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A-level - Geography > Topic 2 - Glaciation EQ1 > Flashcards

Topic 2 - Glaciation EQ1 Flashcards

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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)
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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
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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
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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)
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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

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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
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7
Q

Give 2 long term causes of climate change?

A
  • Milankovitch cycles
  • plate tectonics
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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

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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)
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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

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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

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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
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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

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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

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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
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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

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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
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18
Q

Give 2 short term causes of climate change?

A
  • variations in solar output
  • volcanic emissions
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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
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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

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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)
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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
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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

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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
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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

A-level - Geography (23 decks)

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