"Such are the numbers to be met with in narratives, and if we suppose that there occurs one great earthquake in three years over the whole earth and that this involves the entombment of only 10,000 human beings, and that such has been the economy of our system for the last 4,000 years, we shall have a number representing above 13,000,000 men thus suddenly swallowed up, with countless bodies of animals of every lower class. Sir Charles Lyell then with good reason suggests that even in our own time we may yet find the remains of men and of their habitations and implements thus buried deep and embalmed, as it were, by earthquakes that occurred in the days of Moses and the Ptolemies."
Necessarily the progress of a great earthquake wave will produce great changes in the earth's surface features; for example, landslides, where immense layers of clay or other material slip or slide to a lower level and are thrown across the course of a river, causing its waters to be dammed up and then by spreading to form great lakes.
Sometimes, after vast bodies of water have been collected in this manner, disastrous floods result later from a sudden giving way of the barrier, and the loss thus caused is occasionally far greater than that directly due to the earthquake.
Permanent changes of level are frequently caused by earthquakes, as, for example, the coast of Chile during the earthquake of November 19th, 1822, where the coast for many miles was raised from three to four feet above its former plane.
In other cases the level of the ground is permanently lowered. This occurred in the Bengal earthquake in 1762, when an area of some sixty square miles suddenly sank, leaving only the tops of the higher points above water.
In some cases of changes in the level of the ground, large areas being raised in one place and lowered in another, rivers take new courses, and their old courses are completely obliterated.
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.