some dozen of these piles, which are
especially striking on account of their great size, and ominous black
color, but the number is by no means limited to this dozen. There are
hundreds of them.
Fig. 19 gives some idea of a part of the view from the edge of the
mesa, and Fig. 20 the appearance of two of these volcanic necks.
But besides high volcanic mountains such as the San Francisco
Mountains and Mt. Taylor, there are, in different parts of the United
States, to be found fragments of huge craters from which, in the
geological past, immense quantities of lava have escaped. In some
instances these craters are but fragments of huge craters, that, like
the crater of Mt. Somma, in Vesuvius, have been nearly completely
blown away by some unrecorded explosion during the far past.
[Illustration: FIG. 19. PANORAMA FROM THE MESA AT THE EDGE OF MT.
TAYLOR _From U. S. Geological Survey_]
A crater of this type, known as Ice Springs Crater, is situated in the
desert valley west of the Wahsatch Mountains, some 125 miles south
of Salt Lake City, Utah. This crater is especially interesting from
the fact that it occupies a position on a plain that was formed by
the deposition of sediment in an immense lake that covered this part
of the United States very long before man lived on the earth. We
are alluding to Lake Bonneville, a lake that existed in a geological
time known as the Glacial Epoch. This lake occupied the territory now
filled by the Great Salt Lake of Utah, but towards the close of the
Glacial Epoch it was immensely larger than it is now. This can be
shown not only by the presence of shore lines, that are clearly marked
on the sides of the surrounding mountains, but also by the ancient
lake beaches, and deltas, that are common in the district, so that
instead of there being the comparatively limited area of Great Salt
Lake as marked on the maps of to-day there was a lake that had an area
of 19,750 square miles, that covered an area on which at least 200,000
people dwell.
[Illustration: FIG. 20. VOLCANIC NECKS, EDGE OF MESA AT MT.
TAYLOR _From U. S. Geological Survey_]
A similar lake, known as Lake Lehontan, existed at the same time,
covering large areas in the western parts of Nevada.
Coming now to Ice Springs Craters in Utah, we find here three small
craters formed of scoriæ and lapilli (volcanic ashes consisting of
small angular stony fragments). Near them lies a fragment of a much
larger crater known as the Crescent. In some respects this crater was
not unlike the crater of Somma that surrounded Mt. Vesuvius. It was
not, however, as large, having a diameter of only 2,200 feet. From
these craters streams of basalt flowed until they covered considerable
areas.
A still more recent crater known as Tabernacle Crater is situated
four miles south of the Ice Springs Crater. Tabernacle Crater takes
its name from the building known in Salt Lake City as the Tabernacle.
According to Gilbert, this crater was formed at a time when Lake
Bonneville stood at a comparatively low level, or when the water was
only from fifty to seventy-five feet above the bottom of the valley
on which the crater now stands. At that time an explosive volcanic
eruption occurred on the bottom of the lake, and the rim of the
crater, built up by this explosion, was gradually pushed above the
surface of the lake, so as to shut out its waters.
Extinct volcanic craters, not unlike those of Utah, occur also near
Ragtown, in Nevada, in a district known as the Carson Valley Desert,
in one of the broadest areas of what was once Lake Lahontan. Ragtown
is twenty-two miles southwest of Wadsworth on the Central Pacific
Railroad. At the present time there are two circular depressions or
volcanic craters filled with pools of strongly alkaline water known
as the Ragtown Pond, or Soda Lake. The large lake covers an area of
268-1/2 acres. Its greatest diameter is over 4,000 feet. Without going
into a detailed description it will suffice to say that the larger
crater probably was destroyed by an explosive volcanic eruption.
Another intensely alkaline lake that fills an extinct volcanic crater
is the Mono Lake, situated in Mono Valley in California at the eastern
base of the Sierra Nevadas. It has an area of about 200 square miles.
The centre of the lake has two small islands named Pacha and Negit.
Immediately south of Mono Lake are a number of craters that occupy
portions of what was once apparently a fissure extending in a general
north and south direction. The highest of these craters are in the
neighborhood of 2,500 feet.
But leaving these inconspicuous craters, let us briefly examine some
of the higher mountain peaks of the United States that are of volcanic
origin. One of the most conspicuous of these is Mt. Shasta. This
mountain is situated in California, at the northern end of the Sierra
Nevadas. It has a height of 14,350 feet. It is a snow-clad mountain of
a conical form, and is a conspicuous object in the landscape, because
it stands alone.
