Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Supervolcano eruptions are triggered by melt buoyancy

06.01.2014
Jointly issued by ETH Zurich, ESRF and CNRS

Supervolcanos are not 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, using an X-ray beam at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. This enabled the scientists 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"

Until now, scientists could only speculate about what triggers a supereruption. One possible mechanism was thought to be the overpressure in the magma chamber generated through density differences between the less dense molten magma and the comparatively more dense rock in the surroundings. "The effect is comparable to the buoyancy of a football filled with air underwater, which is forced upwards by the denser water around it," says Wim Malfait, first author of the study, until recently at ETH Zurich and now a researcher at the Swiss Laboratories for Materials Science and Technology (Empa).

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 have now succeeded in determining the density of supervolcanic magma for the first time with the aid of X-rays. "X-rays can probe the state – liquid or solid – and the change in density when magma crystallises into rock," explains Mohamed Mezouar, scientist at the ESRF and a co-author of the publication in "Nature Geoscience". The scientists used a special press to study artificially produced magma melts under the same extreme pressure and temperature conditions as inside a volcanic magma chamber. Both the melts and the pressure and temperature conditions corresponded to the natural conditions of a supervolcano. 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.

"The 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 their study.

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

Press Office | EurekAlert!
Further information:
http://www.ethz.ch

More articles from Earth Sciences:

nachricht GPM sees deadly tornadic storms moving through US Southeast
01.12.2016 | NASA/Goddard Space Flight Center

nachricht Cyclic change within magma reservoirs significantly affects the explosivity of volcanic eruptions
30.11.2016 | Johannes Gutenberg-Universität Mainz

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>