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physical part 2 Flashcards

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1
Q

what is weathering

A

the breakdown of rock in situ

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2
Q

what are the three main types of weathering

A
  • physical / mechanical
  • chemical
  • biological
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3
Q

what is physicalweathering

A

main processes. rock is broken down into small pieces

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4
Q

what is chemical weathering

A

chemical reactions to breakdown rock to it’s chemical constituents

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5
Q

what is biological weathering

A

consists of physical and chemical actions linked to plant growth

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6
Q

3 types of physical weathering

A
  • freeze thaw
  • frost shattering
  • pressure release (dilation)
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7
Q

freeze thaw (physical weathering)

A

Water seeps into cracks in rock
When water freezes, it expands by 9% which wedges rock apart
With repeated cycles, the rock breaks into pieces

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8
Q

frost shattering (physical weathering)

A

water trapped in rock pores will freeze and expand at very low temp. expansion causes stress which causes rock to disintegrate to small bits

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9
Q

pressure release (physical weathering)

A

the underlying rock expands and fractures parallel to the surface.
The parallel fractures are sometimes known as pseudo-bedding planes

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10
Q

when is chemical weathering particularly important

A

when meltwater is present and in contact with rocks

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11
Q

what are the main types of chemical weathering in glacial environments

A
  • carbonation
  • solution
  • hydrolosis
  • hydration
  • oxidation
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12
Q

carbonation

A

carbonic acid reacts with calcium carbonate in rock to produce calcium bicarbonate

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13
Q

oxidation

A

minerals in rock react with oxygen (either 02 in water or air)

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14
Q

hydrolysis

A

minerals in rock, can undergo a chemical reaction when in contact with water.
Hydrogen is involved

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15
Q

solution

A

any process where a mineral dissolved in water is known as solution - some become soluble when water is more acidic

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16
Q

hydration

A

when water molecules are added to rock minerals they create minerals of a larger volume causes flaking

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17
Q

types of biological weathering

A
  • tree roots
  • chelation
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18
Q

tree roots (biological weathering)

A

grow into cracks into joints in rock, they exert pressure forcing the rock apart

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19
Q

chelation (biological weathering)

A

As plant and animal litter decomposes, organic acids are released causing soil water to become more acidic

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20
Q

what is mass movement

A

when the forces on a slope material exceed the forces acting to keep material on the slope
Gravity Vs friction

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21
Q

examples of mass movement affecting valley sides in glacial environments

A
  • rock fall
  • slides and slumps
  • solifluction
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22
Q

where does rock fall happen

A

on slopes of 40° or more

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23
Q

what happens during a rock fall

A

Due to gravity and physical weathering
Material might collect at the bottom of be removed by transport

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24
Q

what happens during land slide

A

Movement along a slight line slip plain
e.g. bedding plain or fault
In glaciers; erosion at base of slope undercuts valley sides

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25
Q

what happens during a slump

A

More rotational movement along a curved slip plain
Common in weaker rock e.g. clay

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26
Q

what happens during solifluction

A

Gradual mass wasting process which occurs on slopes
Direct translation is ‘flowing soil’

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27
Q

what is erosion

A

the wearing away and removal of soil, rock, or dissolved material

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28
Q

what are the types of erosion in glacial environments

A
  • plucking
  • abrasion
  • sub glacial streams
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29
Q

what are the geomorphic processes in a glacial environment

A
  • weathering
  • mass movement
  • erosion
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30
Q

when is plucking most necessary

A

Mainly happens when meltwater seeps into rocks of valley sides
Particularly effective at the base where PMP causes meltwater

