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Chalk is a soft, white, porous, sedimentary carbonate rock.It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor.
The density of limestone depends on its porosity, which varies from 0.1% for the densest limestone to 40% for chalk. The density correspondingly ranges from 1.5 to 2.7 g/cm 3 . Although relatively soft, with a Mohs hardness of 2 to 4, dense limestone can have a crushing strength of up to 180 MPa . [ 13 ]
Physical weathering, also called mechanical weathering or disaggregation, is the class of processes that causes the disintegration of rocks without chemical change.. Physical weathering involves the breakdown of rocks into smaller fragments through processes such as expansion and contraction, mainly due to temperature
Carbonate rocks are also crucial components to understanding geologic history due to processes such as diagenesis in which carbonates undergo compositional changes based on kinetic effects. [2] The correlation between this compositional change and temperature can be exploited to reconstruct past climate as is done in paleoclimatology. Carbonate ...
The Chalk Group (often just called the Chalk) is the lithostratigraphic unit (a certain number of rock strata) which contains the Upper Cretaceous limestone succession in southern and eastern England.
Sediments containing more clay tend to be more resistant to erosion than those with sand or silt, because the clay helps bind soil particles together. [44] Soil containing high levels of organic materials are often more resistant to erosion, because the organic materials coagulate soil colloids and create a stronger, more stable soil structure ...
The chalk often contains larger fossils, including ammonites, belemnites, and brachiopods. Flint occurs throughout in both nodule and tabular layers. [57] The iridium-rich layer of sediment, found around the world at the K-Pg boundary, is missing in Dorset. This may be due to the uplift and erosion that removed the upper layers of the chalk. [58]
Geological resistance is a measure of how well minerals resist erosive factors, and is based primarily on hardness, chemical reactivity and cohesion. [1] The more hardness, less reactivity and more cohesion a mineral has, the less susceptible it is to erosion.