Question: How sea's converts in to the deserts ie -Thar India? 

Answer: Need more detail...  Continental uplift (geological plate techtonics) can bring the sea floor above the water.  Particularly in India, because it is its own subcontinent that has been on the move a lot over the last couple of million years.  However, that does not mean it will become desert.  Forests become deserts when the trees die or are cut down (there is a huge problem with forest clearing in India) and the soil erodes, leaving nothing for plants to grow on.
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