Pseudo craters crater caused by a steam explosion over a lava flow.

Formation and characteristics

When hot lava flows over a wetland, where it may be swamps, but also to lakes or ponds, the water evaporates abruptly. The steam breaks through the lava bed in a phreatomagmatic explosion. Here, the lava, and partly also the underground material, raised fragmented and as a tephra crater.

The resulting structure resembles a real volcano crater, which also bears the name of rootless cone ( rootless cones) in English. It has no roots, so to speak, so no direct magma supply from the Earth's interior.

The formation of pseudo craters could be the first time directly observed during the eruption of Eyjafjallajökull in 2010 in history on March 25, 2010.


Known examples of pseudo craters are found around Lake Mývatn in Iceland, in the form of Skutustadagigar in the community Skútustaðir, but also near the capital of Reykjavík in the craters Rauðhólar and in eastern Iceland as Landbrotshólar.

Another example is the cave Tintron, in Gjábakkalavafeld in Northeast Iceland. In this case it is a hornito. Hornitos be expected by some scientists also to the pseudo craters.

Also in the Massif Central in France pseudo craters were discovered, such as below the cinder cone Puy Montchal which is adjacent to the Lac Pavin.

In eruptions of Kilauea in Hawaii in 1999, also formed pseudo craters Volcanologen the USGS called rootless shields. The pseudo crater pictured in the photo has a height of 20 m and a diameter of 500 m, was temporarily in the summit area of ​​a small lava lake of 175 m diameter.

Pseudo craters have been found on Mars, which seems to prove that the planet was once water was to be found.