Here’s what you’ll learn when you read this story:

• Supervolcanoes like Yellowstone sit right above bodies of magma, and most show evidence of past eruptions.
• Researchers used ambient noise tomography and image vibrations to analyze a region of Tuscany that was suspected to hold accumulations of magma.
• What’s now known as the Larderello geothermal system is indeed a supervolcano, but the magma is so thick that an eruption isn’t likely.

Supervolcanoes don’t always take the form of hulking mountains belching smoke and lava. Some, like Yellowstone, look deceptively tranquil, with only geysers erupting here and there. Other supervolcanoes experienced their last outburst hundreds of thousands of years ago, and have been quiescent ever since. Then, there are supervolcanoes that conceal invisible—but massive—pockets of molten magma right beneath the feet of unsuspecting tourists.

Tuscany might be the last place anyone would expect a supervolcano to be hiding. This picturesque region of central Italy—whose sprawling vineyards and landscapes have provided backdrops for lyrical films like Under the Tuscan Sun—definitely looks more like an inviting vacation destination than it does a stereotypical lava-ravaged volcanic landscape. But beneath the Instagram-worthy scenery is a subsurface magma ocean. Spread out over 3,728 cubic miles (6,000 cubic km) and buried 5 to 9 miles (8 to 15 km) below the surface, it rivals the expanse of magma under Yellowstone.

But don’t worry, you can finish that cappuccino in peace—it’s unlikely to erupt anytime soon.

What’s now known as the Larderello geothermal system was discovered by researchers from Italy’s National Institute of Geophysics and Volcanology (INGV), the Institute of Geosciences and Earth Resources (CNR-IGG), and the University of Geneva (UNIGE) in Switzerland. The supervolcano was able to remain in hiding for so long because of the absence of any surface evidence. Usually, volcanoes leave behind giveaways like craters and other ground deformations, cooled lava that has long since hardened, and gas emissions. But in Tuscany, even seismic imaging and extensive searches for gravimetric or electromagnetic signals had long come up with nothing.

“Unfortunately, previous passive seismic imaging studies in southern Tuscany have either covered large areas with sparse seismic networks or focused on small regions with dense seismic deployments,” the researchers said in a study recently published in Communications Earth & Environment. “This resulted in incomplete imaging of the geothermal system, in particular its deeper feeding regions.”

Determined to find out if there really was a sleeping dragon lurking deep within the crust of Tuscany, the scientists monitored its southern region with a network of broadband seismometers integrated with the INGV, which reconstructed seismic wave velocity in the middle to upper crust of the area. The research team then turned to ambient noise tomography (ANT), a highly precise method of analyzing and imaging vibrations in the ground. Hi-res sensors on the surface detect and record seismic waves propagating through the ground, and wave velocities that are unusually low—which often occurs when they’re passing through something viscous—can indicate magma.

Scientists had already suspected that there was a great deal of magma hidden deep inside Tuscany’s middle crust for some time. What’s now understood to be a region of liquid rock was previously thought to perhaps be a tectonic boundary or an underground deformation. Seismic wave velocity usually increases the deeper the waves propagate, but it can be slowed down by magma and other hydrothermal fluids. ANT revealed that this velocity transition from higher to lower speeds was being caused by the presence of magma in the mid-crust. The researchers also used their findings to create a 3D image of the system, illustrating how expansive it is and where the highest concentrations of magma are stored. The discovery will offer researchers a significant opportunity to advance their understanding of the evolution of supervolcanoes.

While the volume of magma and heat flow of the Larderello geothermal system are estimated to be close to those other supervolcanoes—including Yellowstone, Taupō, and Long Valley, all of which show evidence of ancient super-eruptions—there’s no reason to cancel vacation plans yet. It’s thought that the Tuscan magma is too thick to come gushing out of the surface anytime soon, and this thickness could also prevent deeper, more fluid molten rock from rising up any further. In the future, this region could possibly be a source of lithium and rare earth elements for use in batteries and other applications.

“Such [magma] volumes are comparable to those of mid-crust reservoirs beneath recognized supervolcanoes,” said the researchers. “The discovery of large volumes of magma is critical to explain the long-term evolution of mature magmatic systems and to understand the behavior of large magmatic provinces.”