Volcanoes: Where does the next vent open?

New model predicts location of future outbreaks

High-risk zone: View of the caldera of the super-volcano Campi Flegrei near Naples. Where in this volcanic area the next lava outbreak could take place now predicts a new model. © Giuseppe Vilardo / INGV-OV GeoLab
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Risk limited: A new model can predict where the next lava exit will take place at a volcano - a challenge that has so far been difficult to achieve. This is made possible by the combination of geophysical data with a statistical method, as researchers report in the journal "Science Advances". At the super volcano Campi Flegrei near Naples, the new model has already proven its accuracy.

Even the prediction of the next breakout time is a challenge for an active volcano. But it gets even more difficult if you want to forecast exactly where the lava will escape at the volcano. Because often the magma breaks new ground and exits on the flanks of the volcano or even miles away, such as the Bardarbunga in Iceland or the Kilauea in Hawaii.

The problem of prognosis

This is even more extreme with super-volcanoes: their huge caldera can be literally perforated by the chimneys of smaller eruptions. "Caldera often look like a lawn covered with molehills, " says first author Eleonora Rivalta of the German Research Center for Geosciences GFZ in Potsdam. In addition: The eruptions of such caldera are rare and are far apart in time. Accordingly, it is difficult to predict the location of the next eruption in such a caldera volcano.

"Models used to date were based on statistics of the locations of past eruptions, " says Rivalta. In the process, volcanologists assumed that existing vents form weak spots in the subsurface, which can make magma rise more easily the next time around. However, it speaks against the fact that many vents are "one-time openings", as Rivalta and her team explain: they are only active during an outbreak and then not again.

Geophysics combined with statistics

Therefore, the research team has now developed a new method for predicting the position of vents. "We use the most up-to-date physical knowledge of how magma spreads underground, combining it with a statistical process and knowing the structure and history of the volcano, " explains Rivalta. Specifically, the researchers determine factors such as the position of the magma chamber, the stress distribution in the ground or the location of volcanic eruptions. display

The scientists then combine this physical model with a static method, the so-called Monte Carlo simulation. "We tune the parameters of the physical model until they match previous eruptive patterns. Then we have a working model and can use it to forecast future outbreaks, "says Rivalta.

Test at the super volcano

How accurate the new model is, the researchers tested using the example of Campi Flegrei near Naples. 40, 000 years ago, 29, 000 years ago and 15, 000 years ago, this super volcano has experienced major eruptions that covered half of Europe with ashes and left behind a giant caldera. Since then, numerous small eruptions have left well over 70 vents in the volcanic area. Recently there are increasing signs that the supervolcano is heading for a new major eruption - which could affect more than one million people.

Monte Nuovo is the chimney of Campi Flegrei's last minor eruption in 1538. Mauro Antonio Di Vito

For their test, the researchers fed their model with the geophysical data of this super volcano and initially reconstructed the location of some earlier vents. Their location information they had not previously fed with. And indeed, the results reflected the gradual shift of the vents and also predicted the location of the last eruption. It took place in 1538 on Monte Nuevo in the northeastern corner of the caldera, an area that was considered unlikely by previous claims.

Future outbreaks are threatening in the northeast

More importantly, the new model also predicts where to expect future outbreaks of the Campi Flegrei. Accordingly, new vents could most likely occur in the northeast of the caldera. The most likely eruption zone forms a ring at 2.3 to 4.5 kilometers from the caldera center, as the researchers report. This risk zone is therefore not located in the submerged part of the volcanic area, but in the middle of the densely populated coastal area.

Whether the model is so accurate with other volcanoes, the researchers want to investigate next. "If our method works well with other volcanoes, it can help to better plan land use in volcanic areas and predict the location of future eruptions with greater certainty than previously, " says Rivalta. (Science Advances, 2019; doi: 10.1126 / sciadv.aau9784)

Source: Helmholtz Center Potsdam GFZ German Research Center for Geosciences

- Nadja Podbregar