[CHAPTER XXXIV]
THE CAUSES OF EARTHQUAKES
Earthquakes occurred long before man appeared on earth. It is natural, therefore, that our early ancestors, experiencing these unwelcome phenomena, vaguely endeavored to explain their causes. These early attempts at explanation have in many cases been of an exceedingly fanciful character.
The ancient Mongolians and Hindoos declared that earthquakes are due to our earth resting on a huge frog and that they occur whenever the frog scratches its head.
In Japan, where earthquakes are very common, the ignorant people even at a much later day declared that there exists in the depth of the sea an immense fish which, when angry, dashes its head violently against the coast of the island, thus making the earth tremble. This is, doubtless, the biggest fish-story extant.
Another folk-lore explanation in Japan attributes the cause of the tremblings of the earth to a subterranean monster whose head lies in the north of the island of Hondo, while his tail lies between the two principal cities. The shaking of his tail causes earthquakes.
Fantastic and foolish as these explanations are, it is worthy of note that the first of the Japanese explanations shows no little observation on the part of the people, since it locates the starting-points of earthquakes as being not on the land, but on the bottom of the sea. In point of fact, nearly all the great earthquakes in Japan seem to start somewhere between the coasts of the islands on the sea-bottom that leads down to a very deep part of the Pacific known as the Tuscarora Deep.
Many years ago nearly everyone believed that earthquakes were caused solely by the forces that produce volcanic eruptions; that all earthquakes, whether in the neighborhood of active volcanoes, or at great distances therefrom, were to be regarded solely as volcanic in their origin.
It is now recognized that the most severe and far-reaching earthquakes have no immediate connection with volcanic explosions, but are due to the sudden slippings of the earth's strata over lines of faults; or, in other words, earthquakes are most frequently of the tectonic type.