Geography Rivers - Key Terms

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Mass Movement/s
Any large-scale movement of the Earth's surface that are not accompanied by a moving agent such as a river, glacier or ocean wave.
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Soil Creep (Slow)
Individual soil particles are pushed or heaved to the surface by wetting, heaving or freezing of water. They move at right angles to the surface as it is the zone of least resistance. They fall due to gravity once the particles have dried.
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Rain-Splash Erosion
Raindrops on flat surfaces compact the soil and dislodge particles equally in all directions. On steep slopes, the downward component, is more effective than the upward motion due to gravity and so erosion downslope increases, with slope angle.
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Surface Wash (Flow)
Occurs when the soil infiltration capacity is exceeded. Can lead to the formation of gullies.
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Sheetwash (Flow)
The unchannelled flow of water through a soil surface. Divided into areas of high and slow velocity.
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Throughflow (Flow)
The movement of water down through the soil.
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Slides (Fast-Mass Movements)
Sliding material maintains its shape and cohesion until it impacts at the bottom of the slope and leads to large, slumped terraces.
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Falls (Fast-Mass Movements)
Rock falls occur on steep slopes greater than 70 degrees. If the fall is short, it produces relatively straight scree (Talus)
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Slumps (Fast-Mass Movements)
Slumps occurs on weaker rocks, especially clay, and have a rotational movement along a curved slip plane. Clay absorbs water and becomes saturated, exceeding its liquid limit and it then follows along a slip plane.
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Climate (Factors)
Slopes in temperate conditions are rounder, due to chemical weathering whereas slopes in arid environments are jagged or straight due to mechanical weathering.
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Rock Types and Structure (Factors)
Slopes are also influenced by rock type. North West Britain has hard, resistant rocks such as granite. To the South and East are younger, weaker rocks such as chalk and clay.
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Aspect (Factors)
In the UK, North facing slopes are in the shade all of the time. South facing slopes experience many freeze-thaw cycles, thus causing erosion.
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Weathering
The decomposition and disintegration of rocks in situ.
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Freeze-Thaw Weathering
Occurs when water in joints and cracks freezes at 0 degrees celsius, expanding by 10%.
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Salt Crystal Growth
In areas where temperatures fluctuate around 26-28 degrees, sodium sulphate and sodium carbonate expand by 300%.
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Disintegration
Found where there is a large diurnal temperature range. Rocks heat up by day and contract by night. As rock is a poor conductor of heat, only the outer layers heat up and stresses take place causing exfoliation.
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Pressure Release
The process where overlying rocks are removed by erosion causing underlying rocks to expand and fracture parallel to the surface.
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Carbonation Solution
Rainfall and dissolved carbon dioxide form a weak carbonic acid. Calcium carbonate on some rocks reacts with the acid and forms calcium carbonate which is soluble and removed by percolating water.
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Hydrolysis
Carbon Dioxide mixes with precipitation and falls on the rock. Feldspar on the granite mixes with the rainfall, turning it into China clay.
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Hydration
The process where certain minerals absorb water, expand and change.
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Oxidation
Occurs when iron compounds react with oxygen in the air to produce a reddish/brown coating.
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Biological Weathering
Involves both mechanical impacts, such as the growth of roots, and chemical impacts, such as the release of organic acids.
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Other cards in this set

Card 2

Front

Individual soil particles are pushed or heaved to the surface by wetting, heaving or freezing of water. They move at right angles to the surface as it is the zone of least resistance. They fall due to gravity once the particles have dried.

Back

Soil Creep (Slow)

Card 3

Front

Raindrops on flat surfaces compact the soil and dislodge particles equally in all directions. On steep slopes, the downward component, is more effective than the upward motion due to gravity and so erosion downslope increases, with slope angle.

Back

Preview of the back of card 3

Card 4

Front

Occurs when the soil infiltration capacity is exceeded. Can lead to the formation of gullies.

Back

Preview of the back of card 4

Card 5

Front

The unchannelled flow of water through a soil surface. Divided into areas of high and slow velocity.

Back

Preview of the back of card 5
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