What is a Limestone Environment?

By Minal Patel
jurassic limestone rocks image by Maria Brzostowska from Fotolia.com

A limestone environment is based chiefly on limestone. It is only found in areas underlain by sedimentary rock. Limestone rock bubbles when exposed to hydrochloric acid because the main mineral in the rock is calcite, which is a crystalline form of calcium carbonate

Formation of Limestone

Coral reef
coral reef image by Christian Schoettler from Fotolia.com

Limestone is a sedimentary rock, which means that layer upon layer of sediment has been deposited and lithified, which is the process whereby the layers change under pressure and become rock. Reefs, for example the Bahama's platform, are a great source of limestone rock. Limestone is almost always oceanic in origin, though it may have been uplifted geologically in the past and now be found inland, and is usually associated with other rock types that are found near the shore. Areas where there is little deposition of mud and/or sand make ideal places for the formation of limestone.

Composition of Limestone

Shells, limestone
sea shells image by Shirley Hirst from Fotolia.com

Limestone rock can be formed in two ways: by the deposition of organic materials such as the shells, coral, fecal debris (excrement) of dead marine organisms and algae. This is called biogenic limestone. Whole reefs and fossils can be preserved in biogenic limestone; coquina for example is limestone formed entirely from sea shells. The rock can also be formed by the precipitation of calcium carbonate from ocean or lake water. This is called a chemical sedimentary rock because there were no organic materials involved in its formation. Biogenic limestone is more commonly found than chemical sedimentary limestone.

How Limestone Is Used

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The rock can be used for building materials, for example in construction and architecture, for window sills and floor tiles. Crushed limestone is used as a weather- and heat-proof coating on shingles and roofing. It is also used in cement and in road ballast, which is basically gravel. It is easily eroded by acid rain. Limestone is effective in treating acidic soils when it is crushed to sand-sized or smaller particles and is used on farms all over the world. It is given to chickens as a supplement to make egg shells stronger and to cows to replace the calcium they lose in the milking process. Limestone is also used as safety dust in mines. According to Geology.com, when pulverized and used as a spray limestone lights up the mine and also reduces the risk of explosion by reducing the amount of coal dust that gets stirred up into the air; this also improves the breathability of the air for mine workers.

Different Types of Limestone Rock

A lithograph
Pierre gravée calligraphiée, Chine image by Bruno Bernier from Fotolia.com

We have already mentioned coquina, which is limestone that is made of sea shells. There are also lots of other types of limestone. Chalk is formed from the remains of tiny marine organisms; tufa is a porous limestone produced when limestone precipitates in a spring or lake. Travertine forms in caves and produces stalactites and stalagmites; fossiliferous limestone contains an abundance of fossils, which usually played a role in the making of that limestone. Oolitic limestone is made from small spheres of calcium carbonate precipitated on sand grains or shell fragments. Lithographic limestone, beginning in the 1700s, was used for lithography.

Karst Landscape

Inside a limestone cave
Cave image by Kiraly Zoltan from Fotolia.com

Scenery containing limestone is sometimes called a karst landscape. Chemical weathering of limestone creates caves and stalagmites and stalactites. It also creates sinkholes, which are natural depressions in the earth that occur when limestone is dissolved. Karst windows are formed when a cave's bedrock roof collapses.

About the Author

Minal Patel has been a writer since 1984, when she began composing poetry. Her work has appeared in "Kindred" magazine in Australia. Patel has a Bachelor of Arts in environmental science and policy from the University of Southern Maine.