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A glacier is a long-standing mass of ice that moves very slowly downhill. They are found at high altitude, even on high mountains close to the equator, and at lower altitude in high latitudes close to the North and South Poles. The formation of glaciers and the process by which they shape the landscape around them is called glaciation.
Glaciers
The Khumbu Glacier, Nepal
Glaciers once covered large areas of the Earth, and in these places they shaped the landscape around them. Long after they have gone the legacy of ancient glaciers lives on - for example in the highlands of Great Britain in areas such as the Lake District.
There are three processes by which glaciation affects the landscape: erosion, transportation, and deposition
Weathering
The predominant weathering process is freeze thaw weathering. Freeze-thaw process describes the action of glacial meltwater on joints, cracks and hollows in rock. At cold temperatures (below freezing point) water in cracks freezes. As the water freezes it expands and causes the cracks to widen. When the temperature rises, the water thaws and contracts. This continuous process eventually causes rocks to break up. For this to be effective the air temperature needs to fluctuate around freezing point.
Freeze thaw weathering leaves behind a jagged landscape and produces angular rock fragments.
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