Pseudocrater

Pseudocrater in Mývatn

Pseudocrater on the Mýrdalssandur in southern Iceland

Pseudocraters (from ancient Greek pseudo = fake, pretended) are craters that are created by a steam explosion over a lava flow .

Origin and characteristics

When hot lava flows over a wetland, which can be swamps , but also lakes or ponds , the water evaporates suddenly. The steam breaks through the lava ceiling in a phreatomagmatic explosion . The lava, and partly also the underground material, is fragmented and thrown up as tephra around a crater.

The resulting structure resembles a real volcanic crater , which is also called rootless cone in English . It has no root, so to speak, so no direct magma feed line from the interior of the earth.

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

Examples

Iceland Mývatn, one of the pseudocraters on the southwestern part of the lake, near the ring road at Skútustaðir.

Well-known examples of pseudocraters can be found in Iceland at Lake Mývatn , in the form of the Skútustaðagígar in the municipality of Skútustaðir , but also near the capital Reykjavík in the Rauðhólar craters and in southeast Iceland as Landbrotshólar .

Another example is the Tintron Cave , in the Gjábakkalava field in northeast Iceland. In that case it is a hornito . Hornitos are also counted among the pseudocratos by some scientists.

Pseudocraters have also been discovered in the Massif Central in France, for example below the cinder cone Puy Montchal , which is right next to Lac Pavin .

When Kilauea erupts in Hawaii in 1999, pseudocraters also formed, which the volcanologists at the USGS called rootless shields . The pseudocrater shown in the photo has a height of 20 m and a diameter of 500 m, at times there was a small lava lake with a diameter of 175 m in its summit area .

Pseudocraters have also been found on Mars , which seems to prove that water was once found on the planet.

Web links

Commons : Pseudocrater  - collection of images, videos and audio files

• German-language explanations about the pseudocraters
• Video recordings of the formation of pseudocratos at Eyjafjallajökull 2010

Individual evidence

1. ↑ Thorleifur Einarson: Geology of Iceland. Rocks and Landscape. Mál og Menning, Reykjavík 1991, 77f.
2. ↑ Thor Thordarson, Armann Hoskuldsson: Iceland. Classic Geology in Europe 3. Terra, Harpenden 2002, 147
3. ↑ Thor Thordarsson, Armann Hoskuldsson: Iceland - Classic Geology third in Europe Harpenden, 2002, p 150
4. ^ Peter Cattermole: Auvergne. Classic Geology in Europe 2. Terra, Harpenden, 2001, 84
5. ↑ [1]
6. ↑ http://hvo.wr.usgs.gov/gallery/kilauea/erupt/19991021-250_CH_caption.html HVO, USGS: Photogallery.Pu`u `O`o - Kupaianaha Eruption of Kilauea Volcano 1999-2000, Intrusion triggers pause in eruption: tube system blocked ; Retrieved September 29, 2012
7. ↑ science.at ( Memento from January 24, 2007 in the Internet Archive )