AQA Geography A - Ice on the Land

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Ice on the Land
Changes to amount of ice on the land
The last Ice Age - Pleistocene
Time scale
· The last ice age was 18,000 years ago.
· It lasted 2 million years
Maximum amount of ice cover in the northern hemisphere.
· There were four ice sheets that covered parts of the northern
hemisphere.
· The laurentide ice sheet covered the upper parts of North America.
· Most of the UK and Ireland was covered.
Present extent of ice cover
Today the ice has retreated leaving the UK without ice caps, sheets or
glaciers.
There is an ice sheet in Greenland 1.7 million km2 large.
There are glaciers and ice caps in Iceland and the European Alps.
New Zealand has some glaciers.
There is a vast ice sheet in Antarctica which, at 14 million km2, holds 90% of
all the fresh water on the earth's surface.
Contrasts and evidence of changes ­ global temperatures.
The earth's air temperature fluctuates between very cold and warmer
periods.
The cold periods are called glacial and the warmer ones interglacials.
The earth is a lot warmer than it used to be.
We are in an interglacial period at the moment: the Holocene.
Therefore the ice sheets have retreated.
Ice retreat
Glacial Budget
The glacial budget is the balance between the inputs and outputs of the
glacier.
Depending on whether accumulation or ablation is greater determines
whether the glacier advances or retreats.
· Accumulation
Mainly in the winter due to decreased temperatures and
snowfall.
· Ablation
Mainly in the summer when temperatures are higher causing
melting, calving evaporation and sublimation of the glacier.
· Advance
In the winter the glacier advances as the inputs are higher
than the outputs due to the high levels of accumulation.
· Retreat
In the summer the glacier retreats as the outputs are higher
than the inputs due to the high levels of ablation.
Glacial retreat CASE STUDY

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South Cascade Glacier, USA
· Causes
Rising global temperatures due to the interglacial period we
are in has caused the glaciers to retreat as ablation is higher
than accumulation.
· Evidence
By looking at and comparing photographs taken of the
glacier in 1900 and 2008the glacier has clearly retreated.
In 1900 the glacier filled the majority of the valley.
But in 2008 the glacier only fills a small proportion.
Other evidence is the scientific data which shows the net
glacial budget over the 21 years.…read more

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However if the glacier moves downhill it is called rotational slip.
Bulldozing
· As the glacier advances, moraine is pushed along at the snout similar
to a bulldozer.
Deposition
Reasons
· As the ice melts the moraine it was carrying or pushing gets
abandoned and dumped as the ice can no longer carry it as it has
melted.
· Also if the ice slows down and loses energy it deposits its material as
it no longer has the energy to hold it.…read more

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Pyramidal peaks
· Characteristics
A sharp edged mountain which peaks have been formed
from three or more corries cutting back into one mountain.
· Formation
Much the same as arêtes except three or more corries are
formed.
Three or more corries are formed on sides of the same
mountain/hill.
The glaciers erode more and more into the hillside
backwards.
After the ice has melted three or more corries are left with a
pyramidal peak left in the middle.…read more

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When a band of softer rock is met, the glacier is able to
erode it more easily therefore creating a rock basin.
When the glacier meets harder rock, erosion less easily
occurs, creating a rock bar.
After glacial periods have passed and the ice has melted,
the depressions left (the rock basins) collect rain water and
form lakes.
The rock bars act as a dam holding the water in.
These lakes are known as ribbon lakes due to their ribbon
like shape: long and thin.…read more

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When the ice has melted it leaves slight ridges on the valley
sides.
Medial moraine
· Characteristics
A line of moraine in the middle of the glacier.
· Formation
When a tributary glacier meets the main glacier the two
lateral moraines combine to create the medial.
On melting a ridge of moraine is left down the centre of the
valley.
Ground moraine
· Characteristics
Material that was dragged under the glacier.…read more

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Local people are employed in hotels, restaurants
and work as tour guides.
Lots of money is brought to the area boosting the
economy.
Negative
Tourism pushes prices up in housing, restaurants and
cafés as it becomes a desirable place to live.
The locals can no longer afford to live in the area as
they can't compete with wealthy visitors.
· Social
Positive
Local people can use the improved health and
transport facilities.
Negative
Conflict between locals and tourists.…read more

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Snowfall
Heavy snowfall that settles on a lighter layer of
snow can cause an avalanche. This is because the
lighter layer of snow is unable to support the
heavier layer of snow and so it gives way, causing a
slab avalanche.
Gradient of slopes
The steeper the slope the easier it is for the snow to
slip downwards: slopes over 30° are most likely to
have avalanches.…read more

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Locals can no longer benefit from the maintenance of their
town.
Less people visit the area.
Poverty as there is no longer a strong, reliable source of
income.
· Environmental
Snow melt due to higher temperatures cause the land to be
unstable possibly resulting in avalanches and flooding.
People look to develop higher level resorts which can
damage the fragile environment for a number of reasons:
Roads have to be built in order to provide access to
the higher slopes.…read more

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