OCR A Level GL - 6 OCR A Level GL 2.2a Geomorphic and Glacial Processes

Question 1

What is weathering?

Answer 1

the in situ breakdown of rocks exposed at, or near, the land surface by physical, chemical and biological processes.

Question 2

What is physical weathering (Mechanical)?

Answer 2

the in situ breakdown of rock in which there is no chemical alteration. In glacial environments, these include “Freeze-thaw”, “Frost-shattering” and “Pressure Release”.

Question 3

What is freeze-thaw weathering?

Answer 3

a form of physical weathering in which water enters cracks/joints in rocks then freezes, expanding by 10% in the process, and causing the rock to split or for pieces to break off. Particularly prevalent in areas where temperatures fluctuate around zero (i.e. areas of high altitude with diurnal changes in temperature).

Question 4

What is frost shattering?

Answer 4

a form of physical weathering in which water trapped in rock pores freezes at extremely low temperatures, exerting stress and disintegrating the rock into small particles.

Question 5

What is pressure release (dilatation)?

Answer 5

a form of physical weathering whereby rock underlying a glacier expands and fractures parallel to the surface when the weight of a glacier is removed when it melts.

Question 6

What is chemical weathering?

Answer 6

the in situ breakdown of rock in which there is a chemical reaction between elements of the weather and some minerals within rocks. These type of weathering includes oxidation, carbonation, solution, hydrolysis and hydration.

Question 7

What is oxidation?

Answer 7

a form of chemical weathering in which minerals in rocks react with the oxygen found in the air. This process particularly happens in rocks with high iron content (such as sandstone).

Question 8

What is carbonation?

Answer 8

a form of chemical weathering in which carbonic acid (formed when rainwater combines with dissolved carbon dioxide) reacts with calcium carbonate, in particular found in limestone.

Question 9

What is solution?

Answer 9

a form of chemical weathering whereby a mineral dissolves in water.

Question 10

What is hydrolysis?

Answer 10

a form of chemical weathering in which water chemically reacts with rock minerals. Examples include: Silicate + Water = clay Feldspar (found in granite) + hydrogen (found in water) = kaolin (china clay)

Question 11

What is hydration?

Answer 11

a form of chemical weathering in which water and rock minerals form new minerals of a larger volume. This process can cause surface flaking of rocks.

Question 12

What is biological weathering?

Answer 12

the in situ breakdown of rock that is caused by the physical actions of plants and/or animals or by organic acids (chelation)

Question 13

What is mass movement?

Answer 13

the movement of material down a slope when the forces acting on the slope (mainly gravity) exceed the forces keeping the material on the slope (friction).

Question 14

What is rock fall?

Answer 14

when rocks dislodge from a steep slope (40 degrees or more) and fall to the foot of the slope under gravity. This mainly occurs in areas where bare rocks are exposed to physical weathering processes.

Question 15

What are rock slides?

Answer 15

When a section of rock or soil moves downhill. This can be Linear - in which movement is along a straight line slip plane. This often occurs between bedding planes. Rotational - movement is along a curved slip plane (also known as slumps). This is a key process in the formation of corries.

Question 16

What is glacial erosion?

Answer 16

The action of removing rock by a glacier

Question 17

What is plucking (quarrying)?

Answer 17

a form of glacial erosion in which meltwater seeps into joints in rock on the valley floor or sides. This then refreezes and becomes reattached to the glacier. As the glacier advances, it pulls pieces of rock away. This mainly takes place at the base of a glacier where pressure melting can take place. If the bedrock is highly jointed then this process will be particularly effective.

Question 18

What is abrasion?

Answer 18

a form of glacial erosion in which as a glacier moves across a surface, the debris that is embedded withing it scours the rock and wears them away. Larger or more coarse material will scrape, scratch and groove the rock - forming striations. Smaller and more fine material will smooth and polish the rock.

Question 19

What factors affect the rate of abrasion?

Answer 19

1. Presence of basal debris
2. Debris size and shape
3. Relative hardness of particles and bedrock
4. Ice thickness.
5. Basal water pressure
6. . Basal sliding
7. . Movement of debris to the base of the glacier
8. . Removal of fine debris

Question 20

How does basal debris affect the rate of abrasion?

Answer 20

more debris increases rate of abrasion, however, it also increases amount of friction, which slows down rate of movement

Question 21

How does debris size and shape affect the rate of abrasion?

