Slopes and how they are affected

Just some brief notes for A Level geography.

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  • Created on: 21-12-11 11:15
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Slope processes ­ AS Level revision
Slopes are defined by as any part of the solid land surface where there is an incline (gradient).
Processes occurring on the slopes often have a major impact on fluvial landscapes. Slope processes
transport material down the slope and into the river, thus, reducing the gradient of the slope.
Mass movements are any large scale movement of the earth's surface not accompanied by a moving
agent such as a river.
Slow movements
Soil creep ­ individual soil particles are pushed or heaved to the surface, by wetting, heating or the
freezing of water. They move at right angles to
the surface, as it's the zone of the least
resistance. They fall under the influence of gravity
once the particles have dried, cooled or the
water has thawed. The rates are slow, 1mm/year
in the UK and up to 5mm/year in the tropical
rainforest.
Rain-splash erosion ­ on flat surfaces, raindrops compact the soil and dislodge particles equally in all
directions. On steep slopes, the downward component is more effective than the upward
component due to gravity and so erosion downslope increases with the slope angle.
Solifluction ­ is a form of accelerated soil creep that can produce braided rivers. The term Solifluction
literally means `flowing soil' and is affected by freezing and thawing in periglacial environments.
Flow movements
Surface wash ­ this is when the soils capacity is exceeded and can lead to the formation of gullies. In
Britain, this commonly occurs in winter as water drains across frozen or saturated soil, following
prolonged or heavy downpours or the melting of snow.
Sheetwash ­ the unchannelled flow of water over a soil surface. On most slopes, sheetwash is
divided into areas of high velocity separated by areas of lower velocity. It is capable of transporting
material from rain-splash erosion.
Throughflow ­ water moving down the soil. It is channelled into natural pipes (very small channels of
water within the soil). This gives it sufficient energy to transport material, added to its solute load,
may amount to considerable volume.

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Fast mass movements
Slides ­ sliding material maintains its shape and cohesion until it impacts at the bottom of the slope
and leads to large, slumped terraces. They can be small scale close to roads, or large scale
movements killing to thousands of people, e.g. Vaiont Dam in Italy over 2000 died in 1963.
Falls ­ rock falls occur steep slopes. The initial cause may be weathering, such as freeze thaw or
disintegration. Once the rocks are detached they fall under the influence of gravity.…read more

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Vegetation ­ trees do more mechanical weathering than grass but grass holds more
moisture and organic acids.
Drainage ­ dry areas suffer less chemical weathering
Aspect ­ the direction of the sun or rain comes from is crucial
Rates of erosion ­ exposes fresh surfaces for weathering
Human activity ­ e.g. pollution causes acid rain.
Key words
Gully ­ a landform created by flowing water, eroding sharply in soil, typically on a hillside.…read more

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