“Unveiling History: How a Megaflood Transformed the Mediterranean 5 Million Years Ago”

New findings present compelling evidence that a massive “megaflood” replenished the Mediterranean Sea, marking the conclusion of a period when it was a vast area of salt flats. The study indicates that the Zanclean Megaflood terminated the Messinian Salinity Crisis, which persisted between 5.97 and 5.33 million years ago.

A global consortium of scientists, including members from the University of Southampton, has detected a range of geological formations around South East Sicily that suggest a significant flooding incident in the area.

“The Zanclean megaflood was an extraordinary natural event, with discharge volumes and flow speeds surpassing any other recorded floods in Earth’s timeline,” stated Dr. Aaron Micallef, the principal author of the research and a scientist at the Monterey Bay Aquarium Research Institute in California. “Our findings offer the strongest evidence to date of this remarkable occurrence.”

Throughout the Messinian Salinity Crisis, the Mediterranean Sea became detached from the Atlantic Ocean and evaporated, resulting in extensive salt deposits that transformed the region’s topography.

For years, researchers believed that this arid period came to an end gradually, with the Mediterranean being replenished over a span of 10,000 years. However, this belief was contested by the discovery of an erosion channel extending from the Gulf of Cadiz to the Alboran Sea in 2009. This finding indicated a singular, monumental flooding episode that lasted from two to 16 years, now known as the Zanclean megaflood.

Estimates indicate that the megaflood had a discharge rate ranging from 68 to 100 Sverdrups (Sv), where one Sv equates to one million cubic meters per second.

The recent study published in the journal Communications Earth & Environment merges newly identified geological features with geophysical data and numerical simulations to offer the most detailed overview of the megaflood to date.

The researchers explored over 300 asymmetric, streamlined ridges situated in a corridor across the Sicily Sill—an underwater land bridge that once divided the western and eastern Mediterranean basins.

“The structure of these ridges aligns with erosion caused by large-scale, turbulent water flow predominantly moving in a northeasterly direction,” explains Professor Paul Carling, an Emeritus professor in the School of Geography and Environmental Science at the University of Southampton and a co-author of this research.

“They showcase the immense strength of the Zanclean Megaflood and how it modified the terrain, leaving permanent marks on the geological record.”

Through sampling the ridges, the team discovered that they were covered with a layer of rocky debris, which contained materials eroded from the ridge sides and nearby areas, indicating it was deposited rapidly and with significant force.

This layer aligns perfectly with the boundary between the Messinian and Zanclean epochs when the megaflood is thought to have occurred.

Utilizing seismic reflection data—a form of geological ultrasound that enables scientists to visualize layers of rock and sediment beneath the surface—the researchers found a “W-shaped channel” on the continental shelf to the east of the Sicily Sill.

This channel, sculpted into the seabed, links the ridges to the Noto Canyon—a profound underwater valley found in the eastern Mediterranean.

The form and placement of the channel imply that it functioned as a considerable funnel. As the waters from the megaflood surged over the Sicily Sill, this channel likely directed the water toward the Noto Canyon and into the eastern Mediterranean.

The team constructed computer simulations of the megaflood to predict its water dynamics. The model indicates that the flood would have altered its course and intensified over time, achieving speeds of up to 32 meters per second (72 miles per hour), cutting deeper channels, dislodging more material, and transporting it over greater distances.

“These revelations not only illuminate a pivotal moment in Earth’s geological timeline but also highlight the durability of landforms over more than five million years,” Dr. Micallef also remarked. “It paves the way for further exploration along the Mediterranean coastlines.”