{{short description|Long, narrow crack opening on a planetary surface}} {{Use dmy dates|date=September 2021}} {{About|cracks that open on a planetary surface|other types of geological cracks|Fracture (geology)|other uses}} [[File:Kamoamoa 2011-03-10 ground cracks.jpg|thumb|250px|Ground cracks at an east–west segment of Kamoamoa after its 2011 fissure eruption. The geologist is about {{cvt|180|cm|ft}} tall.<ref name="Volcano watch"/>]]
A '''fissure''' is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word {{wikt-lang|la|fissura}}, which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes.
== Ground fissure == [[File:Fissure in the ground – Almannagjá.jpg|thumb|240px| A fissure in the lava field of Þingvellir National Park, Iceland]] A {{em|ground fissure}}, also called an {{em|earth fissure}}, is a long, narrow crack or linear opening in the Earth's crust. Ground fissures can form naturally, such as from tectonic faulting and earthquakes, or as a consequence of human activity, such as oil mining and groundwater pumping.<ref name="Elsevier"></ref><ref name="Berkeley"/> Once formed, ground fissures can be extended and eroded by torrential rain.<ref name="CGLCJ"/> They can be hazardous to people and livestock living on the affected surfaces and damaging to property and infrastructure, such as roads, underground pipes, canals, and dams.<ref name="Elsevier"/><REF name="AZGS"/><REF name="USGS"/><ref name="ADS"/>
In circumstances where there is the extensive withdrawal of groundwater, the earth above the water table can subside causing fissures to form at the surface.<REF name="LDKM"/><REF name="ILLK"/> This typically occurs at the floor of arid valleys having rock formations and compacted soils with a high percentage of fine-grained material.<ref name="ADS"/><ref name="AZGS"/>
== Crevasse == {{Main article|Crevasse}} [[File:Crevasse-Tangra-Mountains.jpg|thumb|240px|A crevasse in the Tangra Mountains, Antarctica]]
A {{em|crevasse}}, also called an {{em|ice fissure}}, is a deep linear crack in an ice sheet or glacier resulting from the opposing force produced by their movement at different rates of speed. The force builds until their associated shear stress is sufficient to break the ice along the faces. The breakage often forms vertical or near-vertical walls, which can melt and create seracs, arches, and other ice formations.<REF name="Crevasses on Glacier"/> A crevasse may be as deep as {{cvt|45|m|ft}} and as wide as {{cvt|20|m|ft}}.<REF name="Auto7A-1"/> A crevasse may be covered, but not necessarily filled, by a snow bridge made of the previous years' accumulation and snow drifts. The result is that crevasses are rendered invisible, and extremely dangerous to anyone attempting to traverse a glacier.<ref name="Dodds"/>
=== Types of crevasses === [[File:Parque estatal Chugach, Alaska, Estados Unidos, 2017-08-22, DD 94.jpg|thumb|240px|Transverse crevasses in Chugach State Park, Alaska]]
* Longitudinal crevasses form parallel to the ice flow where the glacier width is expanding.<ref name="transverse crevasses"/> * Splaying crevasses appear along the edges of a glacier. * Transverse crevasses form in a zone of longitudinal extension where the principal stresses are parallel to the direction of glacier flow.<ref name="transverse crevasses"/>
== Fissure vent == {{Main article|Fissure vent}} thumb|240px|A volcanic fissure and lava channel
A {{em|fissure vent}}, also known as a {{em|volcanic fissure}} or {{em|eruption fissure}}, is a long volcanic vent through which lava erupts. Fissure vents are connected to deep magma reservoirs and are typically found in and along rifts and rift zones.<ref name="discovery"/> They are commonly associated with shield volcanoes. Over time fissure vents form spatter cones and can feed lava channels and lava tubes.<ref name="SDSU"/>
== Karst terrain == {{main article|Karst}} [[File:Causse de Sauveterre doline.jpg|thumb|240px|Doline in the causse de Sauveterre, Lozère, France]] {{em|Karst terrain}} or simply {{em|karst}} are vast regions of barren land with rocky ground and generally consisting of nearby caves, fissured ground, and sinkholes. Although these regions normally have moderate to heavy rainfall, they are noticeably devoid of vegetation and characteristically have no lakes, rivers, or streams on their surface. They form when large to massive veins of soluble aggregate like limestone, gypsum, or dolomite are excavated by underground torrents of flowing water.<REF name="EB Karst"/><REF name="USGS Karst"/>
=== Karst aquifers === {{main|Karst aquifer}} thumb|240px|Map of major US aquifers by rock type In the United States, about 40% of the groundwater used for drinking comes from {{em|karst aquifers}}.<ref name="USGS Aquifers"/> Some of these areas are well known vacation destinations like Carlsbad Caverns and Mammoth Cave. Karst aquifers are a vital resource in the US; about 20 percent of the land surface in the US is classified as karst. Other parts of the world with large areas of karst include the Caribbean, China, and Australia.
