GC Leong Test: Landforms Of Glaciation - 1 for UPSC Indian Geography

• The peaks of the loftier mountains project above the surface as nunataks. When the ice sheets reach the sea, they often extend outwards into the polar waters and float as ice shelves. 

• They terminate in precipitous cliffs. When they break into individual blocks, these are called icebergs.

Both statements are correct.

Statement 1 is generally true - glaciers erode the landscape as they move downhill, resulting in erosional features such as U-shaped valleys, cirques, arêtes, and horns in the highlands. As glaciers melt and deposit the sediments they have transported, they form depositional features such as moraines, drumlins, eskers, and kames in lowland areas.

Statement 2 is also true - glaciers erode the landscape as they move, transport large amounts of rock and sediment, and deposit this material elsewhere. This is why glaciers are often described as "agents of erosion, transportation, and deposition."

• The glacier scratches, scrapes, polishes, and scours the valley floor with the debris frozen into it by abrasion. 

• By plucking the glacier freezes the joints and beds of the underlying rocks, tears out individual blocks and drags them away.

• Large angular fragments cut deep into the underlying rocks, so all glaciated floors bear evidence of striation or scratching. The finer materials smooth and polish the rock surfaces and produce finely ground rock flour.

• The rate of erosion is determined by several factors such as the velocity of flow, gradient of the slope, the weight of the glacier, the temperature of the ice, and the valley's geological structure.

• The plucking process operates on the back-wall, steepening it and the ice's movement abrades the floor, deepening the depression into a steep, horse-shoe-shaped basin called a cirque (in French).

• It is also known as a corrie in Scotland and a cwm in Wales. There is a rocky ridge at the exit of the corrie and, when the ice eventually melts, water collects behind this barrier, to form a corrie lake or tarn.

Both statements are correct.

Statement 1 is describing the formation of aretes, which are narrow, knife-edged ridges that form between two adjacent corries (also known as cirques) that have eroded back towards each other on opposite sides of a mountain.

Statement 2 is describing the formation of a horn, which is a pointed mountain peak that forms when three or more cirques erode back towards a central point, resulting in a sharp, angular peak.

Therefore, neither statement is incorrect.

• Bergschrund: At the head of a glacier, where it begins to leave a corrie's snowfield, a deep vertical crack opens up called a bergschrund (in German) or rimaye (in French).

• This happens in summer when, although the ice continues to move out of the corrie, there is no new snow to replace it. In some cases, not one but several such cracks occur.

• The bergschrund presents a major obstacle to climbers. Further down where the glacier negotiates a bend or a precipitous slope, more crevasses or cracks are formed.

• The Matterhorn in the Swiss Alps is a classic example of a pyramid peak.
• A pyramid peak is a sharply pointed mountain summit with multiple steep faces, formed by the headward erosion of three or more cirques.
• The Matterhorn is well-known for its distinctive pyramid shape, making it a textbook example of this type of landform.
• The other options are incorrect:
  • A bergschrund is a type of glacier crevasse.
  • A corrie lake (or tarn) is a small lake in a glacially eroded hollow.
  • A cirque is a bowl-shaped depression on the side of a mountain.
    
     

• A valley which has been glaciated takes a characteristic U-shape, with a wide, flat floor and very steep sides.

• After the ice's disappearance, the deep sections of these long, narrow glacial troughs may be filled with water forming ribbon lakes, such as Loch Ness and Lake Ullswater in Britain. They are sometimes referred to as Trough lakes and Finger lakes.