Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Supervolcano eruptions are triggered by melt buoyancy

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:

More articles from Earth Sciences:

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

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

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>