Stalactite


Stalactite

A stalactite (Greek "stalaktites", (Σταλακτίτης), from the word for "drip" and meaning "that which drips") is a type of speleothem (secondary mineral) that hangs from the ceiling or wall of limestone caves. It is sometimes referred to as dripstone.

Formation and type

Stalactites are formed by the deposition of calcium carbonate and other minerals, which is precipitated from mineralized water solutions. Limestone is calcium carbonate rock which is dissolved by water that contains carbon dioxide forming a calcium hydrogencarbonate solution. The chemical formula for this reaction is:

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Every stalactite begins with a single mineral-laden drop of water. When the drop falls, it leaves behind the thinnest ring of calcite. Each subsequent drop that forms and falls deposits another calcite ring. Eventually, these rings form a very narrow (0.5 mm), hollow tube commonly known as a "soda straw" stalactite. Soda straws can grow quite long, but are very fragile. If they become plugged by debris, water begins flowing over the outside, depositing more calcite and creating the more familiar cone-shaped stalactite. The same water drops that fall from the tip of a stalactite deposit more calcite on the floor below, eventually resulting in a rounded or cone-shaped stalagmite. Unlike stalactites, stalagmites never start out as hollow "soda straws." Given enough time, these formations can meet and fuse to create "columns".

Stalactites can also form in lava tubes, although the mechanism of formation is much different.

Concrete

Stalactites can also form on concrete, and on plumbing where there is a slow leak and limestone (or other minerals) is in the water supply, although they form much more rapidly there than in the natural cave environment (description and experiments see literature).

The way stalactities form on concrete due to different chemistry then those that form naturally in limestone caves and is the result of the presence of calcium oxide in concrete. This calcium oxide reacts with with any rainwater that penetrates the concrete and forms a solution of calcium hydroxide. The chemical formula for this is:

Over time this calcium hydroxide solution reaches the edge of the concrete and, if the concrete is suspended in the air, for example, in a ceiling or a beam, then this will drip down from the edge. When this happens the solution comes into contact with air and another chemical reaction takes place. The solution reacts with carbon dioxide in the air and precipitates calcium carbonate.

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External links

* [http://www.goodearthgraphics.com/virtcave/staltite/staltite.html The Virtual Cave's page on stalactites]
*" [http://demonstrations.wolfram.com/Stalactites/ Stalactites] " by Enrique Zeleny, The Wolfram Demonstrations Project.


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Look at other dictionaries:

  • stalactite — [ stalaktit ] n. f. • 1644; du gr. stalaktos « qui coule goutte à goutte » ♦ Concrétion calcaire qui se forme à la voûte d une grotte par l évaporation des gouttes d eau qui filtrent. Stalactites et stalagmites. « Une grotte que les stalactites… …   Encyclopédie Universelle

  • Stalactite — Sta*lac tite ( t[imac]t), n.; pl. {Stalactites} ( t[imac]ts). [Gr. stalakto s oozing out in drops, dropping, fr. stala zein to drop: cf. F. stalactite.] (Geol.) (a) A pendent cone or cylinder of calcium carbonate resembling an icicle in form and… …   The Collaborative International Dictionary of English

  • stalactite — stalactite, stalagmite A stalactite hangs down from the roof of a cave, and is formed from dripping water containing rich minerals. A stalagmite rises up from the floor and is formed from deposits also caused by dripping. Both words are derived… …   Modern English usage

  • stalactite — (n.) 1670s, Anglicized from Mod.L. stalactites (used 1654 by Olaus Wormius), from Gk. stalaktos dripping, from stalassein to trickle, from PIE root *stag to seep, drip, drop (Cf. Ger. stallen, Lith. telziu to urinate ) …   Etymology dictionary

  • stalactite — ► NOUN ▪ a tapering structure hanging from the roof of a cave, formed of calcium salts deposited by dripping water. ORIGIN from Greek stalaktos dripping , from stalassein to drip …   English terms dictionary

  • stalactite — [stə lak′tīt, stal′ək tīt΄] n. [ModL stalactites < Gr stalaktos, trickling or dropping < stalassein, to let fall drop by drop: see STALE2] an icicle shaped, secondary mineral deposit, usually calcite, that hangs from the roof of a cave and… …   English World dictionary

  • stalactite —    1. Speleothem, generally of calcite, formed by dripping water and hanging from a cave roof. Stalactites embrace an enormous variety of sizes and shapes. They form where percolation water seeps from a cave ceiling and becomes saturated with… …   Lexicon of Cave and Karst Terminology

  • stalactite — UK [ˈstæləktaɪt] / US [stəˈlækˌtaɪt] noun [countable] Word forms stalactite : singular stalactite plural stalactites science a long pointed piece of rock that hangs down from the roof of a cave, formed by chemicals in water drops that have fallen …   English dictionary

  • Stalactite — Excentriques, Grotte de Torrinha, Chapada Diamantina, Bahia, Brésil Une stalactite (du grec stalaktos qui coule goutte à goutte ) se forme à la voûte des grottes et des souterrains, ou sous des plafonds ou dalles de béton de mauvaise qualité ou… …   Wikipédia en Français

  • stalactite — See stalactite, stalagmite …   Dictionary of problem words and expressions