Lithosphere (glaciation)

Question 1

Glacial erosion

Answer 1

• The glacier freezes on to bedrock and, as it moves downhill due to gravity, it pulls away large chunks of rock from the backwall - a process known as plucking.
• This allows meltwater and rock fragments to get to the base of the glacier increasing erosive power.
• Abrasion occurs when the angular rock embedded in the ice grinds the hollow.
• Frost shattering/freeze thaw weathering occurs when water in cracks in the rock freezes, expands and contracts weakening the rock until fragments break off.

Question 2

Glacier formation

Answer 2

1. Snow accumulates in north facing hollows when more snow falls in winter than melts in the summer.
2. North/north-east facing slopes are more shaded so snow lies longer with accumulated snow compressed into glacial ice.

Question 3

Corrie

Answer 3

1. Glacier formation.
2. Glacial erosion.
3. Glacier moves downhill due to gravity.
4. Bergschrund crevasse opens up at the back of the hollow.
5. This allows meltwater and rock fragments to get to the base of the glacier, increasing erosive power.
6. The weight of the glacier pushes down causing rotational sliding, which deepens the hollow.
7. Friction causes the ice to slow down at the front edge of the corrie, allowing a rock lip to form which traps rain water.
8. Eg. Brown Cove.

Question 4

U-shaped valleys

Answer 4

1. Glacial formation.
2. Glacial erosion.
3. Gravity causes the glaciers causes them to flow downhill, following existing V-shaped valleys.
4. Former interlocking spurs may be cut off by the glacier as it flows downhill leaving truncated spurs and steep valley sides.
5. The width and shape of the resulting glacial trough will depend on the nature of the rock type and the intensity and weight of the glacial and its erosion.
6. The valley becomes wider and straighter, often with a misfit stream which no longer fits the valley floor.
7. Eg. Glencoe.

Question 5

Arête

Answer 5

1. Glacial formation.
2. Glacial erosion.
3. Glacier moves downhill due to gravity.
4. Rotational sliding over deepens the hollow.
5. An arête is formed when two corries erode back towards each other.
6. Frost shattering can make the ridge more pronounced, and can cause scree slopes to develop.
7. Eg. Striding Edge.

Question 6

Pyramidal peak

Answer 6

1. Arête
2. A pyramidal peak has steep, triangular faces divided by sharp ridges or arêtes.
3. Erosion over time may culminate in a high triangular peak or horn formed by three or more glaciers eroding toward each other.
4. Eg. Matterhorn.

Question 7

Hanging valley

Answer 7

1. Glacial formation.
2. Glacier moves downhill due to gravity, following existing V-shaped valleys.
3. Glacial erosion
4. The degree to which glaciers can erode down into the landscape is dictated by their size: the larger the glacier, the deeper the valley it can erode.
5. A hanging valley is a shallow valley carved by a small glacier and thus the elevation of the valley floor is ‘hanging’ high above the elevation of the valley floor carved out by the larger glacier.
6. Eg. Stank Glen

Question 8

Ribbon lake

Answer 8

1. Glacial formation.
2. Glacier moves downhill due to gravity.
3. Glacial erosion.
4. Former interlocking spurs may be cut off by glacier resulting in steep crags or truncated spurs.
5. Over time the valley becomes straightened, widened and deepened.
6. Ribbon lakes can form where softer bedrock is eroded more deeply than the
7. surrounding area.
8. Ribbon lakes can form where a terminal or recessional moraine creates a dam.
9. Eg. Lake Windermere.

Question 9

Drumlins

Answer 9

1. Drumlins are elongated, oval shaped hills made up of unsorted glacial deposits, comprising till, boulder or clay.
2. Drumlins are formed as the glacier becomes overloaded with sediment and deposits it, streamlining the sediment as it flows over it.
3. The steep ‘stoss’ slope faces up-valley and the more gently-sloping ‘lee’ slope faces down-valley.
4. Drumlins are found in groups or swarms, with the tapered end of each hill pointing in the direction of glacier flow.
5. Each drumlin is a small hill, tending towards an egg shape, with its steepest slopes and summit at the up-ice end.
6. Eg. Buchlyvie

Question 10

Esker

Answer 10

1. Eskers are meandering ridges along a valley floor formed by meltwater streams in/underneath a glacier.
2. They are made up of meltwater sands and gravels. These are sorted by size because heavier stones are dropped first by flowing water.
3. The stones also tend to be more rounded than glacial deposits because of the action of flowing water rounding the edges by erosion.
4. On reaching lower altitudes and when temperatures rise, the glacier begins to
5. melt, and sub-glacial streams deposit in the tunnels.

Question 11

Terminal moraine

Answer 11

1. Terminal moraine is a ridge across the valley and made up of glacial deposits which are unsorted.
2. As the glacier moves downhill it acts like a bulldozer, pushing sediment in front of its snout as it goes.
3. On reaching lower altitudes and when temperatures rise, the glacier melts, losing power and depositing the moraine.
4. Terminal moraine marks the furthest point that the glacier reaches.
5. Once the ice has retreated, the terminal moraine can often form a natural dam, creating a ribbon lake.