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Glaciers Revision - Coggle Diagram
Glaciers Revision
Glacial processes
Glacial movement
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More melting around protruding rocks (more pressure lowers melting point), so faster flow around obstruction than downstream
Extensional flow -- gravitational force strong at the head of a glacier, so ice moves quickly. The ice may fracture and then slip downwards
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Compressional flow -- lower down the slope is less steep so the glacier moves more slowly. The head of the glacier compresses it, and layers are formed and pushed forward
Nivation
When ice freezes it expands, so frost shattering breaks off bits of rock at the base. Meltwater then carries this debris away
Slopes collapse because they're waterlogged and they've been eroded, material then washed away by meltwater
When temperatures fluctuate around 0°C, freezing and thawing happens
Hollow becomes deeper and wider, leading to nivation hollows (can be the beginning of a corrie)
When snow gets into a hollow, it increases the size of it
Cold-based glaciers -- found in very cold areas e.g. Antarctica. Bases below melting point, so very little melting. Ice is frozen to the base of the valley, so very little movement and erosion.
Frost action
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When temperature drops below 0°C, the water in the cracks freezes and expands
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Warm-based glaciers -- occur in milder areas. Bases are warmer because of the heat caused by friction, or geothermal heat. Meltwater underneath and on top means the glacier is lubricated. There is lots of movement, and therefore lots of erosion.
Erosion
Plucking -- ice thaws and refreezes around protruding rocks, when the glacier flows, it plucks the rocks away from the valley sides and floor
Abrasion -- debris carried along on the bottom of glaciers scrape material off valley sides and floor
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Deposition
Ablation till -- dropped when glacier melts, close to snout where most ablation happens
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Till -- unsorted mixture of material ("boulder clay"), includes massive boulders to pebbles and clay
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Glacial systems
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Inputs
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Bits of rock carved away by glaciers, or fallen from above
Outputs
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Glaciers may break and fall from the snout into the sea or lake, to form icebergs
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Glacier budget
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The glacier budget is the balance between accumulation and ablation -- determines whether it has advanced or retreated
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Changes throughout the year -- more ablation in the summer, but more accumulation in the winter
Can change over several years, depending on levels of ablation and accumulation
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Feedbacks
Negative feedback -- e.g. if the ice input increases, the glacier may speed up so more water and ice is output, leaving the glacier's mass constant
Positive feedback -- e.g. if glaciers retreat there is less ice, so the Sun's energy cannot be reflected -- temperatures rise and glaciers retreat further
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Svalbard
Key ideas
Coal mining, fishing and tourism largest industries
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Considered Europe's largest wilderness area, despite extreme environmental challenges, offers many economic opportunities
Local people demonstrate resilience, mitigation and adaptation
Norwegian territory in the Arctic Ocean, most northerly inhabited archipelago
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Opportunities
However, reserves are only expected to last until 2030
Stopping coal mining has concerned many residents, who rely upon Store Norske for their employment
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Research
Students study geophysics, arctic biology, geology and arctic technology
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1993, Norwegian universities opened a University Centre on Svalbard, which draws in 300 students per year
British Antarctic Survey have a research station there, and Russia, Norway and Poland run permanent research stations
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Svalsat
Satellite receiving station that has had a lot of investment from NASA, NOAA and ESA
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Tourism
In 2013, there were around 95,000 guest nights in hotels and boarding houses in Longyearbyen
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Activities include dog sledding, ATV safari, boat trips and horse activities
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Glacial landforms
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Moraines
Medial moraine -- deposited in the centre, when two glaciers converge (two lateral moraines join together)
Terminal moraine -- builds up at the end of the glacier, deposited in semicircular hillocks of till
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Till plain -- large expanse of gently rolling hills of till, when an ice sheet melts where it is
Corries
Snow collects in hollows and turns to ice; basal sliding, abrasion and plucking deepen the hollow into a corrie
When the ice in the hollow is thick enough, it flows over the lip as a glacier. Frost shattering and plucking steepen the back wall of the corrie
Glaciers usually form on one side of a mountain peak -- the side that gets the least sun and coldest winds (most accumulation, least ablation)
Drumlins
Scientists aren't sure about the process of formation of drumlins -- till may have got stuck around a protruding rock, or an original mound of dropped till got streamlined when a glacier readvanced over it
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Half-egg shaped hills of till, up to 1500m long and 100m high. Upstream end is wide and tall, downstream end is narrow and low
Erratics
Boulders that have been picked up by a glacier and dropped in an area of completely different geology
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