Results for stalactite and stalagmite
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(stə′lak′tīt)

(geology) A conical or roughly cylindrical speleothem formed by dripping water and hanging from the roof of a cave; usually composed of calcium carbonate.


 
 
Sci-Tech Encyclopedia: Stalactites and stalagmites

Stalactites, stalagmites, dripstone, and flowstone are travertine deposits in limestone caverns, formed by the evaporation of waters bearing calcium carbonate. Stalactites grow down from the roofs of caves and tend to be long and thin, with hollow cores. The water moves down the core and precipitates at the bottom, slowly extending the length while keeping the core open for more water to move down.

Stalagmites grow from the floor up and are commonly found beneath stalactites; they are formed from the evaporation of the same drip of water that forms the stalactite. Stalagmites are thicker and shorter than stalactites and have no central hollow core. See also Cave; Limestone.


 
Britannica Concise Encyclopedia: stalactite and stalagmite

Elongated forms of various minerals deposited from solution by slowly dripping water. A stalactite hangs like an icicle from the ceiling or side of a cavern. A stalagmite rises from the floor of a cavern. The two are not necessarily paired; when they are, continual elongation of one or both may eventually join them into a column. The dominant mineral in such deposits is calcite (calcium carbonate), and the largest displays are formed in caves of limestone and dolomite.

For more information on stalactite and stalagmite, visit Britannica.com.

 
Columbia Encyclopedia: stalactite (stəlăk'tīt
) and stalagmite (stəlăg'mīt) , mineral forms often found in caves; sometimes collectively called dripstone. A stalactite is an icicle-shaped mass of calcite attached to the roof of a limestone cavern. Groundwater trickling through cracks in the roofs of such caverns contains dissolved calcium bicarbonate. When a drop of water comes in contact with the air of the cavern, some of the calcium bicarbonate is transformed into calcium carbonate, which is precipitated out of the water solution and forms a ring of calcite on the roof of the cavern. By repetition of this process the length and thickness of the stalactite is increased. A stalagmite is a cone of calcite rising from the floor of a cavern. Stalagmites and stalactites are often found in pairs, the stalagmite being formed as a result of further evaporation and precipitation from solution after the trickle of water falls from the stalactite. Stalactites and stalagmites often meet each other to form solid pillars. Curtains of dripstone sometimes form when water drips from the ceiling of a cave along joint planes. Since stalactites, stalagmites, and curtains of dripstone form only in the presence of air, their existence in a cave indicates that the cave was above the water table while the dripstone was forming. The many colors often seen in these formations are caused by the presence of impurities. Celebrated caverns that owe much of their beauty to their stalactites and stalagmites are Mammoth Cave, Ky.; the Luray Caverns, Va.; and the Carlsbad Caverns, N.Mex. Onyx marble (Mexican onyx, Egyptian alabaster, or Oriental alabaster), used as a decorative stone, is derived from stalagmites and stalactites, as well as from similar deposits.


 
Wikipedia: stalactite
Water droplet coming out of the central canal of a stalactite
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Water droplet coming out of the central canal of a 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.

Stalactites from a cave in Yucatán.
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Stalactites from a cave in Yucatán.

Formation

Stalactite in Doolin Cave, Ireland measuring 20ft (6.54m) long.
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Stalactite in Doolin Cave, Ireland measuring 20ft (6.54m) long.

Stalactites are formed by the deposition of calcium carbonate and other minerals, which is precipitated from mineralized water solutions. The corresponding formation on the floor underneath a stalactite is known as a stalagmite. Given enough time, these formations can meet, resulting in formations known as columns.

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.


Experiment modeling drip stone formation in the lab.
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Experiment modeling drip stone formation in the lab.

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."

While it has been claimed that the longest stalactite known hangs in the Chamber of Rarities in the Gruta Rei do Mato (Sete Lagoas, Minas Gerais, Brazil) and is 20 metres long, vertical cavers have often encountered longer stalactites while exploring. The longest stalactite viewable by the general public is in Doolin Cave, County Clare, Ireland, in a karst region known as The Burren.

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

See also

Mineralized water drop forming at bottom of stalactites.
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Mineralized water drop forming at bottom of stalactites.

References

  • Dripstone in time-lapse ("Tropfsteine im Zeitraffer") - Schmidkonz, B.; Wittke, G.; Chemie Unserer Zeit, 2006, 40, 246. doi:10.1002/ciuz.200600370

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Sci-Tech Dictionary. McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved.  Read more
Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.  Read more
Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved.  Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Stalactite" Read more

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