As erosion removes the tops of mountains, the crust will rise upwards. this is an example of orogenesis isostatic adjustment normal faulting mountain building due to uplift

As erosion removes the tops of mountains, the crust will rise upwards. This is an example of isostatic adjustment. This movement of of land once burdened by ice-age glacier,is also known as the Mattress Effect. Erosion, deposition, water loading, desiccation, ice accumulation, and deglaciation can be the reason for this movement.

Isostatic adjustment