Typical karst hydrogeology consists of a network of interconnected fissures, fractures, and conduits emplaced within permeable rock. Most of the groundwater flow occurs through a network of openings, while groundwater is held in storage within the geological structures themselves.
== See also == * Fabric (geology) * Fissure vein * Thermokarst * Topography
== References == <references> <ref name="Volcano watch">{{cite web |title=Volcano Watch — A recap of the Kamoamoa fissure eruption on its third anniversary |url=https://www.usgs.gov/center-news/volcano-watch-a-recap-kamoamoa-fissure-eruption-its-third-anniversary |website=www.usgs.gov |access-date=25 September 2021}}</ref>
<ref name="Elsevier">{{citation|url=https://www.smu.edu/-/media/Site/Dedman/Academics/Departments/EarthSciences/PDF/Lu/166_Yang_Longyao_ground_fissure_PSInSAR_JAG_2018.pdf?la=en|journal=International Journal of Applied Earth Observation and Geoinformation|title=Deformation at longyao ground fissure and its surroundings, north China plain, revealed by ALOS PALSAR PS-InSAR|page=1|volume=67|date=May 2018|first1=Chengshen|last1=Yang|first2=Zhong|last2=Lu|first3=Qin|last3=Zhang|first4=Chaoying|last4=Zhao|first5=Jianbing|last5=Peng|first6=Lingyun|last6=Ji|doi=10.1016/j.jag.2017.12.010|bibcode=2018IJAEO..67....1Y}}</ref>
<ref name="Berkeley">{{cite web |last1=Berkeley |first1=UC |title=The Mystery about Earthquake Fissures |url=https://seismo.berkeley.edu/blog/2017/05/04/The-mystery-about-earthquake_fissures.html |website=seismo.berkeley.edu |language=en}}</ref>
<ref name="CGLCJ">{{cite book |last1=Carlson |first1=Grace |last2=Carnes |first2=Lorraine K. |last3=Cook |first3=Joseph P. |title=Geologic Excursions in Southwestern North America |chapter=Exploring Arizona earth fissures: An anthropogenic geologic hazard |chapter-url=https://pubs.geoscienceworld.org/books/book/2196/chapter/122801749/Exploring-Arizona-earth-fissures-An-anthropogenic |access-date=24 September 2021 |language=en |doi=10.1130/2019.0055(04) |date=4 September 2019|isbn=978-0-8137-5655-4 }}</ref>
<ref name="AZGS">{{cite web |title=Earth Fissures, Subsidence & Karst in Arizona |url=https://azgs.arizona.edu/center-natural-hazards/earth-fissures-subsidence-karst-arizona |website=AZGS |access-date=21 September 2021 |language=en |date=12 July 2017}}</ref>
<ref name="USGS">{{cite web |title=USGS: Volcano Hazards Program Glossary - Fissure |url=https://volcanoes.usgs.gov/vsc/glossary/fissure.html#:~:text=In%20geology%2C%20a%20fissure%20is,surface%20from%20which%20lava%20erupts. |website=volcanoes.usgs.gov |access-date=21 September 2021}}</ref>
<ref name="ADS">{{cite news |last1=Star |first1=Tony Davis Arizona Daily |title=Record Pinal County fissure shows Arizona is still prone to shifting earth levels |url=https://tucson.com/news/local/record-pinal-county-fissure-shows-arizona-is-still-prone-to-shifting-earth-levels/article_7746322e-e4a4-55f7-bdd3-5ff9bed82662.html |access-date=22 September 2021 |work=Arizona Daily Star |language=en}}</ref>
