Ice Levels Over Time
- The Earth goes through ice ages which are cold periods that last for millions of years. During ice ages, large masses of ice cover parts of the Earth's surface.
- The last ice age was the Pleistocene that began around 2.6 million years ago.
- During ice ages there are cooler periods called glacial periods. In glacial periods the ice advances to cover more of the Earth's surface. Glacial periods last about 100,000 years.
- There are also warmer periods inbetween the glacial periods called interglacial periods. During interglacial periods the ice retreats to cover less of the Earth's surface. Interglacial periods last for about 10,000 years.
- The last glacial period began around 100,000 years ago and ended around 10,000 years ago.
- Since the beginning of Pleistocene there have been permenant ice sheets on Greenland and Antarctica. Ice has also covered other parts of the world during colder glacial periods.
- Ice covered over 30% of the Earth's land surface about 20,000 years ago (during the last glacial period).
- We're currently in an interglacial period that began around 10,000 years ago. Today only about 10% of the Earth's land surface is covered by ice, the only ice sheet are in Greenland and Antarctica.
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Ice Levels Over Time - Continued
- Evidence of changing temperature come from 3 main sources; Chemical evidence - the chemical composition of ice and marine sediments change as temperature changes so they can be used to work out how global temperature has changed. Geological evidence - some landforms today were created by glaciers in the past (e.g erratics). This shows that areas that aren't covered in ice now, were in the past. Fossil evidence - this shows the distribution of plants and animals that are adapted to cold and warm climates at different times in the past.
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- Glaciers are masses of ice that fill valleys and hollows. They move downhill under the force of gravity.
- A glacier has a zone of accumulation and a zone of ablation. Accumulation is the input of snow and ice into the glacier. Ablation is the output of water from the glacier as the ice melts. You get more accumulation in the upper part of the glacier so it's called the zone of accumulation. In the lower part of the glacier you get more ablation than accumulation so it's called the zone of ablation.
- The difference between accumulation and ablation for one year is the glacial budget. The amount of ice in a glacier and whether it's advancing or retreating depends on the glacial budget.
- A positive glacial budget is when accumulation (input) exceeds ablation (output). The glacier gets larger and the snout advances down the valley.
- A negative glacial budget is when ablation exceeds accumulation. The glacier gets smaller and the snout retreats up the valley.
- If there's the same amount of ablation and accumulation in a year the glacier stays the same size and the position of the snout doesn't change.
- Glaciers advance and retreat seasonally. In the summer there's more ablation than accumulation because the ice melts when it's warm - negative glacial budget. In the winter there's more accumulation because there's snowfall and less melting - positive glacial budget. Global warming is causing the glaciers to retreat - there is a negative glacial budget.
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Glacier Case Study
**The Rhone Glacier, the Swiss Alps**
- The Rhone Glacier is currently 7.8km long but like most glaciers in the world, it has been retreating since the 19th Century.
- Evidence for glacial retreat comes from various sources; Pictures from different times show the glacier has retreated. Monitoring data - the length of the glacier has been measured since 1879 and these measurement show that the glacier is retreating. Amount of meltwater - as the glacier retreats it produces more meltwater. The meltwater has formed a new lake in front of the glacier which is getting larger, which shows that the glacier has been melting quickly.
- Global warming is the main cause of glacial retreat. In recent decades, parts of Switzerland have had above average temperature rises . A weather station near the Rhone Glacier has recorded an increase of 1.8 degrees celsius between 1937 and 2005.
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- Glaciers erode the landscape as they move. The weight of the glacier makes it move downhill (advance), eroding the landscape as it goes.
- There are three main methods in which a glacier erodes the landscape; Abrasion - erosion caused by the rubbing and scouring action against the rock below the glacier by rock fragments stuck in the glacier. Plucking - ice freezes onto the weathered rock and as the glacier moves, large pieces of rock are pulled away with the glacier. Bulldozing - the sheer power of the glacier breaks off rocks from the bed and sides of the valley or when it moves already shattered material.
- At the top end of the glacier the ice doesn't move in a staright line, it moves in a circular motion, called rotational slip. This can erode hollows into the landscape and deepen them into bowl shapes.
- Ice also weathers the landscape through freeze-thaw weathering (frost shattering). It is a process of physical weathering in which rock is broken up due to water in cracks freezing (and therefore expanding, which widens the crack) and thawing. The rock breaks into several pieces after repeated freezing and thawing.
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Glacial erosion produces seven different landforms.
- Arete - an arete is a steep-sided ridge formed when two glaciers flow in parallel valleys. The glaciers erode the sides of the valleys, which sharpens the ridge between them - Striding Edge, Lake District.
- Pyramidal Peak - a pointed mountain peak with at least three sides. It's formed when three or more back to back glaciers erode a mountain - Mount Snowdon, North Wales.
- Corries - they begin as hollows containing a small glacier. As the ice moves by rotational slip, plucking, abrasion, freeze-thaw weathering and compressed ice, it erodes the hollow into a deep bowl shape with a steep back wall, a rock basin and a lip at the bottom end. When the ice melts it can leave a small circular lake called a tarn - Red Tarn, Lake District.
- Truncated Spurs - cliff-like edges on the valley sides formed when ridges of land that stick out into the main valley are cut off as the glacier moves past.
- Hanging Valleys - valleys formed by smaller glaciers (called tributary glaciers) that flow into the main glacier. the glacial trough is eroded much more deeply by the larger glacier, so when the glacier melt, the valleys are left at a higher level.
