A rootless cone, also formerly called a pseudocrater,[1] is a volcanic landform which resembles a true volcanic crater, but differs in that it is not an actual vent from which lava has erupted. They are characterised by the absence of any magma conduit which connects below the surface of a planet.
Rootless cones are formed by steam explosions as flowing hot lava crosses over a wet surface, such as a swamp, a lake, or a pond. The explosive gases break through the lava surface in a manner similar to a phreatic eruption, and the tephra builds up crater-like forms which can appear very similar to real volcanic craters.
Well known examples are found in Iceland such as the craters in the lake Mývatn (Skútustaðagígar), the Rauðhólar in the region of the capital city Reykjavík or the Landbrotshólar of South-Iceland's Katla UNESCO Global Geopark near Kirkjubæjarklaustur. Rootless cones have also been discovered in the Athabasca Valles region of Mars, where lava flows superheated groundwater 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 the first eruption of Eyjafjallajökull in March 2010.[3]
^Burr, Devon M.; Bruno, Barbara C.; Lanagan, Peter D.; Glaze, Lori S.; Jaeger, Windy L.; Soare, Richard J.; Wan Bun Tseung, Jean-Michel; Skinner, James A.; Baloga, Stephen M. (2009). "Mesoscale raised rim depressions (MRRDs) on Earth: A review of the characteristics, processes, and spatial distributions of analogs for Mars". Planetary and Space Science. 57 (5–6): 579–596. Bibcode:2009P&SS...57..579B. doi:10.1016/j.pss.2008.11.011.
^Jaeger, W. L. et al. (2008) Morphologic Characteristics and Global Distribution of Phreato-volcanic Constructs on Mars as seen by HiRISE, Lunar and Planetary Science XXXIX [1] PDF. Retrieved 2010-07-11.
^Kvöldfréttir Stöðvar Tvö "Viðtal við Ármann Höskuldsson eldfjallafræðing" Fréttastofa Stöðvar Tvö
A rootlesscone, also formerly called a pseudocrater, is a volcanic landform which resembles a true volcanic crater, but differs in that it is not an...
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association with lava caves and the formation of rootlesscones due to their mechanism of formation and a rootlesscone was suggested to exist at Wiri being Matukutūreia...
produces a cone or ring. Features like these are found in Iceland, when lavas cover water-saturated substrates. Wide view of field of rootlesscones, as seen...
steam which blows out a ring or cone. RootlessCones, as seen by HiRISE under HiWish program. These group of rings or cones are thought to be caused by lava...
elevation (red) to lowest (dark blue) is 170 m (560 ft). So-called "rootlesscones" are caused by explosions of lava with ground ice under the flow. The...
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volcano-like landforms called pseudocraters, or rootlesscones. Features that resemble terrestrial rootlesscones occur in Elysium, Amazonis, and Isidis and...
explosions on a swamp or more probably on small lake which produced the rootlesscone group Rauðhólar. The pseudocraters are located immediately at the western...
McPhie, J.; Carey, R.J. (November 2021). "Apparently 'dry' littoral rootlesscones in Hawaiʻi formed by sustained, "confined" mixing of lava and sea water"...
Discoveries: Rootlesscones on Mars". www.psrd.hawaii.edu. Retrieved 20 November 2018. Lanagan, P., A. McEwen, L. Keszthelyi, and T. Thordarson. 2001. Rootless cones...
termed by some authors as volcanic rootless constructs (VRC). This class of lava-water interactions includes rootlesscones, but have fewer genetic implications...
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