EARTHQUAKES AND THEIR EFFECTS.
Earthquakes and their effects--Deficiency of ancient
accounts--Ordinary atmospheric phenomena--Changes produced by
earthquakes in modern times considered in chronological
order--Earthquake in Syria, 1837--Earthquakes in Chili in 1837 and
1835--Isle of Santa Maria raised ten feet--Chili, 1822--Extent of
country elevated--Aleppo and Ionian Isles--Earthquake of Cutch in
1819--Subsidence in the Delta of the Indus--Island of Sumbawa in
1815--Earthquake of Caraccas in 1812--Shocks at New Madrid in 1811
in the valley of the Mississippi--Aleutian Islands in
1806--Reflections on the earthquakes of the nineteenth
century--Earthquake in Quito, Quebec, &c.--Java, 1786--Sinking down
of large tracts.
In the sketch before given of the geographical boundaries of volcanic
regions, I stated, that although the points of eruption are but thinly
scattered, constituting mere spots on the surface of those vast
districts, yet the subterranean movements extend simultaneously over
immense areas. We may now proceed to consider the changes which these
movements produce on the surface, and in the internal structure of the
earth's crust.
_Deficiency of ancient accounts._--It is only within the last century
and a half, since Hooke first promulgated, in 1688, his views respecting
the connection between geological phenomena and earthquakes, that the
permanent changes affected by these convulsions have excited attention.
Before that time, the narrative of the historian was almost exclusively
confined to the number of human beings who perished, the number of
cities laid in ruins, the value of property destroyed, or certain
atmospheric appearances which dazzled or terrified the observers. The
creation of a new lake, the engulfing of a new city, or the raising of a
new island, are sometimes, it is true, adverted to, as being too
obvious, or of too much geographical or political interest to be passed
over in silence. But no researches were made expressly with a view of
ascertaining the amount of depression or elevation of the ground, or any
particular alterations in the relative position of sea and land; and
very little distinction was made between the raising of soil by volcanic
ejections, and the upheaving of it by forces acting from below. The same
remark applies to a very large proportion of modern accounts: and how
much reason we have to regret this deficiency of information appears
from this, that in every instance where a spirit of scientific inquiry
has animated the eye-witnesses of these events, facts calculated to
throw light on former modifications of the earth's structure are
recorded.
_Phenomena attending earthquakes._--As I shall confine myself almost
entirely, in the following notice of earthquakes, to the changes brought
about by them in the configuration of the earth's crust, I may mention,
generally, some accompaniments of these terrible events which are almost
uniformly commemorated in history, that it may be unnecessary to advert
to them again. Irregularities in the seasons preceding or following the
shocks; sudden gusts of wind, interrupted by dead calms; violent rains
at unusual seasons, or in countries where such phenomena are almost
unknown; a reddening of the sun's disk, and a haziness in the air, often
continued for months; an evolution of electric matter, or of inflammable
gas from the soil, with sulphurous and mephitic vapors; noises
underground, like the running of carriages, or the discharge of
artillery, or distant thunder; animals uttering cries of distress, and
evincing extraordinary alarm, being more sensitive than men of the
slightest movement; a sensation like sea-sickness, and a dizziness in
the head, experienced by men:--these, and other phenomena, less
connected with our present subject as geologists, have recurred again
and again at distant ages, and in all parts of the globe.
I shall now begin the enumeration of earthquakes with the latest
authentic narratives, and so carry back the survey retrospectively, that
I may bring before the reader, in the first place, the minute and
circumstantial details of modern times, and thus enable him, by
observing the extraordinary amount of change within the last 150 years,
to perceive how great must be the deficiency in the meager annals of
earlier eras.
EARTHQUAKES OF THE NINETEENTH CENTURY.[622]
_Syria_, January, 1837.--It has been remarked that earthquakes affect
elongated areas. The violent shock which devastated Syria in 1837 was
felt on a line 500 miles in length by 90 in breadth:[623] more than 6000
persons perished; deep rents were caused in solid rocks, and new hot
springs burst out at Tabereah.
_Chili--Valdivia_, 1837.--One of the latest earthquakes by which the
position of solid land is known to have been permanently altered is that
which occurred in Chili, on November 7th, 1837. On that day Valdivia was
destroyed by an earthquake, and a whaler, commanded by Captain Coste,
was violently shaken at sea, and lost her masts, in lat. 43 degrees 38
minutes S. in sight of the land. The captain went on the 11th of
December following to a spot near the island of Lemus, one of the Chonos
archipelago, where he had anchored two years before, and found that the
bottom of the sea had been raised more than eight feet. Some rocks
formerly covered at all times by the sea were now constantly exposed,
and an enormous quantity of shells and fish in a decaying state, which
had been thrown there by the waves, or suddenly laid dry during the
earthquake, attested the recent date of the occurrence. The whole coast
was strewed with uprooted trees.[624]
_Chili--Conception_, 1835.--Fortunately we have a still more detailed
account of the geographical changes produced in the same country on the
20th of February, 1835. An earthquake was then felt at all places
between Copiapo and Chiloe, from north to south, and from Mendoza to
Juan Fernandez, from east to west. "Vessels," says Mr. Caldcleugh,
"navigating the Pacific, within 100 miles of the coast, experienced the
shock with considerable force."[625] Conception, Talcahuano, Chillan,
and other towns were thrown down. From the account of Captain Fitz Roy,
R. N., who was then employed in surveying the coast, we learn that after
the shock the sea retired in the Bay of Conception, and the vessels
grounded, even those which had been lying in seven fathoms water: all
the shoals were visible, and soon afterwards a wave rushed in and then
retreated, and was followed by two other waves. The vertical height of
these waves does not appear to have been much greater than from sixteen
to twenty feet, although they rose to much greater heights when they
broke upon a sloping beach.
