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{{short description|Structure formed in a cave by the deposition of minerals from water}}
{{For|secondary deposits, derived from concrete, lime, or mortar, outside the cave environment|Calthemite}}
[[File:labeled speleothems.jpg|thumb|upright=1.4|Cave labeled with the six most common types of speleothems: [[flowstone]], [[Stalagnate|columns]], drapery, [[stalagmite]]s, [[stalactite]]s and [[soda straw|straws]]]]

A '''speleothem''' ({{IPAc-en|ˈ|s|p|iː|l|i|ə|θ|ɛ|m}}; {{etymology|grc|''{{wikt-lang|grc|σπήλαιον}}'' ({{grc-transl|σπήλαιον}})|cave||''{{wikt-lang|grc|θέμα}}'' ({{grc-transl|θέμα}})|deposit}}) is a [[geological formation]] by [[mineral]] [[deposition (geology)|deposits]] that accumulate over time in natural [[cave]]s.<ref>{{cite journal |last=White |first=W. B. |date=2019 |title=Speleothems |url=https://www.sciencedirect.com/science/article/pii/B9780128141243001175 |journal=Encyclopedia of Caves |language=en |pages=1006–17 |doi=10.1016/B978-0-12-814124-3.00117-5 |isbn=9780128141243}}</ref> Speleothems most commonly form in [[calcareous]] caves due to carbonate dissolution reactions. They can take a variety of forms, depending on their depositional history and environment. Their chemical composition, gradual growth, and preservation in caves make them useful [[paleoclimatology|paleoclimatic]] proxies.

==Chemical and physical characteristics==
More than 300 variations of cave mineral deposits have been identified.<ref name=":2">{{cite journal |last=White |first=William |date=2016 |title=Chemistry and karst |journal=Acta Carsologica |language=en |volume=44 |issue=3 |doi=10.3986/ac.v44i3.1896 |issn=0583-6050 |doi-access=free}}</ref> The vast majority of speleothems are calcareous, composed of [[calcium carbonate]] (CaCO3) minerals ([[calcite]] or [[aragonite]]). Less commonly, speleothems are made of [[calcium sulfate]] ([[gypsum]] or [[mirabilite]]) or [[opal]].<ref name=":2" /> Speleothems of pure calcium carbonate or calcium sulfate are translucent and colorless. The presence of [[iron oxide]] or [[copper]] provides a reddish brown color. The presence of [[manganese oxide]] can create darker colors such as black or dark brown. Speleothems can also be brown due to the presence of mud and [[silt]].<ref name=":2" />

Many factors impact the shape and color of speleothems, including the chemical composition of the rock and water, water seepage rate, water flow direction, cave temperature, cave humidity, air currents, aboveground climate, and aboveground plant cover. Weaker flows and short travel distances form narrower stalagmites, while heavier flow and a greater fall distance tend to form broader ones.

==Formation processes==
Most cave chemistry involves [[calcium carbonate]] (CaCO3) containing rocks such as [[limestone]] or [[dolomite (rock)|dolomite]], composed of [[calcite]] or [[aragonite]] minerals. Carbonate minerals are more [[solubility|soluble]] in the presence of higher [[carbon dioxide]] (CO2) and lower temperatures. Calcareous speleothems form via carbonate dissolution reactions whereby rainwater reacts with soil CO2 to create weakly acidic water via the reaction:<ref>{{cite book |last=J. |first=Fairchild, Ian |url=https://www.worldcat.org/oclc/813621194 |title=Speleothem science: from process to past environments |date=2012 |publisher=Wiley-Blackwell |isbn=978-1-4051-9620-8 |oclc=813621194}}</ref>
:H2O + CO2 → [[carbonic acid|H2CO3]]

As the acidic water travels through the calcium carbonate bedrock from the surface to the cave ceiling, it dissolves the bedrock via the reaction:
:CaCO3 + H2CO3 → Ca2+ + 2 HCO3−

When the solution reaches a cave, the lower [[pCO2|pCO2]] in the cave drives the [[precipitation (chemistry)|precipitation]] of CaCO3 via the reaction:
:Ca2+ + 2 HCO3− → CaCO3 + H2O + CO2

Over time, the accumulation of these precipitates form dripstones ([[stalagmite]]s, [[stalactite]]s), and [[flowstone]]s, two of the major types of speleothems.

