What is Isostasy? Meaning and Definition.

A wide variety of landforms such as mountains, dissected plsteaus, flat plains, low lying Ocean basins, etc. exists on the earth surface. These landforms differ from each other in respect of their size, height, extent, etc., and yet all of them exist in a state of isostatic balance according to a definite law. There must be some unseen force behind creating such balance. It is known as isostasy.

Isostasy :

The word 'isostasy' has been derived from the Greek word 'iso-stasious' which means 'equal position'. In other words the gravitational adjustment of Earth's crust is isostasy, a state of balance. The term isostasy was first used by the famous American geophysicist C.E. Dutton According to him the doctrine of isostasy implies a position or condition of mechanical equilibrium under the control of of natural laws between the high mountain parts and low lying basins and oceanic parts over the rotating Earth.

Various concepts of Isostasy :

All scholars believe in the doctrine of Isolation. However, their presentation and explanation is different.

1. Pratt's Concept : According to Pratt, inverse relation exists between height and density. Therefore, all the landforms above the level of compensation have different densities, but below it equal density exists.

To prove his point, he made an experiment. He took some blocks of iron, lead, antimony and zinc of different sizes and densities but equal weight and put them into a basin filled with mercury. The level at which they sink equally is called the 'line of compensation'.

Airy's Concept : Airy was a British astronomer. On the basis of the principles of flotation he formulated another hypothesis which appears to be more authentic. He said that The Rocks of different land masses of the earth have the same density.

To prove his point, Airy made an experiment. Two blocks of iron of the same density but different height and put them in Mercury field basin. This blocks sink to different depths according to their size. The highest block was found to sink to the greatest depth.

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