Rivers Flashcards
Vertical erosion
Deepens the river valley making it very shaped.
Dominant in upper course.
High turbulence causes rough angular particles to scrape along river bed, causing intense downward erosion
Lateral erosion
Widens river valley during formation of meanders.
Dominant in middle and lower course
Mechanical weathering
When Rock is broken down without any changes to its chemical composition
Chemical weathering
When rock is broken down due to changes in its chemical composition
Biological weathering
When rock is broken down by living things
Examples of mechanical weathering
Freeze-thaw- occurs when temp fluctuates.
Water expands when it turns to ice so when rainwater repeatedly freezes and thaws inside cracks, it puts pressure on them. This widens cracks over times
Examples of chemical weathering
Dissolution- some minerals that make up rocks are soluble in water. Minerals are dissolved in rainwater and are washed away, breaking the rock down
Carbonation- rainwater is slightly acidic so this can react with certain minerals in rocks causing them to dissolve. Rock gradually breaks down
Examples of biological weathering
Plant roots can break rocks down by growing into cracks and splitting them apart
Hydraulic action
Force of water breaks rock particles away from river channel
Abrasion
Eroded rocks picked up by river scrape and rub against channel, wearing it away
Attrition
Eroded rocks picked up by river smash into each other and break into smaller fragments
Solution
River water dissolves some types of rock e.g. chalk and limestone
Transportation
Movement of eroded material by the river
Traction
Large particles like boulders are pushed along river bed by force of water
Suspension
Small particles like silt and clay are carried along by water