Mt. Shasta is a double-coned mountain. Besides the cone on its summit
there is a well-developed cone known as Shastina on the western side
of the mountain, 2,000 feet lower than the main summit.
There are well-defined lava streams on the slopes of Mt. Shasta. One
of these, which issued from the southern side of the mountain at
an elevation of 5,500 feet, divided into two streams. One of these
streams is twelve miles in length. The other entered the canyon of the
Sacramento River, thus displacing the water.
Coming now to the Cascade Mountains, in Oregon and Washington, we
will find in them a number of giant peaks of volcanic origin. The
most important of these are in regular order from south to north, as
follows: Mt. Pitt, 9,760 feet; Mt. Mazana, 8,223; Mt. Union, 7,881;
Mt. Scott, 7,123; Three Sisters, Mt. Jefferson, 10,200, and Mt. Hood,
11,225, in Oregon; Mt. Adams, 9,570; Mt. St. Helen's, 9,750; Mt.
Rainier, 14,525, and Mt. Baker in Washington, 10,877.
Nearly all these mountains have craters either on their summits or on
their sides. They are extinct volcanic mountains, that were, for the
most part, thrown up during the Tertiary Geological Period, so that
they have all been greatly affected by erosion.
One of the most remarkable of the above volcanic mountains is Mt.
Mazana, in Oregon. This mountain has on its summit an approximately
circular cavity from five to six miles in diameter, that is occupied
by a lake of water known as Crater Lake. This lake is 6,239 feet above
the level of the sea, and has a depth of 1,975 feet. It is surrounded
by nearly vertical walls ranging from 900 to 2,200 feet deep, so that
the vast caldera of which this great depression consists has a depth
of at least 4,000 feet.
Mt. Pitt, situated about sixty miles north of Mt. Shasta, in southern
Oregon, has a regularly shaped volcanic cone, and the remnant of a
crater at its summit. The Three Sisters and Mt. Jefferson lie to
the north of Mt. Pitt. Like the others they are ancient volcanic
mountains. But little is accurately known concerning them.
Mt. Hood, 11,225 feet high, rises from the crest of the Cascade
range in Northwest Oregon, about twenty-five miles south of the
Columbia River. Mt. Hood is an exceedingly majestic mountain. At its
summit there are only portions of the walls of the original crater.
When ascended in 1888, streams of sulphur vapor were escaping from
fumaroles on its northeastern slopes, at an elevation of 8,500 feet
above the sea.
Mt. Adams and Mt. St. Helen's lie to the north of Mt. Hood. Mt. Adams
about sixty miles to the north, and beyond this, Mt. St. Helen's.
Accurate information concerning the summit of Mt. Adams is still
lacking. Mt. St. Helen's in Washington has more of a conical summit.
Russell states that according to frontiersmen, St. Helen's has been
in a state of activity within the past fifty years. A French-Canadian
asserts that the mountain was in actual eruption during the winter of
1841-43, that at this date the light from the volcano was sufficiently
bright to enable one to see and pick up a pin in the grass at midnight
near his cabin some twenty miles distant. Mt. St. Helen's was ascended
in 1889, when fumaroles were found on the northeast side.
Mt. Rainier in Washington is plainly visible from Puget Sound. It is
a most magnificent mountain. The summit has a bowl-shaped crater, of
an almost perfectly circular form. The inside of the crater, when
last ascended, was filled to within thirty or thirty-five feet of its
rim with ice and snow. There was, however, evidences of heat, since
numerous jets of steam were seen issuing from its interior rim.
Mt. Baker, Washington, is the northernmost of the volcanoes of the
Cascade Mountains, south of the boundary line between the United
States and Canada. But little is known of this mountain. The summit
appears as a conical peak from Puget Sound, so that its form would
seem to show that it is of volcanic origin. According to Gibbs,
officers of the Hudson Bay Company, as well as the Indians, declared
that Mt. Baker was in eruption in 1843, when it broke out at the same
time as Mt. St. Helen's, covering the country with ashes.
