Glacier & Iceberg

Glacier

» A mass of ice sliding down the slope from a snow-clad region is called a glacier. On an average a glacier moves I to 15 metres a day.
» While a glacier is moving, the friction of the ice at the bottom slows down the movement of the bottom layers.
» There are two main types of glaciers :
1. Continental Glacier
2. Alpine Glacier.

1. Continental Glacier
» An extensive sheet of ice spreading across a vast region sometimes begins to move due to the pressure of the ice.
» This moving sheet of ice is called a continental glacier.
» Such glaciers are seen in Antarctica and Greenland.

1. Alpine or mountain glacier
» There are snow-field in the mountainous regions of the Himalayas, the Alps, the Andes, the Rocky mountains etc.
» The ice accumulating in these areas starts sliding down the slopes.
» This mass of ice sliding down from the mountains is called a mountain glacier or an alpine glacier.

Iceberg

» Blocks of ice break off from the continental glaciers and float away into the sea.
» A block of ice floating in the sea is called an iceberg.
» These icebergs are huge in size.
» The density of ice being slightly less than that of water, a very little portion of an iceberg is seen above the water and the rest of it is submerged under water.

Land forms of glaciation

Various land forms are created on account of the transportation, erosion and depositional work of a glacier. Let us consider the major land forms thus created.

Cirque

» When the snow from the mountain peaks slides, it gets deposited in a hollow, if there is one on any side of the peak.
» The accumulated snow starts sliding down the slope. This causes friction at the floor and at the sides of the hollow, thus enlarging it further. This is called a cirque.
» The back wall of a cirque is like a high cliff and the floor is concave and huge in size. The total shape resembles an armchair.
» When a glacier melts completely, water accumulates in the cirque and forms a lake which is known as tarn.

Fiord

» Where the lower end of the trough is drowned by the sea it forms a deep steep- side inlet called ' Fiord' as on the Norwegian and South Chilean Coasts.

U-shaped valley

» When a glacier is flowing through a valley in a mountainous region, the sides of the valley get eroded. Ice causes friction on the sides of the valley.
» As the erosion of the sides is greater than that of the floor, a valley is formed with vertical sides and a wide floor. This valley is called a U-shaped valley.

Hanging valley

» In the mountainous region, many tributaries join the main glacier.
» The quantity of ice in a tributary is comparatively smaller. Hence, it causes less friction.
» The valley of a tributary is at a higher level than a valley of the main glacier, the valley of the tributary appears to be hanging. That is why, such a valley is called a hanging valley.

Moraine

» The material transported and deposited by a glacier is known as moraine.
» Moraines are made up of pieces of rocks that are shattered by frost action and are brought down the valley.
» Moraines are of the following types : 1. lateral moraine, 2. medial moraine, 3. terminal moraine and 4. ground moraines.
» After a glacier has melted, different land forms of deposition are seen.
» The oval-shaped hills of lesser height are called drumlins.
» Zig-zag hills, with many steep slopes, made up of long stretches of sand and gravel are called eskers.