Hidden Supervolcano-Sized Magma Reservoir Discovered Beneath Tuscany

A Massive Underground Discovery

Scientists have uncovered one of the most significant geological discoveries in recent memory: a vast reservoir containing approximately 6,000 cubic kilometres of magma buried deep beneath Tuscany – a volume comparable to the magma systems beneath some of the world's most powerful supervolcanoes . The sheer volume of the network is on par with "those of some of the largest eruptive systems worldwide, such as Taupō, Long Valley, and Yellowstone. All these volcanic systems featured super-eruptions."

What makes this discovery particularly remarkable is that the region shows almost none of the surface signs that typically betray the presence of large magma bodies underground – no major craters, no significant eruptions in hundreds of thousands of years, and no dramatic ground deformation . The last volcanic eruption in the area, from Mount Amiata, occurred around 300,000 years ago and was relatively minor .

Revolutionary Detection Technology

The study, led by Matteo Lupi of the University of Geneva and published in Communications Earth & Environment, used a technique called ambient noise tomography to map the reservoirs at depths of 8 to 15 kilometers below the iconic Tuscan countryside . This molten rock was detected using ambient noise tomography, a subsurface imaging technique that makes it possible to "X-ray" the Earth's crust by harnessing natural environmental vibrations generated by ocean waves, wind, or human activity .

Magma slows down seismic waves significantly compared to solid rock. The tomographic images revealed large zones of anomalously slow wave speeds at 8–15 km depth, consistent with reservoirs of partially molten rock . Around 60 instruments were used in this study to create detailed three-dimensional images of the underground structure.

Solving the Geothermal Mystery

The discovery explains one longstanding puzzle about the region – why it has such extreme geothermal activity despite lacking an obvious volcanic source. The Larderello area of Tuscany, once known as the Devil's Valley for its fumarolic activity, hosts one of the world's most productive geothermal energy systems, which has been generating electricity since the early twentieth century .

The magma sits between 8 and 15km below the surface and has a core of predominantly liquid melt surrounded by a larger shell of crystal-rich partially molten rock. The researchers estimate around 3,000 km³ of liquid melt at the centre, encased in roughly 5,000km³ of crystal mush .

Future Implications and Safety

The reservoirs appear stable — they've likely been in place for millions of years. Tuscany shows none of these warning signs that would indicate imminent volcanic activity. Although this magma body could, in theory, contribute to the formation of a supervolcano over geological timescales, it currently poses no threat .

The study demonstrated the practical potential of ambient noise tomography as a rapid and relatively cheap tool for subsurface exploration. "These results are important both for fundamental research and for practical applications, such as locating geothermal reservoirs or deposits rich in lithium and rare earth elements," noting that the formation of such deposits is closely linked to deep magmatic systems . This discovery could revolutionize how we locate sustainable energy sources and critical minerals needed for modern technology, from electric vehicle batteries to renewable energy systems.