Collapsed volcano with hot rock at shallow depth. Thermal gradient measurements show temperatures reach 250°C at just 2km depth, and exploration wells tap this heat for power generation.
Kweedado2, Public domain, via Wikimedia Commons
A Collapsed Volcano's Hot Heart
The Latera caldera is an elliptical depression, with its longest axis stretching nearly nine kilometers, located in Italy's Vulsini Volcanic District. This feature is not a typical mountain crater but the result of a massive collapse following a series of violent eruptions that occurred between 380,000 and 150,000 years ago. The volcanic activity was primarily explosive, ejecting enormous volumes of pyroclastic material and causing the ground to subside into the partially emptied magma chamber below. This geological history created the area's geothermal potential.
Beneath the surface, a residual body of magmatic rock remains intensely hot, creating an unusually high thermal gradient. This means that temperature increases rapidly with depth. Exploratory drilling has confirmed this, recording temperatures of 210°C and finding fluids up to 230°C. The heat source is so close to the surface that a temperature of 250°C is reached at a depth of only about two kilometers. This makes the Latera caldera one of Italy's most promising geothermal fields, alongside the famous Larderello region.
Tapping into Earth's Energy
The geothermal reservoir itself is primarily located within fractured carbonate rocks of the Tuscan geologic unit, which lie beneath the layers of volcanic deposits. This reservoir contains water with a salinity of 8-12 grams per liter. At the top of this superheated water system, there is a gas cap composed mainly of carbon dioxide (CO2) with traces of hydrogen sulfide (H2S). The presence of H2S is a remnant of the volcanic activity and is responsible for the "stink" or sulfurous smell noted in some local surface manifestations.
Geothermal exploration in the Latera region began in earnest in the latter half of the 20th century. Over 20 wells were drilled to map the resource and understand its characteristics. While about half of these wells proved productive, the project has faced challenges. The geothermal fluids are corrosive, and the high gas content requires specialized technology for energy conversion. Despite these hurdles, the immense energy potential has kept interest in the site active for decades. The exploration here is part of Italy's long history with geothermal energy, which began with the world's first geothermal power generator in Larderello in 1904.
💡Fun Facts
The Vulsini Volcanic District, where Latera is located, covers an area of about 2,200 square kilometers and includes over 100 different eruptive centers.
The last confirmed volcanic activity in the broader Vulsini region occurred around 150,000 years ago.
Some geothermal fluids in the greater Latium region are extremely rich in minerals, with brines in the nearby Cesano field reaching a salinity of up to 350 grams per liter.
The caldera was once filled by a lake after its formation, and a smaller lake, Lago di Mezzano, still exists within a secondary depression.
