A team of geophysicists has discovered a deep, ancient freshwater underground pool beneath part of the Sicilian mountains. In his study published in the journal Contact Earth and EnvironmentThe team used publicly available data collected during oil exploration to examine groundwater in and around the Gela Formation beneath mountains on the island of Sicily.

As the number of people living on the islands increases, scientists continue to search for resources to support them. One of these islands is Sicily, located off the coast of Italy in the Mediterranean. Authorities are concerned about providing water to the growing population. So researchers set out to explore untapped underground freshwater reserves.

The researchers analyzed maps and data from previous studies searching for oil fields. They discovered what they believe to be previously unknown groundwater thousands of meters below the Ghibli Mountains. They made 3D models of the aquifer to support their findings and found evidence that it was not just an aquifer, but contained approximately 17.5 cubic kilometers of water.

The team then set out to explain how there could be so much fresh water trapped beneath the mountain range. They suggest it was trapped millions of years ago during the Messinian salinity crisis, a 700,000-year period when the Strait of Gibraltar was closed, causing much of the Mediterranean to dry out and expose the seabed to rainwater.

The research team suggests that this rainwater seeps into the earth’s crust. As the researchers note, this type of rainwater can accumulate underground because it is absorbed by carbonate rock, which acts as a sponge. While sea levels returned to normal, underground freshwater was blocked due to seawater pressure.

The researchers also discovered what they believe to be a possible conduit for ancient rainwater in the Malta Escarpment, which extends across the eastern parts of Sicily.