A theory that explains the uplift of geosynclines
to form a new continent. The rock of the lower crust, down to the Moho at
10-30km, is basalt. Below the Moho is the upper mantle. There the great pressure
has transformed the basalt into a denser material, eclogite. As sediments pile
up on the surface, the pressure below increases, and more of the basalt turns
into eclogite. This adds eclogite to the mantle, so the level of the Moho rises.
Since the eclogite is more dense than basalt, the volume of material under the
crust decreases and the surface subsides. This allows more sediment to
accumulate to form a geosyncline.