<ref name="LDKM">{{cite book | last1=Lund | first1=W.R. | last2=DuRoss | first2=C.B. | last3=Kirby | first3=S.M. | last4=McDonald | first4=G.N. | last5=Hunt | first5=G. | last6=Vice | first6=G.S. | title=The Origin and Extent of Earth Fissures in Escalante Valley, Southern Escalante Desert, Iron County, Utah | publisher=Utah Geological Survey | series=Special Study | year=2005 | isbn=978-1-55791-730-0 | url=https://books.google.com/books?id=yucwzDh7XSQC | access-date=21 September 2021}}{{pn|date=September 2021}}</ref>
<ref name="ILLK">{{cite book | last1=Inkenbrandt | first1=P. | last2=Lund | first2=W. | last3=Lowe | first3=M. | last4=Knudsen | first4=T. | last5=Bowman | first5=S. | title=Investigation of land subsidence and earth fissures in Cedar Valley, Iron County, Utah | publisher=Utah Geological Survey | series=Special Study | year=2014 | isbn=978-1-55791-891-8 | url=https://books.google.com/books?id=7ARaBAAAQBAJ | access-date=21 September 2021}}{{pn|date=September 2021}}</ref>
<ref name="Crevasses on Glacier">{{cite journal | title=Crevasses on Glaciers | author=van der Veen, C | journal=Polar Geography | year=1990 | volume=23 | issue=3 | pages=213–245 | doi=10.1080/10889379909377677}}</ref>
<ref name="Auto7A-1">[https://www.nationalgeographic.org/encyclopedia/crevasse/ Crevasse] {{Webarchive|url=https://web.archive.org/web/20211024171658/https://www.nationalgeographic.org/encyclopedia/crevasse/ |date=24 October 2021 }} by National Geographic</ref>
<ref name="Dodds">{{cite web |last1=Dodds |first1=Klaus |title=Fissure |url=https://culanth.org/fieldsights/fissure |website=Society for Cultural Anthropology |date=24 October 2017 |access-date=26 September 2021 |language=en}}</ref>
<ref name="transverse crevasses">{{cite journal | title=Primary Transverse Crevasses | author=Holdsworth, G | journal=Journal of Glaciology |date=October 1956 | volume=8 | issue=52 | pages=107–129| doi=10.1017/S0022143000020797 | doi-access=free }}</ref>
<ref name="discovery">{{cite web|website=www.volcanodiscovery.com|url=https://www.volcanodiscovery.com/geology/glossary/fissure-vent.html|title=Geology glossary|access-date=September 25, 2001}}</ref>
<ref name="SDSU">{{cite web |title=How Volcanoes Work |url=http://sci.sdsu.edu/how_volcanoes_work/index.html |website=sci.sdsu.edu |access-date=26 September 2021 |archive-date=28 February 2018 |archive-url=https://web.archive.org/web/20180228090151/http://www.geology.sdsu.edu/how_volcanoes_work/index.html |url-status=dead }}</ref>
<ref name="EB Karst">{{cite web |title=Karst {{!}} geology |url=https://www.britannica.com/science/karst-geology |website=Encyclopedia Britannica |access-date=26 September 2021 |language=en}}</ref>
<ref name="USGS Karst">{{cite web |title=Karst Aquifers: Colorado Plateau Karst |url=https://www.usgs.gov/mission-areas/water-resources/science/karst-aquifers-colorado-plateau-karst?qt-science_center_objects=0#qt-science_center_objects |website=www.usgs.gov |access-date=26 September 2021}}</ref>
<ref name="USGS Aquifers">{{cite web |title=Karst Aquifers |url=https://www.usgs.gov/mission-areas/water-resources/science/karst-aquifers?qt-science_center_objects=0#qt-science_center_objects |website=www.usgs.gov |access-date=27 September 2021 |language=en}}</ref> </references>
== External links == * [https://www.alamy.com/stock-photo/almannagja-fissure.html External images of Almannagja fissures]
{{structural geology|state=collapsed}}
Category:Geomorphology Category:Patterned grounds Category:Structural geology