Chapter 28, Problem 17RQ

To determine

The conditions under which a glacier front advances and the reason for glacier retreat.

Answer to Problem 17RQ

Glacier advances when accumulation exceeds ablation and the glacier retreats when ablation exceeds accumulation.

Explanation of Solution

The mass of the glacier changes from season to season due to several reasons. In the winter season, glacier grows as the snow gets accumulated over the glacier. This process of adding snow over the glacier is known as accumulation. On the other hand, when the glacier loses the snow due to certain reasons, this process is known as ablation.

When accumulation and ablation are equal, then the size of the glacier remains constant. But, when accumulation surpasses ablation, the glacier advances, it means that the glacier will grow. In case when ablation surpasses accumulation, glacier retreats, it means that the glacier will shrink.

Conclusion:

Therefore, the glacier front advances when accumulation surpasses ablation and the glacier retreats when ablation exceeds accumulation.