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Rocks and Weathering


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Lithosphere
the crust and upper mantle. Either solid or highly viscous, this layer is not easily deformed or manipulated
Crust
upper layer of the earth, divided into continental and oceanic crust
Mantle
the layer of the earth between crust and core, the upper part is the lithosphere and the majority is the asthenosphere
Continental drift
the movement of continents across the surface of the globe
Sea-floor spreading
it occurs at constructive margins, where ocean floors grow as plates move apart
Subduction zones
the movement of an oceanic plate beneath another crustal plate. As the plate reaches the asthenosphere it melts.
Trenches
long, narrow depressions in the ocean floor with depths of over 6000m
Weathering
the decomposition and disintegration of rocks in situ
Physical weathering
the disintegration of rock into smaller, angular fragments of the same rock, such as scree
Chemical weathering
the decomposition of rock, creating altered rock substances, such as kaolinite from granite
Biological weathering
when plants and animals chemically alter rocks and physically break them thorough their growth and movement
Freeze-thaw/frost shattering
when water in joints or cracks freezes at 0°C and expands by 10% exerting pressure on the rock
Granular disintegration
alternate expansion and contraction of minerals in rocks causes the rock to break down into small pieces
Block disintegration
when rocks split along joints into large rectangular shaped blocks
Disintegration
found in hot desert areas where there is a large diurnal temperature range.
Exfoliation
a type of disintegration where the outer layers of rock peel off due to stresses caused by heat
Wetting and drying
Physical weathering process where rocks are mechanically disintegrated by the accumulation of successive layers of water molecules in between the mineral grains of a rock
Salt crystallisation
the decomposition of rock by solutions of salt
Pressure release
overlying rocks are removed by erosion causing underlying rocks to expand and fracture
Hydrolosis
occurs on rocks with orthoclase feldspar
Hydration
the process whereby certain minerals absorb water expand and change
Oxidation
when iron compounds react with oxygen to produce a reddish brown coating
Humic acids
acids dervived from the decomposition vegetation
Chelation
the process in which plant roots can absorb relatively insoluble minerals
Limestone
a rock consisting of calcium carbonate, therefore susceptible to carbonation-solution
Granite
a rock prone to hydrolysis because of the presence of feldspar
Speleothems
cave deposits such as stalactites and stalagmites
Tufa
calcium deposits around springs
Stalactites
deposits of calcium carbonate which form from the top of caves
Stalagmites
deposits of calcium carbonate formed on the base of the cave
Limestone pavements
large areas of bare exposed limestone containing clints and grykes
Swallow holes/sinks
small-scale depressions in limestone pavement
Dolines
large depressions in limestone pavement up to 30m in diameter
Resurgent streams
these arise when the limestone is underlain by an impermeable rock
Geological structure
an important influence on slop development including faults, angle of dip and vulcanicity
Climatic geomorphology
a branch of geography that studies how different processes operate in different climatic zones to produce different slop forms or shapes
Regolith
superficial and unconsolidated material found at the Earth’s surface
Aspect
the direction in which a slope faces
Mass movement
any large-scale movements of the Earth’s surface that is not accompanied by a moving agent such as a river, glacier or ocean wave
Shear strength
the internal resistance of the slope
Shear stress
the forces attempting to pull a mass downslope
Heave/creep
a slow, small-scale process of mass movement that occurs mostly in winter
Talus creep
the slow movement of fragments on a scree slope
Falls
mass movement that occurs on steep slopes, especially bare rock faces where joints are exposed
Slides
mass movement that occurs when an entire mass of material moves along a slip plane