Rivers

Four Processes of Erosion

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Hydraulic action

Physical force of water

Vertical Erosion

(http://content.swgfl.org.uk/rivers/images/flashimages/xsect01.gif)

Normally happens in the upper course of the river

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Attrition

Stones and Pebbles reduce in size

(http://www.soton.ac.uk/~imw/jpg/jagged.jpg) ---------------------> (http://www.thenervousbreakdown.com/photos/uncategorized/2007/06/04/pebble.jpg)

Upper Course ---------------------> Lower Course

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Abrasion

Stones and Pebbles drill downwards

(http://www.picturesof.net/_images_300/Cartoon_Washer_Royalty_Free_Clipart_Picture_081130-010811-904042.jpg)

The movement of the washing in the machine is like the stones and pebbles

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Solution

Limestone dissolves into water eg. River Thames

Process

Rain poicks up CO2

Rain water becomes weak

Carbonic Acid reacts with Calcium Carbonate

Form calcium bicarbonate of dissoved limestone

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