[Illustration: Fig. 69.]
According to Mr. Caldcleugh and Mr. Darwin, the whole volcanic chain of
the Chilian Andes, a range 150 miles in length, was in a state of
unusual activity, both during the shocks and for some time preceding and
after the convulsion, and lava was seen to flow from the crater of
Osorno. (See Map, fig. 69.) The island of Juan Fernandez, distant 365
geographical miles from Chili, was violently shaken at the same time,
and devastated by a great wave. A submarine volcano broke out there
near Bacalao Head, about a mile from the shore, in sixty-nine fathoms
water, and illumined the whole island during the night.[626]
"At Conception," says Captain Fitz Roy, "the earth opened and closed
rapidly in numerous places. The direction of the cracks was not uniform,
though generally from southeast to northwest. The earth was not quiet
for three days after the great shock, and more than 300 shocks were
counted between the 20th February and the 4th of March. The loose earth
of the valley of the Biobio was everywhere parted from the solid rocks
which bound the plain, there being an opening between them from an inch
to a foot in width.
[Illustration: Fig. 70.]
"For some days after the 20th of February, the sea at Talcahuano," says
Captain Fitz Roy, "did not rise to the usual marks by four or five feet
vertically. When walking on the shore, even at high water, beds of dead
mussels, numerous chitons, and limpets, and withered seaweed, still
adhering, though lifeless, to the rocks on which they had lived,
everywhere met the eye." But this difference in the relative level of
the land and sea gradually diminished, till in the middle of April the
water rose again to within two feet of the former high-water mark. It
might be supposed that these changes of level merely indicated a
temporary disturbance in the set of the currents or in the height of the
tides at Talcahuano; but, on considering what occurred in the
neighboring island of Santa Maria, Captain Fitz Roy concluded that the
land had been raised four or five feet in February, and that it had
returned in April to within two or three feet of its former level.
Santa Maria, the island just alluded to, is about seven miles long and
two broad, and about twenty-five miles southwest of Conception. (See
Map, fig. 70.) The phenomena observed there are most important. "It
appeared," says Captain Fitz Roy, who visited Santa Maria twice, the
first time at the end of March, and afterwards in the beginning of
April, "that the southern extremity of the island had been raised eight
feet, the middle nine, and the northern end upwards of ten feet. On
steep rocks, where vertical measures could be correctly taken, beds of
dead mussels were found ten feet above high-water mark. One foot lower
than the highest bed of mussels, a few limpets and chitons were seen
adhering to the rock where they had grown. Two feet lower than the same,
dead mussels, chitons, and limpets were abundant.
"An extensive rocky flat lies around the northern parts of Santa Maria.
Before the earthquake this flat was covered by the sea, some projecting
rocks only showing themselves. Now, the whole flat is exposed, and
square acres of it are covered with dead shell-fish, the stench arising
from which is abominable. By this elevation of the land the southern
port of Santa Maria has been almost destroyed; little shelter remaining
there, and very bad landing." The surrounding sea is also stated to have
become shallower in exactly the same proportion as the land had risen;
the soundings having diminished a fathom and a half everywhere around
the island.
At Tubal, also, to the southeast of Santa Maria, the land was raised six
feet, at Mocha two feet, but no elevation could be ascertained at
Valdivia.
Among other effects of the catastrophe, it is stated that cattle
standing on a steep slope, near the shore, were rolled down into the
sea, and many others were washed off by the great wave from low land and
drowned.[627]
In November of the same year (1835), Conception was shaken by a severe
earthquake, and on the same day Osorno, at the distance of 400 miles,
renewed its activity. These facts prove not only the connection of
earthquakes with volcanic eruptions in this region, but also the vast
extent of the subterranean areas over which the disturbing cause acts
simultaneously.
_Ischia_, 1828.--On the 2d of February the whole island of Ischia was
shaken by an earthquake, and in the October following I found all the
houses in Casamicciol still without their roofs. On the sides of a
ravine between that town and Forio, I saw masses of greenish tuff which
had been thrown down. The hot-spring of Rita, which was nearest the
centre of the movement, was ascertained by M. Covelli to have increased
in temperature, showing, as he observes, that the explosion took place
below the reservoirs which heat the thermal waters.[628]
_Bogota_, 1827.--On the 16th of November, 1827, the plain of Bogota, in
New Granada, or Colombia, was convulsed by an earthquake, and a great
number of towns were thrown down. Torrents of rain swelled the
Magdalena, sweeping along vast quantities of mud and other substances,
which emitted a sulphurous vapor and destroyed the fish. Popayan, which
is distant 200 geographical miles S. S. W. of Bogota, suffered greatly.
Wide crevices appeared in the road of Guanacas, leaving no doubt that
the whole of the Cordilleras sustained a powerful shock. Other fissures
opened near Costa, in the plains of Bogota, into which the river Tunza
immediately began to flow.[629] It is worthy of remark, that in all such
cases the ancient gravel bed of a river is deserted and a new one formed
at a lower level; so that a want of relation in the position of alluvial
beds of the existing water-courses may be no test of the high antiquity
of such deposits, at least in countries habitually convulsed by
earthquakes. Extraordinary rains accompanied the shocks before
mentioned; and two volcanoes are said to have been in eruption in the
mountain-chain nearest to Bogota.