There are but few volcanoes in the Rocky Mountains which extend from
north to south through the United States at a considerable distance to
the east of the Sierra Nevadas and Cascade Ranges. The Spanish Peaks,
situated in the southeastern part of Colorado about sixty miles south
of Pueblo, are the remains of ancient volcanoes. Two of the most
prominent of these peaks rise from 12,720 to 13,620 feet above the sea.
We shall make no effort to attempt to describe the volcanic mountains
that may exist in those portions of the Rocky Mountain Ranges or the
Cascade Range lying in Canada. Comparatively little is known of them,
but inasmuch as volcanic activity has been manifested in Alaska, it
would seem highly improbable, as Russell remarks, that volcanoes
should suddenly cease at the northern boundaries of the United States
and then begin again at the most southern part of Alaska. It will be
sufficient to say that Mt. Edgecome, situated on an island in the
neighborhood of Sitka, is of volcanic origin, and that the Aleutian
Islands, beginning at Alaska on the east at the head of Cook's Inlet,
extend westward through the Peninsula of Alaska to the Peninsula of
Kamtschatka for a distance of nearly 1,600 miles. This belt, which
is called by Russell "the Aleutian Volcanic Belt," contains numerous
volcanoes that are known to have been active in historical times.
Mt. Wrangell, on the Copper River, 200 miles northeast of the head
of Cook's Inlet, is a lofty volcanic mountain that is said to have
been in eruption in 1819, and at the time of last report was still
throwing out columns of steam. While much remains to be ascertained
about the volcanoes of the Aleutian Islands, it would appear that
there are active volcanoes on twenty-five of these islands, on which
some forty-eight craters have been found. Eruptions are common in the
district.
CHAPTER XI
THE CATASTROPHE OF MARTINIQUE AND THE VOLCANIC ISLANDS OF THE LESSER
ANTILLES
The West Indies Island chain consists of two groups of islands; i. e.,
the Greater Antilles, including Cuba, Jamaica, Hayti, and Porto Rico,
on the west, and the chain of the Lesser Antilles on the east.
The Lesser Antilles consists of two parallel chains, the westernmost
of which is for the greater part mountainous with peaks several
thousand feet in height. All these islands are volcanic. The chain
on the east consists of low, calcareous rocks, or rocks consisting
largely of lime.
In the western chain the islands beginning on the south are, Grenada,
St. Vincent, St. Lucia, Martinique, Dominica, Guadeloupe, Montserrat,
Nevis, and St. Eustace, while in the calcareous chain are found the
Tobago, Barbadoes, and others.
Prior to 1902, the greatest volcanic eruption in this part of the
world occurred on the island of St. Vincent, with the volcano of
Soufrière. Although the forces displayed were exceedingly great, yet
they become insignificant when compared with the appalling eruption
that took place in Martinique only a short time ago; namely, May the
8th, 1902, when the volcano of Mt. Pelée, situated on the northwestern
part of the island, burst into an eruption so terrible that in
destruction of life it far exceeded the eruption of Krakatoa, although
the amount of energy causing the eruption was much smaller.
[Illustration: FIG. 21. THE LESSER ANTILLES]
Heilprin, in a book called "Mt. Pelée and the Tragedy of Martinique,"
from whom most of the information of this chapter has been obtained,
calls attention to the fact that before the eruption of Pelée there
were plenty of warnings for those intelligent enough to note them. For
two or three weeks prior to May 8th, 1902, the volcanic activity of
Pelée had been rapidly increasing, the mountain throwing out clouds
of ashes and sulphurous vapors from its crater. By April 25th the
sulphurous vapors had so increased in quantity as to make breathing
difficult in St. Pierre. The ashes fell on the surrounding country and
by the 2d of May had so covered the streets of St. Pierre as to stop
traffic.
Three days later, May 6th, shortly before noon, an avalanche of mud
poured down the slopes of the mountain with the rapidity of an express
train. These torrents of mud and water deluged the towns and villages
in the neighborhood. The activity of Mt. Pelée increased until the
morning of May 8th, 1902, when, almost at exactly 8 A. M., an
eruption occurred, so terrible in its effects that in two minutes the
city of St. Pierre was almost completely destroyed.
St. Pierre, the principal town of Martinique, is situated on the
island of Martinique, on the northwestern coast, about ten miles
southwest of Mt. Pelée. St. Pierre was settled as far back as 1635. It
is situated on an open roadstead without any harbor.
