Isostasy, crustal thinning, mantle changes, and the disappearance of ancient land masses

Abstract

Current theories on geosynclinal subsidence and on disappearance of ancient land masses, such as Appalachia along the Atlantic Coast, postulate crustal thinning by subcrustal processes. Hsu proposes that changes in surface elevation are due to changes in density of the subcrustal mantle, and that crustal thinning is due to supracrustal processes, such as erosion, gravity sliding, and overthrusting from elevated regions overlying abnormally low-density mantle. Subsequent increase in mantle density due to a lowering of mantle temperature leads to subsidence of regions of thin crust.