Glacial Drift: material
deposited by a glacier.
Two types of drift are Till
(unsorted, unstratified debris deposited directly from ice) and Stratified Drift (sorted and stratified debris
deposited from glacial meltwater).
landforms composed mostly of till that form
on or within a glacier, or a re left behind when the glacier melts.
Moraines: low ridges that form on each side of a glacier
largely from rocks falling from valley walls.
Moraine: ridge that forms in the middle of a glacier when
two valley glaciers merge and combine lateral moraines.
End Moraines: ridges that form when a glacier achieves equilibrium
for a period of time before retreating. The front edge of the glacier
remains stationary while the conveyor belt of ice brings down more material.
A glacial advance will destroy an end moraine.
Ground Moraine: the uneven blanket
of till between the other moraines.
Deposits are the most prominent at the end of the glacier.
They consist of:
Outwash: sand and
gravel washed out of the glacier by running water.
Valley Train: outwash
deposited in a valley (common in areas of alpine glaciation).
Outwash Plain: braided
meltwater streams deposit sediment over a wide area (common in areas of
in outwash plains formed by the melting of buried blocks of ice.
Kettle Lakes: Kettles
now filled with water.
Esker: long, narrow,
winding ridge formed by deposition from a stream flowing within or at the
base of the ice.
mound formed where meltwater flowed into a depression or hole in the ice.
Eskers and Kames
are common features of continental glaciation, but are usually destroyed
in alpine settings.
elongate hills (400-800 m long, 8-60 m high) that are steeper on one end.
The steeper end faces the direction from which the ice advanced. They form
swarms near the outer edge of continental glaciers and appear to have been
molded from glacial drift by the advancing ice.
meltwater may pond on the perimeter of the melting glacier.
Sedimentation in such lakes produces a flat surface, recognizable
long after the water has drained away.
In some lakes, the lake drained away in stages and former shorelines
Rivers draining these lakes may carve large valleys, which are later
occupied by much smaller rivers = underfit streams (e.g., the Minnesota River
occupies a broad valley cut by Glacial River Warren as it drained Glacial
Annual changes in deposition can produced Varved