Formation of circular hollows and new lakes.—In the report of the Academy, we find that some plains were covered with circular hollows, for the most part about the size of carriage-wheels, but often somewhat larger or smaller. When filled with water to within a foot or two of the surface, they appeared like wells; but, in general, they were filled with dry sand, sometimes with a concave surface, and at other times convex. (See [fig. 81].) On digging down, they found them to be funnel shaped, and the moist loose sand in the centre marked the tube up which the water spouted. The annexed cut ([fig. 82]) represents a section of one of these inverted cones when the water had disappeared, and nothing but dry micaceous sand remained.
Circular hollows in the plain of Rosarno, formed by the earthquake of 1783.
Section of one of the circular hollows formed in the plain of Rosarno.
A small circular pond of similar character was formed not far from Polistena (see [fig. 83]); and in the vicinity of Seminara, a lake was suddenly caused by the opening of a great chasm, from the bottom of which water issued. This lake was called Lago del Tolfilo. It extended 1785 feet in length, by 937 in breadth, and 52 in depth. The inhabitants, dreading the miasma of this stagnant pool, endeavored, at great cost, to drain it by canals, but without success, as it was fed by springs issuing from the bottom of the deep chasm.
Vivenzio states, that near Sitizzano a valley was nearly filled up to a level with the high grounds on each side, by the enormous masses detached from the boundary hills, and cast down into the course of two streams. By this barrier a lake was formed of great depth, about two miles long and a mile broad. The same author mentions that, upon the whole, there were fifty lakes occasioned during the convulsions: and he assigns localities to all of these. The government surveyors enumerated 215 lakes; but they included in this number many small ponds.