Ice on the Land
- Created by: felixshears
- Created on: 28-04-17 19:54
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
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
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
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
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
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
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
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
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
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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