An international team of scientists from Italy, Switzerland and the United Kingdom discovered that a large amount of magma is accumulating under the Phlegrean fields (Italy). In the future, this could lead to a catastrophic eruption that will affect a densely populated area with more than 1.5 million people. An article by volcanologists was published in the journal Science Advances.
The Phlegrean Fields is an active volcanic caldera near Naples. The mega-eruption of the Phlegraean Fields (event CI) occurred about 40 thousand years ago and probably caused the onset of a volcanic winter. The second major eruption (the Neapolitan yellow tuff, or NYT event) happened about 15 thousand years ago. In addition, over the past 60 millennia, the supervolcano has consistently produced weaker eruptions, including Monte Nuovo in 1538.
Scientists analyzed samples of rocks, minerals and volcanic glass associated with 23 eruptions of the Phlegraean Fields, including the CI and NYT events. This made it possible to trace the evolution of the magmatic system and understand how it goes from weak eruptions to mega-eruptions. It turned out that eruptions like Monte Nuovo are characterized by the release of magma, poor in crystals, relatively cold, with a high water content. Such eruptions usually occurred during the pre-caldera phase, followed by a mega-eruption.
The eruption of Monte Nuovo was characterized by critical changes in the magmatic system of the Phlegrean fields. First, tens and hundreds of years before the eruption, the water content in the magma reached saturation, as a result of which the active release of fluids (volatile components) from the magma began to occur. Secondly, crystallization processes have intensified, including feldspars. All of this began to create excess pressure in the magma reservoir, which led to the eruption.
After Monte Nuovo, the caldera entered a new phase of dormancy. However, since the 1950s, a number of weak earthquakes have occurred in the area of the Phlegrean fields due to the rise of magma from the main reservoir at a depth of 7-8 kilometers to a small hydrothermal system at a depth of three kilometers. Scientists believe that the accumulation of volatile-rich magmas began in the upper crust. Thus, the Phlegrean fields entered a phase of pressure build-up, which precedes a new major eruption. However, this phase can last for hundreds or thousands of years.