crust–mantle model

crust–mantle model, postulation of conditions that would explain the phenomena observed about the crust, the mantle, and their interface. Many years ago, seismic evidence showed a discontinuity, called the Mohorovičić Discontinuity, anywhere from 3 to 60 kilometres (about 2 to 40 miles) beneath the Earth’s surface. The model used to explain this discontinuity and the nature of volcanic materials envisions a crust of lower density siliceous and aluminous material, such as granite, floating on a...