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H GEOG 23/24 > 4 - Lithosphere > Flashcards

4 - Lithosphere Flashcards

1
Q

CORRIE:SETTING

A
  1. Snow accumulates in north facing hollows where more snow falls in winter than melts in summer. ​
  2. North and north-east facing slopes are more shaded, so snow lies longer and is compressed into firn, then ice.
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2
Q

CORRIE:PROCESSES

A
  1. Plucking occurs when ice freezes onto bedrock pulling loose rocks away from the backwall. ​
  2. Abrasion occurs when the angular rock embedded in the ice grinds the hollow as the glacier moves. ​
  3. Freeze-thaw weathering occurs when water in cracks in the rock freezes, expands and contracts weakening the rock until fragments break off.
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3
Q

CORRIE:OVERTIME

A
  1. Glaciers move downhill due to gravity. ​
    ​7. The bergshrund crevasse opens up at the back of the hollow. ​
  2. This allows meltwater and rock fragments to get to the base of the glacier, increasing erosive power.​
  3. The weight of the glacier pushes down causing rotational sliding, which deepens the hollow. ​
  4. Friction causes the ice to slow down at the front edge of the corrie, allowing a rock lip to form which traps rainwater. ​
  5. This creates a corrie lochan, a small loch which fills up with rainwater long after the glacier has gone.​
    Example = Corrie Cas
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4
Q

FORMATION OF ANARETE

A

Formed when two corries erode back towards each other, creating a narrow ridge between them. ​
Example = Striding Edge

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5
Q

FORMATION OF A PYRAMIDAL PEAK

A

When three or more corries erode form around a mountain, creating a jagged peak in the centre. ​
Example = Matterhorn

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6
Q

U-SHAPED VALLEY:SETTING

A
  1. Snow accumulates in north facing hollows where more snow falls in winter than melts in summer. ​
  2. North and north-east facing slopes are more shaded, so snow lies longer and is compressed into firn, then ice. ​
  3. Glaciers travel downhill through a V-shaped valley due to gravity.
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7
Q

U-SHAPED VALLEY: PROCESSES

A
  1. Plucking occurs when ice freezes onto bedrock pulling loose rocks away from the valley walls making them steeper. ​4. Abrasion occurs when the angular rock embedded in the ice grinds the base of the valley as the glacier moves, deepening the valley. ​
  2. Freeze-thaw weathering occurs on the steep sides of the valley. This is when water in cracks in the rock freezes, expands and contracts weakening the rock until fragments break off resulting in scree slopes.
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8
Q

U-SHAPED VALLEY:OVER TIME

A
  1. Interlocking spurs are cut off by the glacier as it flows downhill. ​
  2. the valley becomes wider and straighter, often with a misfit stream that no longer fits the valley floor. ​
    Example = Glencoe
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9
Q

FORMATION OF A HANGING VALLEY

A
  1. A smaller valley that has been formed by a tributary glacier. ​
  2. Tributary glacier is smaller and weighs less so it has less erosive power. ​
  3. As such, a steep drop is found where the hanging valley meets the main u-shaped valley. ​
  4. This often forms a waterfall.
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10
Q

FORMATION OF ARIBBON LOCH

A
  1. a long thin loch which forms on the floor of a u-shaped valley. ​
  2. form where differential erosion has created a deeper area of less resistant rock, surrounded by more resistant rock. ​3. Also form when the deposition of glacial material forms a dam. ​
  3. An example = Loch Avon.
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11
Q

WHAT IS AN ESKER?

A

Eskers are meandering ridges of sediment along a valley floor, formed by meltwater streams in or underneath a glacier.

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12
Q

WHERE DO ESKERS FORM?

A

In the zone of ablation, the glacier is primarily losing mass via melting. ​
Meltwater streams which travel through the glacier deposit sand and gravel in the channels and tunnels that they make.

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13
Q

WHAT IS THE MATERIAL THAT FORMS ESKERS LIKE?

A

These are sorted by size because heavier stones are dropped first by flowing water. ​
The stones are more rounded compared to those deposited by a glacier because of the action of flowing water around the edges which wear them down by erosion.

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14
Q

WHAT IS A TERMINAL MORAINE?

A

Terminal moraine is a ridge across a u-shaped valley which is made up of unsorted glacial deposits.

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15
Q

WHEN DOES A TERMINAL MORAINE GET DEPOSITED?

A

As the glacier moves downhill it acts like a bulldozer, pushing sediment in front of its snout as it goes. ​
On reaching lower altitudes, or when temperatures rise, the glacier melts, losing power and depositing the moraine.

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16
Q

WHAT DOES A TERMINAL MORAINE MARK?

A

Terminal moraine marks the furthest point the glacier reaches. ​
Multiple periods of glaciation may produce different terminal moraines in the same valley.

17
Q

WHAT CAN TERMINAL MORAINES FORM?

A

Once the ice has retreated, the terminal (or end) moraine can sometimes form a natural dam, creating a ribbon loch.

18
Q

WHAT IS A DRUMLIN?

A

Drumlins are elongated hills made up of unsorted glacial deposits.
Drumlins are found in swarms described as ‘basket of eggs’ topography.

