The force of a Glacier

Glaciers are very heavy and powerful. As a glacier flows along, the ice and rocks caught in it scrape soil and the rock from the sides and the floor of the valley,carving a deep channel. When the ice melts, it deposits thick layers of debris, called moraine, and boulders, known as erratics on the valley floor.

Picture taken from http://www.nature.com/ngeo/journal/v1/n5/images/ngeo186-i1.jpg