A desert from the destruction of forests.—Between the dolines is found a veritable desert with jutting limestone angles and little if any vegetation. The water which falls upon the surface either runs off quickly or goes down to the subterranean caverns by which so much of the country is undermined. Hence it is that the gardens which furnish the sustenance for the scattered population are all included within the narrow limits of the doline bottoms. Although to-day so largely a barren waste, we know that the Karst upon the Adriatic was in remote antiquity a heavily forested region and that it supplied the myriads of wooden piles upon which the city of Venice is supported. The vessels which brought to this port upon the Adriatic its ancient prosperity were built from wood brought from this tract of modern desert. In the days of Venetian grandeur the fertile terra rossa formed a veneer upon the rock surface of the Karst and so retained the surface waters for the support of the luxuriant forest cover. After deforestation this veneer of rich soil was washed by the rains into the dolines or into the few stream courses of the region, thus leaving a barren tract which it will be all but impossible to reclaim ([plate 6 A]).
Fig. 198.—Sharp Karren of the Ifenplatte Allgäu (after Eckert).
Upon the steeper slopes over the purer limestones, the rain water runs away, guided by the joints within the rock. There is thus etched out a more or less complete network of narrow channels ([Fig. 190], [p. 181]), between which the remnants rise in sharp blades to produce a structure often simulated upon the fissured surface of a glacier that has been melted in the sun’s rays ([Fig. 401]). These almost impassable areas of karst country are described as Schratten or Karrenfelder ([Fig. 198]).
The ponore and the polje.—To-day large areas of the Karst are devoid of surface streams, nearly all the surface water finding its way down the crevices of the limestone into caverns, and there flowing in subterranean courses. The foot traveler in the Karst country is sometimes suddenly arrested to find a precipice yawning at his feet, and looking down a well-like opening to the depth of a hundred feet or more, he may see at the bottom a large river which emerges from beneath the one wall to disappear beneath the other. These well-like shafts are in the Austrian Karst known as Ponores, while to the southward in Greece they are called Katavothren.
Plate 6.
A. Barren Karst landscape near the famous Adelsberg grottoes. (Photograph by I. D. Scott.)
B. Surface of a limestone ledge where joints have been widened through solution. Syracuse, N.Y. (Photograph by I. D. Scott.)