Topic 2 - Glaciation EQ1 Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Explain the Pleistocene glaciation?

A
  • roughly every 200-250 million years there are major periods of ice activity
  • most recent is Pleistocene epoch of the quaternary period which lasted 2 million years
  • led to significant fluctuations in global temperatures (led to glacial and interglacial period)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Outline what happens during glacial periods?

A

Climate cools significantly allowing precipitation to fall as snow - led to formation and growth of huge ice masses

  • ice masses spread south over large parts of Europe, Asia and North America
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Explain the position of ice during the extent of the Pleistocene epoch?

A
  • about 20,000 years ago - vast ice sheets covered much of North America and Europe
  • extensive glaciers and ice caps especially in mountainous regions - led to decrease in global sea levels (130m)
  • ice extended over much of the UK - southern most remained ice-free
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Outline the 3 main characteristics of the Pleistocene epoch?

A
  • not single ice age - temperatures fluctuating allowing ice advances and retreats (50 interglacial cycles)
  • extent of ice advance during each glacial was different
  • were fluctuations within each major glacial - most recent stadial in British isles was Loch Lomond stadial (marked end of epoch)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Explain what stadial and interstadials are?

A

Stadials - relatively short-live pulses of ice advance (most recent was Loch Lomond)

Interstadials - warmer periods characterised by ice retreats

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What can be concluded from the characteristics of the Pleistocene epoch?

A
  • medium and large scale glacial erosional landforms are likely to be the result of several glacial advances
  • depositional features tend to be the result of conditions and processes at work during the most recent glacial-interglacial cycle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Give 2 long term causes of climate change?

A
  • Milankovitch cycles
  • plate tectonics
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Outline an explain how Milankovitch cycles can explain climate change?

A

Changes in earth’s orbit around sun seen as primary cause of the oscillations between glacial and interglacial conditions - looks at eccentricity cycle, precession and obliquity cycle

Over 100,000 year period when they all combine it causes major temperature changes (0.5 and 1 degrees) affecting glacial ice volumes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Explain the quaternary ice age, what are the two epochs?

A

5 known ice ages in earths history - most recent is the quaternary ice age (started approx 2.6 mill years and extends to present day)

  • divided into Pleistocene (12,000 years ago) and Holocene epoch (started 10,000 and continues today)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Explain the obliquity cycle aspect of Milankovitch’s theory for causes of climate change?

A

Tilt of earth’s axis varies between 21.5 and 24.5 degrees - changes every 41,000 years - which affects the severity of the seasons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Explain the eccentricity cycle aspect of Milankovitch’s theory for causes of climate change?

A

Shape of earth’s orbit varies from circular to elliptical over period of 100,000 years - earth receives less solar radiation in elliptical orbit, characterised by glacial period

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Explain the precession aspect of Milankovitch’s theory for causes of climate change?

A

Earth wobbles as it spins on its axis - affects whether the northern hemisphere is tilted away or towards the sun - happens every 21,000 years

  • affects intensity of seasons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Outline and explain how positive feedback can increase warming?

A

Melting of ice cover by carbon dioxide emissions decreases albedo - methane is emitted as permafrost melts (increases greenhouse effect) causes rise in temperature leading to enhanced rates of calving and melting - loss of more snow cover further reduces surface albedo and decreases reflectivity of solar radiation - enhancing warming

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Outline and explain how positive feedback can increase cooling rates?

A

Small increase in snow raises surface albedo so more solar energy is reflected back into space, leading to cooler temps - allowing more precipitation to fall as snow/ice

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Outline and explain how negative feedback can decrease cooling rates?

A

Increasing global warming leads to more evaporation - pollution from industrialisation adds to global cloud cover, increasingly cloudy skies could reflect more solar energy back into space

  • global warming could be less intense due to global dimming
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Outline and explain how negative feedback can decrease warming?

A

Ice sheet dynamics can disrupt thermohaline circulation - warming water in arctic disrupts ocean currents, less warm water from gulf stream is drawn north which could lead to global cooling in Northern Europe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Explain how plate tectonics can lead to climate change?

A
  • start of quaternary ice age linked to changing position of the continents due to tectonics
  • NA and SA plates collided, re-routed ocean currents which now forced the warm Caribbean waters towards Europe, creating the Gulf Stream
  • Gulf Stream transported extra moisture into artic atmosphere which fell as snow building Greenland ice sheet
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Give 2 short term causes of climate change?

A
  • variations in solar output
  • volcanic emissions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Explain how variations in solar outputs can lead to climate change?

A

Sunspots are caused by intense magnetic activity in sun’s interior - increase in sunspots suggests sun is more active, and giving of more energy

  • vary over 11 year period
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Explain how sunspot activity has been linked to the little ice age?

A

Evidence suggest that the little ice age may have been triggered by volcanic emissions and variations in solar output - observations of the sun during the little ice age indicate very little sunspot activity on sun’s surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Explain how volcanic emissions can lead to climate change?

A

Most significant impact of volcanic eruptions on the climate is the injection of large quantities of sulphur dioxide gas into the atmosphere

  • remains in atmosphere for up to 3 years - forming sulphate aerosols which increase reflection of suns radiation back into space (albedo effect)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Give evidence for volcanic emissions affect on climate change?

