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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).
Glacial speed is affected by factors such as slope, ice thickness, snowfall, longitudinal confinement, basal temperature, meltwater production, and bed hardness. A few glaciers have periods of very rapid advancement called surges. These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous movement state ...
This gives the glacier a much smoother surface on which to move as opposed to a harsh surface that tends to slow the speed of the sliding. Although meltwater is the most common source of basal sliding, it has been shown that water-saturated sediment can also play up to 90% of the basal movement these glaciers make.
Glacial surges in the Karakoram occur in the presence of "extreme uplift and denudation." [7] In 1980, there were several mini-surges of Variegated Glacier in Alaska. Mini surges typically show lag times of basal flow of 5–10 hours, which correlates to differences between the surging part of a glacier and the output of water and sediment. [14]
As the glacier transitions below the icefall, the topography of the glacier bed plays a crucial role in modifying its dynamics, leading to a flatter and/or wider bed that significantly reduces the velocity of ice movement. This change in speed and pressure causes crevasses to close up, resulting in a smoother glacier surface that presents fewer ...
A National Park Service report on Alaska's glaciers noted glaciers within Alaska national parks shrank 8% between the 1950s and early 2000s and glacier-covered area across the state decreased by ...
[1] [18] In 2012 a significant acceleration of Jakobshavn was observed, with summer speeds up to 4 times its speed in the 1990s, and average annual speeds of 3 times its 1990s speed. Movement reached more than 17,000 metres per year. Jakobshavn has afterwards slowed to near its pre-1997 speed, with the terminus retreat still occurring until 2015.
The Columbia Glacier, a glacier in Prince William Sound on the south coast of the U.S. state of Alaska, is one of the fastest moving glaciers in the world, and has been retreating since the early 1980s. It was named after Columbia University, one of several glaciers in the area named for elite U.S. colleges by the Harriman Alaska Expedition in ...