physical part 2 Flashcards
(98 cards)
1
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
2
Q
examples of mass movement affecting valley sides in glacial environments
A
- rock fall
- slides and slumps
- solifluction
3
Q
where does rock fall happen
A
on slopes of 40° or more
4
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
5
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
6
Q
what happens during a slump
A
More rotational movement along a curved slip plain
Common in weaker rock e.g. clay
7
Q
what happens during solifluction
A
Gradual mass wasting process which occurs on slopes
Direct translation is ‘flowing soil’
8
Q
what is erosion
A
the wearing away and removal of soil, rock, or dissolved material
9
Q
what are the types of erosion in glacial environments
A
- plucking
- abrasion
- sub glacial streams
10
Q
what are the geomorphic processes in a glacial environment
A
- weathering
- mass movement
- erosion
11
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
12
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
13
Q
factors affecting rates of plucking
A
- nature of rock (joints)
- weakening of rock by weathering
- PMP - need meltwater
14
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
15
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
16
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
17
Q
landforms created by glacial erosion
A
- Corrie
- arete
- pyramidal peak
- glacial trough
- Roche moutonnee
- ellipsoidal basins
- striations, grooves and chatter marks
18
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
19
Q
arete description
A
- knife edges ridge which separated two corries or troughs
- crib Goch, Snowdonia
20
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
21
Q
glacial trough description
A
- steep sides
- might have truncated spurs
- also known as U-shaped
- might contain a misfit stream
22
Q
example of glacial trough
A
Nant Ffrancon Valley, Snowdonia
23
Q
formation of glacial trough
A
- glacial sides are eroded by moving ice
- glacier straightens, widens, and deepens the vakkey
24
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
25
size of Roche moutonnee
often upto 1km in length and 100m high
26
example of Roche moutonnee
Nant Ffrancon Valley, Snowdonia
27
formation of Roche moutonnee
- 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
28
what are glacial striations
scratches made on rock by debris embedded in the base of the glacier
- indicate the direction of movement of a glacier alongside other evidence
29
what are glacial grooves
gouged into the rock as rocks and debris in the base of the ice as the glacier pushes and pulls them along
30
what are chatter marks
- series of often Cresent chapes gauges chipped out of the bedrock as a glacier drags rock fragments underneath it
31
ellipsoidal basins
- formed by the impact of large ice sheets on the landscapes
- deep elongated lakes
32
landforms formed by glacial deposition
moraines
drumlins
till plains
erratics
33
where does the material carried by glaciers come from?
- rockfall
- debris flows
- abrasion
- plucking
- Aeolian deposits
- volcanoes
- avalanches
34
what are the two types of drift
till and outwash
35
till
directly deposited by ice
36
outwash
deposited by meltwater
37
types of glacial till
- lodgement till
- ablation till
38
lodgemt till
- deposited at base of advancing glaciers
- due to melting
- material is smeared onto underlying rock due to pressure
Less common
39
ablation till
- material deposited as ice melts/retreats
40
characteristics of glacial till
- unsorted and ungraded
- angular/sub angular
- ranging in size from rock flour to angular rocks
- unstratified - in mounds not layers
41
glacio fluvial deposits
material deposited by meltwater during a period of retreat
42
characteristics of glacio-fluvial deposits
- smaller than glacial till
- rounded and smooth due to contact with water
- sorted vertically in layers
43
lateral morains
- 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
44
example of lateral moraines
Athabasca Glacier, Canada
45
scale of lateral moraine example
1.5km long
124m high
46
medial moraines
- form where two glaciers meet
- material is often supra glacial and only 1m of coarse debris
- they rarely give significant landforms
47
example of medial moraines
Athabasca Glacier
48
scale of medial moraines
long upto 20km
wide upto 100m
height upto 10m
49
terminal moraines
- 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
50
terminal moraines important detail
- few glaciers today have terminal moraines in contact with ice - due to rapid glacial retreat
- mark boundary between unsorted and sorted material
51
recessional moraines
series of ridges running transversely across a glacial trough
52
how are recessional moraines made
deposited by a glacier as it retreats during a temporary still stand
Longer the pause the greater the size
53
push moraine
if glacier re-advances, previously deposited material may be shunted back
54
ground moraine
is used to describe the blanket of till deposited between more prominent moraine ridges
55
end moraine
another term used for recessional/terminal moraines
56
characteristics of drumlins
- smooth elongated mounds of till
- long axis parallel to direction of ice movement
- where found in clusters - drumlins swarm
57
size of drumlins
- 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
58
how to calculate shape of drumlins
length of drumlin÷max width
59
theories of drumlins formations
- 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
60
examples of drumlins
Hellifield, Ribblesdale - North Yorkshire
New York State - largest drumlin field - 10,000
61
how are till plains formed
When large masses of unstratified drift, deposited at the end of an advance, smother the surface
62
how are till plains transported
- mainly as supraglacial debris
- later deposited to form moraines
63
description of till plains
- stones are sub-angular
- NOT rounded like river material
- NOT sharp edges of rocks recently broken up by frost-shattering
64
example of till plains
- East Anglia - covered by chalky till - as ice passed over a chalk escarpment
65
size of till plain
- 300km2 area covered
- 140m deep in places
66
what is an erratic
- peices of rock that geologically are out of place
- vary from small to boulders
67
how do erratics form
- initially supraglacial debris
- transported and deposited into area of differing rock type
68
what is the case study of a landscape associated with the action of ice sheets?
