Scientists Found Evidence of a Megaflood that Shaped Earth's Geologic History

Yahoo

27-01-2025

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For 600,000 years during the tail end of the Miocene epoch, the Mediterranean was a dried-up salt plain cut off from the Atlantic Ocean.
Around 5.3 million years ago, the eastern and western Mediterranean basins were suddenly refilled during an event known as the Zanclean megaflood.
Now, a new study finds evidence of this flood in ridges along the Sicily Sill and in channels that likely formed from this sudden and powerful deluge.
Ages, epochs, periods, and even eras are often defined by some sort of geologic trauma. The Chicxulub asteroid, for example, pushed the Earth into the Cenozoic Era, and 65 million years later, experts are pondering if we've entered a new geologic age induced by modern humans (and their predilection for greenhouse gasses). In many ways, Earth's story for the past 550 million years has largely been a cyclical tale of trauma and recovery—one that consistently yields to new forms of life.
However, one particular geologic event in that half-a-billion-year-long epic still has scientists scratching their heads. Around 6 million years ago, between the Miocene and Pliocene epochs—or more specifically, the Messinian and Zanclean ages—the Mediterranean Sea was cut off from the Atlantic Ocean and formed a vast, desiccated salt plain between the European and African continents. Until, that is, this roughly 600,000-year-long period known as the Messinian Salinity Crisis suddenly came to an end.
At first, scientists believed that the water's return to the Mediterranean took roughly 10,000 years. But the discovery of erosion channels stretching from the Gulf of Cadiz to the Alboran Sea in 2009 challenged this idea, suggesting instead that a powerful megaflood may have refilled the Mediterranean Basin in as little as two to 16 years. That likely means this flooding event—now known as the Zanclean megaflood—featured discharge rates of roughly 68 to 100 Sverdrups (one Sverdrup equals one million cubic meters per second).
New research by an international team of scientists has uncovered more evidence of this incredible event, and also developed a computer model showing exactly how this geologic deluge unfolded. The results of the study were published in the journal Communications Earth & Environment.
'The Zanclean megaflood was an awe-inspiring natural phenomenon, with discharge rates and flow velocities dwarfing any other known floods in Earth's history,' Aaron Micallef, lead author of the study from the Monterey Bay Aquarium Research Institute, said in a press statement. 'Our research provides the most compelling evidence yet of this extraordinary event […]. 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.'
Researchers spotted this new evidence along 300 asymmetric ridges in the Sicily Sill, which was once a landbridge that separated the eastern and western Mediterranean basins. In finding that the tops of these ridges contained rocky material eroded from the ridge flanks, the scientists realized that this rock must've been deposited quickly and with a stunning amount of force.
The researchers also note that this particular rock layer lies directly on the boundary where the Messinian transitions into the Zanclean, which is around the time of this landscape-altering megaflood.
'The morphology of these ridges is compatible with erosion by large-scale, turbulent water flow with a predominantly north easterly direction,' Paul Carling, a co-author of the study from the University of Southampton, said in a press statement.
The authors also found evidence of w-shaped flood channels using seismic data and developed computer models to simulate how the flood waters would've refilled the Mediterranean Basin. This model shows that flooding could have reached speeds of 72 miles per hour, carving deep channels as observed in the seismic data.
The geologic story of Earth may be somewhat cyclical, but that doesn't mean it can't be exciting.
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