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chalk (rock)

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Chalk (rock)

chalk cliffs on the Isle of Purbeck, Dorset - Click to enlarge chalk soil - Click to enlarge

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Soft, fine-grained, whitish sedimentary rock composed of calcium carbonate, CaCO3, extensively quarried for use in cement, lime, and mortar, and in the manufacture of cosmetics and toothpaste. Blackboard chalk in fact consists of gypsum (calcium sulphate, CaSO4.2H2O).

Chalk was once thought to derive from the remains of microscopic animals or foraminifera. In 1953, however, it was seen under the electron microscope to be composed chiefly of coccolithophores, unicellular lime-secreting algae, and hence primarily of plant origin. It is formed from deposits of deep-sea sediments called oozes.

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atmosphere (earth science)
basalt
calcium carbonate
calcium hydroxide
carbon cycle
carbon dioxide
carbonate
cementation
chalk (rock)
chemical weathering
coastal erosion
conglomerate (geology)
continental drift
core (earth science)
crust
earthquake
erosion
evaporation
exfoliation
extrusive rock
fault
fertilizer
fold
fossil
freeze–thaw
global warming
gneiss
granite
gravel
greenhouse effect
helium
igneous rock
intrusive rock
krypton
lava
limestone
lithosphere
magma
mantle
marble
metamorphic rock
metamorphism
mineral
neon
nitrate
nitrogen
nitrogen cycle
ocean
oxygen
physical weathering
plate
plate tectonics
plutonic rock
pollution
Precambrian era
rock
rock cycle
sandstone
schist
seafloor spreading
seawater
sediment
sedimentary rock
shale
silica
slate
soil
volcano
water
water cycle
water pollution
weathering

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