6 million year old intact underground water tank under Italian mountains

Freshwater flowing through the Earth's crust 6 million years ago was trapped thousands of metres below the Hyblaea Mountains in Sicily, forming an aquifer that has remained unchanged ever since.

Diagram showing the amount of fresh water trapped in the Gela Formation. Photo: National Institute of Geophysics and Volcanology of Italy

A large amount of fresh water that percolated through the Earth’s crust 6 million years ago is still buried deep beneath a mountain range in Italy, according to research published in the journal Communications Earth & Environment. The freshwater was likely trapped underground during the Messinian salinity crisis, when the Mediterranean Sea dried up after a global cooling event that deposited seawater beneath ice shelves and glaciers. That event could have exposed the seafloor to rainwater that percolated through the Earth’s crust.

Rainwater accumulated and formed an aquifer that stretched between 700 and 2,500 meters below the Hyblea Mountains in southern Sicily, Italy, and has remained intact ever since. In the new study, experts studied the deep groundwater in and around the Gela Formation. They built a 3D model of the aquifer and estimated that it contains 17.5 cubic kilometers of water, more than twice as much as Scotland's Loch Ness.

The team then used 3D models to go back in time and reconstruct the geologic past of the region spanning the Hyblaea and Malta Plateaus in the central Mediterranean. During the Messinian period (5.3 to 7.2 million years ago), freshwater percolated through the Earth’s crust to depths of several thousand meters below present-day sea level due to a salinity crisis. The crisis caused sea levels to drop to 2,400 meters below present-day levels on the Mediterranean side.

The “fossil” groundwater pool then accumulated in the carbonate layer, acting as a sponge where liquid exists inside the pores between the rock grains, according to the study’s lead author Lorenzo Lipparini, a geoscientist at the University of Malta, Roma Tre University, and Italy’s National Institute of Geophysics and Volcanology. For this explanation to be convincing, Lipparini and his colleagues would need to find a pathway for rainwater and snowwater from the Mediterranean seabed to reach the Gela Formation. The Malta Escarpment, an underwater cliff that stretches 300 kilometers south from Sicily’s eastern edge, could be a direct connection, the team said. In other words, the missing conduit could lie inside the cliff.

The Messinian salinity crisis, which lasted about 700,000 years, ended abruptly with a rapid rise in sea level, changing the pressure conditions and shutting down the entire mechanism. Another possibility is that sediments and mineral deposits blocked the path along the Malta Wall during the salinity crisis, preventing seawater from mixing with freshwater in the Gela Formation for millions of years. The team hopes to tap into a new freshwater source to alleviate Sicily’s water shortages.

An Khang (According to Live Science )

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