Ice on the Land

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Ice Levels Over Time

Ice ages:

  • cold periods which last for millions of years
  • last ice age was Pleistocene that begun around 2.6 million years ago
  • during ice ages there are cooler periods called glacial periods where ice advances to cover larger area
  • in between glacial periods are warmer periods called interglacial periods
  • interglacial periods last 10,000 years + most recently in holocene period which was from 10,000 years ago to now
  • last glacial period began around 100,000 years ago and ended around 10,000 years ago

Since the beginningof the Pleistocene there has been permanent ice sheets over greenland + antartica and during colder periods ice covered more

Around 20,000 years ago over 30% of earths surface covered by ice including UK compared to around 10% now

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Evidence of Changing Temperatures

Chemical evidence:

  • the chemical composition of ice and marine sediments change as temperature changes so samples taken to work out temperature change over different periods

Geological evidence:

  • glacial landforms created show which areas were covered by ice

Fossil evidence:

  • shows the distribution of plants + animals that have adapted to either warm or cold conditions
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Glacial Budget

Accumulation - input of snow + ice into the glacier

Ablation - output of water from glacier as ice melts

Zone of accumulation - upper part of glacier with more accumulation

Zone of ablation - lower part of glacier with more ablation

Positive glacial budget - when accumulation exceeds ablation so glacier gets larger + advances down valley

Negative glacial budget - when ablation exceeds accumulation so glacier gets smaller + receeds up valley

Glaciers follow a seasonal pattern of negative budget in summer and positive budget in winter

Global warming means since 1950 overall overall negative glacial budget

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Glacial Erosion

The weight of ice in a glacier means that it moves downhill

Erodes the landscape from:

  • plucking - when meltwater at the back, base or sides of a glacier freezes onto a rock and as glacier moves forward the pieces of rock pulled out
  • abrasion - where bits of rock stuck on bottom of glacier grind against the rock below the glacier and wear it away

At the top end of a glacier the ice moves in a circular motion (rotational slip) that erodes hollows in landscape to bowl shapes

The rocks above glaciers damaged from freeze thaw weathering where water gets into cracks in rocks, freezes + expands - putting pressure on the rocks and breaking them up

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Glacial landforms

Arete - steep sided ridge formed when two glaciers flow back to back

Pyramidal peak - formed from 3 or more back to back glaciers

Truncated spurs - cliff like edges on valley side when interlocking spurs cut off

Hanging valleys - valleys in side of mountains formed from smaller, tributary glaciers flowing into larger, deeper glacier

Glacial troughs - u-shaped valleys with steep sides and flat bottoms that start off in v-shape 

Ribbon lakes - long, thin lakes that form after glacial retreat in hollows created by softer rock eroding more than surrounding hard rock

Corries - begin as hollows containing a small glacier and as ice moves by rotational slip it erodes the hollow into a steep-sided armchair shape with lip at bottom end + when ice melts a small tarn lake left

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Glacial Transport + Deposition

Glaciers move material such as rocks + earth over large distances (transportation)

The material is either frozen in the glacier, carried on its surface or pushed in front (bulldozing)

When ice melts the matrial being carried is dropped on the valley floor (deposition)

Deposited material forms landforms such as morains + drumlins

Drumlins - elongated hills of glacial deposits that can be 1km long, 500m wide + 50m high

Morains:

  • lateral - long mounds of material at side of where glacier was
  • medial - two lateral moraines joining together where glaciers join together
  • terminal moraines - build up at snout (end) of glacier
  • ground - thin layer deposited over large area as glacier melts
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Impacts of Glacial Retreat

Economic impacts:

  • less winter sports results in less tourism which local businesses rely on
  • no meltwater once glacier melted so bussinesses such as agriculture for irrigation + HEP will be less successful

Social impacts:

  • water supply to settlements reduced
  • loss of HEP disrupts power supply
  • young people will have to move away to find work if businesses close and this poulation decline will result in local services + facilities shutting down

Environmental impacts:

  • rapid melting can cause flooding, rockslides + avalanches which are dangerous to humans + destroy habitats
  • meltwater contributes to rising sea levels
  • fish species have adapted to live in meltwater + these may die
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Rhone Glacier

In Swiss Alps + source of the Rhone glacier

Around 7.8km long

Has been retreated since the 19th century

Evidence:

  • photos
  • length - decreased by over 100 metres in past 5 years
  • more meltwater produced

Causes:

  • global warming
  • Switzerland has had temperature increase of 1.8°c between 1937 + 2005 because Switzerland has no coastine so no cooling effect occuring
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Chamonix Attraction + Management

Eastern France at the foot of Mont Blanc close to the border of Italy + Switzerland

5 million visitors a year

Has several glaciers including the Mer de Glace, the longest glacier in France 7km long + 200m deep

Attractions:

  • 6 ski areas
  • 350 km in hiking trails + 40km of bike tracks
  • alpine museum + exhibition centre

Management:

  • System of avalanche bariers maintained in resort
  • people kept informed about avalanche risks by daily bulletins + awareness courses
  • free public transport provided on low emmision buses to reduce air pollution
  • hotels use solar panels + automatically turn lights off to reduce carbon emissions
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Chamonix Impacts

Economic impacts:

  • 2500 seasonal jobs a year
  • companies make money from tourism e.g. Compagnie de Mont Blanc that runs ski lifts + rail transport has a turnover of €50 million per year
  • more businesses set up which boost local economy

Social impacts:

  • types of jobs changed from farm labouring to jobs in restaurants + hotels
  • infrastructure improved
  • more congestion
  • increased avalanche risk e.g. in 1999 12 deaths from an avalanche

Environmental impacts

  • increased traffic + air pollution e.g. from 2002-2004 pollution worse than centre of Paris
  • environment damaged by people trampling on snow, causing soil erosion
  • visually damages environment
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