That there were many points of resemblance between the position of St.
Pierre and the destroyed city of Pompeii will be recognized as the
description of the catastrophe is given.
St. Pierre was a beautiful city, and formed the natural outlet to one
of the richest districts in Martinique for the production of sugar
cane and cocoa. It contained many fine houses, the homes of planters,
wealthy bankers, merchants, and shippers, who, besides their regular
houses in the city, had constructed handsome villas on heights on the
outskirts of the city. The houses were to a great extent one or two
stories in height, and were in many cases surrounded by fine gardens.
The city extended along the coast for about two miles. The streets
were well lighted.
The eruption of Mt. Pelée on May 8th, 1902, was of a very unusual
character, containing a feature that--with the exception of a volcanic
eruption of Soufrière, a volcanic mountain on the neighboring island
of St. Vincent, and an eruption of Kilauea in Hawaii--so far as I am
aware, never before occurred. This was a blast of highly heated air,
mingled with white hot or incandescent dust, that swept down the side
of the mountain with a velocity of one or two miles per minute, or
possibly more.
Nearly all of the people in St. Pierre were killed. From the
appearance of the bodies it seemed that death was practically
instantaneous, and was due either to scorching or burning, or
asphyxiation by the breathing of highly heated air. The number of
people so killed, including almost the entire population of St.
Pierre, as well as a number of adjoining settlements, was not less
than 30,000.
The zone of absolute destruction was limited to an area the extent
of which did not greatly exceed eight or nine square miles. On the
outskirts of this zone the destruction, though considerable, was less
complete.
There was almost an entire absence of great earthquake shocks during
the eruption.
Following the terrible eruption of May 8th were a number of less
violent eruptions on May 20th, 26th, June 6th, July 9th, and August
31st. According to Heilprin these eruptions were of the same character
as that of May 8th.
There has been considerable discussion as to the exact causes of the
tornadic incandescent blast that caused the awful destruction of life.
Without entering this discussion it is sufficient to say that it is
now generally considered that the blast consisted of highly heated
air, and super-heated steam loaded with great quantities of finely
divided red hot or even white hot dust particles.
While, perhaps, the force producing the awful eruption of Mt. Pelée
was greatly excelled in the case of many other volcanic eruptions;
such as Papandayang, in 1772; Asamayama, in 1783; Skaptar Jökul, in
1783; Tomboro, in 1815; Coseguina, in 1835; and Krakatoa, in 1883;
yet, in the words of Heilprin, "in intensity and swiftness of its
death-dealing blast ... the eruption of May 8th, and of later dates,
stands unique in records of volcanic manifestations."
While the amount of ashes that accompanied the blast of white hot
steam and air was comparatively small, yet during the time between
this and the subsequent eruptions, the amount of ashes that were
thrown from the surface of Mt. Pelée was exceedingly great.
According to Russell, in a paper on the volcanic eruptions of
Martinique and St. Vincent, in 1902, the amount of ashes and solid
matter generally thrown out from the crater of Mt. Pelée would be
equal to 40,000,000 cubic feet every minute, or one and a half times
the sediments discharged by the Mississippi in the course of a whole
year.
According to Heilprin, however, the actual amount of dust thrown from
the crater of Mt. Pelée was, probably, 500 times greater than the
amount discharged by the Mississippi River in the course of a year,
and, consequently, considerably greater than that of all the rivers of
the world combined, or, as he says:
"Mont Pelée has now been in a condition of forceful
activity for upwards of two hundred days; can we assume
that during this time it may have thrown out a mass of
material whose cubical contents are hardly less than
a quarter of the area of Martinique as it now appears
above the waters? One is, indeed, almost appalled by the
magnitude of this work, and yet the work may even be very
much greater than is here stated. We ask ourselves the
questions, what becomes of the void that is being formed in
the interior? What form of new catastrophe does it invite?
There can be no answer to a question of this kind--except
in the future happening that may be associated with this
special condition. But geologists must take count of the
force as being one of greatest potential energy, whose
relation to the modelling and the shaping of the destinies
of the globe is of far greater significance than has
generally been conceived."