_Chili_, 1822.--On the 19th of November, 1822, the coast of Chili was
visited by a most destructive earthquake. The shock was felt
simultaneously throughout a space of 1200 miles from north to south. St.
Jago, Valparaiso, and some other places, were greatly injured. When the
district round Valparaiso was examined on the morning after the shock,
it was found that the coast for a considerable distance was raised above
its former level.[630] At Valparaiso the elevation was three feet, and
at Quintero about four feet. Part of the bed of the sea, says Mrs.
Graham, remained bare and dry at high water, "with beds of oysters,
mussels, and other shells adhering to the rocks on which they grew, the
fish being all dead, and exhaling most offensive effluvia.[631]
An old wreck of a ship, which before could not be approached, became
accessible from the land, although its distance from the original
sea-shore had not altered. It was observed that the water-course of a
mill, at the distance of about a mile from the sea, gained a fall of
fourteen inches, in little more than one hundred yards; and from this
fact it is inferred that the rise in some parts of the inland country
was far more considerable than on the borders of the ocean.[632] Part of
the coast thus elevated consisted of granite, in which parallel fissures
were caused, some of which were traced for a mile and a half inland.
Cones of earth about four feet high were thrown up in several districts,
by the forcing up of water mixed with sand through funnel-shaped
hollows,--a phenomenon very common in Calabria, and the explanation of
which will hereafter be considered. Those houses in Chili of which the
foundations were on rock were less damaged than such as were built on
alluvial soil.
Mr. Cruickshanks, an English botanist, who resided in the country
during the earthquake, has informed me that some rocks of greenstone at
Quintero, a few hundred yards from the beach, which had always been
under water till the shock of 1822, have since been uncovered when the
tide is at half-ebb: and he states that, after the earthquake, it was
the general belief of the fishermen and inhabitants of the Chilian
coast, _not_ that the land had risen, but that the ocean had permanently
retreated.
Dr. Meyen, a Prussian traveller, who visited Valparaiso in 1831, says
that on examining the rocks both north and south of the town, nine years
after the event, he found, in corroboration of Mrs. Graham's account,
that remains of animals and sea-weed, the _Lessonia_ of Bory de St.
Vincent, which has a firm ligneous stem, still adhered to those rocks
which in 1822 had been elevated above high-water mark.[633] According to
the same author, the whole coast of Central Chili was raised about four
feet, and banks of marine shells were laid dry on many parts of the
coast. He observed similar banks, elevated at unknown periods, in
several places, especially at Copiapo, where the species all agree with
those now living in the ocean. Mr. Freyer also, who resided some years
in South America, has confirmed these statements;[634] and Mr. Darwin
obtained evidence that the remains of an ancient wall, formerly washed
by the sea, and now 11-1/2 feet above high-water mark, acquired several
feet of this additional elevation during the earthquake of 1822.[635]
The shocks continued up to the end of September, 1823; even then,
forty-eight hours seldom passed without one, and sometimes two or three
were felt during twenty-four hours. Mrs. Graham observed, after the
earthquake of 1822, that besides a beach newly raised above high-water
mark, there were several older elevated lines of beach, one above the
other, consisting of shingle mixed with shells extending in a parallel
direction to the shore, to the height of fifty feet above the sea.[636]
_Extent of country elevated._--By some observers it has been supposed
that the whole country from the foot of the Andes to a great distance
under the sea was upraised in 1822, the greatest rise being at the
distance of about two miles from the shore. "The rise upon the coast was
from two to four feet:--at the distance of a mile inland it must have
been from five to six or seven feet."[637] It has also been conjectured
by the same eye-witnesses to the convulsion, that the area over which
this permanent alteration of level extended may have been equal to
100,000 square miles. Although the increased fall of certain
water-courses may have afforded some ground for this conjecture, it must
be considered as very hypothetical, and the estimate may have exceeded
or greatly fallen short of the truth. It may nevertheless be useful to
reflect on the enormous amount of change which this single convulsion
occasioned, if the extent of country moved upward really amounted to
100,000 square miles,--an extent just equal to half the area of France,
or about five-sixths of the area of Great Britain and Ireland. If we
suppose the elevation to have been only three feet on an average, it
will be seen that the mass of rock added to the continent of America by
the movement, or, in other words, the mass previously below the level of
the sea, and after the shocks permanently above it, must have contained
fifty-seven cubic miles in bulk; which would be sufficient to form a
conical mountain two miles high (or about as high as Etna), with a
circumference at the base of nearly thirty-three miles. We may take the
mean specific gravity of the rock at 2.655,--a fair average, and a
convenient one in such computations, because at such a rate a cubic yard
weighs two tons. Then, assuming the great pyramid of Egypt, if solid, to
weigh, in accordance with an estimate before given, six million tons, we
may state the rock added to the continent by the Chilian earthquake to
have more than equalled 100,000 pyramids.
But it must always be borne in mind that the weight of rock here alluded
to constituted but an insignificant part of the whole amount which the
volcanic forces had to overcome. The whole thickness of rock between the
surface of Chili and the subterranean foci of volcanic action may be
many miles or leagues deep. Say that the thickness was only two miles,
even then the mass which changed place and rose three feet being 200,000
cubic miles in volume, must have exceeded in weight 363 million
pyramids.
