the influence of geology in the development of glacial landforms. ionalfea.jpg
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The Influence of Geology in the Development of Glacial Landforms.
http://www.ufrsd.net/staffwww/stefanl/Geology/glacier/erosionalfea.jpg
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Rock character (lithology)
Porosity / perviousness allows water to enter rock and assist plucking process
What landform?
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Raised Beach at Low Tide - Little Gruinard, Scotland
Earth movement processes e.g. isostatic uplift in post glacial times
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Weathering – freeze thaw creates scree. E.g. post glacial north Wales on Snowdon.
Most effective in uplands created by uplift. With well jointed rocks.
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Mass Movements – affected by steepness of slope, porosity,Weathered / rock layering
e.g. Solifluction on gentle periglacial slopes (lobes), falls on steep slopes (scree)
Solifluction in weathered layer above permafrost layer
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Tal-y-Llyn – a landslide dammed lake (below Cader Idris
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Erosion more effective on steep slopes
e.g. mountain glaciers in the tropics (Pakistan Himalayas)
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Differential erosion of hard and soft layers
Produces Paternoster Lakes, Washington State, USA (Mount Rainier)
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Almost vertically tilted bedding planes allowed steep back wall to Llyn Cau, Cader Idris to develop
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Resistant sill of igneous rock deflected the glacier from Llyn Cau round to the east
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SILL
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Fault controlled valley of Tal-y-Llyn
• effectiveness of erosion
• direction of erosion
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Striations –material carried in the ice. Scratches caused by resistant hard material in the ice by the process of abrasion
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Less resistant material gets ground down by abrasion into rock flour.
Lake Louise, Canada has a turquoise colour due to ground down rock flour sediment in the meltwater.
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Transport and Deposition –
change of gradient perhaps from high land hard rock to lowland softer rock
Knock and Lochan landscape of eroded resistant roche moutonnnees (knocks) and eroded hollows (lochans)
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Braided meltwater stream depositing outwash just beyond the ice front of a glacier
Fluvioglacial deposits – coarser gravels are deposited nearer the snout and finer material is transported further away before deposition.