isostasy

isostasy (īsŏs`təsē): see continent.

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isostasy

Theory describing the mass balance in the Earth's crust, which treats all large portions of the crust as though they were floating on a denser underlying layer, about 70 mi (110 km) below the surface. In this theory, a mass above sea level is supported below sea level, so high mountains must be regions where the crust is very thick, with deep roots extending into the mantle. This is analogous to an iceberg floating on water, in which the greater part of the iceberg is under water.

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isostasy [ī′säs·tə·sē]

(geophysics)

A theory of the condition of approximate equilibrium in the outer part of the earth, such that the gravitational effect of masses extending above the surface of the geoid in continental areas is approximately counterbalanced by a deficiency of density in the material beneath those masses, while deficiency of density in ocean waters is counterbalanced by an excess in density of the material under the oceans.