Unit 3 Notes

Question 1

What is the first stage of freeze thaw weathering?

Answer 1

Water enters a crack in a rock, as temperature goes below 0 degrees, it expands by 9%.

Question 2

What is the second stage of freeze thaw weathering?

Answer 2

Cryostatic pressure is exerted on a rock, and cracks begin to get bigger, as water solidifies.

Question 3

What is the third stage of freeze thaw weathering?

Answer 3

Temperature fluctuates either side of 0 degrees, and cracks begin to get bigger, and the process repeats.

Question 4

What is the fourth step of freeze thaw weathering?

Answer 4

Process is repeated multiple times, as more pressure is exerted, and rock fractures.

Question 5

What is cryostatic pressure?

Answer 5

Pressure exerted onto a rock, as ice freezes.

Question 6

What are porous rocks?

Answer 6

Rocks with holes in.

Question 7

What are the conditions needed for freeze thaw weathering?

Answer 7

Porous rocks, pervious rocks, temperature fluctuations above and below 0 degrees.

Question 7

What are pervious rocks?

Answer 7

Rocks with cracks.

Question 8

What is abrasion?

Answer 8

Weathered debris of a rock scraping against the bedrock, wearing it away, leading to the rock becoming smooth. Sub glacial debris is worn down and converted into rock flour.

Question 9

Which factors affect glacial erosion?

Answer 9

Speed of glacier movement, supply of debris, ice thickness, shape of debris, subglacial meltwater, hardness of debris and bedrock.

Question 10

How does speed of glacier movement affect abrasion?

Answer 10

The more rapid the rate of movement, the more rapid the rate of abrasion. Faster moving glacier may scratch the surface more.

Question 11

How does supply of debris affect abrasion?

Answer 11

More supply of debris means a greater rate of abrasion.

Question 12

How does ice thickness affect abrasion?

Answer 12

At the base of the glacier, there is more pressure going downwards, when rock scrapes against the bed.

Question 13

How does shape of debris affect abrasion?

Answer 13

The more angular the debris, the more it erodes.

Question 14

How does subglacial meltwater affect erosion?

Answer 14

Enables basal sliding, which is necessary for abrasion, and more meltwater reduces abrasion.

Question 15

Which factors lead to the most abrasion?

Answer 15

High speed, hard debris, with lots of supply, subglacial meltwater is present, angular debris.

Question 16

How does hardness of debris affect abrasion?

Answer 16

Softer rock is more easily eroded, Debris which is harder than bedrock leads to more erosion.

Question 17

Which rocks are susceptible to plucking?

Answer 17

Highly jointed or fractured rocks.

Question 18

How does plucking occur on the down valley side of the glacier?

Answer 18

As ice is moving over by the process of regelation slip.

Question 19

Why is plucking effective at the base of a glacier?

Answer 19

The presence of meltwater due to pressure melting.

Question 20

How does sub glacial meltwater erosion work?

Answer 20

Meltwater may be more channelled beneath a glacier, before emerging at the snout.

Question 21

Why are subglacial streams more powerful than ordinary streams?

Answer 21

Increased hydrostatic pressure.

Question 22

Why is there more hydrostatic pressure?

Answer 22

They are confined beneath the glacier, so they’re under immense amounts of pressure, as they’re constricted.

Question 23

Why are subglacial discharge patterns different to normal?

Answer 23

They’re dependent on temperature fluctuations rather than precipitation channels. They flow slowest in winter, as temperature is reduced at night time, so melting is reduced.

Question 24

What are the macroscale erosional landforms?

Answer 24

Cirques, Aretes, Pyramidal peaks, Glacial troughs, Truncated spurs, ribbon lakes.

Question 25

What are the meso scale landforms?

Answer 25

Roche moutonnees, crag and tails.

Question 26

What are the micro scale landforms?

Answer 26

Striations, chatter marks, polished rock.

Question 27

What are the two stages of a cirque forming?

Answer 27

The development of a nivation hollow, the enlargement of a hollow after a cirque glacier has formed within the hollow, and begins to move.

Question 28

What are the first and second steps in the formation of a nivation hollow?

Answer 28

North facing slopes receive little insolation, Temperature remains cold, allowing snow to remain all year round.

Question 29

What are the third and fourth steps?

Answer 29

Freeze thaw weathering occurs due to temperature fluctuation. Surface of glacier thaws in summer, producing meltwater.

Question 30

Stage 1 of nivation hollow

What are the last 3 steps?

Answer 30

Rock debris removed by meltwater streams or movement of sediment, Combined process of freeze thaw and removal of rock created, the ground experiences permafrost.

Question 31

What are the first 2 steps of stage 2 of nivation formation?

Answer 31

Further accumulation of ice adds weight, leading to rotational movement, ice moves more quickly, because of meltwater creating pressure at the base of the glacier.

Question 32

What are the third and fourth steps of stage 2?

Answer 32

Movement of glacial ice, initiating cirque formation. Fragments of rock are removed from the backwall of valleys, which become frozen to the glacier.

Question 33

What are the fifth and sixth steps of stage 2?

Answer 33

Fragments are transported by ice rotations, causing abrasion. Rotational movement of glacier is helped by meltwater, which is created by surface melting. This enters a crevasse near the backwall of the cirque.

Question 34

What are the seventh and eighth steps of stage 2?

Answer 34

Erosion causes enlargement to the cirque, and ice moves rotationally, causing underlying rock to weaken. Rotational slip, as it starts to move over the cirque, as it exhibits abrasion.

Question 35

What is an Arete?

Answer 35

A knife edge ridge, produced by two cirques eroding towards each other.

Question 36

What are the examples of an Arete?

Answer 36

Lake district - striding edge.

Question 37

What is a pyramidal peak?

Answer 37

Where three or more cirques around a mountain develop so the central area of the mountain becomes sharper.

Question 38

What are the examples of pyramidal peaks?

Answer 38

Glyder Fawr - above cwm idwal.

Question 39

What is a glacial trough?

Answer 39

They develop where glaciers flow into pre-existing valleys.

Question 40

What is a truncated spur?

Answer 40

Steep, almost vertical side walls, where interlocking spurs have been cut away by glacial erosion.

Question 41

What is a hanging valley?

Answer 41

They occur when a small side tributary glacier meets a larger main valley glacier.

Question 42

What is a ribbon lake?

Answer 42

A longer, narrow finger shaped lake, usually found in a glacial trough. Glacier erodes soft rock, forming a rock basin, where ribbon lakes form.

Question 43

What is a roche moutonne?

Answer 43

A piece of resistant rock on the floor of a glacial trough that has undergone abrasion on the up valley side of the glacier, plucking on down valley side.

Question 44

Where do crag and tails occur?

Answer 44

They occur where glacier ice is forced to flow around a large and resistant rock obstacle such as a volcanic plug. Leads to a steep stoss glacier end.

Question 45

What are striations?

Answer 45

Scratches on hard bedrock produced by the process of glacial abrasion. Debris frozen in basal ice is dragged across bedrock to produce them.

Question 46

What are chatter marks?

Answer 46

Small intermittent fractures in bedrock, formed when basal debris within it isn’t in continuous contact with bedrock.

Question 47

What is polished rock?

Answer 47

Ice can polish rock, if sand and silt is found in the basal ice layer, as opposed to angular rock fragments.