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31
Q

plucking

A
  • removed large fragments of rock
  • meltwater gets into cracks and then as water refreezes around the preweathered rock it becomes part of glacial and ‘plucks’ it
  • ice doesn’t have enough power
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32
Q

factors affecting rates of plucking

A
  • nature of rock (joints)
  • weakening of rock by weathering
  • PMP - need meltwater
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33
Q

abrasion

A
  • ice with rock fragments scrapes along valley bed and sides
  • coarse rock will make scratches (striations)
  • may create chatter marks
  • fine material embedded in nice will polish rocks smooth
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34
Q

factors affecting the rates of abrasion

A
  • presence of basal debris
  • debris size and shape
  • relative hardness of particles and bedrock
  • ice thickness
  • basal water pressure
  • movement of debris to the base
  • removal of fine debris
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35
Q

sub-glacial water erosion

A
  • temperate glaciers which plunge down deep crevasses right to the valley floor
  • streams carry vast quantities of weathered and glacial sediments
  • beneath the glacial the steams erode the base rock
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36
Q

landforms created by glacial erosion

A
  • Corrie
  • arete
  • pyramidal peak
  • glacial trough
  • Roche moutonnee
  • ellipsoidal basins
  • striations, grooves and chatter marks
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37
Q

Corrie description

A

Armchair shaped hollow with steep back wall
The hollow is over deepened and is often characteristics by a rock lip
- might contain a small lake

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38
Q

arete description

A
  • knife edges ridge which separated two corries or troughs
  • crib Goch, Snowdonia
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39
Q

pyramidal peaks

A
  • angular glaciated mountain peak with three or more very steep sides
  • usually back walls of corries
  • each side is separated by arete
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40
Q

glacial trough description

A
  • steep sides
  • might have truncated spurs
  • also known as U-shaped
  • might contain a misfit stream
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41
Q

example of glacial trough

A

Nant Ffrancon Valley, Snowdonia

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42
Q

formation of glacial trough

A
  • glacial sides are eroded by moving ice
  • glacier straightens, widens, and deepens the vakkey
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43
Q

Roche moutonnee description

A
  • masses of more resistant rock that are smooth and rounded with striations
  • the down valley side is teep and jagged
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44
Q

size of Roche moutonnee

A

often upto 1km in length and 100m high

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45
Q

example of Roche moutonnee

A

Nant Ffrancon Valley, Snowdonia

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46
Q

formation of Roche moutonnee

A
  • as glacier can’t erode hard rock, if flows over the hard rock
  • leaving behind striations
  • the down valley side is jagged due to plucking of the soften rock
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47
Q

what are glacial striations

A

scratches made on rock by debris embedded in the base of the glacier
- indicate the direction of movement of a glacier alongside other evidence

48
Q

what are glacial grooves

A

gouged into the rock as rocks and debris in the base of the ice as the glacier pushes and pulls them along

49
Q

what are chatter marks

A
  • series of often Cresent chapes gauges chipped out of the bedrock as a glacier drags rock fragments underneath it
50
Q

ellipsoidal basins

A
  • formed by the impact of large ice sheets on the landscapes
  • deep elongated lakes
51
Q

landforms formed by glacial deposition

A

moraines
drumlins
till plains
erratics

52
Q

where does the material carried by glaciers come from?

A
  • rockfall
  • debris flows
  • abrasion
  • plucking
  • Aeolian deposits
  • volcanoes
  • avalanches
53
Q

what are the two types of drift

A

till and outwash

54
Q

till

A

directly deposited by ice

55
Q

outwash

A

deposited by meltwater

56
Q

types of glacial till

A
  • lodgement till
  • ablation till
57
Q

lodgemt till

A
  • deposited at base of advancing glaciers
  • due to melting
  • material is smeared onto underlying rock due to pressure
    Less common
58
Q

ablation till

A
  • material deposited as ice melts/retreats
59
Q

characteristics of glacial till

A
  • unsorted and ungraded
  • angular/sub angular
  • ranging in size from rock flour to angular rocks
  • unstratified - in mounds not layers
60
Q

glacio fluvial deposits

A

material deposited by meltwater during a period of retreat

61
Q

characteristics of glacio-fluvial deposits

A
  • smaller than glacial till
  • rounded and smooth due to contact with water
  • sorted vertically in layers
62
Q

lateral morains

A
  • run along edge of glacial valley
  • formed from debris frost shattered and lands on top of glacier
  • when melting takes place, embankment of material left against valley sides as it’s deposited
63
Q

