{{Short description|Natural opening where surface water enters caves}} {{other uses|Ponor (disambiguation)}} [[File:Djulin ponor jama.jpg|thumb|The river Dobra enters a 17 km long cave system at {{ill|Đulin ponor|hr}} in Ogulin, Croatia.|276x276px]] A '''ponor''' is a natural opening where surface water enters into underground passages; they may be found in karst landscapes where the geology and the geomorphology is typically dominated by porous limestone rock. Ponors can drain stream or lake water continuously or can at times work as springs, similar to estavelles.<ref name=":0">{{Cite book|last=Bonacci|first=Ognjen|url=https://books.google.com/books?id=bhiJ10Xx9VwC|title=Encyclopedia of Caves and Karst Science|date=2004|publisher=Taylor & Francis|isbn=978-1-57958-399-6|editor-last=Gunn|editor-first=John|pages=1282–1284|language=en|chapter=Ponor}}</ref> Morphologically, ponors come in forms of large pits and caves, large fissures and caverns, networks of smaller cracks, and sedimentary, alluvial drains.<ref name=":0" />
==Etymology== {{wiktionary|ponor}} The name for the karst formation ''ponor'' comes from Serbo-Croatian and Slovene.<ref>{{cite journal|last1=Dicken|first1=Samuel N.|date=November 1935|title=Kentucky Karst Landscapes|journal=The Journal of Geology|volume=43|issue=7|pages=708–728|doi=10.1086/624363|jstor=30057941|s2cid=140553389|quote=Since local terms such as "sink," "sink hole", "kettle", "bottom", etc., are vague and confusing the Slovene terminology ("ponor", "doline", etc.) is used for the karst forms.}}</ref> It derives from the proto-Slavic word ''*nora'', meaning ''pit'', ''hole''.<ref>{{Cite web|title=Ponor/ponirati|url=https://hjp.znanje.hr/index.php?show=search_by_id&id=eVpnXRE=&keyword=ponirati|access-date=2021-11-03|website=Hrvatski jezični portal}}</ref>
Several places in southeast Europe (Bulgaria, Bosnia and Herzegovina, Croatia, Czech Republic, Hungary, Romania, Montenegro, Serbia, and Slovenia) bear the name ''Ponor'' due to associated karst openings.
==Description== [[File:RakovSkocjan3.jpg|left|thumb|189x189px|One of few ponors of the Rak River, Slovenia]] Whereas a sinkhole (doline) is a depression of surface topography with a pit or cavity directly underneath, a ponor is kind of a portal where a surface stream or lake flows either partially or completely underground into a karst groundwater system.<ref name=":0" />
Steady water erosion may have formed or enlarged the portal in (mainly limestone) rock, in a conglomerate, or in looser materials. Karst terrains are known for surface water losses through small ''ponors'' and its resurgence after having traveled through vast underground systems.<ref name=":0" />
==Prevalence== Ponors are found worldwide, but only in karst regions. The entire Adriatic watershed within Bosnia and Herzegovina sits on Dinaric karst, with numerous explored and probably many more unexplored ponors and underground flows.<ref name="Bosnia-Devon">{{cite web|title=The Karstography of the Dinaric Karst in Bosnia and Hercegovina|url=http://www.devonkarst.org.uk/Karstography%20of%20DINARIC%20KARST%20in%20BiH.html|access-date=4 September 2016|publisher=The Devon Karst Research Society|language=en}}</ref><ref name="home-Devon">{{cite web|title=The Devon Karst Research Society|url=http://www.devonkarst.org.uk/INDEX.html|website=www.devonkarst.org.uk|publisher=Devon Karst|access-date=4 September 2016|language=en|format=.html}}</ref> There are significant geological ponors in the Carpathian Mountains, the Dinaric Alps, Greece, Turkey, and parts of the southern United States.{{citation needed|date=September 2016}}
<gallery> File:Katavothra-Feneos ponor karst-depression Peloponnese Feneos mit katavothre.jpg|Polje of Feneos, Greece, lake until late 19. Century. Rain showers flood large parts even today File:Avenul campeneasca.jpg|Closeup of ponor in Câmpeneasca cave near Izbuc village, Romania File:Skocjanske-Ponor3.jpg|A ponor where the Reka River disappears into Škocjan Caves, Slovenia File:Risle ponor.jpg|The Risle River disappears into a ponor between Ajou and La Houssaye (Eure, France) File:Jakovica, Logatec - požiralnik Pod stenami na Planinskem polju.jpg|A man-made ponor in Logatec, Slovenia File:Katavothra ponor Nestani-Polje Peloponnes Greece.jpg|In Polje "Argon Pedion" (untilled plain). Plain and ponor documented since 2nd century AD by Pausanias </gallery>
== Dams and reservoirs in karst == Reservoirs in karst are prone to losses due to leakage through ponors. The construction of dams to capture water in karst terrains may pose a great financial risk despite initial investigations and thorough sealing treatments.<ref name=":1">{{Cite book|last=Milanović|first=Petar|url=https://books.google.com/books?id=bhiJ10Xx9VwC|title=Encyclopedia of Caves and Karst Science|date=2004|publisher=Taylor & Francis|isbn=978-1-57958-399-6|editor-last=Gunn|editor-first=John|pages=571–575|language=en|chapter=Dams and reservoirs on karst}}</ref> It wasn't until the twentieth century that the first dams in karst were built, some of which famously failed.<ref name=":1" />
== See also == * Karst spring * Losing stream
==References== {{Reflist|colwidth=30em}}
{{Caves}} {{Rivers, streams and springs}}
. Category:Karst formations Category:Dinaric Alps Category:Dinaric karst formations Category:Sinkholes