The Italian supervolcano Phlegrean Fields is one of the most dangerous in the world, not least because more than a million people live around it.
A new study, published in Scientific Reports, has identified a magma source that fuels the dormant and sinister cauldron. Unfortunately, this volcano is more dangerous than previously thought.
Finding the hot zone of the supervolcano
Scientists usually use the seismic waves that magma emits as it makes its way through the crust to determine where it is at any given moment. But since this supervolcano as a whole has remained calm since the mid-1980s, its magma source is much more difficult to find.
An international team led by experts from the University of Aberdeen tried to solve this puzzle. Using specialized mathematical analysis of seismic data collected since the mid-1980s, the team identified a hot zone 4 km below Pozzuoli, near Naples.
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According to the study, the hot zone is either a small amount of magma, or the molten tip of a massive magma chamber, whose liquid fire is spread deep below the earth's surface. In any case, scientists have found compelling evidence for an active heat source that supplies magma to one of the most dangerous volcanoes in the world. But the story doesn't end there.
Ground level rise above the caldera
One of the key mysteries of the Phlegrean fields is their periodic and frightening growth. Between 1982 and 1984, the ground in the crater rose 1.8 meters. Whatever the reason - magma, gas moving through the earth's crust, or the movement of superheated water - the crater soon sank.
The new study helps explain why this growth did not end with a volcanic eruption. Seismic imaging shows that a very tough shallow rock form above it prevented magma from breaking through to the surface. That is why the magma spread laterally and could not break through.
This means that the risk from the caldera has migrated. "The Phlegrean fields are now like a pot of boiling soup beneath the surface," says lead author Dr. Luca de Siena, a geologist in Aberdeen.
This means that instead of a single eruption point, a new caldera can form.
How the Phlegrean fields were formed
The Phlegrean Fields remain a monster that scientists have very little understanding. The caldera was formed 40 thousand years ago during one of the most energetic paroxysms of the last few million years. At that time, the supervolcano threw out about 500 cubic kilometers of debris, which could even reach Greenland, despite the distance of 4,600 kilometers.
Since then, there have been several eruptions, but he left most of the fireworks to volcanoes located near or within the crater itself, such as Vesuvius and the ominous sulfuric Solfatara. Volcanologists are still acutely aware of the risk to the 6 million people living in the "explosion zone" of this monster, and therefore constantly monitor it.
Is it worth fearing a new eruption
What's really worrying is that the Phlegrean Fields are growing again, although the risk of eruption is now 24 times lower than it was in the early 1980s. As always, volcanologists do not know what is really going on, but they believe that the volcano is heading for a critical moment when an eruption is imminent.
Regardless of whether the eruption will form a new caldera, or it will be common, de Siena believes that the volcano is becoming more dangerous.
Forget Yellowstone. Phlegrean Fields is a supervolcano really worth worrying about.
Anna Pismenna