It may be instructing to consider these results in connection with
others already obtained from a different source, and to compare the
working of two antagonistic forces--the levelling power of running
water, and the expansive energy of subterranean heat. How long, it may
be asked, would the Ganges require, according to data before explained
(p. 283), to transport to the sea a quantity of solid matter equal to
that which may have been added to the land by the Chilian earthquake?
The discharge of mud in one year by the Ganges was estimated at 20,000
million cubic feet. According to that estimate it would require about
four centuries (or 418 years) before the river could bear down from the
continent into the sea a mass equal to that gained by the Chilian
earthquake. In about half that time, perhaps, the united waters of the
Ganges and Burrampooter might accomplish the operation.
_Cutch_, 1819.--A violent earthquake occurred at Cutch, in the delta of
the Indus, on the 16th of June, 1819. (See Map, fig. 71.) The principal
town, Bhooj, was converted into a heap of ruins, and its stone buildings
were thrown down. The movement was felt over an area having a radius of
1000 miles from Bhooj, and extending to Kbatmandoo, Calcutta, and
Pondicherry.[638] The vibrations were felt in Northwest India, at a
distance of 800 miles, after an interval of about fifteen minutes after
the earthquake at Bhooj. At Ahmedabad the great mosque, erected by
Sultan Ahmed nearly 450 years before, fell to the ground, attesting how
long a period had elapsed since a shock of similar violence had visited
that point. At Anjar, the fort, with its tower and guns, was hurled to
the ground in one common mass of ruin. The shocks continued until the
20th; when, thirty miles northwest from Bhooj, the volcano called
Denodur is said by some to have sent forth flames, but Capt. Grant was
unable to authenticate this statement.
[Illustration: Fig. 71. MAP of THE COUNTRIES at THE MOUTH OF THE
INDUS.]
_Subsidence in the delta of the Indus._--Although the ruin of towns was
great, the face of nature in the inland country, says Captain Macmurdo,
was not visibly altered. In the hills some large masses only of rock and
soil were detached from the precipices; but the eastern and almost
deserted channel of the Indus, which bounds the province of Cutch, was
greatly changed. This estuary, or inlet of the sea, was, before the
earthquake, fordable at Luckput, being only about a foot deep when the
tide was at ebb, and at flood-tide never more than six feet; but it was
deepened at the fort of Luckput, after the shock, to more than _eighteen
feet at low water_.[639] On sounding other parts of the channel, it was
found, that where previously the depth of the water at flood never
exceeded one or two feet, it had become from four to ten feet deep. By
these and other remarkable changes of level, a part of the inland
navigation of that country, which had been closed for centuries, became
again practicable.
[Illustration: Fig. 72.
Fort of Sindree, on the eastern branch of the Indus, before it was
submerged by the earthquake of 1819, from a sketch of Capt. Grindlay,
made in 1808.]
_Fort and village submerged._[640]--The fort and village of Sindree, on
the eastern arm of the Indus, above Luckput, are stated by the same
writer to have been overflowed; and, after the shock, the tops of the
houses and wall were alone to be seen above the water, for the houses,
although submerged, were not cast down. Had they been situated,
therefore, in the interior, where so many forts were levelled to the
ground, their site would, perhaps, have been regarded as having remained
comparatively unmoved. Hence we may suspect that great permanent
upheavings and depressions of soil may be the result of earthquakes,
without the inhabitants being in the least degree conscious of any
change of level.
A more recent survey of Cutch, by Sir A. Burnes, who was not in
communication with Capt. Macmurdo, confirms the facts above enumerated,
and adds many important details.[641] That officer examined the delta of
the Indus in 1826 and 1828, and from his account it appears that, when
Sindree subsided in June, 1819, the sea flowed in by the eastern mouth
of the Indus, and in a few hours converted a tract of land, 2000 square
miles in area, into an inland sea, or lagoon. Neither the rush of the
sea into this new depression, nor the movement of the earthquake, threw
down entirely the small fort of Sindree, one of the four towers, the
northwestern, still continuing to stand; and, the day after the
earthquake, the inhabitants who had ascended to the top of this tower,
saved themselves in boats.[642]
_Elevation of the Ullah Bund._--Immediately after the shock, the
inhabitants of Sindree saw, at the distance of five miles and a half
from their village, a long elevated mound, where previously there had
been a low and perfectly level plain. (See Map, fig. 71.) To this
uplifted tract they gave the name of "Ullah Bund," or the "Mound of
God," to distinguish it from several artificial dams previously thrown
across the eastern arm of the Indus.
_Extent of country raised._--It has been ascertained that this
new-raised country is _upwards of fifty miles_ in length from east to
west, running parallel to that line of subsidence before mentioned,
which caused the grounds around Sindree to be flooded. The range of this
elevation extends from Puchum Island towards Gharee; its breadth from
north to south is conjectured to be in some parts _sixteen miles_, and
its greatest ascertained height above the original level of the delta is
ten feet,--an elevation which appears to the eye to be very uniform
throughout.
For several years after the convulsion of 1819, the course of the Indus
was very unsettled, and at length, in 1826, the river threw a vast body
of water into its eastern arm, that called the Phurraun, above Sindree;
and forcing its way in a more direct course to the sea, burst through
all the artificial dams which had been thrown across its channel, and at
length cut right through the "Ullah Bund," whereby a natural section was
obtained. In the perpendicular cliffs thus laid open Sir A. Burnes found
that the upraised lands consisted of clay filled with shells. The new
channel of the river where it intersected the "bund" was eighteen feet
deep, and forty yards in width; but in 1828 the channel was still
farther enlarged. The Indus, when it first opened this new passage,
threw such a body of water into the new mere, or salt lagoon, of
Sindree, that it became fresh for many months; but it had recovered its
saltness in 1828, when the supply of river-water was less copious, and
finally it became more salt than the sea, in consequence, as the natives
suggested to Sir A. Burnes, of the saline particles with which the "Runn
of Cutch" is impregnated.
