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Glaciation > EQ1 > Flashcards

EQ1 Flashcards

1
Q

What are the two dominant stages the Earth fluctuates between and what are their definitions ?

A

Greenhouse Earth: When there are no continental glaciers on the planet due to the warming processes of greenhouse gasses
Icehouse Earth: a global ice age when large ice sheets are present on Earth, this period fluctuates between glacial and interglacial periods

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2
Q

How is geological time divided ?

A

Era, Period, Epoch

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3
Q

What geological time are we in now and how long as out epoch lasted ?

A

Era: Cenzoic
Period: Quaternary
Epoch: Holocene
-2.6 million years

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4
Q

What is the Pleistocene epoch known as and why?

A

Known as the ice age and is characterised by over 50 glacial-interglacial cycles where glaciers reached their maximum

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5
Q

What was the last glacial maximum and glacial advance and what were they called ?

A

Last glacial maximum:
-Devensian (approx. 18,000 years ago)
Last glacial advance:
-Loch Lomond Stadial (12,000-10,000 years ago)

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6
Q

Name the characteristics of the Pleistocene period

A
  • Not a single ice age over the 2 million years, but temperature fluctuations allowed a number of ice advances and retreats
  • Fluctuations between each major glacial:
  • -Short lived advances known as stadials
  • -Warmer periods of retreats known as interstadial
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7
Q

What are the long term causes of climate change ?

A

Milankovitch cycles:

  • Shift in obliquity, 3 degree shift over 41,000 years
  • Eccentricity, Earths solar orbit varies in distance due to shift in elliptical orbit and circular orbit
  • Precession, Earths wobble on its axis due to the tidal forces of the sun and moon
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8
Q

What are the positive feedback mechanisms present in increasing the warming or cooling rates?

A
  • Decreased temperatures increase snow cover, snow cover increases albedo leading to further cooling
  • Melting snow/ice cover by GHG decreases albedo and methane is emitted as permafrost melts which leads to further Greenhouse effects
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9
Q

What are the negative feedback mechanisms present in increasing the warming or cooling rates?

A
  • When warming, evaporation increases, greater pollution from industrialisation leafs to increases cloud cover and increasingly cloudy skies and particulates causing global dimming which reduces solar radiation and warming
  • Ice sheet dynamics disrupt thermohailine circulation which disrupts ocean currents such as the gulf stream, less warm water is drawn north which leads to cooling in Northern Europe
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10
Q

What are the short term causes of climate change?

A

Solar output variation:
-Variations in solar activity causes variations in thermal energy transferred to Earth
-vary over 11 years, cooler temperatures occurred from 1300-1870, period known as little ice age
Volcanic emissions:
-Volcanic eruptions inject many particulates and sulphur dioxide into the atmosphere which causes a blanket effect on the atmosphere which blocks solar radiation, these can stay in the atmosphere for up to 3 years

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11
Q

Describe the characteristics of the Loch Lomond Stadial

A
  • Abrupt period of renewed cooling with regrowth of glaciers in upland Britain about 12,500 years ago
  • Temperatures were 6-7C lower leading to advance of many glaciers in Scotland and the formation of ice caps in Northern Scotland from which cirque valley glaciers moved outwards with smaller cirque glaciers in northern wales
  • Ice core data suggests 7C rise after the event
  • suggested that it was caused by drainage of huge proglacial lake Agassiz which disrupted THC and cut off pole ward transport to gulf stream
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12
Q

Describe the characteristic of the Little Ice age:

A

-Between 1550-1750
Effects:
-Abandonment of northern Scandinavia
-Re-advancement of European glaciers down valleys, predominantly positive mass balance leaving terminal moraines from which glaciers retreated
-Arctic sea ice spread further south (polar bears seen in Iceland), rivers in UK and Europe froze
-Holocene period
-different attributed causes (volcanic eruption, solar output)
-since lil ice age, glaciers in swiss alps retreated 2.3km
-Many crops failed

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13
Q

What are ice shelfs

A

Ice sheets which extend out to sea, unconstrained, e.g. princess Elizabeth in east antarctica

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14
Q

What are the 3 types of glaciers

A

Cold based, warm based, polythermal

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15
Q

What are warm based glaciers

A
  • Occur in high altitude areas outside polar regions e.g. alps
  • base is above the melting point, either from friction or geothermal heat so meltwater created acts as a lubricant causing it to move easily
  • ice at the top of the glacier melts during summer months which increases lubrication due to an increase in meltwater
  • high levels of erosion cause many debris to be entrained in the base
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16
Q

what are cold-based glaciers

A
  • high altitudes in polar regions e.g. Antarctica and Greenland
  • average temperature of ice is usually well below 0, due to extreme surface temperature (-20 to -30) and accumulation of geothermal sources is not enough to raise its temperature above 0c, despite ice sometimes being up to 500m thick
  • little surface melt in short polar summer
  • glacier is permanently frozen to its bed so no entrained debris
17
Q

