1. It's the erosion of granite rock.

2. The Aquifers of this region are made up of fractures in the granite rock

3. The Kerala cave - temples of a rather indeterminate authorship , however , form an important landmark in southern cave architecture combining as they do the features of the Pandya and the Adigaiman cave - temples of the adjoining territory and like them are essentially of the Pallava Mahendra - style model both in their granite rock material and the plan and technique of excavation , though with an import often of some Chalukyan motifs .