ABSTRACT
Examination of the karst system may offer several distinctive contributions to our general understanding of thresholds in geomorphology. First, attention is focused upon thresholds in chemical reactions and resistances. Most work has considered physical, especially mechanical, thresholds. Second, it is concerned with a few types of rocks, where other systems must consider all rocks. Third, in most geographical regions, more water is in storage and transit underground than is at the surface. Finally, concepts of climatic control have been investigated more thoroughly in karst geomorphology than in other branches of the subject, offering a special opportunity to investigate climatic thresholds of morphogenesis. These four points are considered in turn in this chapter. Bulk chemical purity, petrography, lithology, structural features, and so on, of the karst rocks are included under the general heading “rock control.” Fracture density determines the mechanical strength of limestones and dolomites subject to karstification in a more real sense than do the compressive tests.
