Correct Answer - Option 4 : 1, 2 and 3
The correct answer is 1, 2 and 3.
- A thick ice sheet covering a vast area of land is called a continental glacier.
- The thickness of ice in such regions goes up to thousands of metres.
- Glaciers of this type build-up at the centre and move outward in all directions.
- The precipitation in these regions occurs in the form of snow. It gets accumulated year by year because of the relatively slower rate of its melting.
- When a mass of ice from the high mountainous regions starts moving down into the pre-existing valleys, it is called a valley glacier or a mountain glacier.
- The shape of the valley glaciers depends on the valley it occupies.
- As a glacier moves over the land, it drags rock fragments, gravel and sand along with it.
- These rock fragments become efficient erosive tools. With their help glacier scrapes and scours the surface rocks with which it comes in contact.
- This action of glacier leaves behind scratches and grooves on rocks.
- The landforms like Cirque, 'U' shaped valley, Hanging Valley etc are created by the glacial erosion. Hence, Statement 1, 2 and 3 are correct.
Snow collects at the upper end in a bowl-shaped depression, is called a cirque.
- Layers of snow in the process of compaction and recrystallization are called firn.
- The deepest parts of these hollows are occupied by accumulated-water to form Corrie Lake.
- There are tributary the glaciers also which join the main glacier after moving over their mountainous path. These tributary glaciers like the main glaciers carve U - shaped valleys.
- The valley of the tributary glacier just looks like hanging downwards at the point of its confluence with the main valley referred to as a hanging valley.
- The longest glacier in India is the Siachen Glacier in Karakoram Range which is 72 kilometres long.
- Gangotri Glacier in Uttarakhand is 25.5 kilometres long.
- The two important rivers of India, the Ganga and Yamuna, originate from Gangotri and Yamunotri glaciers respectively.