The pauses between volcanic eruptions are often so long people settle the surrounding slopes, believing they are safe. Predicting when and where future eruptions will take place could save countless lives, but so far has proven beyond volcanologists. A new model hopes to rectify this, and has been able to back-predict the last eruption of the Campi Flegrei volcanic field, raising hopes it can anticipate future events elsewhere.
When a volcanic eruption empties a magma chamber the weight of the rock above can come crashing down, forming a caldera, sometimes many miles wide. The name comes from the Spanish for cooking pot, giving an idea of the typical shape.
More often than not, magma continues to build up below ground, and eventually reaches the surface. Rather than neatly escaping near the top, as in a cone-shaped volcano, however, it will often force its way through a side vent, with disastrous consequences for anyone living on that side of the volcano. Dr Eleonora Rivalta of the GFZ German Research Centre for Geosciences has built a model to predict where magma will emerge next, and therefore who needs to be ready to run.
"Calderas often look like a lawn covered in molehills," Rivalta said in a statement, owing to all the spots where magma has burst through in the past. Statistical methods to predict future eruption sites based on past locations have had limited predictive power, but Rivalta explained, "Our method combines physics and statistics: we calculate the paths of least resistance for ascending magma and tune the model based on statistics."
In Science Advances, Rivalta describes using recent developments in the way magma fractures underground rocks to map the likely route.
She then applied the work to Campi Flegrei, near Naples, which is considered one of the world’s most dangerous calderas, as well as possibly the best studied. At least 80 vents have been used by Campi Flegrei’s magma to escape over the last 15,000 years, and with these up to 10 kilometers (6 miles) apart, it makes a major difference where the eruption occurs.
The most recent 1538 eruption, which formed a new hill near Naples, occurred at a site far from its immediate predecessors. However, when she removed knowledge of this eruption from the system, Rivalta’s model correctly calculated the location now known as Monte Nuovo as the most likely place for the 1538 eruption to occur.
Rivalta now hopes to generalize the model, saying: “If our method works well on other volcanoes too, it may help planning land usage in volcanic areas and forecasting the location of future eruptions with a higher certainty than previously possible." If so, it could prevent a lot of heartache.