- Glacial Trough - steep-sided valleys with flat bottoms. They start off as v-shaped river valleys but change into a U-shaped valley as the glacier erodes the sides and bottom, making it deeper and wider - Nant Ffrancon, Snowdonia
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Landforms - Continued
- Ribbon Lakes - long think lakes that form after a glacier. they form in hollows where softer rock was eroded more than the surrounding hard rock. It is a long narror lake - Windermere, Lake District.
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Transportation and Deposition
- Glaciers can move material such as rocks and earth over a very large distance. This is transportation.
- The material is frozen inside the glacier, carried on it's surface or pushed in front of it. It's called bulldozing when the ice pushes loose material in front of it.
- When the ice carrying the material melts, the material is dropped on the valley floor. This is deposition. It also occurs when the ice is overloaded with material.
- Glacial deposits aren't sorted by weight like river deposits, rocks of all shapes and sizes are mixed up together. The dropped materials makes moraines
- Moraine - moraines are landforms made out of angular rock debris dropped by a glacier as it melts. There are 5 types of moraine; Lateral, Medial, Terminal, Ground and recessional moraine.
- Lateral moraine is a long mound of material deposited where the side of the glacier was.
- Medial moraine is a long mound of material deposited in the centre of a valley where two glaciers met (the two lateral moraines join together).
- Terminal moraine builds up at the snout of the glacier when it remains stationary. It's deposited as semi circular mounds.
- Ground moraine is a thin layer of material deposited over a large area as a glacier melts.
- Recessional moraine is a ridge marking an interuption in the retreat of a glacier when it remained stationary for long enough.
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- Material can also be deposited as Drumlins.
- Drumlins are elongated hills of glacial deposits - the largest ones can be over 1000m long and 50m high.
- They're round, blunt and steep at the upstream and tapered, pointed and gently sloping at the downstream end.
- Drumlins can be found in Ribble Valley, Lancashire.
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Impacts and Management of Tourism on Ice
- Areas covered in snow and ice attract a lot of tourists for winter sports and sightseeing.
- Problems with the fargile environment are; there's only a short growing season (when there's enough light and warmth) so plants don't have much time to recover if they are damaged, decay is slow because it's so cold. Litter and pollution remains for a long time.
- Economic impacts of tourism; lots of businesses are set up for the tourists (such as restaurants, hotels, etc) which boosts the local economy and new businesses mean there are job opportunities for people.
- Social impacts; infrastructure (roads and railways) becomes congested, more job opportunities mean that young people stay in the area rather than leaving to find work, tourists can trigger avalanches on ski slopes which can cause injuries and deaths.
- Environmental impacts; fragile glacial environment is damaged by people trampling on the snow and soil beneath which causes soil erosion, glacial landforms like moraines are eroded by people walking on them, there's increased noise, poluution and litter from the toursits, the developments in the area (buildings, ski lifts, etc) have a visual impact.
- Management stratergies to manage the impacts (the environment needs to be conserved); tourists are kept informed of avalanche risks s that they know areas to avoid, resorts build structures to slow and divert the moving snow, plant trees to act as barriers, set off controlled avalanches to dsilodge snow, improve public transport systems, nature reserves to protect the environment.
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Tourism on Ice - Case Study
**Chamonix Valley, eastern France**
- The Chamonix Valley is in eastern France, at the foot of Mont Blanc. It's close to the border with Italy and Switzerland.
- The region has lots of glaciers including the Mer de Glace. The Mer de Glace is the longest glacier in France - it's 7km long and 200m deep.
- It's one of the most popular tourist destinations in the world with 5 million visitors a year.
- There are many other tourist attractions such as 6 ski areas, 350km of hiking trails, 40km of mountain bike tracks, an Alpine museum and an exhibition centre.
- Economic impacts on the region; the tourism industry in Chamonix creates a lot of jobs, companies make a lot of money from tourism.
- Social impacts; they types of jobs have changed from farm labouring to jobs in restaurants and hotels, etc, tourist developments have increased the risks of avalanches. Therefore there is more deaths from avalanches (in 1999 an avalanche killed 12 people).
- Environmental impacts; large numbers of tourists cause traffic, which increases pollution (a survey in 2004 showed that traffic pollution was worse in Chamonix than in the centre of Paris), lots of energy is used to run the facilities for tourists(ski lifts, hotels, etc), this increases CO2 emissions, which increases global warming.
- Management; avalanche barriers, avalanche awareness courses, public transport for tourists (low emission buses), hotels install solar panels and automatic lights.
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Impacts of Global Retreat
- Glacial retreat is affecting areas covered in snow and ice that rely on tourism for the economy.
- Glacial retreat means that the ice will no longer be available for winter sports such as climbing and sightseeing, so there will be fewer tourists.
- Unreliable snow fall means that there might not be enough snow for winter sports such as skiing and snowboarding, so there will be fewer tourists.
- Fewer tourists mean that businesses that rely on tourism may shut down. This would lead to increased unemployment.
- Glacial retreat economic impacts; once a glacier has melted the amount of meltwater decreases, so industries that rely on the supply of mletwater such as hydroelectric power companies may shut down.
- Social impacts; water supply to settlements is reduced (less meltwater), disruptions to power supplies from HEP could leave some people with an unreliable power supply, if businneses shut down people will move away to find work, if the population declines recreational facilities will shut down, ice will no longer be available for recreational use for the local people (such as trekking and ice climbing)
- Environmental impacts; glacial retreat is linked to an increase in natural hazards (flooding, rockslides, avalanches) which could destroy habitats and disrupt food chains, meltwater contributes to rising sea level. when glaciers have completely melted, fish adapted to the cold conditions may die out, harmful pollutants trapped in the glacier will be released into the enviroment.
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