The Influence of Geology in the Development of Glacial Landforms.

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The Influence of Geology in the Development of
Glacial Landforms.
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ier/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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Earth movement processes e.g. isostatic uplift in
post glacial times
Raised Beach at Low Tide - Little Gruinard,
Scotland
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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) Solifluctio
n 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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Fluvioglacial deposits coarser gravels are
deposited nearer the snout and finer material is
transported further away before deposition.
Braided meltwater stream depositing outwash just
beyond the ice front of a glacier