What are polythermal glaciers

A
  • Hybrid glacier where underneath is warm (wet) based and the margin is cold-based
  • many glaciers are cold-based in the upper region and warm in the lower region when they extend to lower climate zones, this is common in Svalbard, Norway
18
Q

ice sheet

A

mass of ice or snow covering an area of 50,000 km^2, they bury entire landscapes including tall mountains, unconstrained, e.g. Antarctic ice sheet

19
Q

Ice Cap

A

Dome-shaped Ice mass which covers less than 50,000km^2, usually on high ground, unconstrained, e.g. Vatnajokull, Iceland

20
Q

Ice field

A

smaller than ice caps and defined by surrounding land, constrained

21
Q

valley glacier

A

glacier bound by walls of a valley, descends from high mountains from an ice cap on a plateau or from an icesheet, constrained

22
Q

Piedmont glacier

A

Glacier that spreads out wide in a love shape as it leaves a narrow valley to enter a wider valley or plain

23
Q

cirque glacier

A

glacier occupying a cirque (corrie), Teton glacier in grand Tetons national park, Wyoming, USA

24
Q

compare present-day distribution of high altitude ice sheets and Pleistocene ice extents

A
  • Ice covers at pleistocene macimum was 3x greater than modern day
  • antartica and Greenland ice sheets only slightly larger in pleistocene
  • major extensions were north american and scandiavian ice sheets which all grw to thickness of 3km-4km
  • other significant extensions were in new zealand, south america, sibera and himalayas
25
Q

what evidence is there for the pleistocene period

A

Depositional: drumlins (Vale of eden, Cumbria), erratics (Bowder Stone, lake district), moraine (ciargorns)

Erosional Evidence: Corries, Aretes, glacial troughs along with roches moutonees, crag and tail and knock and lochan landscapes (in lake district, cairgorns and snowdonia)

Meltwater evidence: Meltwater channels (North Yorkshire), glacial till (norfolk)

26
Q

Define permafrost

A

Soil and rock that remains frozen as long as temperatures do not exceed 0C in summer months for at least 2 consecutive years

27
Q

Name the cahracteristics of continuous permafrost

A

Latutude: 75 - 65 N
Temperature: -6c -40C
Depth of Permafrost: 0.5-400+m
Depth of active later: 0.5m

28
Q

name the characteristics of discountinuous permafrost

A

Latutude: 65-60C
Temperature: -1C to -6C
Depth of Permafrost: 1.5 - 40m
Depth of active later: 1 - 1.5m

29
Q

What is the active layer

A

energy balance is positive in the summer, overlying snow and ice melts to produce a seasonally unfrozen zone above the permafrost called the active layer, which varies from a few centimetres to 3m (sporadic)

30
Q

what factors affect the distribution and character of permafrost

A

Climate: main control as temperature and the amount of moisture available determine the persence or absence, depth and extent of permafrost
Proximity to water: areas near water have little to no permafrost called Taliks
Slope orientation: Less sunlight in south
Character of ground surface: some soils freeze more easily than others e.g. light coloured soils

31
Q

name the periglacial features

A

solufluction fields
blockfields
ice wedge polygons
nivation hollows

32
Q

describe the process of solufluction

A
  • summer thaw of active layer creates meltwater
  • meltwater is unable to percolate down to rocks so it saturates the soil
  • internal friction coupled with lack of stability via vegitation causes the soil to flow on the slope
  • this flow causes the formation of solufluction lobes which are stepped features
  • most common where vegitation is spares with impermeable rocks
33
Q

describe the process of ground contraction

A

(downward-tapeing bodies of ice)

when the active layer refreezes during the winter months, the soil begins to contract
as the meltwater contains fine sediments, it begins to fill the crack. The process contimues through the cycle of winter and summer months, widening and deepening the crack to form an ice wedge which over a period of hundreds of years can become 1m wide and 2-3m deep
-The craking produces a pattern on the surface which when viewed from above is similar to the polygons produced by frost heaving
-these are therefore known as ice-polygons when an ice wedge melts. it may fill with sediment to form an ice wedege cast

34
Q

explain the process of nivaton

A
  • beneath the patches of snow in hollows particularly at high altitudes on North and East facing slopes
  • when snow gets into a hollow in the ground, it can increase the size of the hollow. The temperature often fluctuates around 0C so lot of freeing and thawing happens when the temperature is above 0C, the snow melts and when it is below 0C, the water refreezes as ice
  • as ice refreezes it expands and contrats and so freeze thaw action and chemical weathering operating under the snow causes the underlying rock to disintergrate
  • As snow melts in the spring (increased solar isnsolation), the weathered rock debri are moved downslope by the meltwater and solufluction
  • over some period of time, the hollows envelope and become wider, the collective process is called nivation
  • hollows formed by nivation are known as nivation hollows

Glaciation (6 decks)

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