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glaciated lanscapes geography > unit three > Flashcards

unit three Flashcards

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1
Q

define weathering

A

the breakdown of rock where it is located involving physical processes such as freeze thaw weathering and chemical processes such as carbonation

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2
Q

what are the two processes of weathering (physical and chemical)?

A

physical: freeze thaw weathering
chemical: carbonation

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3
Q

define erosion

A

the removal of rock by ice water wind or gravity

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4
Q

what are the two key weathering processes?

A

freeze thaw weathering and dialation

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5
Q

describe freeze thaw weathering

A

when water freezes it expands by 9% in volume, and exerts pressure on any cracks or crevasses on the glacier. repeated freeze thawing eventually causes the rock to fracture

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6
Q

by how much does water expand by when frozen?

A

9%

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7
Q

what conditions must be met for freeze thaw weathering to occur?

A
  • the rock must be permeable to allow movement of water
  • precipitation must occur
  • temperatures must fluctuate
  • the altitude must be high enough to drop below freezing
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8
Q

what is dialation?

A

when rocks fracture due to overlying pressure being released. this typically occurs when a glacier is melting and exerting less downwards pressure. the rock then expands and fractures to release pressure

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9
Q

what is the dialation process sometimes called?

A

pressure release or unloading

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10
Q

what are the three types of erosional processes?

A

abrasion, plucking and subglacial meltwater erosion

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11
Q

describe the process of abrasion

A

as a glacier moves the embedded rock debris in its base scrape against the bedrock wearing it away

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12
Q

how does rock flour form?

A

during abrasion the subglacial debris are worn down and this is converted into tiny clay particles or rock flour

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13
Q

what are the factors that affect abrasion?

A
  • the speed of glacial movement
  • the ice thickness/weight
  • the amount of meltwater
  • the hardness of the debris/rock
  • the shape/supply of debris
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14
Q

how does plucking occur?

A

when meltwater seeps into cracks in the rock of the valley floor and sides and unfreezes causing freeze thaw weathering. as the glacier moves it “plucks” pieces of bedrock

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15
Q

where does plucking occur?

A

on the down valley side of rock obstacles that the ice is moving over via regelation slip. it occurs at the base of the glacier

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16
Q

how does regelation slip cause plucking?

A

regelation slip occurs when the pressure melting point is close to the temperature at the base of the ice, resulting in increased pressure which creates crevasses. the meltwater then fills into the crevasses and freeze thaw weathering occurs, which then results in plucking as it moves

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17
Q

what is attrition?

A

when rocks and pebbles wear down on eachother, becoming smaller and rounder

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18
Q

what is corrosion?

A

chemical erosion of rocks

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19
Q

what is hydraulic action?

A

when water crashes against something causing material to become dislodged and carried away

20
Q

why are subglacial streams powerful?

A

they form a system of tunnels with water flowing under extreme pressures. the flow direction is also determined by the pressure gradient and topography, not gravity.

21
Q

what are the two stages of cirque formation?

A
  1. the development of a niviation hollow
  2. the enlargement of the hollow after a cirque begins to move
22
Q

describe the formation of a niviation hollow

A
  1. north facing slopes recieve little insolation and so the temperature remains pretty cold even during the summer
  2. freeze thaw weathering occurs due to temperature fluctuations which results in loose material
  3. the surface of the glacier thaws in the summer producing meltwater which removes rock debris in the solifluction stream
23
Q

describe stage two of cirque formation

A
  1. further accumulation of ice adds weight resulting in the rotational movement of ice which is aided by the meltwater caused by pressure melting
  2. as the ice rotates it removes rock frangments from the back wall, this plucking occurs a steep, jagged and angular backwall
  3. the rock fragments picked up by plucking are transported by the rotating ice causing abrasion of the floor, deepening the hollow
  4. as erosion enlarges the hollow pressure release causes dialation cracks to form in the underlying rock, weakening it aiding further erosion
  5. as the glacier continues to slip it moves over the cirque and out of the basin creating a lip, which may experience abrasion as pressure icreases
24
Q

what are aretes?

A

sharp, knife edge ridges which have been produced by two cirques eroding back into eachother

25
Q

what are pyramidal peaks?

A

pyramidal peaks are where three or more cirques around a mountain have been formed, eroding the centre creating a sharp and steep central area. frost shattering enhances the shape further

26
Q

what are glacial troughs?

A

glacial troughs are formed when glaciers flow into pre-existing river valleys and alter them

27
Q

what are truncated spurs?

A

in a normal river valley interlocking spurs are created as the river erodes downwards and meanders from side to side, however as a glacier moves down a river valley it erodes each spur and over time create truncated spurs which have a steep cliff face

28
Q

what are hanging valleys?

A

just like large rivers have smaller tributaries which join them together, glaciers have smaller glaciers joining them, however the smaller glaciers may have their flow impaired by the larger glacier and this causes less erosive potential. this causes ice to hang above the much larger main valley after the ice has gone.

29
Q

what do hanging valleys sometimes create?

A

smaller waterfalls

30
Q

what are ribbon lakes?

A

ribbon lakes are long narrow lakes found in a glacial trough, certain parts of the valley erode more deeply through abrasion than others due to thicker ice or areas of softer rock and this creates a hollow called a rock basin. the harder rock on either side are known as rock bars which act as dams which fill up with rainwater

31
Q

what are the macro scale landforms?

A

cirque, arête, pyramidal peak, glacial trough, hanging valleys, truncated spurs and ribbon lakes

32
Q

what are the two meso scale landforms?

A

rouhee moutonees and crag and tails

33
Q

what are the micro scale landforms?

A

striatations, chatter marks and polished rock

34
Q

what are rouché moutonees?

A

a peice of resistant rock on the floor of a glacial trough that has undergone abrasion on the upper valley side and plucking on the down valley side

35
Q

what process allows rouche motonees to form?

A

regelation slip

36
Q

how do rouche moutonees form?

A
  • plucking takes place on the downside of the glacier. pressure water seeps into the cracks in the rocks and re freezes due to reduced temperatures, which causes water to expand, then debris break off and are plucked away causing a jagged side
  • abrasion takes place on the upper glacier side where high pressures push debris into the obstacle which polishes it giving it a smooth side
  • pressure melting occurs due to meltwater allowing the glacier to slide
37
Q

when do craig and tails form? (not how)

A

when a glacier moves over a band of resistant rock surrounded by less resistant rock

38
Q

how do crag and tails form ?

A

• plucking and abrasion erode the stoss side of the rock
• the less resistant rock gives the tail which has a gentler gradient
• moraines are often found on the top of the tail

39
Q

what are striations?

A

scratches on the hard bedrock produced during abrasion. debris frozen in the basal ice are dragged across the bedrock to produce them and they give a clear indication of what direction the ice was moving

40
Q

what are chatter marks ?

A

small intermittent chips/fractures in the bedrock formed when the basal debris within the ice is not in continuous contact with the bedrock

41
Q

describe the micro scale landform: polished rock

A

as well as scratching and gouging the rock the ice can polish it if sand and silt are found in the basal ice layer as opposed to angular rock fragments

42
Q

where is our example of a rouche mountonee?

A

at the floor of the nant ffrancon valley

43
Q

where is our example of an arête ?

A

cwm idwal

44
Q

where is our example of lateral morraines?

A

cwm idwal

45
Q

where is our example of a pyramidal peak?

A

cwm idwal

46
Q

where is our example of a cirque?

A

cwm idwal

glaciated lanscapes geography (7 decks)

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