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AS Geography (physical) > Cold Environments Landforms > Flashcards

Cold Environments Landforms Flashcards

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1
Q

Describe the weathering of rocks?

A

It is the breakdown of rocks in situ. The finer particles produced can be moved away by agents of erosion such as water and wind

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2
Q

In cold environments physical weathering processes dominate name the main one

A

Frost shattering

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3
Q

Describe Frost shattering

A

Water enters a crack in a rock. At night when temperatures drop below 0°C the water expands by approximately 9%. Exerting pressure on the rock. This will happen thousands of times, widening the crack and eventually will cause pieces of the rock to break off.

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4
Q

What is the collection of material produced by Frost shattering known as?

A

Scree

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5
Q

Describe the process of abrasion (in glaciers)

A

When angular material embedded in the glacier rubs against the valley floor wearing it away finer material leaves are polished surface while course the material leaves striations. The material caught up in the ice and worn down by abrasion is known as rock flour.

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6
Q

Describe the process of plucking

A

When glacial ice freezes on to rocky outcrops and as the glacier moves away it takes the piece of rock with, it is mainly found at the base of the glacier where pressure and friction result in the melting of ice. It can also result in plucking.

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7
Q

What rocks is plucking common in and what does it leave?

A

It is common in weldjoint rocks that have been weakened by Frost shattering and leaves a jagged surface.

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8
Q

Describe a corrie

A

An arm chair shaped hollow with a steep back wall and deep base and it may contain a tarn and often has a raised lip

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9
Q

Describe the process of corrie formation

A
  1. Snow accumulation on NE and E facing slopes with little insolation
  2. The hollow is deepened by nivation
  3. Snow accumulates and the pressure causes it to turn to ice
  4. The weight of the ice causes it to rotate and move
  5. The ice pulls away from the back of the hollow, plucking occurs
  6. Frost shattering causes rock to drop onto the ice, this material supplied by plucking allows the glacier to abraded the floor and over deepen the Corrie basin
  7. A large crevasse forms at the back of the hollow called a Bergschrund
  8. The front of the corrie the ice is thinner and failed to produce the same level of abrasion and the rock lip develops
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10
Q

Give an example of a tarn

A

Red tarn in the Lake District

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11
Q

Describe and arête

A

When two or more corrie glaciers erode back to back from opposing side they produce a knife edge ridge called an arête

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12
Q

Give examples of and arête

A

Striding edge in the Lake District

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13
Q

What happens when three or more corries erode back towards each other and what is an example of this?

A

Pyramidal peak forms and example of this is the Matterhorn in Switzerland

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14
Q

What do glaciers do to pre-existing river valleys?

A

They straighten, widen and deepen these valleys, they change the original V shape to a U shape

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15
Q

How does glacial erosion differ to river erosion?

A

Wild Rivers Road vertically any of the sections glaciers erode horizontally as well as vertically they are better able to road obstructions that streams and rivers would meander around

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16
Q

Does the action of ice have a great erosive power than that of water?

A

Yes, along with meltwater and subglacial debris

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17
Q

What is the technical term for a Valley shaped by a glacier

A

A glacial trough

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18
Q

Why are some places in glacial valleys deeper than others?

A

Compressional flow means that more erosion will occur leading to the formation of rock basins

over deepening can also occur at the confluence of two glaciers

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19
Q

In post glacial times what mate over deep parts of the valley be filled by?

A

Ribbon lakes

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20
Q

Give an example of a ribbon lake

A

Wastwater in the Lake District

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21
Q

What may extension flow leave?

A

Less eroded, more resistant rock steps

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22
Q

What happened to some glacial troughs once sea levels rose?

A

They became submerged and fjords formed

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23
Q

What is it called when a glacial Valley ends abruptly and what lies above it?

A

It is called trough end and above it lie a number of corries

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24
Q

What is left when a tributary glacier joins a larger glacier after both glaciers have disappeared?

A

A hanging valley is left due to differing rates of erosion, they may be marked by a waterfall

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25
Q

In some areas glaciers do not remove small areas of resistant rock what does this leave?

A

Roche Moutonnées with an upvalley side (stoss) and a downstream side left jagged from abrasion

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26
Q

What may abrasion have left on the upValley side of the Roche moutonnees?

A

Striations

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27
Q

What is another feature similar to a roche moutonnees and give an example of it

A

A crag and tail is the same thing only the opposite way around and an example is in Edinburgh on the site of the castle and the Royal mile

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28
Q

Name the three types of glacial debris

A
  1. Supraglacial debris- on the surface of glaciers
  2. Englacial debris- inside glaciers
  3. Sub glacial debris- beneath the ice
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29
Q

What are glacial deposits often called?

A

Drift, to distinguish them from the underlying geology

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30
Q

What are the two types of glacial deposit?

A

Number one: till or boulder clay

Number two: fluvioglacial material

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31
Q

Describe boulder clay

A

All material deposited directly by the ice, it is unsorted.

