Scientists have made a breakthrough in their efforts to understand what causes so-called supervolcanoes to erupt.
Supervolcanoes are capable of eruptions thousands of times larger than normal outpourings.
It was thought that an external trigger, such as an earthquake, was needed to bring about a giant blast.
But tests at the European Synchrotron Radiation Facility in Grenoble show the sheer volume of liquid magma is enough to cause a catastrophic super-eruption.
…..One possible mechanism was thought to be the overpressure in the magma chamber generated by differences between the less dense molten magma and more dense rock surrounding it.
“The effect is comparable to holding a football under water. When you release it, the air-filled ball is forced upwards by the denser water around it,” said Wim Malfait, of ETH Zurich.
But whether this buoyancy effect alone was enough was not known. It could be that an an additional trigger – such as a sudden injection of magma, an infusion of water vapour, or an earthquake – was required.
To simulate the intense pressure and heat in the caldera of a supervolcano, the researchers visited ESRF in Grenoble, where they used an experimental station called the high pressure beamline.
Scientist at ESRF loading a speck-sized magma rock sample into the anvils of a press. Scientists studied a magma-like substance under extreme heat and pressure at the ESRF in Grenoble
They loaded synthetic magma into a diamond capsule and fired high-energy X-rays inside – to probe for changes as the mixture reached critically high pressures.
The experiment showed that the transition from solid to liquid magma creates a pressure which can crack more than 10 kilometres of Earth’s crust above the volcano chamber.
But if Yellowstone happened to be on the brink of an eruption, the good news is that we will still see a warning, Dr Malfait told BBC News.
“The ground would probably rise hundreds of metres – a lot more than it does now.
“We think Yellowstone currently has 10-30% partial melt, and for the overpressure to be high enough to erupt would take about 50%.”
More: http://www.bbc.co.uk/news/science-environment-25598050