==Climate proxies==
Speleothem transects can provide paleoclimate records similar to those from [[Ice core|ice cores]] or [[Dendrochronology|tree rings]].<ref>{{cite book |last=Bradley |first=Raymond S. |url=https://www.sciencedirect.com/science/article/pii/B9780123869135000089 |title=Paleoclimatology: Reconstructing Climates of the Quaternary |date=2015 |publisher=Academic Press |isbn=978-0-12-386913-5 |pages=291–318 |language=en |doi=10.1016/b978-0-12-386913-5.00008-9}}</ref> Slow geometrical growth and incorporation of radioactive elements enables speleothems to be accurately and precisely dated over much of the late [[Quaternary]] by [[radiocarbon dating]] and [[uranium-thorium dating]], as long as the cave is a closed system and the speleothem has not undergone [[recrystallization (geology)|recrystallization.]]<ref>{{cite journal |last1=Richards |first1=David A. |last2=Dorale |first2=Jeffrey A. |date=2003 |title=Uranium-series Chronology and Environmental Applications of Speleothems |journal=Reviews in Mineralogy and Geochemistry |language=en |volume=52 |issue=1 |pages=407–460 |bibcode=2003RvMG...52..407R |doi=10.2113/0520407 |issn=1529-6466}}</ref> Oxygen ([[Δ18O|δ18O]]) and carbon ([[Δ13C|δ13C]]) stable isotopes are used to track variation in rainfall temperature, precipitation, and vegetation changes over the past ~500,000 years.<ref name=":0">{{cite journal |last1=Fairchild |first1=Ian J. |last2=Smith |first2=Claire L. |last3=Baker |first3=Andy |last4=Fuller |first4=Lisa |last5=Spötl |first5=Christoph |last6=Mattey |first6=Dave |last7=McDermott |first7=Frank |last8=E.I.M.F. |date=2006 |title=Modification and preservation of environmental signals in speleothems |url=http://pure-oai.bham.ac.uk/ws/files/2918999/Fairchild_et_al_ESR_2006_pre-print.pdf |journal=Earth-Science Reviews |series=ISOtopes in PALaeoenvironmental reconstruction (ISOPAL) |volume=75 |issue=1–4 |pages=105–153 |bibcode=2006ESRv...75..105F |doi=10.1016/j.earscirev.2005.08.003}}</ref><ref>{{cite journal |last=Hendy |first=C. H |date=1971 |title=The isotopic geochemistry of speleothems–I. The calculation of the effects of different modes of formation on the isotopic composition of speleothems and their applicability as palaeoclimatic indicators |journal=Geochimica et Cosmochimica Acta |volume=35 |issue=8 |pages=801–824 |bibcode=1971GeCoA..35..801H |doi=10.1016/0016-7037(71)90127-X}}</ref> Variations in precipitation alter the width of speleothem rings: closed rings indicates little rainfall, wider spacing indicates heavier rainfall, and denser rings indicate higher moisture. Drip rate counting and trace element analysis of the water drops record short-term climate variations, such as [[El Niño–Southern Oscillation]] (ENSO) climate events.<ref>{{cite journal |last1=McDonald |first1=Janece |last2=Drysdale |first2=Russell |last3=Hill |first3=David |date=2004 |title=The 2002–2003 El Niño recorded in Australian cave drip waters: Implications for reconstructing rainfall histories using stalagmites |journal=Geophysical Research Letters |language=en |volume=31 |issue=22 |pages=L22202 |bibcode=2004GeoRL..3122202M |doi=10.1029/2004gl020859 |issn=1944-8007 |doi-access=free}}</ref> Exceptionally, climate proxy data from the early [[Permian]] period have been retrieved from speleothems dated to 289 million years ago sourced from infilled caves exposed by quarrying at the [[Richards Spur]] locality in Oklahoma.<ref>{{cite journal |last1=Woodhead |first1=Jon |last2=Reisz |first2=Robert |last3=Fox |first3=David |last4=Drysdale |first4=Russell |last5=Hellstrom |first5=John |last6=Maas |first6=Roland |last7=Cheng |first7=Hai |last8=Edwards |first8=R. Lawrence |date=2010-05-01 |title=Speleothem climate records from deep time? Exploring the potential with an example from the Permian |url=https://www.researchgate.net/publication/215768326 |journal=Geology |language=en |volume=38 |issue=5 |pages=455–458 |doi=10.1130/G30354.1 |bibcode=2010Geo....38..455W |issn=0091-7613 |hdl=1959.13/931960 |hdl-access=free}}</ref>

