Ridge Push from asthenospher is responsible for isostatic uplift.
Step-by-step explanation:
A driving force for the motion of the plates in plate tectonics which occurs at the mid ocean ridges is called as Ridge push. It is caused due to the rigid lithosphere that slides down from hot and raised asthenosphere under mid ocean ridges.
The fresh crust and upwelling mantle which are less dense and hotter that the crust and mantle that are surrounding, which are cool and they come in contract with age until equilibrium is reached with the old crust.
This causes an Isostatic response. Due to this the young regions that are nearer to the plate boundary rises above older regions.