Predicting volcanic eruptions: Discovery helps pinpoint where and when better than ever before

GENEVA, Switzerland — Predicting where and when the next volcano will erupt has been made much easier, according to a new study. The factors which determine whether a volcanic eruption is likely to take place and whether it will be no big deal or cataclysmic have been discovered, say scientists.

Volcanic eruptions are hard to predict at the best of times, even when they are being monitored very closely. While some volcanoes erupt regularly, others can remain dormant for up to 10,000 years before suddenly blowing their top. Now, scientists led by experts at the University of Geneva (UNIGE) in Switzerland have figured out what makes active volcanoes tick and how bad their bang is likely to be.

Being able to predict when and where the next eruption will take place could help protect the 800 million people worldwide who live near active volcanoes.

Stromboli eruption
One of the strombolian explosions that have occurred at Stromboli about every 10 minutes for at least 2000 years. (© UNIGE, Luca Caricchi)

“There are currently 1,500 active volcanoes, and about 50 of them erupt each year. Knowing whether or not to evacuate the population is crucial and we hope that our study will contribute to decrease the impact of volcanic activity on our society,” says study author Luca Caricchi, a professor with the Department of Earth Sciences at UNIGE, in a statement.

Existing research on the stages which proceed a volcanic eruption was collected and analyzed by the researchers. One of the first stages is where magma, or molten rock, rises from tens of kilometers deep inside the earth to the surface.

“During its journey, magma can get trapped in reservoirs within the Earth’s crust, where it may stagnate for thousands of years and potentially never erupt,” explains Meredith Townsend, a researcher with the Department of Earth Sciences at the University of Oregon.

How magma can dictate a volcanic eruption

Using mathematical models, the researchers were able to calculate how much pressure was needed for the magma to break free of the rocky reservoir and rise to the surface. They then examined how quickly the magma rose to the surface and what path it was most likely to take.

While it could take a variety of routes, including vertical, horizontal and inclined, the amount of time largely depended on what it contained, the researchers found.

“If it is runny enough, that is if it does not contain too many crystals, magma can rise very quickly by a sort of self-propelled fracking,” says co-author Eleonora Rivalta, a professor at the University of Bologna in Italy. “If magma crystallizes more than 50 percent, it becomes too viscous and its march towards the surface stops.”

Other external factors such as earthquakes, tides or rain were also taken into account as they are commonly linked with triggering volcanic eruptions.

“These alone cannot cause an eruption, the magma has to be ready and awaiting a trigger,” adds co-author Atsuko Namiki, an associate professor at Nagoya University in Japan.

‘A different story with old volcanoes’

How old a volcano is also plays an important part in determining the size of its reservoir and the eruption which could follow.

“When a volcano is just starting to be active, its reservoir is rather small and the surrounding crust is relatively cold, which leads to many frequent, but small and rather predictable eruptions,” says Caricchi. “It’s a different story with old volcanoes. Their reservoir is bigger and the rocks around them are hotter. When new magma is injected, it does not generate much overpressure because the rocks around the reservoir deform and the growth continues.”

For example, Mount Saint Helens in Washington started erupting 40,000 years ago. Its last eruption in 2008 was small and “not dangerous.” In comparison, Toba in Indonesia, has been blowing its top for over 1.2 million years and its last eruption 74,000 years ago was “cataclysmic.”

A volcano’s age can be determined by analyzing certain minerals in the rocks known as zircon. The findings could help protect the millions of people around the world who live near active volcanoes.

“The chemistry of magma and the crystals it contains provide vital information on the sequence of events leading to a volcanic eruption, which is valuable to better interpret the monitoring signals of active volcanoes and anticipate- whether an eruption might occur,” says Caricchi. “Hopefully our findings will be tested on volcanoes that have been studied extensively, such as those in Italy, USA and Japan, and transferred to other volcanoes for which there are less data, such as in Indonesia or South America.”

The findings are published in the journal Nature Reviews Earth and Environment.

SWNS writer Tom Campbell contributed to this report.