example of lateral moraines

A

Athabasca Glacier, Canada

64
Q

scale of lateral moraine example

A

1.5km long
124m high

65
Q

medial moraines

A
  • form where two glaciers meet
  • material is often supra glacial and only 1m of coarse debris
  • they rarely give significant landforms
66
Q

example of medial moraines

A

Athabasca Glacier

67
Q

scale of medial moraines

A

long upto 20km
wide upto 100m
height upto 10m

68
Q

terminal moraines

A
  • marks max extent of glacier form at snout
  • steeper up valley side due to the ice supporting the deposits making them less likely to collapse
69
Q

terminal moraines important detail

A
  • few glaciers today have terminal moraines in contact with ice - due to rapid glacial retreat
  • mark boundary between unsorted and sorted material
70
Q

recessional moraines

A

series of ridges running transversely across a glacial trough

71
Q

how are recessional moraines made

A

deposited by a glacier as it retreats during a temporary still stand
Longer the pause the greater the size

72
Q

push moraine

A

if glacier re-advances, previously deposited material may be shunted back

73
Q

ground moraine

A

is used to describe the blanket of till deposited between more prominent moraine ridges

74
Q

end moraine

A

another term used for recessional/terminal moraines

75
Q

characteristics of drumlins

A
  • smooth elongated mounds of till
  • long axis parallel to direction of ice movement
  • where found in clusters - drumlins swarm
76
Q

size of drumlins

A
  • range from small mounds to huge hills
  • shape is measured using elongated ratio
  • between 25:1 and 4:1 - greater elongation suggest more powerful ice flow
77
Q

how to calculate shape of drumlins

A

length of drumlin÷max width

78
Q

theories of drumlins formations

A
  • formed as ice become overloaded
  • as glacier re-advances, deposited material is reshaped
  • accumulation around a bedrock obstruction
  • thinning of ice results in reduction in competence of glacier
79
Q

examples of drumlins

A

Hellifield, Ribblesdale - North Yorkshire
New York State - largest drumlin field - 10,000

80
Q

how are till plains formed

A

When large masses of unstratified drift, deposited at the end of an advance, smother the surface

81
Q

how are till plains transported

A
  • mainly as supraglacial debris
  • later deposited to form moraines
82
Q

description of till plains

A
  • stones are sub-angular
  • NOT rounded like river material
  • NOT sharp edges of rocks recently broken up by frost-shattering
83
Q

example of till plains

A
  • East Anglia - covered by chalky till - as ice passed over a chalk escarpment
84
Q

size of till plain

A
  • 300km2 area covered
  • 140m deep in places
85
Q

what is an erratic

A
  • peices of rock that geologically are out of place
  • vary from small to boulders
86
Q

how do erratics form

A
  • initially supraglacial debris
  • transported and deposited into area of differing rock type
87
Q

what is the case study of a landscape associated with the action of ice sheets?

A

Minnesota and the impact of the laurentide ice sheet

88
Q

what is Minnesota’s landscape a result of?

A
  • largely of glacier activity in the quaternary period
  • laurentide ice sheet advanced and retreated following climate change
89
Q

laurentide ice sheet details

A
  • covered millions of km2
  • significant impact on geology and landscape of Minnesota
90
Q

Minnesota’s geology

A
  • rocks lie in alternating belts of volcanic and sedimentary rocks
  • between these belts is granitic rock materials
  • gneisses have been folded and faulted to form some of the more mountainous areas of north Minnesota
91
Q

how did the ice move across Minnesota?

A
  • there were 4 lobes
  • the lobes advanced and retreated based on the climate
92
Q

how did the ice affect the geology of Minnesota ?

