The Rusk Glacier is a medium-sized glacier

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

 located on the eastern face of Mount Adams

Mount Adams (Washington)

Mount Adams is a potentially activestratovolcano in the Cascade Range and the second-highest mountain in the U.S. state of Washington.Adams is a member of the Cascade Volcanic Arc, and is one of the arc's largest volcanoes,...

 in Washington. Starting at an elevation of over 10200 feet (3,109 m) at just below The Castle, the glacier flows eastward down slope. A significant portion of the glacier is covered by rock debris and in the middle of the glacier, at about 9200 feet (2,804.2 m), there is a small ice-free island of rock. The glacier terminates at about 7500 ft (2,286 m) at its rock-covered moraine

Moraine

A moraine is any glacially formed accumulation of unconsolidated glacial debris which can occur in currently glaciated and formerly glaciated regions, such as those areas acted upon by a past glacial maximum. This debris may have been plucked off a valley floor as a glacier advanced or it may have...

. The glacier has decreased in surface area by 23% between 1904 and 2006.

The glacier is named for Claude Ewing Rusk, who made the first ascent of the Castle in 1921.