==Types and categories==
[[File:Tropfsteine.svg|thumb|upright=1.4|Types of speleothem: 
(A) Stalactite
(B) Soda straws
(C) Stalagmites
(D) Coned stalagmite
(E) Stalagnate or column
(F) Drapery
(G) Drapery
(H) Helictites
(I) Moonmilk
(J) Sinter pool, rimstone
(K) Calcite crystals
(L) Sinter terrace
(M) Karst
(N) Body of water
(O) Shield
(P) Cave clouds
(Q) Cave pearls
(R) Tower cones
(S) Shelfstones
(T) Baldacchino canopy
(U) Bottlebrush stalactite
(V) Conulite
(W) Flowstone
(X) Trays
(Y) Calcite rafts
(Z) Cave popcorn or coralloids
(AA) Frostworks
(AB) Flowstone
(AC) Splattermite
(AD) Speleoseismites
(AE) Boxworks
(AF) Oriented stalactite
(AG) collapsed rubble]]

Speleothems take various forms, depending on whether the water drips, seeps, condenses, flows, or ponds. Many speleothems are named for their resemblance to man-made or natural objects. Types of speleothems include:<ref name="Hill&Forti1997">Hill, C A, and Forti, P, (1997). Cave Minerals of the World, (2nd edition). [Huntsville, Alabama: National Speleological Society Inc.] pp. 217, 225</ref>
* '''Dripstone''' is calcium carbonate in the form of stalactites or stalagmites
** [[Stalactite]]s are pointed pendants hanging from the cave ceiling, from which they grow
*** [[Soda straw]]s are very thin but long stalactites with an elongated cylindrical shape rather than the usual more conical shape of stalactites
*** [[Helictite]]s are stalactites that have a central canal with twig-like or spiral projections that appear to defy gravity
**** Include forms known as ribbon helictites, saws, rods, butterflies, hands, curly-fries, and "clumps of worms"
*** Chandeliers are complex clusters of ceiling decorations
*** Ribbon stalactites, or simply "ribbons", are shaped accordingly
** [[Stalagmite]]s are the "ground-up" counterparts of stalactites, often blunt mounds
*** Broomstick stalagmites are very tall and spindly
*** Totem pole stalagmites are also tall and shaped like their namesakes
*** Fried egg stalagmites are small, typically wider than they are tall
** [[Stalagnate]] results when stalactites and stalagmites meet or when stalactites reach the floor of the cave
* '''[[Flowstone]]''' is sheet like and found on cave floors and walls
** Draperies or curtains are thin, wavy sheets of calcite hanging downward
*** Bacon is a drapery with variously colored bands within the sheet
** [[Rimstone|Rimstone dams]], or gours, occur at stream ripples and form barriers that may contain water
** Stone waterfall formations simulate frozen cascades
* '''Cave crystals'''
** [[Dogtooth spar]] are large calcite crystals often found near seasonal pools
** [[Frostwork]] is needle-like growths of calcite or aragonite
** [[Moonmilk]] is white and cheese-like
** [[Anthodite]]s are flower-like clusters of aragonite crystals
** ''Cryogenic'' calcite crystals are loose grains of calcite found on the floors of caves formed by segregation of solutes during freezing of water.
* '''[[Speleogen]]s''' (technically distinct from speleothems) are formations within caves that are created by the removal of [[bedrock]], rather than as secondary deposits. These include:
** Pillars
** Scallops
** Boneyard
** [[Boxwork]]
* '''Others'''
** [[Cave popcorn]], also known as "coralloids" or "cave coral", are small, knobby clusters of calcite
** [[Cave pearl]]s are the result of water dripping from high above, causing small "seed" crystals to turn over so often that they form into near-perfect spheres of calcium carbonate
** [[Snottite]]s are colonies of predominantly sulfur [[Redox|oxidizing]] bacteria and have the consistency of "snot", or mucus
** [[Calcite rafts]] are thin accumulations of calcite that appear on the surface of cave pools
** [[Hells Bells (cave formations)|Hells Bells]], a particular speleothem found in the El Zapote [[cenote]] of [[Yucatan]] in the form of submerged, bell-like shapes
** [[Lava tubes]] contain speleothems composed of sulfates, mirabilite or opal. When the lava cools, precipitation occurs.

