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Earthshapes Unit RIVERS Vincent Raeburn Linlithgow Academy
Malcolm McDonald Bathgate Academy Linlithgow Academy
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How rivers erode HYDRAULIC ACTION The force of the water weakens and breaks up the rocks ABRASION The material carried in the river wears away the river bed ATTRITION As the pebbles carried by the river crash into each other,they become smaller and rounder SOLUTION The water in the river dissolves the minerals in the rocks
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How rivers transport Traction Suspension Saltation Solution
Rolling stones along the river bed.( needs lots of energy) Traction Suspension Clay sized particles are carried along by the river flow river flow Saltation Sand sized particles bounce along the riverbed Solution Some minerals are dissolved by the riverwater
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River Basin Watershed of River Aye Source of River Aye Tributary
(boundary between basins) Source of River Aye Tributary of River Aye Confluence of River Aye and tributary Flood plain Mouth of River Aye Estuary of River Aye Sea
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THE RIVER MODEL Source of river Upper Course Middle Course Lower
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FEATURES OF THE UPPER COURSE
V-SHAPED VALLEYS WITH INTERLOCKING SPURS WATERFALLS AND RAPIDS POT HOLES ON RIVER BED
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Formation of a waterfall
Retreats upstream Hard rock Soft rock Steep sides ( gorge ) Undercutting erodes the softer rock forming an overhang The overhang Eventually collapses The process starts again Vertical erosion Forms plunge pool Eroded rock
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WATERFALL RETREATS . . UPSTREAM . . OVERHANG PLUNGE POOL UNDERCUTTING OF SOFT ROCK
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The River Avon has smoothed off parts
of this hard igneous rock. . . What is this process called?
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MEANDERS Meanders Flood plain Possible break through point Possible
ox-bow lake Most erosion on the outside of the bend .. Fastest flow Flood plain © Used with the permission of the Geological Survey of Canada, Natural Resources Canada Available at – Terrain Science Division
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River bend Fastest current slowest current Bank will collapse Small
cliff Slip off slope ( river beach ) Deposition of Sand and shingle Outer bank Is undercut Deepest part of the river
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Formation of an ox-bow lake
Most erosion The river now follows the new route Eventually during a period of heavy river flow it cuts through Some bends get closer and closer The meanders change shape through time Most deposition (Slip off slope) Small river cliff is formed © Used with the permission of the Geological Survey of Canada, Natural Resources Canada Available at – Terrain Science Division The bends migrate Sideways leaving deposits on the inside Of the bend At the bends the river flows faster at the outside The neck gets narrower and narrower The old meander Is left as a small lake (OX - BOW lake) The erosion makes the Meanders more pronounced
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Want to see that again ?
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NARROW MEANDER NECK FUTURE OX-BOW LAKE
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River is actually flowing above
The floodplain !! Gentle valley sides Levees is often artificially strengthened Flat floodplain Coarse material Forms natural levees Layers of silt Deposited during floods
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River features Slope usually steep quite steep gentle Width narrow
Characteristics Upper Course Middle Course Lower Course Slope usually steep quite steep gentle Width narrow quite wide wide Depth shallow quite deep deep Straightness winding meandering big meanders Load some lots little small+ rounded medium/small rounded Type of load large/small angular Main work erosion transportation Transportation transportation deposition Valley width narrow quite wide wide
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tributaries V shaped valley Steep Valley sides meander ox-bow lake
Flood plain Reproduced with kind permission of Ordnance Survey © Crown Copyright NC/03/18990
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