Supervolcanoes don't erupt; instead they explode, leaving a huge hole in the Earth's crusts as opposed to the "volcanic cone" left behind by regular eruptions.
Since scientists have started recording volcanic activity no supervolcano explosions have been seen; this makes determining what caused these explosions extremely difficult, an ETH Zurich news release reported. Researchers believe supervolcanic explosions only take place every 100,000 years.
A research team believes that have finally determined what triggers these powerful explosions. They used an X-ray beam at the European Synchrotron Radiation Facility (ESRF) to determine the density of supervolcano magma.
"This enabled the scientists to demonstrate that the overpressure generated by density differences in the magma chamber alone can trigger a supereruption," the news release reported.
This new research could help determine how supervolcanic magma sits in its magma chamber below the surface, as well as how quickly the magma could penetrate the Earth's crust.
A supervolcano is located in Yellowstone Caldera in the U.S., the structure can also be found in places such as Indonesia, Italy and New Zealand.
Scientists have long-known that supervolcano eruptions are caused by more than pressure from magma recharge in the magma chamber. A supervolcano's magma chamber is much too big to experience sufficient pressure.
One theory suggested these eruption were "generated through density differences between the less dense molten magma and the comparatively more dense rock in the surroundings," the news release reported.
"The effect is comparable to the buoyancy of a football filled with air underwater, which is forced upwards by the denser water around it," Wim Malfait, first author of the study, said in the news release.
Magma requires an overpressure level 100 to 400 times above the air pressure level in order to break through to the Earth's surface. Researchers must determine the density of the magma and surrounding rock in order to determine if adequate amounts of pressure could be reached. This has not been possible until now.
The team used X-rays to successfully determine the density of supervolcanic rock.
"X-rays can probe the state - liquid or solid - and the change in density when magma [crystallizes] into rock," Mohamed Mezouar, scientist at the ESRF and a co-author of the publication, said.
Researchers used a special pressing device in order to artificially reproduce the conditions inside of a supervolcano's magma chamber.
"The melts and the pressure and temperature conditions corresponded to the natural conditions of a supervolcano," the news release reported.
The team also used mathematical equations to help them determine how the phenomenon works.
"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," Sanchez-Valle said.
