What is definition of isotasy?

Answer 1

Isotasy is suppose to be spelt as Isostasy which means:The equilibrium that exists between parts of the earth's crust, which behaves as if it consists of blocks floating on the underlying mantle, rising if material (such as an ice cap) is removed and sinking if material is deposited.

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Answer 2

Isostasy is the balance between the floating lithospheric plates and the underlying asthenosphere in the Earth's crust. It explains how the Earth's crust floats on the semi-fluid asthenosphere to maintain equilibrium. Changes in the thickness and density of the crust can cause adjustments in isostatic equilibrium, leading to processes like subsidence and uplift.