Minnesota and the impact of the laurentide ice sheet
69
what is Minnesota's landscape a result of?
- largely of glacier activity in the quaternary period
- laurentide ice sheet advanced and retreated following climate change
70
laurentide ice sheet details
- covered millions of km2
- significant impact on geology and landscape of Minnesota
71
Minnesota's geology
- 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
72
how did the ice move across Minnesota?
- there were 4 lobes
- the lobes advanced and retreated based on the climate
73
how did the ice affect the geology of Minnesota ?
- 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
74
erosional impact on relief in minnesota
- as ice was sometimes 1km thick, it wore down many of the mountains
- now highest peaks only 500-700km
75
erosional impact on the creation of lakes in minnesota
- earlier techtonic tilting revealed weaker shales which are less resistant than overlaying rock
- caused ellipsoidal basins containing many lakes
76
landscape of SE minnesota
- se wasnt covered by ice, and has many steep hills and deep valleys
77
Minnesota - wadena lobe
- deposited drumlins and glacial drift in wadena county
- the till left the ground moraines with a reddish colour (iron rich sediments)
78
Minnesota - rainy and superior lobe
- left behind a coarse textured till with fragments of basalts, gabbro, red sandstone, slate and greenstone
79
Minnesota - ded Moines lobe
- till which is tan to buff coloured and clay rich and calcareous
80
Minnesota pro glacial lake
- 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
81
how did lake agassiz affect the SE landscape of minnesota
- it cut the valley of the Minnesota river valley
- responsible for forming a huge valley in SE minnesota
82
case study of a landscape shaped by the action of valley glaciers
- snowdonia
83
Snowdonia glaciation
- 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
84
u shaped valley in Snowdonia
- Nant Ffrancon
- carved by outlet valley moving NW to Anglesey
- the glacial trough has many erosion features
85
Snowdonia rock step
- 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
86
Snowdonia ribbon lake
- once filled the valley floor, overtime fills with sediment making flat floor
87
snowdonia truncated spurs
- as ice formed a straight path to Irish Sea it created truncated spurs
- Remnants of interlocking spurs
88
Snowdonia erosional features
- corrie
- aretes and pyramidal peaks
- ribbon lake
- truncated spurs
- hanging valleys
- roche moutonnee
- rock step
- U-shaped valley
89
Snowdonia hanging valleys
- along west side, smaller glaciers didn't cut upper courses so deeply as main glaciers
- makes hanging valleys
90
Snowdonia roche moutonnee
- smooth upside due to abrasion
- jagged plucked downside
91
Snowdonia corries
- 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
92
Snowdonia ribbon lake
- Where over-deepening due to softer rock being eroded by laminar flow
93
Snowdonia aretes and pyramidal peaks
- many aretes in Snowdonia
- Crib Goch rises to 923m which falls 300m either sides
94
Snowdonia depositional features
- tills and moraines
- drumlins
- eskers
- kames
95
what tills and morains are found in Snowdonia
- 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
96
Snowdonia drumlins
- number of large drumlins
- deposited under large glacier flowing from North wales
97
Snowdonia eskers
- formed by a stream under the glacier
- sediments built up on floor
- leaving a raised feature when the ice melts
98
Snowdonia Kames
- formed by deposition of moraines and glacial deposits by meltwater streams
-whilst still in contact with melting ice