A

Indonesian mount tambora (most powerful volcanic eruption recorded in history) - accounts of very cold weather were documented in subsequent year in many regions (lasted 5 years - short period)

  • originally believed to be a result of the ash emitted into the atmosphere which blocked suns radiation however the ash returns to the surface within a few months
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Explain what the lock Lomond stadial was?

A

significant period of climatic cooling that occurred towards the end of the last glacial period (Pleistocene epoch - about 12,000 years ago) - led to formation of ice caps in Scottish highlands which flowed outwards, glaciers in Lake District

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Explain 2 causes of the Loch Lomond stadial?

A
  • freshwater discharge from NA ice sheets - disrupted THC - cut of poleward heat transport from Gulf Stream
  • impact hypothesis - asteroid impact could have triggered cooing - presence of extra-terrestrial material in sedimentary rock record
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What was the little ice age?

A

Occurred during Holocene epoch - was a period of cooling (lasted from 1550 - 1850) - lowered globally temperatures by around 1 to 2 degrees

Mostly affected Europe and North America

26
Q

What were the causes of the little ice age?

A
  • volcanic activity
  • decreased sunspot activity
27
Q

What were some of the affects of the little ice age?

A
  • affected crop growth across Europe - led to famines
  • sea ice extended out from Iceland for miles
  • brought colder winters - caused rivers and canals to freeze - allowed markets and festivals to be held on the river Thames
28
Q

Give 2 shorter-term climate events?

A
  • Loch Lomond stadial (Pleistocene)
  • little ice age (Holocene)
29
Q

Explain what the cryosphere is?

A

Frozen part of the earth’s hydrological system (made up of ice sheets in Greenland and Antarctica) includes ice caps, glaciers and areas of permafrost

  • plays role in regulating temps (albedo effect)
30
Q

Explain why the cryosphere is important - 2 points?

A
  • large ice sheets act as stores within the hydrological cycle
  • vital for the earths climate - the snow reflects solar energy (albedo effect)
31
Q

Explain 3 ways ice masses can be classified?

A
  • scale
  • location
  • thermal characteristics
32
Q

Outline and explain what temperate glaciers are?

A
  • occur in high altitude areas (outside polar regions, eg in the Alps)
  • temperature of surface layer fluctuates above and below melting point
  • increased pressure of overlying ice allows PMP to be met - water exists at 0 degrees
  • meltwater lubricates base allowing for movement
33
Q

Explain why temperate glaciers are not frozen to the base?

A
  • temperature of surface layer fluctuates above and below melting point
  • temperature of ice extending downwards is close to melting point due to overlying mass
  • water can exist below 0 degrees - causes basal ice to melt continuously preventing freezing
34
Q

Explain what prevents temperate glaciers from freezing to the bedrock?

A
  • presence of meltwater - causes basal ice to melt continuously (produced as PMP is met)
  • effects of pressure
  • geothermal energy
35
Q

Outline and explain what polar glaciers are?

A
  • glaciers which occur in high latitude regions (Antarctica and Greenland)
  • average temp of ice is well below 0 degrees, due to extremely low surface temps (-20 degrees)
  • PMP not reached, not enough geothermal source to raise temp at base of glacier
  • permanently frozen to the base
36
Q

Explain why polar glaciers are frozen to the base?

A
  • surface temp is so low so temperature of ice is well below 0 degrees
  • geothermal sources is not great enough - no meltwater present
  • no debris-rich basal layer
37
Q

Outline and explain what polythermal glaciers are?

A
  • further subdivision
  • underneath is warm ‘wet’ based and the margin cold based
  • many glaciers are cold based in upper regions and warm based lower down (common in Norway)
38
Q

Outline 4 main types of cold environments?

A
  • polar (high latitude) regions
  • periglacial (tundra) regions
  • alpine/mountainous (high altitude) regions
  • glacial environments
39
Q

Outline and explain polar and periglacial regions?

A

Polar - areas of permanent ice (eg vast ice sheets of Antarctica and Greenland)

Periglacial - at the ‘edge’ of permanent ice - characterised by permafrost (eg Alaska)

40
Q

Outline and explain alpine and glacial regions?

A

Alpine - high altitude, mountainous regions for example the Himalayas

Glacial - found at edges of ice sheets, particular high mountainous regions - eg Himalayas

41
Q

Outline what permafrost is?

A

Soil and rock that remains frozen as long as temperatures do not exceed 0 degrees in the summer months for two consecutive years

  • 3 types - continuous, discontinuous and sporadic
42
Q

Explain what continuous and discontinuous permafrost is?

A
  • forms in coldest regions of world (average temp below -6 degrees)
  • extends downwards hundreds of meters
  • temp -5 to -50 degrees

Discontinuous is similar but fragmented and thinner (temp -1.5 to -5 degrees)

43
Q

Explain what sporadic permafrost is?

A
  • occurs at the margins of periglacial environments
  • very fragmented and only few meters thick
  • occurs on shady hillsides or beneath peat
  • temp range of 0 to -1.5 degrees
44
Q

What is the active later of permafrost regions?