In 1828 Sir A. Burnes went in a boat to the ruins of Sindree, where a
single remaining tower was seen in the midst of a wide expanse of sea.
The tops of the ruined walls still rose two or three feet above the
level of the water; and standing on one of these, he could behold
nothing in the horizon but water, except in one direction, where a blue
streak of land to the north indicated the Ullah Bund. This scene
presents to the imagination a lively picture of the revolutions now in
progress on the earth--a waste of waters where a few years before all
was land, and the only land visible consisting of ground uplifted by a
recent earthquake.
Ten years after the visit of Sir A. Burnes above alluded to, my friend,
Captain Grant, F. G. S., of the Bombay Engineers, had the kindness to
send at my request a native surveyor to make a plan of Sindree and Ullah
Bund, in March, 1838. From his description it appears that, at that
season, the driest of the whole year, he found the channel traversing
the Bund to be 100 yards wide, without water, and incrusted with salt.
He was told that it has now only four or five feet of water in it after
rains. The sides or banks were nearly perpendicular, and nine feet in
height. The lagoon has diminished both in area and depth, and part near
the fort was dry land. The annexed drawing, made by Captain Grant from
the surveyor's plan, shows the appearance of the fort in the midst of
the lake, as seen in 1838 from the west, or from the same point as that
from which Captain Grindlay's sketch (see fig. 72) was taken in 1808,
before the earthquake.
[Illustration: Fig. 73.
View of the Fort of Sindree, from the west, in March, 1838.]
The Runn of Cutch is a flat region of a very peculiar character, and no
less than 7000 square miles in area: a greater superficial extent than
Yorkshire, or about one-fourth the area of Ireland. It is not a desert
of moving sand, nor a marsh, but evidently the dried-up bed of an inland
sea, which for a great part of every year has a hard and dry bottom
uncovered by weeds or grass, and only supporting here and there a few
tamarisks. But during the monsoons, when the sea runs high, the
salt-water driven up from the Gulf of Cutch and the creeks at Luckput
overflows a large part of the Runn, especially after rains, when the
soaked ground permits the sea-water to spread rapidly. The Runn is also
liable to be overflowed occasionally in some parts by river-water: and
it is remarkable that the only portion which was ever highly cultivated
(that anciently called Sayra) is now permanently submerged. The surface
of the Runn is sometimes incrusted with salt about an inch in depth, in
consequence of the evaporation of the sea-water. Islands rise up in some
parts of the waste, and the boundary lands form bays and promontories.
The natives have various traditions respecting the former separation of
Cutch and Sinde by a bay of the sea, and the drying up of the district
called the Runn. But these tales, besides the usual uncertainty of oral
tradition, are farther obscured by mythological fictions. The conversion
of the Runn into land is chiefly ascribed to the miraculous powers of a
Hindoo saint, by name Damorath (or Dhoorunnath), who had previously done
penance for twelve years on the summit of Denodur hill. Captain Grant
infers, on various grounds, that this saint flourished about the
eleventh or twelfth century of our era. In proof of the drying up of
the Runn, some towns far inland are still pointed out as having once
been ancient ports. It has, moreover, been always said that ships were
wrecked and engulphed by the great catastrophe; and in the jets of black
muddy water thrown out of fissures in that region, in 1819, there were
cast up numerous pieces of wrought-iron and ship nails.[643] Cones of
sand six or eight feet in height were at the same time thrown up on
these lands.[644]
We must not conclude without alluding to a _moral_ phenomenon connected
with this tremendous catastrophe, which we regard as highly deserving
the attention of geologists. It is stated by Sir A. Burnes, that "these
wonderful events passed _unheeded_ by the inhabitants of Cutch;" for the
region convulsed, though once fertile, had for a long period been
reduced to sterility by want of irrigation, so that the natives were
indifferent as to its fate. Now it is to this profound apathy which all
but highly civilized nations feel, in regard to physical events not
having an immediate influence on their worldly fortunes, that we must
ascribe the extraordinary dearth of historical information concerning
changes of the earth's surface, which modern observations show to be by
no means of rare occurrence in the ordinary course of nature.
Since the above account was written, a description has been published of
more recent geographical changes in the district of Cutch, near the
mouth of the Koree, or eastern branch of the Indus, which happened in
June, 1845. A large area seems to have subsided, and the Sindree lake
had become a salt marsh.[645]
_Island of Sumbawa_, 1815.--In April, 1815, one of the most frightful
eruptions recorded in history occurred in the province of Tomboro, in
the island of Sumbawa (see Map, fig. 39, p. 351), about 200 miles from
the eastern extremity of Java. In April of the year preceding the
volcano had been observed in a state of considerable activity, ashes
having fallen upon the decks of vessels which sailed past the
coast.[646] The eruption of 1815 began on the 5th of April, but was most
violent on the 11th and 12th, and did not entirely cease till July. The
sound of the explosions was heard in Sumatra, at the distance of 970
geographical miles in a direct line; and at Ternate, in an opposite
direction, at the distance of 720 miles. Out of a population of 12,000,
in the province of Tomboro, only twenty-six individuals survived.
