Supervolcanoes Erupt without External Triggers
Super-volcanoes can erupt spontaneously, without the need for an external trigger such as an earthquake, new research suggests.
Supervolcanic eruptions, such as the one that occurred in Wyoming thousands of years ago, can change the entire climate of the earth. Two new studies published in the journal Nature Geoscience have said that such cataclysmic events can occur spontaneously and do not need triggers such as earthquakes.
According to an experiment at the European Synchrotron Radiation Facility (ESRF) in Grenoble, the difference in the density between magma and the surrounding rocks in these super-volcanoes is enough to tear open a huge crack in the earth's crust.
Supervolcanoes, unlike average volcanoes don't actually erupt, they "explode," tearing a massive hole in the earth's crust. Earlier, it was assumed that earthquakes might be connected with these eruptions.
Researchers at ETH Zurich have now been able to determine the density of the magma using X-rays from ESRF. They used the latest technique to "artificially produce magma melts under different pressure and temperature conditions." Researchers even accounted for varying water content in the magma melt. The team then constructed mathematical models to explain the conditions in a supervolcano.
"Until now, nobody had measured the density of the magma that is present in the magma chambers of super-volcanoes," EZH's Wim Malfait told AFP. "Magma is less dense than solid rock, the magma in a magma chamber pushes on the roof of the chamber."
In a separate study on the same subject, researchers at the University of Geneva and their colleagues concluded that buoyancy of the magma is important in the supervolcano explosion.
"It is comparable to a football filled with air under water, which is forced upwards by the denser water around it," lead author Wim Malfait of ETH Zurich explained in a news release.
Supervolcanoes have large magma chambers and are located in areas where the heat flow from the interior of the earth to surface is very high. Conventional volcanoes have rigid magma chambers, which crack under pressure. But, the conditions in supervolcanoes make the magma chambers very plastic, meaning that the chambers keep changing their shapes with the inflow of hot magma. It is this plasticity that lets these monster volcanoes control pressure, which is why they don't erupt too often.
This is good news for earth's inhabitants because when these volcanoes erupt, they can cause large-scale damage and even change earth's climate. A single supervolcano eruption occurred 600,000 years ago in Wyoming in the United States and created a huge crater called a caldera. The caldera is present in the Yellowstone National Park. At the time of the explosion, it released nearly 1000 cubic kilometers of lava and ash, which substantially dwarfs any other recent volcano eruption.
There are about 20 known super-volcanoes on earth including those found in Indonesia and New Zealand, BBC reported. As pointed out earlier, these sleeping giants rarely burst, it happens once in every 100,000 years or so.