Any large-scale movements 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, heating or freezing of water.
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Terracettes (slow)
Small terraces from a few centimetres to 0.5m across the face of a slope caused by soil creep or solifluction
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Surface wash (slow)
This occurs when the soil's infiltration capacity is exceeded and can lead to the formation of gullies
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Sheetwash (slow)
is the unchannelled flow of water over a soil surface
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Throughflow (slow)
water moving down through soil.
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Rain-splash erosion (slow)
on flat surfaces raindrops compact the soil and dislodge particles equally in all directions
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Slides (fast)
Sliding material maintains its shape and cohesion until it impacts at the bottom of a slope and leads to large, slumped terraces
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Falls (fast)
rock falls occur on steep slopes. The initial cause of the fall may be weathering.
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Slumps (fast)
occur on weaker rocks, especially clay, and have a rotational movement along a curved slip plane
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Aspect
the direction a slope faces
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Weathering
is the decomposition and disintegration of rocks in situ.
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Decomposition
chemical weathering of rocks creating new materials
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disintegration
mechanical weathering of rocks resulting in smaller fragments of the same type
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in situ
on the spot, that is, without any lateral movement
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Freeze thaw
this occurs when water in joints and cracks freezes at 0 degrees, expands by 10% and then exerts pressure up to 2100kg/cm3
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salt crystal growth
this occurs in two main ways. First, in areas where temps fluctuate around 26-28 degrees c, sodium sulphate and sodium carbonate expand by 300%; Second, when water evaporates, salt crystals may be left behind to attack the structure (hot desert)
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Disintegration
this is also found in hot desert regions 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, stresses take place only in the outer layers and cause peeling or exfoliation
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Exfoliation
peeling of rocks on their outer edges as a result of repeated thermal expansion and contraction
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Pressure release
this is the process where overlying rocks removed by erosion cause underlying ones to expand and fracture parallel to the surface. The removal of a great weight has the same effect (eg. glacier)
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Carbonation solution
this occurs on rocks with calcium carbonate; eg. limestone, chalk. Rainfall and dissolved co2 forms a weak carbonic acid. calc.carb. reacts with acid & forms calc.bicarb. which is soluble & removed by percolating water
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Hydrolysis
occurs on rocks with orthoclase feldspar; eg. granite. Orthoclase reacts with acid water & forms kaolinite/china clay, silicic acid & potassium hydroxyl. The acid&hydrox. are removed in the solution leaving china clay behind as end product
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Hydration
the process where certain minerals absorb water, expand and change; eg. anhydrate is changed to gypsum during hydration
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Oxidation
Occurs when iron compounds react with oxygen to produce a reddish brown coating
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Other cards in this set
Card 2
Front
Individual soil particles are pushed or heaved to the surface by wetting, heating or freezing of water.
Back
Soil creep (slow)
Card 3
Front
Small terraces from a few centimetres to 0.5m across the face of a slope caused by soil creep or solifluction
Back
Card 4
Front
This occurs when the soil's infiltration capacity is exceeded and can lead to the formation of gullies
Back
Card 5
Front
is the unchannelled flow of water over a soil surface
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