Imagine the equivalent of 40,000 Olympic swimming pools flowing into the Mediterranean Sea every second: this may be what happened 5 million years ago, as the Zanclean geological age began, according to a study published in December in the journal Communications Earth & Environment (A. Micallef et al.2024).
According to estimates made by the authors of this work using geological indices collected in the south-east of Sicily, the region would have experienced a “mega-flood“ with a flow rate of 68 to 100 Sverdrups (Sv), 1 Sv being equal to one million cubic meters (400 Olympic swimming pools) per second.
The so-called “Messinian” crisis (named after the geological age preceding the Zanclean), during which the water in the Mediterranean Sea evaporated to give way to vast deposits of salt, would therefore have ended much more brutally than We didn’t believe it until now.
The flood that “eclipses” all others?
Indeed, scientists have long thought that the Messinian crisis ended gradually, over a period of around 10,000 years. This idea was, however, called into question by the discovery, in 2009, of an erosion channel extending from the Gulf of Cádiz to the Alboran Sea, revealing flooding “unique et massive” lasting from two to 16 years.
For Dr. Aaron Micallef, researcher at the Monterey Bay Aquarium Research Institute in California and lead author of the study, cited in a press release from the University of Southampton (United Kingdom), the news estimates of flow rates and flow velocities “eclipse all other known floods in Earth’s history.”
“Our research provides the most compelling evidence for this extraordinary event”he emphasizes.
Rock debris torn away by the waves
The authors of the new study examined more than 300 asymmetrical ridges along a geological corridor crossing the “Threshold of Sicily”a submerged land bridge that once separated the western and eastern Mediterranean basins.
-By taking samples from these ridges, the team discovered that they were topped by a layer of rock debris corresponding to the boundary between the Messinian and Zanclean periods, and containing material eroded from the surrounding region – indicating that these materials were deposited there quickly and with “considerable strength”.
Then, by analyzing seismic imaging data, the researchers discovered a “W-shaped channel” on the continental shelf east of the “Sicily threshold”, whose shape and location suggest that it may have acted as a “huge funnel” towards a canyon, that of the underwater valley of Noto, at the time of the mega-flood.
A flow propelled up to 115 km/h
The authors also developed computer models of the megaflood to simulate the behavior of the water. According to the results, the flow changed direction and increased in intensity over time, reaching up to 115 kilometers per hour. Thus digging deeper channels, eroding more material and transporting it longer distances.
“These results not only highlight a critical moment in Earth’s geological history, they also demonstrate the persistence of landforms over five million years.”insists Dr. Micallef (press release).
Other researchers had recently announced the discovery of an immense underwater canyon in the heart of the Mediterranean, in the Levant basin. Its formation would have taken place shortly before the Messinian crisis, thus shedding light on an even more distant past.
