A rootless cone, also formerly called a pseudocrater, 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 like the craters in the lake Mývatn (Skútustaðagígar), the Rauðhólar in the region of the capital city Reykjavík or the Landbrotshólar located in South-Iceland in the Katla UNESCO Global Geopark in the vicinity of Kirkjubæjarklaustur. Rootless cones have also been discovered in the Athabasca Valles region of Mars, where lava flows superheated groundwater in the underlying rocks.
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- 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. doi:10.1016/j.pss.2008.11.011.
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- Kvöldfréttir Stöðvar Tvö "Viðtal við Ármann Höskuldsson eldfjallafræðing" Fréttastofa Stöðvar Tvö