Violent whirlwinds carried up men, horses, cattle, and whatever else
came within their influence into the air; tore up the largest trees by
the roots, and covered the whole sea with floating timber.[647] Great
tracts of land were covered by lava, several streams of which, issuing
from the crater of the Tomboro mountain, reached the sea: So heavy was
the fall of ashes, that they broke into the Resident's house at Bima,
forty miles east of the volcano, and rendered it as well as many other
dwellings in the town uninhabitable. On the side of Java the ashes were
carried to the distance of 300 miles, and 217 towards Celebes, in
sufficient quantity to darken the air. The floating cinders to the
westward of Sumatra formed, on the 12th of April, a mass two feet thick,
and several miles in extent, through which ships with difficulty forced
their way.
The darkness occasioned in the daytime by the ashes in Java was so
profound, that nothing equal to it was ever witnessed in the darkest
night. Although this volcanic dust when it fell was an impalpable
powder, it was of considerable weight when compressed, a pint of it
weighing twelve ounces and three quarters. "Some of the finest
particles," says Mr. Crawfurd, "were transported to the islands of
Amboyna and Banda, which last is about 800 miles east from the site of
the volcano, although the southeast monsoon was then at its height."
They must have been projected, therefore, into the upper regions of the
atmosphere, where a counter-current prevailed.
Along the sea-coast of Sumbawa and the adjacent isles, the sea rose
suddenly to the height of from two to twelve feet, a great wave rushing
up the estuaries, and then suddenly subsiding. Although the wind at Bima
was still during the whole time, the sea rolled in upon the shore, and
filled the lower parts of the houses with water a foot deep. Every prow
and boat was forced from the anchorage, and driven on shore.
The town called Tomboro, on the west side of Sumbawa, was overflowed by
the sea, which encroached upon the shore so that the water remained
permanently eighteen feet deep in places where there was land before.
Here we may observe, that the amount of subsidence of land was apparent,
in spite of the ashes, which would naturally have caused the limits of
the coast to be extended.
The area over which tremulous noises and other volcanic effects
extended, was 1000 English miles in circumference, including the whole
of the Molucca Islands, Java, a considerable portion of Celebes,
Sumatra, and Borneo. In the island of Amboyna, in the same month and
year, the ground opened, threw out water, and then closed again.[648]
In conclusion, I may remind the reader, that but for the accidental
presence of Sir Stamford Raffles, then Governor of Java, we should
scarcely have heard in Europe of this tremendous catastrophe. He
required all the residents in the various districts under his authority
to send in a statement of the circumstances which occurred within their
own knowledge; but, valuable as were their communications, they are
often calculated to excite rather than to satisfy the curiosity of the
geologist. They mention that similar effects, though in a less degree,
had, about seven years before, accompanied an eruption of Carang Assam,
a volcano in the island of Bali, west of Sumatra; but no particulars of
that great catastrophe are recorded.[649]
_Caraccas_, 1812.--On the 26th of March, 1812, several violent shocks of
an earthquake were felt in Caraccas. The surface undulated like a
boiling liquid, and terrific sounds were heard underground. The whole
city with its splendid churches was in an instant a heap of ruins,
under which 10,000 of the inhabitants were buried. On the 5th of April,
enormous rocks were detached from the mountains. It was believed that
the mountain Silla lost from 300 to 360 feet of its height by
subsidence; but this was an opinion not founded on any measurement. On
the 27th of April, a volcano in St. Vincent's threw out ashes; and, on
the 30th, lava flowed from its crater into the sea, while its explosions
were heard at a distance equal to that between Vesuvius and Switzerland,
the sound being transmitted, as Humboldt supposes, through the ground.
During the earthquake which destroyed Caraccas, an immense quantity of
water was thrown out at Valecillo, near Valencia, as also at Porto
Cabello, through openings in the earth; and in the Lake Maracaybo the
water sank. Humboldt observed that the Cordilleras, composed of gneiss
and mica slate, and the country immediately at their feet, were more
violently shaken than the plains.[650]
_South Carolina and New Madrid, Missouri_, 1811-12.--Previous to the
destruction of La Guayra and Caraccas, in 1812, earthquakes were felt in
South Carolina; and the shocks continued till those cities were
destroyed. The valley also of the Mississippi, from the village of New
Madrid to the mouth of the Ohio in one direction, and to the St. Francis
in another, was convulsed in such a degree as to create new lakes and
islands. It has been remarked by Humboldt in his Cosmos, that the
earthquake of New Madrid presents one of the few examples on record of
the incessant quaking of the ground for several successive months _far
from any volcano_. Flint, the geographer, who visited the country seven
years after the event, informs us, that a tract of many miles in extent,
near the Little Prairie, became covered with water three or four feet
deep; and when the water disappeared a stratum of sand was left in its
place. Large lakes of twenty miles in extent were formed in the course
of an hour, and others were drained. The grave-yard at New Madrid was
precipitated into the bed of the Mississippi; and it is stated that the
ground whereon the town is built, and the river-bank for fifteen miles
above, sank eight feet below their former level.[651] The neighboring
forest presented for some years afterwards "a singular scene of
confusion; the trees standing inclined in every direction, and many
having their trunks and branches broken."[652]
The inhabitants relate that the earth rose in great undulations; and
when these reached a certain fearful height, the soil burst, and vast
volumes of water, sand, and pit-coal were discharged as high as the tops
of the trees. Flint saw hundreds of these deep chasms remaining in an
alluvial soil, seven years after. The people in the country, although
inexperienced in such convulsions, had remarked that the chasms in the
earth were in a direction from S. W. to N. E.; and they accordingly
felled the tallest trees, and laying them at right angles to the chasms,
stationed themselves upon them. By this invention, when chasms opened
more than once under these trees, several persons were prevented from
being swallowed up.[653] At one period during this earthquake, the
ground not far below New Madrid swelled up so as to arrest the
Mississippi in its course, and to cause a temporary reflux of its waves.
