Page:Popular Science Monthly Volume 2.djvu/534

516 to 4,000 feet high, extending 60 miles, but of not more than 18 inches in average width.

During the Calabrian earthquake of 1783 the surface of the ground opened and closed in immense fissures, by means of which new lakes were formed and others drained or were dried up.

At Jerocarne the earth is described, by Sir Charles Lyell, as lacerated in an extraordinary manner. "Fissures ran in every direction, like cracks in a broken pane of glass."



In another instance, several dwellings were engulfed in a fissure, and were found to be jammed with their contents into a compact mass. Chasms of immense length and depth were formed. Some were crescent-shaped, and a mile in length.

The plains of Calabria were covered in many places with circular hollows from one foot to three or four feet in diameter. Some of these were filled with water, others with dry sand.

Fig. 4 is a section of one of these circular holes, which appears to be funnel-shaped.

But changes in the earth's crust occur during earthquakes, on a still grander scale. Evidences of local disturbance, however disastrous it may have been, are often effaced if not forgotten in a few centuries frequently in a few years. But the slow upheaval of mountain-chains and the dislocation of strata through profound depths are results which alter at last the physical aspect and contour of the surface of the globe. It would not be proper, however, to say that these changes are caused by earthquakes, but rather that the earthquake vibration is a concomitant of the displacement by which they are produced.

Humboldt, Lyell, Dana, and other authorities, consider earth