The earths crust is deeply eroded in a vast area, but widespread thick sedimentary layers are depositied

Question

elsewhere. How do you think the crust will respond to the decreased load in the first area and the increased load in the other?

Answer 1

In the end, this is a matter of hydrostatics.  Continental crust is lighter then oceanic crust, so it rides higher.  But as you point out, that means that it gets eroded.  So there is uplift on the eroded areas, while the sedimentary areas tend to subside. These are among the factors contributing to deformation of the crust, in addition to the primary effect of plate tectonics.

Answer 2

Are you studying glaciation, specifically post-glacial geological processes?

You might want to look up these terms: glacial rebound, continental rebound, isostatic rebound, isostatic adjustment. (See link below.)