August 1968 southwest-looking photograph of the surface of the Bucher Glacier, an outlet glacier of the Juneau Icefield, showing several glacier tables, several conical mounds of sediment-covered ice, and several small piles of sediment left on the ice surface marking the position of former mounds, Coast Mountains, Tongass National Forest, Alaska. Credit: USGS.
Moraine is an accumulation of boulders and rock fragments carried or deposited by a glacier. Ground moraine is drift left in a sheet as a glacier retreats. Terminal moraine are ridges deposited when the ice is melting prior to the glacial retreat; a series of ridges may mark pauses in the retreat. Lateral moraines are formed of debris that falls onto the glacier: when two glaciers merge their lateral moraines may unite to form a medial moraine.