THE EARTHQUAKE OF CALABRIA IN 1783
All students of elementary geography are quick to notice that the
extreme southeastern part of Italy is shaped something like a boot,
which appears to be kicking at the island of Sicily. This part of the
Mediterranean Sea has for very many years been the arena or storm
centre of more or less intense volcanic activity. To the northwest is
the active volcano of Vesuvius, as well as the volcanic regions of the
Phlegræan Fields. Immediately opposite the point of Italy, near the
toe of the foot, is the active volcanic mountain, Etna, while not far
from this point is the volcano of Stromboli.
In 1783 this part of the world was visited by a very severe
earthquake. Since at that time the country was divided into two
parts, known as Upper Calabria and Lower Calabria, this earthquake is
sometimes spoken of as the earthquake of the Calabrias, or more simply
as the Calabrian earthquake.
The great mountain range of the Apennines, mainly of granite
formation, extends through the central part of Italy. The lands
adjoining the mountains on each side are flat and marshy, and
consequently unhealthy.
Numerous observers have compiled excellent accounts of the Calabrian
earthquake. These, having been made by educated persons, are, to a
large extent free from the inconsistencies and exaggerations apt to
characterize descriptions by ignorant persons, especially when in
a condition of excitement or alarm. Among reliable writers was Sir
William Hamilton, who made a personal examination of the region, soon
after the first severe shock, and collected much valuable information
for a paper which was afterwards published in the Philosophical
Transactions of the Royal Society. Then, too, Dolomieu, another
scientific man of high ability, made a careful study of the effects
produced by the earthquake.
[Illustration: FIG. 42. MAP OF THE CALABRIAN EARTHQUAKE OF
1783]
As can be seen by an examination of the map presented in Fig. 42, the
part of Italy included in the Calabrias covers an area from north to
south almost equal to two degrees of latitude. Although the shock
extended beyond the limits of Calabria, since it reached as far north
as Naples, as well as over a great part of the Island of Sicily, the
territory in which the greatest damage was done did not exceed in area
about 500 square miles.
The southern part of Italy is subject to frequent earthquake shocks.
Pignatari, an Italian physician, asserts that this region was visited
during 1783 by no less than 949 earthquakes, of which 501 were of the
first class, or degree of intensity, while in 1784, there were 151
earthquakes, of which ninety-eight were of the first class.
It seems that the city of Oppido, marked on the above map as midway
between the two coasts, was the point from which the severe earthquake
of 1783 started. If one draws a circle, with a radius of twenty-two
miles, around Oppido as a centre, the portions of the Calabrias that
were the most affected will all lie within this circle.
The great Calabrian earthquake was attended by numerous shocks. The
first and the most severe shock, that of February 5th, 1783, was only
two minutes in destroying most of the houses in all cities, towns, and
villages on the western side of the Apennines in this part of Italy.
Another severe shock occurred on the 28th of March. This shock was
almost as severe as that of February 5th.
In order to understand many of the effects produced by this
earthquake, inquiry must be made into the geological character of the
region. According to Dolomieu, the flat country at the slopes of the
Apennines, known as the Plain of Calabria, is covered with sand and
clay mixed with sea shells. These strata have been deposited by the
sea from materials that have been obtained by the decomposition of the
granite mountain ranges in the Apennines. The plain is quite level
except where it is crossed by deep valleys or ravines, which have
been eroded or cut by the swift mountain torrents. In many cases,
these ravines or valleys have depths as great as 600 feet. Their sides
are generally almost perpendicular. Consequently, as Lyell remarks,
throughout the length of the mountain chain, the soil, which adheres
but loosely to the granite base of the mountain chain, could therefore
be easily separated from the mountain, and sliding over the solid
steeps of the mountain could readily move, especially through the
ravines or gorges, to distances in some cases as great as from nine to
ten miles.
This peculiarity of the country must be thoroughly understood, since,
otherwise, it would seem impossible that lands could be carried
several miles from their former position, and often bear along
with them almost undisturbed houses, olive groves, vineyards, and
cultivated fields.
