Changes

[[Image:Four of the Seven Sisters.jpg|thumb|200px|Four of the "Seven Sisters" along the [[Sussex]] coast, [[England]]]]

[[Image:Four of the Seven Sisters.jpg|thumb|200px|Four of the "Seven Sisters" along the [[Sussex]] coast, [[England]]]]

'''Chalk''' is a white, sedimentary rock, composed of [[calcium carbonate]]. The calcium carbonate originates from the calcareous liths deposited by blooms of species of [[coccolithophore]] [[phytoplankton]].  

'''Chalk''' is a white, sedimentary rock, composed of [[calcium carbonate]]. The calcium carbonate originates from the calcareous liths deposited by blooms of species of [[coccolithophore]] [[phytoplankton]].  

One of the most dramatic outcrops of chalk is along the south coast of [[England]] where it forms the "white cliffs of [[Dover]]", the Seven Sisters and parts of Englands [[Jurassic Coast]], now a [[World Heritage Site]] in reckognition of its unusual geology.

One of the most dramatic outcrops of chalk is along the south coast of [[England]] where it forms the "white cliffs of [[Dover]]", the Seven Sisters and parts of England's [[Jurassic Coast]], now a [[World Heritage Site]] in recognition of its unusual geology.

As a useful commodity, chalk has been replaced by other substances. For example, the "chalk" that is used in blackboard writing or in sidewalk chalk is actually [[gypsum]].

As a useful commodity, chalk has been replaced by other substances. For example, the "chalk" that is used in blackboard writing or in sidewalk chalk is actually [[gypsum]].

[[Category:Sedimentary Rocks]]

[[Category:Sedimentary Rocks]]