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Most lakes in the world occupy basins scoured out by glaciers. Glacial motion can be fast (up to 30 metres per day (98 ft/d), observed on Jakobshavn Isbræ in Greenland) [1] or slow (0.5 metres per year (20 in/year) on small glaciers or in the center of ice sheets), but is typically around 25 centimetres per day (9.8 in/d). [2]
Ice caps have an area less than 50,000 km 2 (19,000 sq mi) by definition. Glacial bodies larger than 50,000 km 2 (19,000 sq mi) are called ice sheets or continental glaciers. [16] Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces.
[1] [2] They can be up to 10 meters wide and are typically found on ice sheets and flat areas of a glacier in a region of transverse crevasses. Moulins can reach the bottom of the glacier, hundreds of meters deep, [3] [4] [5] or may only reach the depth of common crevasse formation (about 10–40 m) where the stream flows englacially. [6]
Glacial plucking both exploits pre-existing fractures in the bedrock and requires continued fracturing to maintain the cycle of erosion. [4] Glacial plucking is most significant where the rock surface is well jointed or fractured or where it contains exposed bed planes, as this allows meltwater and clasts to penetrate more easily. [2]
Basal sliding is the act of a glacier sliding over the bed due to meltwater under the ice acting as a lubricant.This movement very much depends on the temperature of the area, the slope of the glacier, the bed roughness, the amount of meltwater from the glacier, and the glacier's size.
Franz Josef Glacier in New Zealand Features of a glacial landscape. Glacier morphology, or the form a glacier takes, is influenced by temperature, precipitation, topography, and other factors. [1] The goal of glacial morphology is to gain a better understanding of glaciated landscapes and the way they are shaped. [2]
Glacial motion can also cause changes in subglacial stream systems, and there are feedbacks present between the two. [7] As subglacial water pressure increases, the speed of glacial sliding increases. The glacier encounters bumps in the bedrock as it slides: as a result, cavities are created between the ice and the bed. [7]
Termination I, also known as the Last Glacial Termination, is the end of Marine isotope stage 2; Termination II is the end of Marine Isotope Stage 6; Termination III is the end of Marine Isotope Stage 8; Termination IV is the end of Marine Isotope Stage 10, and so forth. [1] [2]