Isostasy

"Isostasy is the state of balance, or equilibrium which exists between the extensive blocks of the earth's crust that rise to different heights." Isostasy therefore, is based on the idea that, there is a minimum depth below sea level where pressure exerted by the weight of the over-lying rocks will force the earth crust rocks to sink. Also one could look at isostasy as an ideal condition of gravitational equilibrium that controls the height of continents and ocean basin-; Or in simple terms one can say that isostasy is the state of balance, or relative equilibrium of the earth's crust. There are two interpretations of isostasy: Density of crustal rocks, and Thickness of crustal rocks.

Its important to note that, density of rocks is not homogenous within the earth crust. Rocks of low-density experience lessened gravitational attraction. This as such leads [o bulges, or continents and formation of mountain ranges. It is important to note that, gravitational pull is greatest where crustal rocks are dense This as such leads to the formation of depression. For example, ocean basins. The thickness of crustal rocks;

This belief points out that, the crust floats on a fluid, or semi-fluid mantle. The mantle as a result exerts buoyancy or upthrust on the crust. This amount of buoyancy (upthrust) corresponds to the size or thickness of the overlying crust. This means that, where the crust is thick, a large proportion will emerge above the mantle below. Where the crust is thin.