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32
Q

Describe fluvioglacial material

A

Sediment deposited by meltwater streams that they are usually sorted with coarser material deposited near the glacier snout and with finer particles carried further

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33
Q

How would till have been transported in a glacier?

A

As supraglacial or englacial material

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34
Q

Where do some deposits in Norfolk come from?

A

Norway

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35
Q

What is till formed from subglacial material that was deposited by and actively moving glacier known as?

A

Lodgement till

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36
Q

Name five types of moraine

A
  1. Terminal moraine
  2. Push moraines
  3. Lateral moraine
  4. Medial moraine
  5. Recessional moraine
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37
Q

What are erratics?

A

They are rocks in the wrong place and maybe very different to the local geology, they are fragments of glacial debris that have been carried large distances before being deposited for example Shap granite erratics are found on the Holderness Coast in East Yorkshire that originally came from Cumbria

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38
Q

What is a lateral moraine?

A

Debris fallen on the sides of a glacial valley after glaciation and it looks like long embankment of debris at the side of the valley

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39
Q

What is medial moraine?

A

It is formed when two places meet and the two lateral moraines may join to form a medial moraine

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40
Q

What is a terminal moraine?

A

It is often a series of high mounds of debris that extends across the valley marking the point that a glacier reached

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41
Q

What is recessional moraine?

A

They are essentially the same as terminal moraines and are formed by glacier retreat

42
Q

What are push moraines?

A

Again essentially the same as terminal moraines but are formed by glacial advance

43
Q

What are drumlins?

A

They are rounded oval-shaped hills which look like the top half of an egg they are formed from insulted till deposited by a moving glacier

44
Q

How long and how high can drumlins be?

A

Up to 1.5 km long and 50 m high although most are smaller

45
Q

What are the two ends of a drumlin called?

A

The steep end is the stoss and the sloping end is the Lee

46
Q

In which direction are drumlins elongated?

A

In the direction of ice advance

47
Q

What is it called when there are multiple drumlins in an area?

A

A swarm or “basket of eggs topography”

48
Q

Where are drumlins often found?

A

On lowland plains such as the central lowlands of Scotland

49
Q

How is it believed that drumlins are formed?

A

When ice becomes overloaded with debris. The ice becomes unable to carry all of the material and so deposition occurs at its base. Once it has been deposited the material becomes streamlined as the ice advances over and around it

50
Q

Give five reasons why meltwater is important

A
  1. Helps enlarge nivation hollows
  2. Lubricates the base of a glacier
  3. If it refreezes, melt water can bind the base of a glacier to broken rock
  4. It can form ‘meltwater’ rivers
  5. It will for several depositional features
51
Q

What is different about fluvioglacial deposits from till?

A

It is sorted

52
Q

How deep can subglacial streams erode and why?

A

They can form valleys deeper than 15m. They carry much more debris than a normal river of the same size and flow under great pressure with a turbulent flow

53
Q

Describe an outwash plain?

A

An extensive, gently sloping area of sands and travels that form in front of a glaciers snout, they are formed from sediments deposited by meltwater rivers

54
Q

How are outwash plains composed?

A

The coarsest material is deposited first and the finest material is deposited last, they reflect the seasonal flow of meltwater streams as they carry coarser deposits further in the summer

55
Q

Where can outwash plains be found?

A

Iceland and Alaska

56
Q

Describe an esker

A

Long, sinuous ridges of sorted material, mainly sand and gravel that run in the direction of ice advance, they are often stratified

57
Q

Give potential measurements of eskers

A

The can be up to 30 M high and can run for several KMs

58
Q

How is it thought that eskers are formed?

A

By subglacial rivers in the final stages of glaciations, when the ice was melting away and no longer moving forward.

59
Q

Why can eskers sometimes run up gentle gradients?

A

The subglacial stream they were formed by were under considerable hydrostatic pressure and so could flow uphill for short distances.

60
Q

How do eskers often appear now?

A

As discontinuous hills, as meltwater and postglacial rivers have eroded them away

61
Q

What are Kames?

A

Deposits of sorted and often stratified sand and gravel left by meltwater along the front of a melting ice sheet

62
Q

Why do kames often collapse?

A

As the ice supporting them melts

63
Q

What shape are kames, often?

A

Conical

64
Q

What are the three types of Kame?

A
  1. Kame Terrace
  2. Kame delta
  3. Crevasse Kame
65
Q

Describe a Kame Terrace

A

Long, bench like features on the side of the valley. They’re formed when a gap between the valley side and ice is filled with fluvioglacial deposits, leaving behind a Terrace as the glacier melts. When the ice finally melts, the Kame Terrace is abandoned as a ridge on the valley side.

66
Q

Describe a Kame delta

A

A Kame delta is a smaller feature that forms when a stream deposits material on entering a marginal lake. Kame deltas form small mound-like hills on the valley floor, and can be identified by their deltaic sedimentation characteristics

67
Q

Describe a crevasse Kame

A

Some kames arise from the fluvial deposition of sediments in surface crevasses. When the ice melts, they are deposited on the valley floor to form small hummocks

68
Q

What is the key to identify Kames and eskers?

