Supereruptions Trigger Found
Until recently, how supervolcanos become active remained a mystery. Geologists have now demonstrated that the pressure generated through the difference in density between magma and the surrounding rock alone can be sufficient to cause one of these geological giants to erupt.
The ash formations in La Garita Caldera in Colorado, USA, are the result of eruptions of a supervolcano approximately 25 million years ago.
Supervolcanos are not your usual volcanos. By effectively “exploding” as opposed to erupting, they leave a giant hole in the Earth’s crust instead of a volcanic cone – a caldera, which can be up to one hundred kilometres in diameter. On average, supervolcanos are active more rarely than once every 100,000 years; since records began, none has been active. Consequently, researchers can only gain a vague idea of these events based on the ash and rock layers that have survived.
A team of researchers headed by ETH-Zurich professor Carmen Sanchez-Valle has now identified a trigger for supereruptions by determining the density of supervolcanic magma. This enabled them to demonstrate that the overpressure generated by density differences in the magma chamber alone can trigger a supereruption. The magma chamber is located in the Earth’s crust beneath the volcano. The new findings could help us to understand “sleeping” supervolcanos better, including how quickly their magma can penetrate the Earth’s crust and reach the surface.
Magma chamber too large
Well-known supervolcanos are located in the Yellowstone Caldera in the USA, Lake Toba in Indonesia and Lake Taupo in New Zealand. However, the somewhat smaller Phlegraean Fields near Naples are also included in the twenty or so known supervolcanos on Earth to date.
The fact that supereruptions – unlike conventional volcanos – are not triggered solely by overpressure due to magma recharge in the magma chamber has long been clear. A supervolcano’s magma chamber can be several kilometres thick and up to one hundred kilometres wide, which makes it far too big to sustain sufficient overpressure through magma recharge.
“Comparable to a football underwater”
Density differences between the magma of a supervulcano and the surrounding rock may cause overpressure, possibly creating fissures through which magma can make makes its way to the surface.
For the magma to break through the crustal rock above the magma chamber and carve out a path to the surface, it needs an overpressure level that is 100 to 400 times higher than air pressure (10 to 40 megapascals). In order to investigate whether the differences in density can generate such high pressure, the density of the magma melt and the surrounding rock material needs to be known. Until now, however, that of the magma melt could not be gauged directly.
Magma density determined for the first time
The researchers from ETH Zurich have now succeeded in determining the density of supervolcanic magma for the first time with the aid of x-rays from the European Synchrotron Radiation Facility in Grenoble, France, which they used to study artificially produced magma melts under different pressure and temperature conditions. Both the melts and the pressure and temperature conditions corresponded to the natural conditions of a supervolcano, according to the scientists. Moreover, the researchers varied the water content of the melts. Via the different parameters, they formulated mathematical equations, which helped them to reconstruct the conditions in a supervolcano.
“Our results reveal that if the magma chamber is big enough, the overpressure caused by differences in density alone are sufficient to penetrate the crust above and initiate an eruption,” says Sanchez-Valle. Mechanisms that favoured conventional volcanic eruptions, such as the saturation of the magma with water vapour or tectonic tension, could be a contributory factor but are not necessary to trigger a supereruption, the researchers stress in a study published in the journal “Nature Geoscience”. In an additional, independent study in the same issue of the journal scientists of the University of Geneva and other research institutions conclude from computational modelling that melt buoyancy is indeed key to the eruption of supervolcanos.
Supervolcanos are considered a rare but serious threat. As they are not easy to spot on account of their unusual appearance, new ones are still being discovered today. Supereruptions generally eject at least 450 but sometimes even several thousands of cubic kilometres of rock material and ash to the surface and into the atmosphere. In the event of explosive eruptions, ash and rock fragments with their environmentally harmful chemical components can rise over thirty kilometres up into the atmosphere and have a devastating impact on the climate and life on Earth. The spectacular and serious eruptions of Krakatoa (1883) and Tambora (1815), both conventional volcanos in present-day Indonesia, were comparatively “harmless” and the masses they emitted only amounted to a few per cent of a supereruption.
Literature Reference
Malfait WJ, Seifert R, Petitgirard S, Perrillat JP, Mezouar M, Ota T, Nakamura E, Lerch P, Sanchez-Valle C: Supervolcano eruptions driven by melt buoyancy in large silicic magma chambers. Nature Geoscience, Advance Online Publication, 5 January 2014, doi:10.1038/ngeo2042
Caricchi L, Annen C, Blundy J, Simpson G, Pinel V: Frequency and magnitude of volcanic eruptions controlled by magma injection and buoyancy. Nature Geoscience, Advance Online Publication, 5 January 2014, doi:10.1038/ngeo2041
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what you dont know is that the dep ocean trenches off indonesia,new guinea,and canary isles and elsewhere are the first indications of a shifting upper crust mantle. you see in the usgs charts every day significant quakes in and around this ring of fire. remember the film 2012: global warming is not the issue ir is magma and heat displaceing rock leading to an eventual surface disruptionm to the earth that is widespread and devastating. global warming is the intl communities smoke and mirror diversion. they will not tell you of the imminant danger to us all it will panic we the sheeple before they can get to their bunkers or the spaceships that will carry them to different places out of harms way. we are fodder and toast. so 2012 didnt happen according to MAYAN calender!!<well it will!
you see the results of the upper surface ocean current displacem,ent due to shift in earths axis due to the mantle displacement as well as the old BP oil explosions and indonesian quake. this phenomenpon is causeing the COLD SNAP in the northeast because the trade winds have also been displaced due to tjhis undersea and sea level activity. it is not global warming at poles causeing this.
my take and research:
charles buchanan 111
veritas lux mea
Very interesting post! Thank you! Thought provoking take, Zeus.
There would be no warning.
Build a man a fire, and he’ll be warm for a day. Set a man on fire, and he’ll be warm for the rest of his life.
nice history lesson on geological formations.
From the photo only on eruption occurred in over a million years and before that there is no telling. I’d be worried about yellowstone