The eruption of a supervulkan is one of the most powerful natural disasters in the earth, the consequences of which can devastate entire continents. One of these dangers is slumbering under the Yellowstone National Park: the Yellowstone is one of the largest super volcanoes worldwide, which has broken out on a large scale at least three times in the past 2.1 million years and covered North America with ash and rock. Smaller eruptions always took place in between; last about 70,000 years ago when Lava flowed in the Caldera. A team led by Ross Maguire from the University of Illinois Urbana-Champaign has measured the volume and composition of the magma chamber of the monster and now presented the results in »Science«.
According to the analyses of the working group, the reservoir of molten rock contains twice the amount of magma as previously known. However, this does not mean that an outbreak has become more likely, the scientists write; this is related to the actual composition of the material in the magma chambers. Yellowstone consists of two chambers, one near the mantle and the other a few kilometers below the surface. Both contain a mixture of completely molten rock and partially crystallized material.
The composition of this slurry determines the probability of eruption of the supervolcano with: the greater the ratio of molten rock to solid crystals, the higher the probability that the magma will move upwards and the volcano will explode. Maguire and Co have therefore evaluated seismic data from the Yellowstone over the past 20 years to determine the ratio of the two materials in the upper magma chamber. They took advantage of the fact that seismic waves move more slowly through sections with higher amounts of molten rock than through firmer and thus "harder" areas.
You feed your data into a computer model to create a three -dimensional image of the chamber and the waves running through it. Previous studies only used linear models. As a result, the geoscientists determined that the magma chamber consists of an average of 16 to 20 percent melted rock, while earlier estimates only had a value of nine percent. The equivalent of this means about 1,600 cubic kilometers and thus almost twice as much as the previous estimate of around 900 kilometers.
Nevertheless, there is no threat of an outbreak in the immediate future, according to Maguire. Even the higher estimate is still well below the 35 to 50 percent proportion of magma that must be necessary for an eruption. "Yellowstone can spend a large part of its life cycle with a certain melt without an eruption," says the scientist. However, when the time comes, there is hardly any time to prepare. According to studies, the first signs of an outbreak appear only a year before.