==Calthemites==
The usual definition of speleothem excludes [[secondary mineral]] deposits derived from [[concrete]], [[lime (material)|lime]], [[mortar (masonry)|mortar]], or other calcareous material (e.g. limestone and dolomite) outside the cave environment or in artificial caves (e.g. mines, tunnels), which can have similar shapes and forms as speleothems. Such secondary deposits in man-made structures are termed [[calthemite]]s. Calthemites are often associated with [[concrete degradation]], or due to [[leaching (chemistry)|leaching]] of lime, mortar, or other calcareous material.

==Gallery==
<gallery>
File:HallOfTheMountainKings.jpg|Various formations in the [[Ogof Craig a Ffynnon|Hall of the Mountain Kings, Ogof Craig a Ffynnon]], [[South Wales]], [[Great Britain]]
File:NaturalBridgeCaverns6.jpg|Stalactites and columns in [[Natural Bridge Caverns]], [[Texas]]
File:NaturalBridgeCaverns7.jpg|More formations in [[Natural Bridge Caverns]], [[Texas]]
File:Kl 0005356.jpg|Cave curtain formation in the [[Marble Arch Caves]], [[County Fermanagh]], [[Northern Ireland]]
File:CaliforniaCaveFormation.jpg|[[California Caverns]], Calaveras County, California; one of many caverns located in the [[Sierra Foothills]] of California
File:Dripstone column in Biserujka Cave, Dobrinj, Island of Krk.jpg|Stalagnates (columns) in the cave [[Biserujka]], [[Dobrinj]], [[Island]] [[Krk]], [[Croatia]]
File:Druipsteen3.jpg|Various formations in the cave of Remouchamps, [[Aywaille]], [[Belgium]]
File:Zuil.jpg|Stalagnate (column) in the cave of Remouchamps, [[Aywaille]], [[Belgium]]
File:Cave pearls.jpg|Image of Cave Pearl formation
File:Flowstone in Mammoth Cave, KY.jpg|Image of flowstone in Mammoth Cave, KY
</gallery>

==See also==
*[[Petrifying well]]

==References==
{{Reflist}}

==External links==
{{Commons category|Speleothems}}
* [http://www.goodearthgraphics.com/virtcave/ The Virtual Cave: an online guide to speleothems]
* [http://mindraw.web.ru/cristall17.htm Mineral aggregates from carst caves, formed in capillary film solutions]
* [https://web.archive.org/web/20130123003018/http://www.nature.nps.gov:80/geology/caves/photo_speleothems.htm Gallery of speleothems] from [[National Park Service|NPS]] Cave and Karst Program (archived on 23 January 2013)

{{Caves}}

[[Category:Calcium minerals]]
[[Category:Dinaric Alps]]
[[Category:Dinaric karst formations]]
[[Category:Incremental dating]]
[[Category:Karst formations]]
[[Category:Karst]]
[[Category:Limestone]]
[[Category:Paleoclimatology]]
[[Category:Speleothems]]

Speleothem - Revision history

JacksonKuester2: Content updated and refined

Ajay Kumar: Created a new article