Sunday, January 5, 2014

Buoyancy of magma: How Super volcanoes erupt - n-tv.de NEWS

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 One of the regular small eruptions of the volcano Stromboli Italian. His last large outbreak is back about 70,000 years. One of the regular small eruptions of the volcano Stromboli Italian. Its last major eruption is about 70,000 years back (photo: dpa).

Monday 06 January 2014

eruptions of super volcanoes can have devastating consequences for the Earth’s climate. So far, researchers have puzzled what blows up the giant magma chambers – it is not only the pressure, the nachflie├čendes magma builds up. Now they find out.

But the density differences in the magma chamber may explode super volcanoes. Two international research teams have discovered this triggered the devastating eruptions. The very fact that the liquid magma is less dense than the surrounding solid rock, can give the magma enough buoyancy to penetrate kilometers thick crustal rocks. The scientists report in two articles in the journal “Nature Geoscience.”

eruption cloud of Pinatubo volcano on the U.S. Clark Air Base in the Philippines. (Image from June 1991) eruption cloud of Pinatubo volcano on the U.S. Clark Air Base in the Philippines. (Image from June 1991) (Photo: AP)

as a common definition – -

a very rare explosions of super volcanoes are at least 1000 cubic kilometers of material ejected. This is around 100 times more than the eruption of Mount Pinatubo in the Philippines in 1991, the most serious eruptions of the 20th Century one.

Instead of a volcanic cone eruptions left a crater in the earth’s crust – the be emptied magma chamber whose diameter can be up to 100 kilometers. Among the remnants of such outbreaks include Yellowstone Caldera in the U.S., the Lake Toba in Indonesia and the Lake Taupo in New Zealand. The last eruption of a super volcano is tens of thousands of years back.


outbreak not only by positive pressure

researchers knew that super volcanoes erupt not only by those overpressure, the nachflie├čendes magma builds up. Since such magma chambers may be several kilometers deep and 100 kilometers wide, but this inflow can not build up enough pressure. Therefore, it was assumed that the overpressure is generated by density differences between the less dense magma and the denser solid rock in the area.

This was confirmed by researchers led by Carmen Sanchez-Valle from the Swiss Federal Institute of Technology (ETH) Zurich. They determined the density of magma in volcanoes Super with the help of X-rays at the European Synchrotron Radiation Facility in Grenoble. So they examined artificially produced magma melting at different pressure and temperature conditions. Thus, differences in density can produce between magma and surrounding rock enough pressure to explode the chamber. “The effect is comparable to the buoyancy of an air-filled soccer ball under water, which is forced by the heavier surrounding water up,” says first author Wim Malfait according to a statement of the university.


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“The results show that at a sufficient size of the magma chamber alone, the excess pressure caused by differences in density is enough to break through the crust above it and to set in motion an eruption,” said Sanchez-Valle. Other mechanisms such as tectonic stresses could contribute to a super eruption, but are not necessary, emphasize the scientists. The findings could help to better assess “sleeping” super volcanoes as fast as you can about magma penetrate the earth’s crust and reach the surface.

researchers led by Luca Caricchi of the University of Geneva came also to the conclusion that the magma buoyancy can cause a super eruption in a huge chamber. They used computer models, data of known super volcanoes and 1.2 million simulations to discover the secret of these explosions on the track.

Source: n-tv.de

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