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Wed 13 Apr 2011 00:58:52 | 0 comments
The word isostasy is derived from a Greek word meaning 'in equipoise' or 'in balance'. The theory of isostasy states that a great continental mass must be formed of lighter materials than that supposed to constitute the ocean floors and further, in order to compensate for its greater height these lighter continental material must extend downward to some distance under the continent and below the ocean floor level, in order that unit areas beneath oceans and continents may remain in stable equilibrium .
Any loading due to sedimentation , deposition or intrusion of igneous materials etc or unloading due to denudation or melting of ice will , therefore, disturb the balance. Compensation in the form of depression or elevation will follow to restore the state of hydrostatic balance. The state of balance can be maintained only if there is a continuous compensation at depth.
Through erosion, material is being removed from the top of the mountains which therefore are becoming lighter. Some other materials should therefore move into the roots of the mountains at depth in the interior of the earth. This movement is termed compensation. The lithosphere behaves like a wooden block floating on water. If a load is put above the wooden block, then it will depress. Conversely , when it is unloaded , the wooden block will rise in response to it.