Isostatic movement & Eustatic movement
Isostatic Movement - Isostasy is the state of equilibrium or balance in Earth's crust. Isostatic movement involves vertical movement under the action of floatation displacement between rock layers of differing density and mobility to achieve balanced crustal columns of uniform mass above a level of compensation in which the topographic elevation is inversely related to underlying rock density.
Example - Mountains have deep roots.
The Scandinavian mountains are experiencing melting of ice sheet and consequently a gradual rising of the land is happening which is evident from a series of raised beaches.
Reason -
Since, we know that the density of continental crust is lower than the density of oceanic crust. So, to maintain stability, i.e., to exert uniform pressure inside; the continental crust is thicker than the oceanic crust.
Also, due to exogenic forces, erosion/weathering took place in mountains and the eroded particles settled down in the oceans. This disturbed the deliciated balance. Thus, to maintain balance, the earth pushes the crust boundary bit downward along continental crust and bit upward along oceanic crust.
In this process, some portion of the mantle gets converted into crust along continents while some portion of the crust along ocean gets converted into mantle.
All these movements which results in maintaining the deliciated balance are called Isostatic movement.
Eustatic Movement - It involves world wide movement of sea level resulting from changes in the total volume of liquid sea water or the capacity if the ocean basin.
Example - Convection in mantle would arch up oceanic ridges and displaced water from the ocean basin, as a result the capacity of ocean basin decreases and the sea level increases.
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Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own.
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