A glacier is a large, slow moving river of ice, formed from compacted layers of snow, that slowly deforms into ice and flows in response to gravity. Glacier ice is the largest reservoir of fresh water on Earth, and second only to oceans as the largest reservoir of total water. Mendenhall Glacier is a glacier about 12 miles long located in Mendenhall Valley, about 12 miles from downtown Juneau, Alaska. The Mendenhall Glacier is a tide-water glacier, meaning that it flows into the sea, while an Apron Glacier is a glacier that forms and remains on a mountainside at high elevation. The Menmdenhall glacier has, over a period of time, receded and has created its own lake and moraine.