Seismic Noise Revealed 6,000 Cubic Kilometers of Magma Hiding Beneath Tuscany, Comparable to Yellowstone
Researchers listening to ocean waves and traffic through 60 seismometers mapped a molten reservoir 8 to 15 kilometers under one of Italy's most visited regions. They say it is not about to erupt.
An international research team has mapped a body of magma beneath Tuscany containing roughly 6,000 cubic kilometers of molten and partly molten rock — a volume the researchers compare to 2.4 billion Olympic swimming pools, and to the reservoirs that sit under supervolcanic systems like Yellowstone. It lies between 8 and 15 kilometers below the surface of one of the most heavily visited regions in Europe.
The finding was published Wednesday in Communications Earth & Environment by scientists from the University of Geneva, Italy's Institute of Geosciences and Earth Resources and the National Institute of Geophysics and Volcanology. Matteo Lupi, an associate professor in the Department of Earth Sciences at Geneva's Faculty of Science, led the work.
"We knew that this region is geothermally active, but we did not realize it contained such a large volume of magma, comparable to that of supervolcanic systems such as Yellowstone," Lupi said.
The method is what makes the result possible, and it involves no drilling and no explosions. The team used ambient noise tomography: instead of generating seismic waves artificially, they recorded the constant low-level vibration of the Earth — ocean waves pounding distant coastlines, wind, road traffic, industry — on a network of about 60 high-resolution seismic sensors. That background hum travels through the crust in every direction. Seismic waves slow down when they pass through hot or partially molten rock, so by comparing arrival times across dozens of station pairs the researchers could reconstruct a three-dimensional picture of where the slow material sits.
Tuscany's geothermal character has been exploited for more than a century. Larderello, in the province of Pisa, hosted the world's first geothermal power plant in 1904 and still generates electricity today. What was not known was the scale of the heat source underneath. The region has no active volcano and no historical eruption, which is precisely why a reservoir of this size went unmapped.
The researchers are explicit that the discovery does not imply an eruption is coming. A large volume of magma at depth is a necessary condition for a major eruption but nowhere near a sufficient one — the material has to be sufficiently melted, sufficiently gas-rich and sufficiently pressurized to move, and there is no evidence of that here. Systems of this kind can sit in a mushy, mostly crystallized state for hundreds of thousands of years.
The practical consequence points in a different direction: energy and minerals. A shallow, well-characterized heat source is the single most valuable input for geothermal power, and the hydrothermal systems that circulate above magma bodies concentrate lithium and rare earth elements. Italy imports essentially all of both. Knowing where the heat is, and how deep, turns a geological curiosity into a resource map.
Originally reported by ScienceDaily.