The heaving of the surface of the earth like the waters of the sea,
so common in severe earthquakes, occurred during the Calabrian
earthquake. In some places this heaving so shook the trees that they
bent until their tops touched the ground near their base.
Parts of the ground were violently thrown upwards into the air as in
the explosive type of earthquakes. In many instances the large paving
stones were thrown into the air and afterwards found with their lower
portions upwards.
During the earthquake deep fissures were made in the earth at various
localities and there were, moreover, marked changes of level. At
Messina in Sicily the shore was fissured and rent and while before the
convulsion the surface had been level, it was afterwards found to be
inclined toward the sea.
According to Dolomieu the following curious incident occurred during
the passage of the earthquake waves. A well in the ground of one of
the convents of the Augustines, lined on the inside with stones, was
so affected by the upward thrust given to the land that its stone
lining was left projecting above the level of the earth in the form of
a small tower some eight or nine feet in height.
Frequent instances occurred of deep fissures in the surface of the
earth. Many of these remained open after the earthquake, although in
other cases they were firmly closed together before the earthquake
shocks ceased.
[Illustration: FIG. 43. FISSURES CAUSED BY THE CALABRIAN
EARTHQUAKE]
Fig. 43 represents the appearance of certain fissures in a part of
Calabria during this earthquake. These cracks, it will be noticed,
radiate or pass outward in all directions from a central point, just
like the cracks that are formed in a glass window pane when it is
fractured by a stone thrown against it.
Of course, the most violent effects were near the origin of the
earthquake at Oppido. Here the formation of deep fissures was common.
In another part of the country a number of buildings were suddenly
swallowed up in a central chasm, which almost immediately closed,
thus permanently burying all these objects.
Some idea of the force with which the fissures were afterwards closed
can be formed by reflecting on a case where, in order to recover some
of the buried articles, the ground was dug up at these points, and it
was found that the materials, human bodies and other objects, were so
jammed together as to make one compact mass.
To Sir William Hamilton a place was shown where the fissures, though,
when he saw them, they were not more than a foot in width, had opened
sufficiently wide during the shock to swallow up a hundred goats as
well as an ox.
An earthquake that caused such marked changes in the appearance of the
earth's surface, naturally made great changes in the direction of the
rivers. In one case the end of a small valley was so completely filled
with stones and dirt that the water was dammed up, producing a lake
two miles in length and one mile in breadth. In a similar manner no
less than 215 lakes were formed in different portions of Calabria.
Of course, in the flat country at the base of the Apennines,
frequent landslides occurred, the land sliding into great chasms and
continuing to move down them for considerable distances, so that in
many places pieces of land containing olive trees, vineyards, and
green fields, were bodily transported for distances of several miles.
This, moreover, was done so quietly as to leave the houses entirely
uninjured, and the trees and other vegetation continuing to grow up
with apparently no marked decrease in vitality.
As is usual in such cases, the sudden and strong blows acting on the
waters of the sea, killed great numbers of fish just as does the
explosion of dynamite at a point below the surface of the water; and
in a similar way the fish that usually live at the bottom of the sea
in the soft mud, being disturbed by the earthquake shocks, came near
the surface where they were caught in vast numbers.
It is an interesting fact that during this earthquake the volcano of
Stromboli showed a marked decrease in the volume of smoke it gave out.
Etna, however, was observed to emit large quantities of vapor during
the convulsion.
Lyell tells the following story of the Prince of Scilla, who with
many of his vassals sought safety in their fishing boats. Suddenly,
on the night of February 5th, while some of the people were sleeping
in the boat, and others were resting on a low plain near the sea,
in the neighborhood, another shock occurred, a great mass was torn
from a neighboring mountain and hurled with a crash on the plain, and
immediately afterwards a wave, twenty feet or more in height, rolled
over the level plain, sweeping away the people. It then retreated, but
soon rushed back again, bringing with it many of the bodies of the
people who had perished. At the same time all the boats were either
sunk or dashed against the beach, and the Prince with 1,430 of his
people was destroyed.
The total number of deaths caused by this earthquake in the Calabrias
and Sicily were estimated by Hamilton at 40,000. Besides these about
20,000 more perished in epidemics that followed the earthquake, or
died for lack of proper food.