Glaciation

Question 1

When do glaciers form?

Answer 1

When multiple snowfalls in mountainous areas turn into ice that flows across the land.

Question 2

What are glaciers able to do to the landscape?

Answer 2

They are powerful therefore they are able to change the shape of the landscape.

Question 3

What are the 2 processes of glacial erosion?

Answer 3

Plucking and abrasion

Question 4

What are the 2 stages of abrasion?

Answer 4

Stage 1: Rocks become embedded in the bottom of the ice flow.
Stage 2: Bedrock surface ‘scratched’ and ‘polished’ by rocks like sandpaper on wood.

Question 5

What are the 2 stages of plucking?

Answer 5

Stage 1: Glacial ice freezes into the bedrock.
Stage 2: When the glacier moves - rocks are ripped out.

Question 6

Name another process which can change the shape of upland areas?

Answer 6

Freeze-thaw weathering / frost shattering

Question 7

Describe the stages of freeze-thaw weathering.

Answer 7

1. Water gets into cracks in rocks and freezes.
2. Water expands as it freezes and crack is made wider.
3. The ice melts and the pressure on the rock is released.

Question 8

As the process of freeze-thaw weathering continues, rocks break apart in sharp, what are the angular pieces called ?

Answer 8

Scree

Question 9

Describe the formation of a corrie before glaciation.

Answer 9

Snow gathers in the north-facing hollows of a hill or mountain and compacts to ice. (1) The action of gravity allows the ice to move downhill.

Question 10

Describe the formation of a corrie during glaciation.

Answer 10

Ice freezes onto rocks on the back wall of the hollow and as it moves, it plucks rocks from the landscape. This helps to create a steep back wall. Rocks on the back wall are also removed by freeze-thaw weathering. Rocks frozen in the base of the ice act like sandpaper and deepens the hollow by abrasion. The rotational movement of the ice helps to create a deep hollow and a rock lip is formed by over-deepening.

Question 11

Describe the formation of a corrie after glaciation.

Answer 11

When the glacier melts, a pool of water is left called a tarn or a corrie loch. The glacier deposits material it has gathered as a pile of moraine, forming a lip. Scree continues to form at the steep back wall due to freeze-thaw weathering.

Question 12

What is a glacier?

Answer 12

A slow moving bulldozer of ice

Question 13

Describe the formation of an arête.

Answer 13

Snow collects in hollows then turns to ice. Ice erodes the mountain on all sides creating corries. The back walls of the corries are eroded back towards each other by the processes of plucking and abrasion until a narrow jagged knife-like ridge us formed. An arête is formed when two corries form back-to-back.

Question 14

Describe the formation of a pyramidal peak

Answer 14

When 3 or 4 corries erode back-to-back around a mountain the arêtes between the corries rise to a central peak, called a pyramidal peak. Plucking of the back walls makes the corries larger until the top of the mountain is eroded and only a sharp pointed peak remains. The exposed rock is also eroded by freeze-thaw weathering.

Question 15

Describe the formation of a U-shaped valley

Answer 15

1. Before the ice age: river has eroded a V-shaped valley.
2. During the ice age: A glacier flows down the valley, deepening & widening due to processes of erosion. (Plucking/abrasion/ftw)
3. After the ice age: A steep sided U-shaped valley with flat bottom is formed.

Question 16

Describe the formation of a hanging valley

Answer 16

A hanging valley is formed when a large glacier is joined by a small tributary glacier.The large glacier moves down a V-shaped valley and through the processes of plucking and abrasion deepens the valley floor and straightens the valley sides, leaving a large U-shaped valley. The interlocking Spurs become truncated Spurs. The same processes of plucking and abrasion take place in the tributary glacier, but at a much slower rate. This is because the large glacier is far heavier and more powerful and therefore can erode the land more quickly. The small tributary glacier does not vertically erode as much as the large glacier. When the ice melts a large U-shaped valley is left where the large glacier had been. The smaller glacier leaves a small valley leading into the main U-shaped valley and is left ‘hanging’ from truncated Spurs. Often a waterfall is left coming from the hanging valley flowing down into the main U-shaped valley.