Formation of collapse calderas

Abstract

Collapse calderas are common in many volcanic regions, but the mechanics of their formation is not well understood. I propose that collapse calderas may form as a result of the growth of associated shallow magma chambers. Excess magmatic pressure in a shallow chamber gives rise to tensile stresses at the surface, but the location and magnitude of the maximum tensile stress depend on the shape of and depth ( d ) to the top of the chamber. This model indicates that penny-shaped chambers, i.e., sill-like chambers of circular horizontal cross sections, are most likely to initiate collapse calderas. For such a chamber with horizontal radius a , the higher the a/d (radius/depth) ratio, the greater the probability of forming a collapse caldera.