{{short description|Type of cave}} [[File:Lechuguilla Chandelier Ballroom.jpg|thumb|Gypsum stalactites in a cave formed via sulfuric acid dissolution (Lechuguilla Cave, New Mexico)]]

A '''solutional cave''', '''solution cave''', or '''karst cave''' is usually formed in a soluble rock like limestone, of which calcium carbonate ({{chem2|CaCO3}}) composes. Being the most common type of cave, it can also form in other rocks, including chalk, dolomite, marble, salt beds, and gypsum.<ref>{{cite web |url=https://nps.gov/subjects/caves/solution-caves.htm |title=Solution Caves - Caves and Karst |publisher=U.S. National Park Service}}</ref>

== Process == Bedrock is dissolved by carbonic acid in rainwater, groundwater, or humic acids from decaying vegetation, that seeps through bedding planes, faults, joints, and the like. Over time, the surface terrain breaks up into clints separated by grikes and punctuated by sinkholes into which streams may disappear, crevices expand as the walls are dissolved to become caves or cave system. These may turn into large caverns or ''dolines'' when the roof collapses.<ref name=dkp>{{cite book|title=The Ultimate Visual Dictionary|chapter=Geology, Geography, and Meteorology|publisher=D.K. Pub.|year=2012|page=284-285|isbn=978-0-1434-1954-9|language=en}}</ref>

The portions of a solutional cave that are below the water table or the local level of the groundwater are flooded.<ref>{{cite web |url=http://www.amazingcaves.com/learn_formed.html |title=Learning about caves; how caves are formed |access-date=September 8, 2009 |first=John |last=Burcham |work=Journey into amazing caves |publisher=Project Underground}}</ref>

== Limestone caves == [[File:Kolbinger Höhle, Tropfsteinhöhle (Tuttlingen).jpg|thumb|Limestone cave ''Kolbinger Höhle''<ref>German Wikipedia: Kolbinger Höhle</ref>]] The largest and most abundant solutional caves are located in limestone. Limestone caves are often adorned with calcium carbonate formations produced through slow precipitation. These include flowstones, stalactites, stalagmites, helictites, soda straws, calcite rafts, and columns. These secondary mineral deposits in caves are called "speleothems".<ref name=dkp/><ref name=ncei>{{cite web|title=Speleothem - National Centers for Environmental Information (NCEI)|url=https://www.ncei.noaa.gov/products/paleoclimatology/speleothem#:~:text=Speleothems%20are%20mineral%20deposits%20formed,to%20determine%20past%20climate%20conditions.|website=National Centers for Environmental Information|access-date=2 January 2025}}</ref><ref name=nss>{{cite web|title=Soda Straws - National Speleological Society|website=National Speleological Society|url=https://caves.org/virtualcave/soda-straw/|access-date=2 January 2025|first=Djuna|last=Bewley}}</ref>

=== Carbonic acid dissolution === Limestone dissolves under the action of rainwater and groundwater charged with H<sub>2</sub>CO<sub>3</sub> (carbonic acid) and naturally occurring organic acids. The dissolution process produces a distinctive landform known as "karst", characterized by sinkholes and underground drainage. Solutional caves in this landform—topography are often called karst caves.

=== Sulfuric acid dissolution === {{main|Sulfuric acid cave}} Lechuguilla Cave in New Mexico and nearby Carlsbad Caverns are now believed to be examples of another type of solutional cave. They were formed by H<sub>2</sub>S (hydrogen sulfide) gas rising from below, where reservoirs of petroleum give off sulfurous fumes. This gas mixes with ground water and forms H<sub>2</sub>SO<sub>4</sub> (sulfuric acid). The acid then dissolves the limestone from below, rather than from above, by acidic water percolating to the surface.

== Gypsum caves == Some solutional caves form in gypsum.<ref name="researchgate ukraine">Alexander Klimchouk, [https://www.researchgate.net/publication/220044221_Ukraine_gypsum_caves_and_karst Ukraine gypsum caves and karst], ''Researchgate.net'', January 2012</ref> Gypsum karst is very rare. It depends on deposits of gypsum or anhydrite, often also called alabaster. Chemically it is calcium sulfate, CaSO<sub>4</sub>.

Gypsum caves can be found in several places on earth, including:

* Optymistychna Cave in Ukraine, considered the longest gypsum cave at 232&nbsp;km<ref name="researchgate ukraine" /> * Orda Cave underneath the Western Ural Mountains, with 5.1&nbsp;km length, including 4.8&nbsp;km underwater<ref>Floro Mercene, [https://www.pressreader.com/philippines/tempo/20170612/281663959988109 The world's greatest underwater gypsum cave], ''Pressreader.com'', 12 June 2017</ref> * Cuevas de Sorbas in Almeria, Spain

Caves noted for large scale gypsum speleothems include:

* Cave of the Crystals in Chihuahua, Mexico * Lechuguilla Cave in New Mexico, US

== Examples == === Australia === * Jenolan Caves, New South Wales

=== Germany === * König-Otto-Tropfsteinhöhle

=== Malaysia === * List of caves in Malaysia

=== Taiwan === * Black Dwarf Cave, Pingtung County

=== United States === * Jewel Cave National Monument, South Dakota * Mammoth Cave National Park, Kentucky * Russell Cave National Monument, Alabama * Cathedral Caverns State Park, Alabama * Wind Cave National Park, South Dakota * Oregon Caves National Monument and Preserve, Oregon * Cumberland Caverns, Tennessee

=== Vietnam === * Hang Sơn Đoòng, Quảng Bình Province

== References == {{Reflist}}

=== Sources === * {{cite book |url={{google books |plainurl=yes |id=bhiJ10Xx9VwC |page=417 |keywords="solution" "karst caves"}} |pages=417, 1421 |first1= John |last1=Gunn |title=Encyclopedia of Caves and Karst Science |publisher=Routledge |edition=2nd |date=2004}} * {{cite book |url={{google books |plainurl=yes |id=qHrF2uqSlUEC |page=27 |keywords="karst caves" "Solutional"}} |page=27 |first1=Rob |last1=Young |first2=Lisa |last2=Norby |title=Geological Monitoring |publisher=Geological Society of America |date=2009}} * {{cite book |url={{google books |plainurl=yes |id=JJHyXx42OQEC |page=124 |keywords="karst caves" "Solutional"}} |page=124 |first1=Andrew |last1=Goudie |first2=Mario |last2=Panizza |title=Encyclopedia of Geomorphology |publisher=Routledge |date=2014}}

== Further reading ==

* {{cite journal |last1=Calaforra |first1=J. M. |last2=Forti |first2=P. |last3=Fernandez-Cortes |first3=A. |date=2008 |title=Speleothems in gypsum caves and their paleoclimatological significance |url=https://www.academia.edu/download/41390065/Speleothems_in_gypsum_caves_and_their_pa20160121-29913-hbty1z.pdf |journal=Environmental Geology |volume=53 |pages=1099–1105 |doi=10.1007/s00254-007-0737-3 |access-date=28 December 2025 |ref={{harvid|1a1=Calaforra et al.|1y=2008}} |via=SpringerLink}}

== External links == * {{Commons category-inline|Karst caves}}

* {{usurped|[https://web.archive.org/web/20071012072806/http://www.caverbob.com/gypcave.htm World's longest gypsum caves compiled]}}

{{Caves}} {{Subterranea}}

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Category:Karst caves