Large magma reservoir discovered deep beneath southern Tuscany
Scientists have reported evidence of a vast deep magma reservoir beneath southern Tuscany after analyzing seismic data from more than 60 stations across the region. The study links the hidden melt system to the intense heat flow beneath Larderello geothermal system, one of Europe’s best-known high-enthalpy geothermal fields.
Renowned for its geothermal activity (here, the Larderello power plant, the oldest in the world), Tuscany also hides vast magma reservoirs beneath its landscapes, similar to those found at Yellowstone in the United States. Image credit: Matteo Lupi
A new seismic tomography study published April 14, 2026, in Communications Earth & Environment has identified a large mid-crustal magma reservoir beneath southern Tuscany, providing new evidence for the deep heat source sustaining the region’s long-lived geothermal systems.
The study reports that more than 5 000 km3 (1 200 mi3) of magma and partial melt may be stored beneath the Larderello geothermal system and wider Tuscan Magmatic Province. The findings improve understanding of deep crustal processes and do not present evidence of current volcanic unrest.
The research was led by Matteo Lupi and colleagues, who used ambient noise tomography to image the upper 15 km (9.3 miles) of the crust beneath southern Tuscany.
The team analyzed seismic data from more than 60 broadband stations, including a temporary deployment active from September 2020 to September 2021, to reconstruct a 3D shear-wave velocity model of the region. Low shear-wave velocities at depth are commonly associated with high temperatures, partial melt, or magmatic fluids.
The most prominent anomaly lies beneath the geothermal districts of Larderello and Radicondoli. The study reports shear-wave velocities dropping to about 1.25 km/s (0.78 miles/s) at around 10 km (6.2 miles) depth in the core of the anomaly.
The authors interpret this as a melt-rich region with liquid fractions exceeding 80% in the lowest-velocity zones, surrounded by a broader crystal-rich mush zone with lower melt fractions. Their volume estimates suggest about 3 000 km3 (720 mi3) of partial melt beneath Larderello, enclosed within a wider magmatic system of roughly 5 000 km3 (1 200 mi3).
The study also identifies a large low-velocity zone extending toward the Monte Amiata geothermal area. The authors suggest that melt volumes there may be at least as large as those inferred beneath Larderello, although they note that the Amiata region lies near the edge of model resolution and requires further study.
The findings help explain why the Tuscan geothermal province has remained one of Europe’s most productive high-enthalpy systems. Heat flow in the Larderello area locally reaches up to 1 000 mW/m², and geothermal gradients exceed 150°C/km (135°F per mile) in some sectors.
Previous borehole data had already pointed to unusually hot conditions. In the Venelle 2 well, drilling encountered temperatures of 512°C (954°F) and pressures of 42.5 MPa at 2.8 km (1.7 miles) depth, conditions consistent with supercritical geothermal fluids. The new seismic results provide a regional crustal framework linking those shallow extreme conditions to a deeper magmatic heat source.
For decades, geophysicists have debated whether active magma intrusions persisted beneath southern Tuscany despite the region’s limited recent volcanism. Unlike major caldera systems such as Yellowstone Caldera or Campi Flegrei, Tuscany lacks large Holocene eruptive deposits or prominent volcanic landforms.
The region’s most recent recognized volcanism is linked to middle Pleistocene activity at Monte Amiata, roughly 300 000 to 200 000 years ago. The new study argues that large volumes of viscous, silica-rich magma may remain stored in the crust for long periods without erupting.
The authors propose that the chemical and physical properties of Tuscan magmas may help explain the lack of major recent eruptions. They suggest that highly viscous peraluminous magmas can accumulate in the crust and hinder upward melt migration, favoring long-term storage and gradual pluton growth instead of surface eruptions. The deep magmatic system may also support widespread hydrothermal circulation and carbon dioxide release across southern Tuscany.
The study adds to a growing body of work showing that large magma reservoirs can persist beneath regions with limited surface volcanic expression. For geothermal research, the findings improve understanding of how deep crustal heat is transferred into productive reservoirs.
For volcanic hazard science, the study offers new insight into hidden magmatic systems without presenting evidence of current short-term volcanic unrest in Tuscany.
References:
1 Lupi, M., Stumpp, D., Cabrera-Pérez, I., Michailos, K., Saccorotti, G., Bonini, M., Farina, F., Jiwani-Brown, E. A., Lanari, R., Papeschi, S., Savard, G., Porras, J., Sfalcin, J., Muñoz-Burbano, F., Minetto, R., Del Ventisette, C., Piccinini, D., & Montanari, D. (2026). High-enthalpy Larderello geothermal system, Italy, powered by thousands of cubic kilometres of mid-crustal magma. Communications Earth & Environment, 7, 269. DOI: 10.1038/s43247-026-02376-1
I'm a dedicated researcher, journalist, and editor at The Watchers. With over 20 years of experience in the media industry, I specialize in hard science news, focusing on extreme weather, seismic and volcanic activity, space weather, and astronomy, including near-Earth objects and planetary defense strategies. You can reach me at teo /at/ watchers.news.
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