A

They are made up of sand and gravel, rather than clay-rich till like the surrounding countryside

69
Q

Describe kettle holes

A

A series of small depressions filled with lakes and marshes. They’re formed when blocks of ice buried beneath fluvioglacial material melt, leaving depressions

70
Q

Describe kettles

A

They’re the opposite of kames, being depressions rather than mounds. They are often found near each other and create a ‘Kame and kettle topography’

71
Q

What are varves?

A

Layers of sediment in meltwater lakes

72
Q

What are the colours and seasons of the different varves in a glacial lake?

A

Heavier sand is deposited in late spring when meltwater streams reach peak discharge. The darker coloured clay is layer down in the cooler autumn, when volumes of meltwater decrease. Discharge in the autumn is lower so streams can only carry finer sediments

73
Q

What are the effects of glaciation on drainage?

A

They can form proglacial lakes and breach drainage divides, the diversion of streams and the excavation of deep overflow channels.

74
Q

When do proglacial lakes form?

A

When deglaciation occurs, lakes form from the accumulation of meltwater, they are known as proglacial lakes

75
Q

What can proglacial lakes do to drainage basins?

A

They can cross the lowest points of watersheds and create new valleys. When the ice damming the proglacial lake melts, the new valleys can be left dry. In some cases however postglacial drainage patterns can be changed by them

76
Q

Give the potential temperature ranges for periglacial areas

A

Up to 15°C in the summer and it can drop to 50°C in the winter in some areas

77
Q

When can ground be called permafrost?

A

When subsoil temperatures fall below 0 degrees, for two years or more

78
Q

How much of the earth’s surface does permafrost cover?

A

Around 1/4

79
Q

In summer an active layer can form in permafrost areas, how deep is this active layer?

A

Up to 4m deep

80
Q

What happens when the surface layer of permafrost thaws?

A

It releases water it is unable to drain and, as there’s little evaporation due to low temperatures, the surface becomes very wet

81
Q

Describe continuous permafrost

A

Found in the coldest regions e.g. The Arctic. There’s little thawing even in the summer. It can affect the rock and soil up to depths of up to 700m in parts of Canada and up to twice this depth of Siberia

82
Q

Describe discontinuous permafrost

A

Slightly warmer regions where freezing conditions do not penetrate such deep depths (20 to 30m). It is discontinuous as it is broken by river, lakes and the sea

83
Q

Describe sporadic permafrost

A

Annual temperatures are around or just below 0. Permafrost only occurs in isolated spots

84
Q

Describe the process of frost heave

A

Upon freezing, fine grained soils expand unevenly upwards to form small domes. Stones in the soil heat up and cool the surrounding materials faster. Cold can pass through the stones very quickly meaning the soil below the ground in likely to freeze and expand. This will continue until the stone reaches the surface

85
Q

How is patterned ground formed?

A

On small domes, larger stones move outwards, effectively sorting the material which, when viewed from above, takes on a pattern.

86
Q

What is solifluction?

A

The slumping or movement of rock and soil material in response to gravity. Most likely to occur in the summer after significant melting

87
Q

When do solifluction lobes form?

A

When thaw melting occurs in the active layer leads to the release of great meltwater. As the water is unable to percolate downwards, saturating the soil, making it highly mobile. The soil begins to ‘flow’ due to in part the lack of substantial vegetation.

88
Q

Describe a pingo

A

A rounded hill with an ice core

89
Q

What are the two types of pingo?

A

Open system and closed system

90
Q

How big can pingos be?

A

Up to 60m in height and 600m in diameter

91
Q

How many pingos are there estimated to be in the Mackenzie delta region of Canada?

A

Over 1400

92
Q

How is a pingo formed?

A

In discontinuous permafrost, water seeps into the upper layers of the ground and freezes and expands outwards causing the overlying soil to ‘heave’ upwards

93
Q

How is a closed system pingo formed?

A

They form in areas with continuous permafrost where there are frozen lakes. The frozen lake insulates the ground beneath it, creating Talik. As the talik freezes in the winter, the water trapped in it expands pushing the layers of soil above it upwards, forming a pingo

94
Q

What happens when a Mackenzie pingo melts?

A

It collapses and forms a depression which could be filled by a small lake

95
Q

Describe the process of ground contraction

A

Essentially freeze thaw weathering in the soil where water enters a crack expands, exerting pressure on the walls of the crack, the ice then melts and the process is repeated.

96
Q

How does wind action work in frozen environments?

A

They can cause abrasion and dislodge fine sediments, leaving polished rock surfaces

97
Q

What is the name of the fine material that is transported of long distances by wind action and where is it found?

A

Loess, it is often found in North America and Eurasia, south of the boundary of the Pleistocene ice sheets

98
Q

In England what depth do loess deposits rarely exceed?

A

More than 2m

99
Q

In China how deep can loess deposits reach?

A

Depths of over 300m

100
Q

What’re loess deposits known as in East Anglia and the London basin?

A

Brick-earth deposits

AS Geography (physical) (19 decks)

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