The phenomenon in which meltwater accumulates at the base of a glacier, so that the mass of the glacier slides on a layer of water or on a slurry of water and sediment.
A vast sheet of ice that spreads over thousands of square kilometers of continental crust.
A low, sinuous ridge of till that develops when the terminus (toe) of a glacier stalls in one position for a while.
The boundary between the zone of accumulation and the zone of ablation on a glacier.
A boulder or cobble that was picked up by a glacier and deposited hundreds of kilometers away from the outcrop from which it detached.
A ridge of sorted sand and gravel that snakes across a ground moraine; the sediment of an esker was deposited in subglacial meltwater tunnels.
The forward movement of a glacier's toe when the supply of snow exceeds the rate of ablation.
The movement of a glacier's toe back toward the glacier's origin; glacial retreat occurs if the rate of ablation exceeds the rate of supply.
Scratches or troughs carved into rock by the sediment embedded in ice at the base of a flowing glacier.
A glacially carved tributary valley whose floor lies at a higher elevation than the floor of the trunk valley.
An interval of time in which the climate was colder than it is today, glaciers occasionally advanced to cover large areas of the continents, and mountain glaciers grew; an ice age can include many glacials and interglacials.
A circular depression in the ground made when a block of ice calves off the toe of a glacier, becomes buried by till, and later melts.
Layers of fine-grained sediments deposited from the wind; large deposits of loess formed from fine-grained glacial sediment blown off outwash plains.
A strip of sediment in the interior of a glacier, parallel to the flow direction of the glacier, formed by the lateral moraines of two merging glaciers.
Climate cycles that occur over tens to hundreds of thousands of years, because of changes in Earth's orbit and tilt.
The deformational process in which mineral grains behave like plastic and, when compressed or sheared, become flattened or elongate without cracking or breaking.
A lake formed to the south of a continental glacier as a result of enhanced rainfall during an ice age.
A glacially eroded hill that becomes elongate in the direction of flow and asymmetric; glacial rasping smoothes the upstream part of the hill into a gentle slope, while glacial plucking erodes the downstream edge into a steep slope.
Our planet during periods in the Precambrian when its entire surface was ice covered.
A glacier that exists in regions where it is warm enough for liquid water to occur in films between the grains of ice.