Key Words: GEOLOGY UNIT 2.3

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Weathering - the in situ chemical alteration and mechanical and biological breakdown of rocks by exposure to the atmosphere, water and organic matter

Carbonation - the reation between carbonic acid and minerals

Hyrdolysis - the reation between minerals and water causing the minerals to decompose

Exfoliation - occurs when sheets of rock split off due to differential expansion and contraction of minerals during diurnal heating and cooling

Frost shattering - caused by the expansion of freezing water in fractures which forces rocks apart

Pressure release - the expansion and fracturing of rock due to removal of overlying rocks

Root action - causes the mechanical and chemical weathering of rocks by the wedging action of plant roots

Burrowing - by invertebrate and vertebrate animals mixes and brings to the surface rock and soil particles. This facilitates weathering at greater depth, by providing access for atmospheric gases and water

Erosion - the wearing away of the land surface and removal of sediment by means of transport

Abrasion - wearing away of the Earth's surface by the wind, water or ice dragging sediment over or hurling it at a surface

Attrition - wearing down of sedimentary grains due to collisions with other grains during transport

Solution - transport of ions dissolved in water

Suspension - the transport of material in water or air, without it touching the Earth's surgace

Saltation - the transport of material by bouncing

Traction - the transport of material by rolling and sliding along a surface

Roundness - defines the relationship of the outline of a grain to a circle. A grain with few sharp corners has a high degree of roundness

Shape - the relationship of a grain to a sphere, rod, disc or blade

Phi scale - expresses the grain size of a logarithmic scale. Phi values increase arithmetically as the grain size decreases geometrically

Grain size - the average diameter of the grains of sediment being studied

Sorting - the degree to which particles are the same size

Clast - a rock fragment or grain resulting from the breakdown of larger rocks

Pyroclast - fragment of rock from a volcanic explosion

Bioclastic - a biologically formed sedimentary rock composed of fragmented organic material

Mechanically formed - the erosion, transport and deposition of clasts are by mechanical processes

Chemically formed - the weathering transport and deposition of these rocks is by chemical processes

Biologically formed - organisms such as sea creatures or trees extract ions that are in solution in sea water or groundwater and turn them into organic tissue, such as shells or wood

Fossil - the remains of an organism that lived more than 10000 years ago including skeletons, tracks, impressions, trails, borings and clasts

Rudaceous - sedimentary rocks are those in which the grain size of clasts is greater than 2 mm

Arenaceous - sedimentary rocks are those in which the grain size of clasts is 0.0625 to 2 mm

Argillaceous - sedimenraty rocks are those in which the grain size of casts is…


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