Geography: Extreme environments

A U-shaped valley is formed by a glacier, it starts off as a V-shaped valley and the snow accumulates and formes a glacier. The U-shaped valley is then widened and deepened when the ice erodes the side and bottom of the valley. This happens by the processes of plucking and abrasion.
Plucking: is when rocks and stones become frozen to the base or sides of the glacier and are plucked from the ground or rock face as the glacier moves. after plucking occurs it leaves behind a jagged landscape.
Abrasion: is when rocks and stones become embedded in the base and sides of the glacier. The rocks and stones are then rubbed against the bedrock which is at the bottom of the glacier, and rock faces which are at the sides of the glacier as the glacier moves. This movement causes the wearing away of the landscape often described to be like the process of sandpaper. After abrasion has ocurred it leaves behing smooth polished surfaces that often have scratches in them called striations. Striations occur by debris which is embedded in the base of the glacier.
U-shaped valleys have a very wide and flat floor which contain long and narrow lakes callled ribbon lakes. The rock that has been eroded by the glacier moving is then deposited at the end of the glacier and its given the name of morraine.

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Freeze thaw weathering: Freeze thaw weathering happens by water getting trapped in the cracks or joints of rocks. If the temperature then drops below freezing the water will then freeze and it will expand by 9 or 10 percent putting pressure on the rock.The ice will then melt when the temperatures get back up above freezing. If this process happens frequently the rock will then weaken and eventually split into many fragments.

This process often happens in places where the temperature fluctuates around 0°C.

It also happens in deserts because deserts have a high diurnal range this means that it is very hot in the day and cold at night. Therefore the water would get into cracks in the rocks and often freeze at night and melt in the day so the process would be repeated frequently. That is why the sound of gunshots can be heard in deserts because it is the sound of rocks cracking.

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Desert environments are classed as extreme due to the isolation of the place. This makes it an extreme environment because if you get lost or you are injured then there would be no places or poeple to help you near by.
Also desert environments are classed as extreme because of the lack of vegetation. A lack of vegetation makes a desert extreme as it could lead to starvation.
Deserts have extreme weather conditions for example a desert has a high diurnal range meaning that it is cold at night and very hot in the day. These temperatures make a desert environment extreme because the high temperatures during the day could lead to heat stroke and dehydration due to the lack of water as well as vegetation.

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The glaciers in the andes have retreated rapidly due to climate change. A glacier has retreated 1300 metres from 1963 to 2004. However it is retreating slower now than it was between 1963 and 1998 but it is still retreating. This suggests that in the future the glaciers in the andes will continue to retreat and that one day there may be no glaciers left in the andes.

There are 18 mountain glaciers in peru, 22% of their surface area has been lost in the last 30 years due to the retreating of the glaciers.The Andes are home to over 30 million people living in Peru and Bolivia and Ecuador. The volume of water lost from melting glaciers so far is equivalent to 10 years water supply for Lima.

Peru gets 80% of it's electricity from hydroelectric power. if the glaciers carry on retreating ther will not be enough water for electricity so Peru will have to resort to burning fossil fuels such as coal.

Chunks of ice falling from melting glaciers into lakes could trigger a big flood. This threatens Huarez a city of 100,000 people.

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