The motion of some of the shocks is described as having been horizontal,
and of others perpendicular; and the vertical movement is said to have
been much less desolating than the horizontal.
The above account has been reprinted exactly as it appeared in former
editions of this work, compiled from the authorities which I have cited;
but having more recently (March, 1846) had an opportunity myself of
visiting the disturbed region of the Mississippi, and conversing with
many eye-witnesses of the catastrophe, I am able to confirm the truth of
those statements, and to add some remarks on the present face and
features of the country. I skirted, as was before related (p. 270), part
of the territory immediately west of New Madrid, called "the sunk
country," which was for the first time permanently submerged during the
earthquake of 1811-12. It is said to extend along the course of the
White Water and its tributaries for a distance of between 70 and 80
miles north and south, and 30 miles east and west. I saw on its borders
many full-grown trees still standing leafless, the bottoms of their
trunks several feet under water, and a still greater number lying
prostrate. An active vegetation of aquatic plants is already beginning
to fill up some of the shallows, and the sediment washed in by
occasional floods when the Mississippi rises to an extraordinary height
contributes to convert the sunk region into marsh and forest land. Even
on the dry ground along the confines of the submerged area, I observed
in some places that all the trees of prior date to 1811 were dead and
leafless, though standing erect and entire. They are supposed to have
been killed by the loosening of their roots during the repeated
undulations which passed through the ground for three months in
succession.
Mr. Bringier, an experienced engineer of New Orleans, who was on
horseback near New Madrid when some of the severest shocks were
experienced, related to me (in 1846), that "as the waves advanced the
trees bent down, and the instant afterwards, while recovering their
position, they often met those of other trees similarly inclined, so
that their branches becoming interlocked, they were prevented from
righting themselves again. The transit of the wave through the woods was
marked by the crashing noise of countless boughs, first heard on one
side and then on the other. At the same time powerful jets of water,
mixed with sand, mud, and fragments of coaly matter, were cast up,
endangering the lives of both horse and rider."
I was curious, to ascertain whether any vestiges still remained of these
fountains of mud and water, and carefully examined between New Madrid
and the Little Prairie several "sink holes," as they are termed. They
consist of cavities from 10 to 30 yards in width, and 20 feet or more in
depth, and are very conspicuous, interrupting the level surface of a
flat alluvial plain. I saw abundance of sand, which some of the present
inhabitants saw spouting from these deep holes, also fragments of
decayed wood and black bituminous shale, probably drifted down at some
former period in the main channel of the Mississippi, from the
coal-fields farther north. I also found numerous rents in the soil left
by the earthquake, some of them still several feet wide, and a yard or
two in depth, although the action of rains, frost, and occasional
inundations, and especially the leaves of trees blown into them in
countless numbers every autumn, have done much to fill them up. I
measured the direction of some of the fissures, which usually varied
from 10 to 45 degrees W. of north, and were often parallel to each
other; I found, however, a considerable diversity in their direction.
Many of them are traceable for half a mile and upwards, but they might
easily be mistaken for artificial trenches if resident settlers were not
there to assure us that within their recollection they were "as deep as
wells." Fragments of coaly shale were strewed along the edges of some of
these open fissures, together with white sand, in the same manner as
round the "sink holes."[654]
Among other monuments of the changes wrought in 1811-12, I explored the
bed of the lake called Eulalie, near New Madrid, 300 yards long by 100
yards in width, which was suddenly drained during the earthquake. The
parallel fissures by which the waters escaped are not yet entirely
closed, and all the trees growing on its bottom were at the time of my
visit less than 34 years old. They consisted of cotton-wood, willows,
and honey-locust, and other species, differing from those clothing the
surrounding higher grounds, which are more elevated by 12 or 15 feet. On
them the hickory, the black and white oak, the gum and other trees, many
of them of ancient date, were flourishing.
_Aleutian Islands_, 1806.--In the year 1806, a new island, in the form
of a peak, with some low conical hills upon it, is said to have risen
from the sea among the Aleutian Islands, east of Kamtschatka. According
to Langsdorf,[655] it was four geographical miles in circumference; and
Von Buch infers from its magnitude, and from its not having again
subsided below the level of the sea, that it did not consist merely of
ejected matter, but of a solid rock of trachyte upheaved.[656] Another
extraordinary eruption happened in the spring of the year 1814, in the
sea near Unalaschka, in the same archipelago. A new isle was then
produced of considerable size, and with a peak three thousand feet high,
which remained standing for a year afterwards, though with somewhat
diminished height.
Although it is not improbable that earthquakes accompanying these
tremendous eruptions may have heaved up part of the bed of the sea, yet
the circumstance of the islands not having disappeared like Sabrina (see
p. 416), may have arisen from the emission of lava. If Jorullo, for
example, in 1759, had risen from a shallow sea to the height of 1600
feet, instead of attaining that elevation above the Mexican plateau, the
massive current of basaltic lava which poured out from its crater would
have enabled it to withstand, for a long period, the action of a
turbulent sea.