A curious circumstance connected with the eruption of Mt. Pelée was
the most pronounced electric and magnetic disturbances. Moreover, as
in the case of the eruption of Krakatoa, there were the same after
glows or red sunsets and sunrises due to the presence of fine volcanic
dust in the higher regions of the air. These phenomena were observed
over widely separated areas.
It appears that this great eruption in Martinique was preceded by
severe earthquakes in the northern part of South America, especially
in Colombia and Venezuela. The most marked was the great earthquake
which on April 18th destroyed the city of Guatamaula; this was,
perhaps, the most destructive earthquake that has occurred in the
Western Hemisphere since the great earthquake of 1812, that destroyed
the city of Caracas. Indeed, Professor Milne suggests that it was this
earthquake that brought about the eruption of Mt. Pelée.
Soufrière, on the island of St. Vincent, had a great eruption on May
7th, 1902, one day before the awful eruption of Mt. Pelée. No lava
flowed during this eruption. There were, however, great discharges
of mud, due to a lake that before the eruption filled the top of
a depression known as the old crater which lay southwest of a new
crater, or the crater that was formed during the eruption of 1812. The
old crater was nine-tenths of a mile across from east to west, and
eight-tenths of a mile from north to south. The depth to the crater
floor was from 1,000 to 2,400 feet. The surface of the new and shallow
boiling lake which occupied the deepest part of the floor during the
latter part of May, and from June to August, was estimated to be
only 1,200 feet above the level of the sea. The sheet of water that
occupied it before the eruption being several hundred feet higher.
Soufrière did not fail to give warnings of its coming eruption.
Rumblings were heard two days before the explosion. On May 5th, 1902,
fishermen who crossed the lake noticed that the water was disturbed
and agitated. On the Tuesday following, May 6th, great clouds were
thrown out during the afternoon, and the volcano was illumined by a
reddish glare of fire. The first explosion was heard shortly before
two o'clock on the following day and the volcano burst into activity.
The explosions, together with great discharges of pumice, ashes, and
boulders, followed one another rapidly. A column of steam was shot up
into the air for a height of 30,000 feet. The severest paroxysm came
shortly after ten A. M., and was succeeded by others nearly
as violent during the next few hours. By this time a reddish curtain
of clouds nearly shut out the island from view, and rapidly advanced
over the land and descended on the sea. This eruption caused a loss of
life of about 1,350.
This eruption of Mt. Soufrière was accompanied by the same tornadic
blast of glowing air. There was not, however, any single blast quite
as severe as that which attended the eruption of Pelée on May 8th,
1902.
CHAPTER XII
SOME OTHER NOTED VOLCANIC MOUNTAINS
Since the limits of our book will prevent any further description
of volcanic districts or regions, we must content ourselves with
descriptions of some of the noted of the remaining volcanoes, although
many we will thus omit contain great wonders.
As we have already seen from the description of Krakatoa, the island
of Java near which Krakatoa is situated is especially noted not only
for the great number of its volcanic mountains, but also for the
frequency and severity of their eruptions.
Perhaps the most destructive eruption of any of the volcanic mountains
of Java was of a volcanic mountain called Papandayang. This volcano,
situated on the southern coast of the island, is 7,034 feet in
height, and was in eruption in 1772. According to Scrope, from whom
the details of this eruption have been obtained, two others of the
many volcanoes on Java, situated at 184 and 352 geographical miles
respectively from Papandayang, broke out at the same time into active
eruption, although several intervening cones were undisturbed.
The eruption of Papandayang was of the explosive type, a large part
of the mountain being broken off by the great force of the eruption,
and its materials scattered far and wide over the surrounding country.
During this eruption forty villages with their inhabitants were
buried by great showers of ashes. An area of fifteen by six miles was
left in the shape of a huge pit by the great eruption. It was at
first believed by some that this pit was due to the actual sinking
in of the ground, but a more careful study has shown that it was in
reality caused by the great force of the eruption, being, in point
of fact, a vast explosive crater that was formed by the expulsion of
the materials that formerly filled it. Some idea of the great extent
of this eruption of Papandayang may be had by the size of this huge
crater that was six by fifteen miles in diameter.
Another great volcanic mountain in Java that had a terrific eruption
was Galungoon, or Galung Gung. According to Lyell, from whom the facts
of this eruption have been obtained, prior to this eruption the slopes
of the mountain were highly cultivated and densely populated. There
was a
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