19
Q

WHEN DO DRUMLINS FORM?

A

Drumlins are formed as the glacier becomes overloaded with ​
sediment and deposits it.
If there is a small obstacle on the ground, this may act as a trigger point and glacial sediment can build up around it. ​
Drumlins may be reshaped by further ice movements after being originally deposited.

20
Q

WHAT IS THE STOSS SIDE OF A DRUMLIN?

A

steep side facing up the valley

21
Q

WHAT IS THE LEE SIDE OF A DRUMLIN?

A

gently sloping side facing down the valley

22
Q

HEADLAND AND BAYS: SETTING

A
  1. Headlands and bays are form at a discordant coastlines where alternate areas of rock erode at different rates. ​
  2. This leads to differential erosion where softer, less resistant rock erodes more quickly than harder, more resistant rock.
23
Q

HEADLAND AND BAYS: PROCESSES

A
  1. Hydraulic action is when the pounding waves compress trapped air in the rocks, creating pressure which weakens and loosens rock fragments over time.​
  2. Abrasion is when rock fragments carried in the waves are thrown against the rock, wearing it away over time. ​
  3. In some areas, rocks which are susceptible to erosion by solution (e.g. limestone and chalk) have minerals dissolved away by slightly acidic seawater.
24
Q

HEADLAND AND BAYS: OVER TIME

A
  1. these processes all work together to erode the less resistant, softer rock at a quicker rate. ​
  2. The more resistant rock juts out into the sea to form a headland. ​
  3. Bays form in the sheltered area of softer rock between the headlands.
25
Q

WAVE-CUT PLATFORM: SETTING

A
  1. At the coast, cliffs often form where harder rock is found on a concordant coastline. ​
  2. Lines of weakness such as joints, faults and cracks are often eroded at high tide or when waves have a lot of energy such as during low pressure systems.
26
Q

WAVE-CUT PLATFORM: PROCESSES

A
  1. Hydraulic action is when the pounding waves compress trapped air in the rocks, creating pressure which weakens and loosens rock fragments over time.​
  2. Abrasion is when rock fragments carried in the waves are thrown against the rock, wearing it away over time. ​
  3. In some areas, rocks which are susceptible to erosion by solution (e.g. limestone and chalk) have minerals dissolved away by slightly acidic seawater.
27
Q

WAVE-CUT PLATFORM: OVER TIME

A
  1. As the cliff is undercut by erosion a wave cut notch develops at the base of the cliff. ​
  2. the notch erodes further into the cliff leaving an overhang above, which eventually collapses under its own weight. ​8. as this process is repeated the cliff retreats and leave a wave-cut platform under the high tide line.
28
Q

SEA STACK: SETTING

A
  1. At a discordant coastline headlands jut out into the sea and are attacked by marine erosional processes.​
  2. Lines of weakness such as joints, faults and cracks are often eroded at a faster rate through hydraulic action, abrasion and solution.
29
Q

SEA STACK: PROCESSES

A
  1. Hydraulic action is when the pounding waves compress trapped air in the rocks, creating pressure which weakens and loosens rock fragments over time.​
  2. Abrasion is when rock fragments carried in the waves are thrown against the rock, wearing it away over time. ​
  3. In some areas, rocks which are susceptible to erosion by solution (e.g. limestone and chalk) have minerals dissolved away by slightly acidic seawater.
30
Q

SEA STACK: OVER TIME

A
  1. cracks are eroded wider and deeper to form sea caves. [blowhole can sometimes develop if air forced upwards]​
  2. If two caves form on either side of the headland and erode further, a natural arch can form. ​
  3. Continued erosion and the base of the arch and weathering on the roof can lead to it collapsing. ​
  4. This leaves a sea stack isolated from the headland in the sea.
31
Q

WHAT IS LONGSHORE DRIFT?

A

Depositional features are formed by longshore drift. ​
Swash is where waves, driven by the prevailing wind push material up the beach at an angle. ​
The returning backwash is dragged back by gravity down the beach at right angles. This repeats over and over, transporting material along the coast.

32
Q

SAND SPITS: SETTING

A
  1. Forms where there is a change in direction along a coastline. ​
  2. This allows a sheltered area to form where deposition is the dominant process through longshore drift.
33
Q

SAND SPITS: OVER TIME

A
  1. sediment builds up until it is above sea level if coastal deposition is greater than erosion. ​
  2. the shape can become hooked or curved due to changes in current or wind direction. ​
  3. a salt marsh can often develop in the sheltered area behind the spit.
34
Q

SAND BARS: SETTING

A
  1. Forms when a spit grows across the entrance to a bay connecting to headlands. ​
  2. This allows a sheltered area to form where deposition is the dominant process through longshore drift.
35
Q

SAND BARS: OVER TIME

A

​

  1. sediment builds up until it is above sea level if coastal deposition is greater than erosion. ​
  2. when a bar cross the bay, a sheltered lagoon can form behind it. ​
  3. When the lagoon gets cut off it no longer has a supply of water and may get infilled by deposition over time.
36
Q

FORMATION OF TOMBOLOS

A

Forms when sediment is deposited so that an island is connected to the mainland by sand or shingle.

H GEOG 23/24 (9 decks)

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