Glacier
Glacier
A Glacier (/ˈɡlæsiər/; from French: glace "ice") is a large, persistent body of dense ice that is constantly moving under its own weight. It forms where the accumulation of snow exceeds its ablation (melting and sublimation) over many years, often centuries.
Etymology
The term "glacier" comes from the French word glace (glah-SAY), which means ice. The word was first used in the 18th century, as a descriptive term for the large, moving ice formations found in mountainous regions.
Formation
Glaciers are formed over many years, as snow accumulates on the ground and is compressed into ice. This process, known as nivation, involves the transformation of snow to neve and finally to glacial ice. The weight of the overlying snow causes the lower layers to compact and recrystallize, forming a dense, grainy ice called firn.
Movement
Glaciers move under the force of gravity. The movement of a glacier is called glacial motion, which can occur through two processes: internal deformation and basal sliding. Internal deformation happens when the weight of the ice causes it to deform and flow. Basal sliding occurs when the glacier slides over the ground beneath it, lubricated by meltwater.
Types of Glaciers
There are two main types of glaciers: Alpine glaciers and Ice sheets. Alpine glaciers form on mountainsides and move downward through valleys. Ice sheets, also known as continental glaciers, cover vast land areas and are not confined by the landscape.
Related Terms
- Ice cap: A glacier that covers less than 50,000 km² of land area (smaller than an ice sheet).
- Ice field: An area less than 50,000 km² of ice that is not constrained by topography.
- Ice shelf: A floating extension of a glacier that extends into the sea.
- Ice stream: A region of an ice sheet that moves significantly faster than the surrounding ice.
- Moraine: A deposit of rock debris carried or deposited by a glacier.
External links
- Medical encyclopedia article on Glacier
- Wikipedia's article - Glacier
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