A
  • during summer when energy balance is positive it causes overlying snow and ice to melt away/thaw to produce a seasonally unfrozen zone - freezes in winter
  • from a few centimetres to 3m deep
45
Q

What are geomorphological processes?

A

Those that result in the modification of landforms on earths surface - most active at margins of cold environments due to high levels of precipitation and the fluctuation of temperatures

46
Q

Explain the process of frost action/freeze-thaw?

A
  • affects bare rocky outcrops on mountainsides
  • water (rain/meltwater) seeps into cracks and pores in rocks
  • temperature falls to 0 degrees causing water to freeze and expand by 9%
  • expansion places stress within rock, enlarging cracks and pores
  • repeats over a period - until chunks of rock break away forming scree at foot of slope
47
Q

What are block fields, what process forms them ?

A
  • block fields - extensive area of broken up angular fragments of rock which accumulate on flat plateau
  • formed through chunks of rock breaking away from outcrop and pilling up as scree at the foot of the slope (freeze-thaw)
48
Q

Outline 5 landforms created through freeze-thaw - explain them?

A
  • block fields - accumulation of angular frost-shattered rock which pile up on flat surface
  • tors - large free standing rock outcrop - form where more resistant areas of rock occur
  • scree/talus slopes - rock fragments fall and accumulate on lower slopes
  • pro-talus ramparts - patch of snow at base of cliff acts as buffer when rocks fall - leaving rampart of boulder after melting
  • rock glaciers
49
Q

Explain how pro-talus ramparts are formed?

A

Created if a patch of snow has settled at base of cliff - when rocks fall (due to frost action) the snow acts as a buffer, the rocks settle at the base of the patch, during summer months the snow melts leaving a rampart of boulders

  • created by freeze-thaw
50
Q

Explain how scree/talus slopes are formed?

A
  • formed when rock fragments fall and accumulate on lower slopes or base of cliffs
  • larger material that makes up the slope, the steeper its angle of rest tends to be
  • created by freeze-thaw
51
Q

Explain how rock glaciers are formed?

A

When large amounts of frost-shattered rock mixes with ice

On the surface rock glaciers look like streams or angular rocks - conjoined with interstitial ice below and move slowly

52
Q

Explain the process of nivation?

A
  • combination of processes which weaken and erode the ground beneath a snow patch
  • processes include freeze-thaw weathering, solifluction and meltwater erosion
  • forms rounded nivation hollow
53
Q

Explain how a nivation hollow is formed?

A
  • formed through nivation (processes like freeze-thaw weathering, solifluction and meltwater erosion)
  • fluctuating temps and meltwater promote frost shattering
  • meltwater carries away rock debris - enlarging hollow
  • slumping - during summer as saturated debris collapses due to gravity
54
Q

Explain how a corrie can form from a nivation hollow?

A
  • as long as weathered material is removed by meltwater, the nivation hollow is continually enlarged
  • if climate cools - the hollow will be occupied by glacial ice which can become enlarged forming corrie
55
Q

Explain the process of frost heave?

A
  • freezing and expansion of soil water causes upward dislocation of soil and rocks
  • ground freezes, large stones become chilled more rapidly than soil
  • water below stones freezes and expands - pushing stones upward forming small drones on the ground surface

Forms pattered ground

56
Q

Explain the landforms formed through frost heave?

A
  • stone polygons - on flat ground, large stones settle around the edges of the domes - smaller stones moved by meltwater or wind
  • stone stripes - on slopes, where sloping can distort the polygons as stones gradually slide downslope
57
Q

Explain the process of ground contraction?

A
  • dry areas of active layer refreezes, ground contracts and cracks
  • meltwater enters cracks causing freeze-thaw weathering - forms ice wedges
  • enlarging and deepening cracks enlarges ice wedges

Can become extensive forming a polygonal pattern (type of patterned ground)

58
Q

Explain the process of solifluction

A
  • downslope movement of saturated active layer - due to influence of gravity
  • occurs in regions of permafrost

Forms a tongue-shaped feature at foot of slope (solifluction lobe)

59
Q

Explain the processes of aeolian action and meltwater erosion?

A

Aeolian action - wind able to pick up fine sediment form ground surface forming extensive accumulation deposits (due to lack of vegetation)

Meltwater erosion - thawing creates meltwater which erodes channels, freezing in winter reduces discharge and increases sediment deposition

60
Q

Explain the two landforms formed by aeolian and meltwater processes?

A

Aeolian action - forms extensive accumulations of wind blown deposits (loess)

Meltwater erosion - forms braided channels separated by islands of deposited material

61
Q

Outline 5 periglacial processes and give the landform they form

A
  • solifluction - solifluction lobe
  • frost heave - stone polygons and stone stripes
  • nivation - rounded nivation hollow
  • meltwater erosion - braided stream
  • aeolian action - loess
62
Q

Outline 3 factors affecting permafrost distribution?

A
  • Soil composition, moisture content, and thermal conductivity influence the formation and maintenance of permafrost
  • main factor is climate (temperature/moisture available) - determines depth and extent of permafrost
  • proximity to body of water