What is isostatic adjustment?

Question

What is isostatic adjustment?

Answer 1

The crust of the Earth is buoyant on the mantle because it is less dense. When the volume of the crust changes due to mountain building or erosion, it has to sink or rebound accordingly.

There are 2 popular models for isostatic rebound: Airy and Pratt. The Airy model is the most accepted and taught. The Airy model proposed there are "roots" beneath crustal thicknesses that keep in buoyant on the mantle.

Here is a good article that probably explains it better than I do: http://en.wikipedia.org/wiki/Isostasy