Ponor

For other uses, see Ponor (disambiguation).

One of several ponors of the Rak River, Slovenia

A ponor is a natural surface opening that may be found in landscapes where the geology and the geomorphology is characterized by some kind of karst.

Etymology

The term "ponor" has become the international geological term for larger karst-induced surface water inlets. The word derives from the proto-Slavic nora (pit, hole, abyss). The word "ponor" itself comes from Slovene in which word ponor has the same meaning.

Description

Whereas a sinkhole is a depression (doline) 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. Steady water erosion may have formed or enlarged the portal in (mainly limestone) rock, in a conglomerate, or in looser materials.

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.
There are also several places in southeast Europe (Bulgaria, Croatia, Czech Republic, Hungary, Romania, Montenegro, Slovenia) with the name "Ponor" due to associated karst openings. There are significant geological ponors in the Carpathian Mountains, the Dinaric Alps, Greece, Turkey, and parts of the southern United States.

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  A ponor where the Reka River disappears into Škocjan Caves, Slovenia
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  Collecting basin, stone rake, ponor (behind viewer), Peloponnese
• 
  A Stubai Alps stream terminates in a ponor
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  A fenced-in ponor south of Grosuplje, Slovenia
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  Closeup of ponor in Câmpeneasca cave near Izbuc village, Romania
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  The Risle River disappears into a ponor between Ajou and La Houssaye (Eure, France)

See also

• Karst spring
• Losing stream