A multidisciplinary research team has reconstructed the dynamics of the Zanclean Mega-Flood which, 5.33 million years ago, caused millions of cubic meters of ocean water to pour into the Mediterranean basin in a very short time, changing the landscape forever.
About 5 million years ago, the Mediterranean Sea was crossed by the most cataclysmic “tsunami” of all time, the so-called “Zanclean Mega-Flood”. This is what emerges from a new study conducted by an international team of scholars, recently published in the scientific journal “Communications Earth & Environment” of 'Nature', in which the National Institute of Geophysics and Volcanology (INGV) and the University of Catania took part, among others.
As already widely demonstrated, between 5.97 and 5.33 million years ago the Mediterranean basin was the scene of the most impressive geological-environmental event that occurred during the Neogene, the so-called "Messinian Salinity Crisis": following a general uplift of the area of the current Strait of Gibraltar, the Mare Nostrum lost its connection with the Atlantic Ocean, becoming an isolated basin and, in a geologically short time (about 600 thousand years), it almost completely dried up.
What remained of the Mediterranean were some hypersaline basins in which, from the evaporating water column, huge quantities of salt and gypsum precipitated, rocks that are now very widespread in central-southern Sicily. The Mediterranean area, therefore, must have appeared as an enormous salty desert, a condition that prevented numerous marine species from surviving, marking their extinction.
The return of the Mediterranean to its current marine conditions has fueled a heated scientific debate for more than 50 years between supporters of a slow filling (which took place over approximately 10 thousand years) on the one hand, and supporters of a rapid and catastrophic filling on the other.
Some studies had already hypothesized, based on hydrological modeling, that the Mediterranean filled up again within a few years (from 2 to 16) due to the sudden collapse of the geological barrier that had isolated it from the Atlantic Ocean, the Isthmus of Gibraltar. However, evidence capable of supporting such a scenario had never been found. If it had occurred, such an impressive natural phenomenon, with rates of seawater discharge from the Atlantic to the Mediterranean estimated at between 65 and 100 million m3 per second - far higher than those of any other catastrophic flood known in the history of the Earth - would necessarily have had to leave its mark on the landscape.
“Our research aimed to identify evidence that could support the theory of the rapid and violent filling of the Mediterranean, and involved scholars from various European and non-European universities and research institutes (Italy, Spain, Germany, England and California)”, explains Giovanni Barreca, Professor of the Department of Biological, Geological and Environmental Sciences of the University of Catania and Research Associate at the Etnean Observatory of the INGV. “We focused on a vast Sicilian area between the provinces of Syracuse and Ragusa, in the southernmost part of the Iblean plateau - between Noto, Portopalo, Rosolini and Pozzallo - and in the submerged areas of the Gulf of Noto. Thanks to a multidisciplinary approach, we were able to provide the most convincing evidence of the passage in the area of the Zanclean Mega-Flood about 5 million years ago”.
“We noted how the studied area is today dominated by more than 300 hills with a narrow and elongated shape, arranged in a North East-South West direction and separated by deep parallel furrows. The morphometric study and hydrodynamic modeling revealed how the hills were likely fluid-dynamically modeled by the large-scale action of a consistent turbulent water flow with a predominant direction towards the North East.
Stratigraphic analyses have allowed us to reconstruct the landscape in the period preceding the arrival of the catastrophic flood (i.e., before 5.33 million years). The area must have appeared as a large shallow sea bay on whose seabed calcareous sediments, gypsum and salts were deposited. Partially emerged at the end of the Messinian Salinity Crisis due to the lowering of the sea level linked to evaporation, the area was then flooded - according to the results of our study - by the imposing mass of water coming from the Western Mediterranean. The force exerted by the weight of the water column and its impetuous flow towards the East have strongly remodeled the landscape with the excavation of deep furrows parallel to the direction of the flow. The erosion of the landscape has produced enormous volumes of rocky debris, probably torn from the nearby Iblean plateau and today preserved on the crests of the hills; the enormous mass of water and debris also dug out a gigantic canyon (the so-called 'canyon of Noto')”, continues Barreca.
The geological-stratigraphic reconstruction carried out by the research team, supported by realistic numerical modelling, therefore provides the most visible and convincing evidence of the largest mega-flood hypothesized on our Planet.
The area analyzed could become a site of global interest in the future for researchers of catastrophic floods, a topic that is increasingly receiving attention especially in periglacial regions (for example, India, Pakistan, China and Peru) where, due to rising temperatures and melting ice, floods from lake collapse could become increasingly frequent and dangerous, exposing a total of approximately 15 million people worldwide to this risk.
Useful links:
National Institute of Geophysics and Volcanology (INGV)
Department of Biological, Geological and Environmental Sciences of the University of Catania
Figure 1: System of furrows and ridges left on the landscape by the passage of the mega-flood Zancleana
Figure 2: Hill with a typical “whaleback” morphology
Figure 3: Evidence on the ground of the deformation of the original seabed (dashed blue line) due to the bottom traction force exerted by the enormous mass of moving water
Figure 4: German Fleet's Meteor Oceanographic Vessel Under Acquisition in the Gulf of Noto