_Reflections on the earthquakes of the nineteenth century._--We are now
about to pass on to the events of the eighteenth century; but before we
leave the consideration of those already enumerated, let us pause for a
moment, and reflect how many remarkable facts of geological interest are
afforded by the earthquakes above described, though they constitute but
a small part of the convulsions even of the last forty years. New rocks
have risen from the waters; new hot springs have burst out, and the
temperature of others has been raised; the coast of Chili has been
thrice permanently elevated; a considerable tract in the delta of the
Indus has sunk down, and some of its shallow channels have become
navigable; an adjoining part of the same district, upwards of fifty
miles in length and sixteen in breadth, has been raised about ten feet
above its former level; part of the great plain of the Mississippi, for
a distance of eighty miles in length by thirty in breadth, has sunk down
several feet; the town of Tomboro has been submerged, and twelve
thousand of the inhabitants of Sumbawa have been destroyed. Yet, with a
knowledge of these terrific catastrophes, witnessed during so brief a
period by the present generation, will the geologist declare with
perfect composure that the earth has at length settled into a state of
repose? Will he continue to assert that the changes of relative level of
land and sea, so common in former ages of the world, have now ceased?
If, in the face of so many striking facts, he persists in maintaining
this favorite dogma, it is in vain to hope that, by accumulating the
proofs of similar convulsions during a series of antecedent ages, we
shall shake his tenacity of purpose:--
Si fractus illabatur orbis
Impavidum ferient ruinae.
EARTHQUAKES OF THE EIGHTEENTH CENTURY.
_Quito_, 1797.--On the morning of February 4th, 1797, the volcano of
Tunguragua in Quito, and the surrounding district, for forty leagues
from south to north, and twenty leagues from west to east, experienced
an undulating movement, which lasted four minutes. The same shock was
felt over a tract of 170 leagues from south to north, from Piura to
Popayan; and 140 from west to east, from the sea to the river Napo. In
the smaller district first mentioned, where the movement was more
intense, every town was levelled to the ground; and Riobamba, Quero, and
other places, were buried under masses detached from the mountains. At
the foot of Tunguragua the earth was rent open in several places; and
streams of water and fetid mud, called "moya," poured out, overflowing
and wasting every thing. In valleys 1000 feet broad, the water of these
floods reached to the height of 600 feet; and the mud deposit barred up
the course of the river, so as to form lakes, which in some places
continued for more than eighty days. Flames and suffocating vapors
escaped from the lake Quilotoa, and killed all the cattle on its shores.
The shocks continued all February and March; and on the 5th of April
they recurred with almost as much violence as at first. We are told that
the form of the surface in the district most shaken was entirely
altered, but no exact measurements are given whereby we may estimate the
degree of elevation or subsidence.[657] Indeed it would be difficult,
except in the immediate neighborhood of the sea, to obtain any certain
standard of comparison if the levels were really as much altered as the
narrations imply.
_Cumana_, 1797.--In the same year, on the 14th of December, the small
Antilles experienced subterranean movements, and four-fifths of the town
of Cumana was shaken down by a vertical shock. The form of the shoal of
Mornerouge, at the mouth of the river Bourdones, was changed by an
upheaving of the ground.[658]
_Canada--Quebec_, 1791.--We learn from Captain Bayfield's memoirs, that
earthquakes are very frequent on the shore of the estuary of the St.
Lawrence, of force sufficient at times to split walls and throw down
chimneys. Such were the effects experienced in December, 1721, in St.
Paul's Bay, about fifty miles N. E. from Quebec; and the inhabitants
say, that about every twenty-five years a violent earthquake returns,
which lasts forty days. In the History of Canada, it is stated that, in
1663, a tremendous convulsion lasted six months, extending from Quebec
to Tadeausac,--a distance of about 130 miles. The ice on the river was
broken up, and many landslips caused.[659]
_Caraccas_, 1790.--In the Caraccas, near where the Caura joins the
Orinoco, between the towns San Pedro de Alcantara and San Francisco de
Aripao, an earthquake, on St. Matthew's day 1790, caused a sinking in of
the granitic soil, and left a lake 800 yards in diameter, and from
eighty to one hundred in depth. It was a portion of the forest of Aripao
which subsided, and the trees remained green for several months under
water.[660]
_Sicily_, 1790.--On the 18th of March in the same year, at S. Maria di
Niscemi, some miles from Terranuova, near the south coast of Sicily, the
ground gradually sunk down for a circumference of three Italian miles,
during seven shocks; and, in one place, to the depth of thirty feet. It
continued to subside to the end of the month. Several fissures sent
forth sulphur, petroleum, steam, and hot water, and a stream of mud,
which flowed for two hours, and covered a space sixty feet long and
thirty broad. This happened far from both the ancient and modern
volcanic district, in a group of strata consisting chiefly of blue
clay.[661]
_Java_, 1786.--About the year 1786, an earthquake was felt at intervals,
for the period of four months, in the neighborhood of Batur, in Java,
and an eruption followed. Various rents were formed, which emitted a
sulphurous vapor; separate tracts sunk away, and were swallowed by the
earth. Into one of these the rivulet Dotog entered, and afterwards
continued to follow a subterraneous course. The village of Jampang was
buried in the ground, with thirty-eight of its inhabitants, who had not
time to escape. We are indebted to Dr. Horsfield for having verified the
above-mentioned facts.[662]