Answer 21

Larger debris is more effective in abrasion because the amount of downward pressure of an object is proportional to its weight. More angular material creates more abrasion as pressure is concentrated onto a smaller area.

Question 22

How does relative hardness of particles and bedrock affect the rate of abrasion?

Answer 22

when the bedrock is more resistant than the debris = little abrasion when the bedrock is weak and softer than the debris = maximum abrasion

Question 23

How does ice thickness affect the rate of abrasion?

Answer 23

it is a complex relationship: In general - the thicker the ice, the more pressure and therefore the more abrasion However, if pressure becomes too great then there is too much friction and no movement and therefore little abrasion

Question 24

How does basal water pressure affect the rate of abrasion?

Answer 24

if basal water is under pressure, glacial debris may not be in as much contact with the bed and so abrasion is reduced

Question 25

How does basal sliding affect the rate of abrasion?

Answer 25

The presence of some water at the base of a glacier acts as a lubricating layer. This increases the rate of movement and therefore increases the rate of abrasion

Question 26

How does movement of debris to the base affect the rate of abrasion?

Answer 26

basal debris is worn away in the process of abrasion and so must be replenished if it is to remain effective

Question 27

How does the removal of fine debris affect the rate of abrasion?

Answer 27

rock flour (fine debris) needs to be removed in order that larger particles can abrade the bedrock.

Question 28

What is rock flour?

Answer 28

the product of glacial erosion where debris is worn down into fine particles (almost dust-like). This gives meltwater its milky white appearance.

Question 29

What is nivation?

Answer 29

a complex process believed to include a combination of freeze-thaw action, solifluction, transport by water and chemical weathering. It is understood to be the main process involved in initially enlarging hillside hollows in the formation of corries.

Question 30

What is solifluction?

Answer 30

the gradual movement of wet soil or other material down a slope, especially where frozen subsoil acts as a barrier to the percolation of water.

Question 31

What is transportation?

Answer 31

The process whereby material is moved from one location to another.

Question 32

What are aeolian deposits?

Answer 32

this is fine material that is carried by wind, often blowing across outwash deposits

Question 33

What is supraglacial material?

Answer 33

debris that is carried on the surface of a glacier. It mostly originates from weathering and rockfall of valley sides

Question 34

What is englacial material?

Answer 34

debris that is carried within a glacier. It often starts as supraglacial material but is then covered by further snowfall but can also include material that falls into creavasses or sinks into the ice due to localised pressure melting.

Question 35

What is subglacial material?

Answer 35

debris that is embedded in the base of a glacier. This material is often derived from plucking and abrasion but can be englacial material that has continued to move down through the ice to the base.

Question 36

What is drift?

Answer 36

All material that has been deposited during glaciation

Question 37

What is till?

Answer 37

a subcategory of drift. This is material that is directly deposited by ice.

Question 38

What characteristics do all forms of till have?

Answer 38

1. Angular in shape
2. Unsorted
3. Unstratified

Question 39

Why is till angular?

Answer 39

material has been embedded in the ice and has not been subjected to further erosion processes, particularly not meltwater, which would make the material more rounded.

Question 40

Why is till unsorted?

Answer 40

when ice melts, all sizes of material are deposited together

Question 41

Why is till unstratified?

Answer 41

when ice melts it deposits material in mounds and ridges, rather than in layers.

Question 42

What is glacio-fluvial material?

Answer 42

a subcategory of drift. This is material that is directly deposited by glacial meltwater.

Question 43

What is lodgement till?

Answer 43

This is material that is deposited by advancing ice.

Question 44

What glacial landform is commonly associated with lodgement till?

Answer 44

drumlins

Question 45

How prevalent are glacial deposits at a global scale?

Answer 45

Estimated that 8% of the Earth’s surface is covered by glacial deposits

Question 46

What is ablation till?

Answer 46

This is material that is deposited by melting ice from glaciers that are stagnant (stationary) or retreating. Most glacial depositional landforms (such including kames, eskers and moraines) are made from ablation till.

Question 47

How prevalent are glacial deposits at a European scale?

Answer 47

nearly 30% of Europe is covered in glacial deposits

Question 48

How significant are glacial deposits in East Anglia?

Answer 48

East Anglia is completely covered by glacial deposits, some of which are 143m thick. They are the reason the region has fertile soils for farming.