Glacier

Glacier is a large, slow-moving mass of ice, formed from compacted layers of snow, that slowly deforms and flows in response to gravity and high pressure. The process of glacier establishment, growth and flow is called glaciation. Glaciers are found in mountain ranges of every continent except Australia, and also in the polar regions.

Formation

Glaciers form where the accumulation of snow and ice exceeds ablation. The area in which a glacier forms is called a 'Glacial zone'. Over time, the layers of snow compress under their own weight and transform into ice. This process is known as 'Firnification'.

Types of Glaciers

There are two main types of glaciers: 'Alpine glaciers', which form on mountainsides and move downward through valleys, and 'Ice sheets', which spread out from their centers.

Alpine Glaciers

Alpine glaciers form on the crests and slopes of mountains. A cirque glacier occupies a bowl-shaped basin at the head of a mountain while a valley glacier is a long, narrow glacier that fills a valley.

Ice Sheets

Ice sheets are much larger than alpine glaciers. They are dome-shaped and spread out from their center. Ice sheets cover Greenland and Antarctica.

Movement

Glaciers move through a combination of internal deformation and sliding at the base. This is called 'Glacial motion'.

Impact on the Environment

Glaciers have a huge impact on the environment. They carve out landscapes, creating valleys and mountains, and deposit large amounts of rock and debris. This process is known as 'Glacial erosion'.

See Also

• Ice age
• Glacial period
• Glacial landforms
• Glacial retreat

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