Millions of years ago, the Mediterranean Sea evaporated. It may have then been refilled by the largest flood event ever experienced on Earth.
An international team of researchers has uncovered new evidence supporting the Zanclean megaflood, a theorized event that replenished the Mediterranean Sea after the Messinian Salt Crisis transformed it into a dry, salty landscape. As detailed in December 28 to study published in the magazine Communications Earth and Environmentthe researchers combined newly identified geological features in Sicily with geophysical data and computer models to potentially provide the most comprehensive look into the ancient megaflood known to date.
“The Zanclean mega-flood was a tremendous natural phenomenon, with discharge rates and flow rates surpassing any other known flood in Earth’s history,” said Aaron Micallef of the Monterey Bay Aquarium Research Institute in California, who led the study, at the University of Southampton. statement. “Our research provides the most compelling evidence yet of this extraordinary event.”
Between 5.97 and 5.33 million years ago, the Messinian Salt Crisis caused the Mediterranean Sea to be cut off from the Atlantic and evaporate into an expanse of salt deposits. Scientists previously theorized that, over a period of 10,000 years, the Mediterranean basin gradually filled up with water. However, the 2009 discovery of an erosion channel that stretches from the Gulf of Cadiz on Spain’s Atlantic coast to the Alboran Sea east of the Strait of Gibraltar challenged that theory, and instead led scientists to suggest a single flood event.
“This megaflood is thought to have been caused by overtopping of Atlantic waters through a Late Messenian isthmus near the modern Strait of Gibraltar, which initially filled the western Mediterranean, and then spilled over the intrabasal Sicilian Sill, filling the eastern Mediterranean,” the researchers wrote in . the new study. Scientists estimate that the megaflood lasted between two and 16 years, and released between 2.4 and 3.5 billion cubic feet (68 and 100 million cubic meters) per second, according to the study.
The team identified more than 300 asymmetric, continuous ridges near the Sicilia Sill, now an underwater land bridge that once separated the western Mediterranean from the eastern Mediterranean. The ridges were layered in debris eroded from the ridge sides and the surrounding area, which point to a rapid and intense depositional process. The layers date to between the Messinian (7.2 million to 5.3 million years ago) and Zanclean (5.3 to 3.60 million years ago) periods, aligning perfectly with the proposed timing of the Zanclean megaflood, about 5.3 million years ago.
“The morphology of these ridges is consistent with erosion by a large-scale, turbulent water flow with a predominantly northeast direction,” Paul Carling of the University of Southampton, who participated in the study, said in the statement. “They reveal the enormous power of the Zanclean Megaflood and how it transformed the landscape, leaving lasting traces in the geological record.”
Carling and his colleagues also discovered a “W-shaped channel” in the seabed east of the Sicilian Threshold, connecting the ridges to an underwater valley in the eastern Mediterranean called the Noto Canyon. The researchers propose that when the Zanclean mega flood filled the western Mediterranean and finally spilled over the Sicilian Threshold, the channel channeled water into the eastern parts of the sea.
The team also developed computer models to reconstruct these dynamics. The simulations indicate that the water changed directions and grew more intense over time, reaching a discharge of up to 72 miles per hour (116 kilometers per hour).
“These findings not only shed light on a critical moment in Earth’s geological history, but also demonstrate the persistence of landforms over five million years,” Micallef added. “It opens the door to further exploration along the Mediterranean margins.”
Although the Zanclean mega-flood remains only a theory, one thing is certain—5.3 million years ago, the Mediterranean probably wasn’t the idyllic travel destination it is today.