"Peeling off" of the layers of rock is called? Describe how this process happens?

"Peeling off" of outer layers of rocks happens through the process of exfoliation. This is a result of thermal stresses developed in the rocks and is an example of thermal weathering (which is a form of physical weathering).

Rocks, when exposed to temperature differences (especially between the day and night times), undergo exfoliation. The rocks are heated by sunlight or forest fires and gets really cold at night times. However, the inner layers are somewhat protected from these temperature variations. It is also to be noted that various minerals have different responses to temperature increase. Thus, outer layers of the rocks will expand during daytime and contract during night time. This expansion and contraction of outer layers is different that that of inner layers, resulting in peeling off of outer rock layers.

Hope this helps.