Glacial Landforms: Erosional and Depositional

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Landforms and Cycle of Erosion

Glacial Landforms and Cycle of Erosion

  • A glacier is a moving mass of ice at speeds averaging few meters a day.
  • Types of Glaciers: continental glaciers, ice caps, piedmont glaciers and valley glaciers.
  • The continental glaciers are found in the Antarctica and in Greenland. The biggest continental ice sheet in
  • Ice caps are the covers of snow and ice on mountains from which the valley or mountain glaciers originate.
  • The piedmont glaciers form a continuous ice sheet at the base of mountains as in southern Alaska.
  • The valley glaciers, also known as Alpine glaciers, are found in higher regions of the Himalayas in our country and all such high mountain ranges of the world.
  • The largest of Indian glaciers occur in the Karakoram range, viz. Siachen (72 km), while Gangotri in Uttar Pradesh (Himalayas) is 25.5 km long.
  • A glacier is charged with rock debris which are used for erosional activity by moving ice.
  • A glacier during its lifetime creates various landforms which may be classified into erosional and depositional landforms.

Glacial Erosional Landforms

Glacial Erosional Landforms-glaciated topography

Cirque/Corrie

  • Hollow basin cut into a mountain ridge.
  • It has steep sided slope on three sides, an open end on one side and a flat bottom.
  • When the ice melts, the cirque may develop into a tarn lake.

Glacial Trough

  • Original stream-cut valley, further modified by glacial action.
  • It is a ‘U’ Shaped Valley. It at mature stage of valley formation.
  • Since glacial mass is heavy and slow moving, erosional activity is uniform – horizontally as well as vertically.
  • A steep sided and flat bottomed valley results, which has a ‘U’ shaped profile.

Hanging Valley

  • Formed when smaller tributaries are unable to cut as deeply as bigger ones and remain ‘hanging’ at higher levels than the main valley as discordant tributaries.
  • A valley carved out by a small tributary glacier that joins with a valley carved out by a much larger glacier.

Arete

  • Steep-sided, sharp-tipped summit with the glacial activity cutting into it from two

Horn

  • Ridge that acquires a ‘horn’ shape when the glacial activity cuts it from more than two sides.

D-Fjord

  • Steep-sided narrow entrance-like feature at the coast where the stream meets the coast.
  • Fjords are common in Norway, Greenland and New Zealand.

D-Fjord - norway - new zealand

Glacial Depositional Landforms

Glacial Depositional Landforms - eskers-morains

Outwash Plain

  • When the glacier reaches its lowest point and melts, it leaves behind a stratified deposition material, consisting of rock debris, clay, sand, gravel etc. This layered surface is called till plain or an outwash plain.

Esker

  • Winding ridge of un-assorted depositions of rock, gravel, clay etc. running along a glacier in a till plain.
  • The eskers resemble the features of an embankment and are often used for making roads.

Kame Terraces

  • Broken ridges or un-assorted depositions looking like hump in a till plain.

Drumlin

  • Inverted boat-shaped deposition in a till plain caused by deposition.

Kettle Holes

  • Formed when the deposited material in a till plain gets depressed locally and forms a basin.

Moraine

  • General term applied to rock fragments, gravel, sand, etc. carried by a glacier.
  • Depending on its position, the moraine can be ground moraine and end moraine.

Glacial Cycle of Erosion

Youth

  • The stage is marked by the inward cutting activity of ice in a cirque.
  • Aretes and horns are emerging. The hanging valleys are not prominent at this stage.

Maturity

  • Hanging valleys start emerging. The opposite cirques come closer and the glacial trough acquires a stepped profile which is regular and graded.

Old Age

  • Emergence of a ‘U’-shaped valley marks the beginning of old age.
  • An outwash plain with features such as eskers, kame terraces, drumlins, kettle holes etc. is a prominent development.

Why are world’s highest mountains at the equator?

  • Ice and glacier coverage at lower altitudes in cold climates is more important than collision of tectonic plates. [Glacial erosion is very strong because of huge boulders of rocks carried by the glacial ice that graze the surface. Though ice moves only few meters a day, it can take along it huge rocks that can peal the outer layers.]
  • Scientists have solved the mystery of why the world’s highest mountains sit near the equator.
  • Colder climates are better at eroding peaks. In colder climates, the snowline on mountains starts lower down, and erosion takes place at lower altitudes.
  • In general, mountains only rise to around 1,500m above their snow lines, so it is the altitude of these lines — which depends on climate and latitude — which ultimately decides their height.
  • At low latitudes, the atmosphere is warm and the snowline is high. Around the equator, the snowline is about 5,500m at its highest so mountains get up to 7,000m.
  • There are a few exceptions [that are higher], such as Everest, but extremely few.
  • When you then go to Canada or Chile, the snowline altitude is around 1,000m, so the mountains are around 2.5km.

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  1. Amazingly concise and lucid information man, makes me check comment every-time to see if you have mentioned anything here.

 

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