Arootless cone, also formerly called apseudocrater,[1] is avolcaniclandform which resembles a truevolcanic crater, but differs in that it is not an actual vent from whichlava has erupted. They are characterised by the absence of anymagma conduit which connects below the surface of a planet.
Rootless cones are formed bysteam explosions as flowing hot lava crosses over a wet surface, such as aswamp, alake, or a pond. The explosive gases break through the lava surface in a manner similar to aphreatic eruption, and thetephra builds up crater-like forms which can appear very similar to real volcanic craters.
Well known examples are found inIceland such as the craters in the lakeMývatn (Skútustaðagígar), theRauðhólar in the region of the capital cityReykjavík or theLandbrotshólar of South-Iceland's Katla UNESCO Global Geopark nearKirkjubæjarklaustur. Rootless cones have also been discovered in theAthabasca Valles region ofMars, wherelava flowssuperheatedgroundwater in the underlying rocks.[2]
Volcanologists witnessed the formation of a rootless cone for the first time in history during a steam explosion in connection with thefirst eruption of Eyjafjallajökull in March 2010.[3]
![Rootless Cones, as seen by HiRISE under HiWish program. These group of rings or cones are believed to be caused by lava flowing over water ice or ground containing water ice.[4][5] The ice quickly changes to steam which blows out a ring or cone.](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aESP_037643_2060cones.jpg)
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