A
  • the origins of the lobes resulted in till with many different characteristics
  • as it advanced and retreated, it transported and deposited till
  • due to differences in lithology in Minnesota to determine the lobe which deposited the till
93
Q

erosional impact on relief in minnesota

A
  • as ice was sometimes 1km thick, it wore down many of the mountains
  • now highest peaks only 500-700km
94
Q

erosional impact on the creation of lakes in minnesota

A
  • earlier techtonic tilting revealed weaker shales which are less resistant than overlaying rock
  • caused ellipsoidal basins containing many lakes
95
Q

landscape of SE minnesota

A
  • se wasnt covered by ice, and has many steep hills and deep valleys
96
Q

Minnesota - wadena lobe

A
  • deposited drumlins and glacial drift in wadena county
  • the till left the ground moraines with a reddish colour (iron rich sediments)
97
Q

Minnesota - rainy and superior lobe

A
  • left behind a coarse textured till with fragments of basalts, gabbro, red sandstone, slate and greenstone
98
Q

Minnesota - ded Moines lobe

A
  • till which is tab to buff coloured and clay rich and calcareous
99
Q

Minnesota pro glacial lake

A
  • lake agassiz
  • as ice had blocked the natural passage of meltwater, lake agassiz formed to s of ice
  • maximum covered 440,000km2 and in places it was 400m in depth
100
Q

how did lake agassiz affect the SE landscape of minnesota

A
  • it cut the valley of the Minnesota river valley
  • responsible for forming a huge valley in SE minnesota
101
Q

case study of a landscape shaped by the action of valley glaciers

A
  • snowdonia
102
Q

Snowdonia glaciation

A
  • ice was at extent around 20,000 years ago
  • at this time, North Wales would have been like a sea of ice with exposed nunataks
  • with rising temp, ice sheet melted and valleys would be fed by Corrie glaciers
103
Q

u shaped valley in Snowdonia

A
  • Nant Ffrancon
  • carved by outlet valley moving NW to Anglesey
  • the glacial trough has many erosion features
104
Q

Snowdonia rock step

A
  • at Nant Ffrancon valley there is a drop of 100m in height and a waterfall
  • the rock is resistant to erosion
  • ice entering then erodes and over-deepened making this valley
105
Q

Snowdonia ribbon lake

A
  • once filled the valley floor, overtime fills with sediment making flat floor
106
Q

snowdonia truncated spurs

A
  • as ice formed a straight path to Irish Sea it created truncated spurs
  • Remnants of interlocking spurs
107
Q

Snowdonia erosional features

A
  • corrie
  • aretes and pyramidal peaks
  • ribbon lake
  • truncated spurs
  • hanging valleys
  • roche moutonnee
  • rock step
  • U-shaped valley
108
Q

Snowdonia hanging valleys

A
  • along west side, smaller glaciers didn’t cut upper courses so deeply as main glaciers
  • makes hanging valleys
109
Q

Snowdonia roche moutonnee

A
  • smooth upside due to abrasion
  • jagged plucked downside
110
Q

Snowdonia corries

A
  • Cwm Idal - linear
  • Half km in length, 1km width
  • lot deeper due to pass above it being low, allowing ice to spill over from Llanberis Pass
111
Q

Snowdonia ribbon lake

A
  • Where over-deepening due to softer rock being eroded by laminar flow
112
Q

Snowdonia aretes and pyramidal peaks

A
  • many aretes in Snowdonia
  • Crib Goch rises to 923m which falls 300m either sides
113
Q

Snowdonia depositional features

A
  • tills and moraines
  • drumlins
  • eskers
  • kames
114
Q

Snowdonia tills and moraines

A
  • terminal, lateral and hummocky moraines found in area of Cwm Idal
  • terminal moraine on west side of Nant Ffrancon formed as material deposited at end of glacier
  • flowed from corrie above U-Shaped valley
115
Q

Snowdonia drumlins

A
  • number of large drumlins
  • deposited under large glacier flowing from North wales
116
Q

Snowdonia eskers

A
  • formed by a stream under the glacier
  • sediments built up on floor
  • leaving a raised feature when the ice melts
117
Q

Snowdonia Kames

A
  • formed by deposition of moraines and glacial deposits by meltwater streams
    -whilst still in contact with melting ice

physical geography (4 decks)

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