The glacier retreats when the rate of forward motion of a glacier is slower than the rate of ablation
Answer: D
Explanation:
The Glacial ice moves with respect to the gravity, glacial ice always flows downwards in response to gravitational force and the front line of the glacier is either calving or melting into water which is also referred as shedding icebergs.
When the rate of flow of the glacier is quicker than the rate of melting or ablation, the advancing end of the glacier moves forward. Whereas, the rate of forward motion of the glacier is about the same as the rate of defrosting, the glacier edge doesn't intend to move at all, and if the rate of glacier's flow lacks behind the rate of defrosting, then it retreats (moves backward).
