The term “Isostasy” is derived from “Isostasios”, a word of Greek language meaning the state of being in balance.
We know that mountains have many peaks and relatively great heights.
Similarly plateau and plain have flat surfaces.
Oceanic beds and trenches have greater depths.
There is a great difference in height among these features.
The earth is rotating while keeping perfect balance among its various features.
Thus, our earth is considered to be in isostatic equilibrium.
There is no complete isostatic balance over the globe.
The earth is unstable.
Endogenetic forces often disturb the crustal balance.
The regular earthquakes and volcanic eruptions along a particular belt do not signify any balance but a sort of adjustment is needed continuously.
Endogenetic forces and their tectonic effects are the causes of imbalance on the surface.
Exogenetic forces are trying to eliminate the differences on the surface of the earth and in this process they are peeling off, transporting down to far-flung places, and depositing them.
In this process, isostatic balance is maintained by the underneath flowage of material by subsidence at the place of deposition and upliftment at the peeling of place in their proportion to the denudation.