Answer :
Glaciers must advance continuously in order to form valleys. Although glaciers appear to be enormous, solid slabs of ice, they really move extremely slowly and are hard to see with the unaided eye.
The weight of the ice exerts pressure on the glacier, causing it to distort. The glacier slides as a result of these changes thanks to the meltwater at its base. As glaciers must continually advance in order to carve out valleys, it is this movement that permits the creation of glaciers. Glaciers must advance continually to form valleys.
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