But even these figures give only a meagre idea of the vast loss of life that has occurred during the past. It is said that during the reign of Justinian, earthquakes repeatedly shook the whole Roman world. The city of Constantinople was visited by earthquake shocks that continued at intervals for forty days. Deep chasms were opened in the earth and huge masses were thrown into the air. Enormous sea-waves were formed. At Antioch, during the earthquake of May 20th, a. d. 526, 250,000 people are believed to have been killed.
On the 31st of July, a. d. 365, in the second year of Valentinian, a dreadful earthquake shook the Roman world, and a great wave rolled in from the Mediterranean and swept two miles inland, carrying ships over the tops of houses. During this earthquake 50,000 people lost their lives at Alexandria.
In the earthquake of Messina in 1692, 74,000 people are said to have been killed; and, according to other accounts, 100,000. In the year a. d. 602, another earthquake at Antioch killed 60,000 people.
During the earthquake of Quito, in 1797, Humboldt estimates that 40,000 natives were either buried in crevices in the earth, under the ruins of buildings, or were drowned in lakes and ponds that were temporarily formed.
In this connection Mallet writes as follows:
"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.