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सेमिनार: अंग्रेज़ी सीखने का अवसर (23 सितंबर: दोपहर 3 बजे)
Glaciers
Nov 28, 2013

Glaciers are usually formed by fallen snow that gets compressed into solid ice over a period of time. This snow keeps on freezing and thawing and finally gets converted into ice. This ice gets compacted and firmer when a new layer of snow falls over it and compresses it under pressure. This is a constant process, making the glacier thicker and bigger over a period of time.

Glaciers are also known as 'rivers of ice' because they are not stationary but moving constantly like the water of a river; only much slower, from a few millimeters a day to a few meters a day. 

Glaciers have played an important role in the shaping of landscapes in the middle and high latitudes and in alpine environments. Their ability to erode soil and rock, transport sediment, and deposit sediment is extraordinary.

Glaciated landforms (erosional and depositional) :

Glacial erosion consists of two processes: (i) plucking or the tearing away of blocks of rock which have become frozen into the base and sides of a glacier, and (ii) abrasion or the wearing away of rocks beneath a glacier by the scouring action of the rocks embedded in the glacier. Some landforms are discussed below:

Cirque :

Cirques are the most common of landforms in glaciated mountains. They are deep, long and wide troughs or basins with very steep concave to vertically dropping high walls at its head as well as sides. A lake of water can be seen quite often within the cirques after the glacier disappears. Such lakes are called cirque or tarn lakes. 

Horns and Serrated Ridges :

Horns form through head ward erosion of the cirque walls. If three or more radiating glaciers cut headward until their cirques meet, high, sharp pointed and steep sided peaks called horns form. 

Glacial stairways :

The advancing ice of glaciers carves out giant stairways through the process of abrasion and plucking of step faults coming across the path of moving glaciers

Moraines :

A valley glacier carries a large amount of rock waste called moraine. These are the depositional landforms. The moraine forming along the sides of a glacier is called lateral moraine; that along the front of a glacier is called terminal moraine; that at the bottom of a glacier is the ground moraine. 

Drumlins :

These are the swarms of rounded hummocks resulting from the deposition of glacial till. They look like inverted boat or spoon.

Eskers :

When glaciers melt in summer, the water flows on the surface of the ice or seeps down along the margins or even moves through holes in the ice. These waters accumulate beneath the glacier and flow like streams in a channel beneath the ice. Such streams flow over the ground (not in a valley cut in the ground) with ice forming its banks. Very coarse materials like boulders and blocks along with some minor fractions of rock debris carried into this stream settle in the valley of ice beneath the glacier and after the ice melts can be found as a sinuous ridge called esker.


Melting of glacier may leads to :

  • Sea level Rise

  • Shortage of fresh drinking water

  • Reduced Agricultural Output 

  • Shortage of hydroelectricity

  • Excessive Flooding 

  • Habitat loss

  • Coral bleaching

  • Change in the chemical composition of the ocean

 


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