Ancient Flood Left Its Mark in the Mediterranean Sea

By Charles Choi | March 23, 2018 2:07 pm
An artist's interpretation of the Zanclean flood. (Credit: Wikimedia Commons)

An artist’s interpretation of the Zanclean flood. (Credit: Wikimedia Commons)

One of the largest floods in Earth’s history may have deluged the Mediterranean Sea more than 5.3 million years ago, leaving behind a mass of debris roughly the size of Greece’s largest island, Crete, researchers say.

Scientists investigated a roughly 640,000-year span of time starting nearly 6 million years ago when the Mediterranean became a hyper-salty lake. This so-called Messinian salinity crisis “was the most abrupt environmental change, at a planetary scale, since the end of the Cretaceous — that is, a sudden mass extinction, including dinosaurs, due to a meteorite impact,” said study lead author Aaron Micallef, a marine geoscientist at the University of Malta.

This event happened because the Mediterranean became isolated from the Atlantic Ocean. The dry climate of the region caused the Mediterranean to evaporate almost completely, with sea levels there dropping by up to 7,800 feet.

During this time, a layer of salt up nearly 1 mile thick was deposited at the bottom of the Mediterranean Sea, equivalent to 5 percent of global salt mass of the oceans.

“The Messinian salinity crisis thus reduced global ocean salinity and had an impact on ocean circulation, ice formation and, thus, climate,” says Micallef.

Previous research suggested the Mediterranean was abruptly restored back to a normal sea at the end of this event. One theory to explain the refilling of the Mediterranean was a catastrophic flood through what is now the Strait of Gibraltar. During this so-called Zanclean megaflood, prior work suggested that 90 percent of the Mediterranean refilled within a few months to two years, with the sea’s waters rising by up to more than 10 meters per day.

Until now, conclusive evidence of debris from this megaflood had eluded scientists. To look for the aftermath of this catastrophe, Micallef and his colleagues analyzed the boundary between the western and eastern Mediterranean Sea, which is marked by a 155-mile-long and more than 1-mile-high limestone cliff called the Malta Escarpment.

“If the Zanclean flood did ever occur, it should have left a mark either on this cliff, or at least at its base,” says Micallef.

Leaving Its Mark

The scientists examined the most comprehensive collection of seafloor data yet from offshore eastern Sicily and the Maltese Islands, which research vessels gathered using sonar over the course of five years. That is where “we found our evidence — a wide seafloor canyon and an extensive buried mass of material,” Micallef said. The scientists detailed their findings in the journal Scientific Reports.

The buried mass of material is equivalent in size to Crete and nearly 3,000 feet thick in places. This mass is consistent with material eroded and transported by a megaflood passing from the western to the eastern Mediterranean via a southeastern Sicilian gateway.

The researchers suggested the Zanclean flood resulted in a waterfall five times the height of the Eiffel Tower. This water carved a canyon 3 miles wide and 12 miles long that is still preserved underwater off the southeastern Sicilian city of Noto.

“We may be dealing with the one of the largest floods that ever occurred on our planet,” Micallef said.

For example, some of the largest known terrestrial megafloods occurred at the end of the last ice age at Missoula in what is now the western United States, and Altai in central Asia, discharging an estimated 2.7 million, 10 million, and 900,000 cubic meters per second, respectively, Micallef said. In comparison, the Zanclean flood discharged “up to 130 million cubic meters per second,” he noted.

The researchers have not yet been able to directly analyze rocks from the Zanclean megaflood debris because those deposits “are buried beneath hundreds of meters of sediment at water depths of 3 kilometers,” Micallef said. He and his colleagues are now planning to drill into those rocks and computationally model the megaflood to shed more light on the catastrophic event.

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  • http://www.mazepath.com/uncleal/EquivPrinFail.pdf Uncle Al

    :with sea levels there dropping by up to 7,800 feet Why do I doubt that number, 1.5 miles vertical depth? “layer of salt up nearly 1 mile thick was deposited” 1.5 vertical miles of ocean evaporated to a vertical mile of salt? NaCl saturation is 360 g/liter solution. NaCl(s) density is 2.2 g/cm³. Was the NaCl deposit augmented by African swallow transport, in tandom?

    • disqus_atlq8Zmtsd

      The volume of water that evaporated in this process would almost certainly be many times the capacity or the basin as the influx of salt laden water likely was not cut off nearly as suddenly as the proposed flood occurred..

    • TLongmire

      The world’s largest salt deposit sits beneath the worlds largest freshwater lake.

    • Graeme Harrison

      The error in your method of looking at salt concentration in such a water body is that it assumes the evaporation event happened just once. But Lake Eyre in South Australia, and Mono Lake in Nevada have ‘way more’ salt than can be explained by the water volume of their lake. They are best understood as the ‘terminus’ of river systems that do not drain to a sea or ocean, so the salt builds slowly over time, left behind from water inflows which then evaporate (similar to stalagmite/stalactite formation)… Though I DO always like to see someone proffer a Pythonesque explanation (paired swallows for carrying coconuts etc).

      • OWilson

        Salt can form extremely slowly, relative to human time scales, but relatively quickly if the planet heated quite rapidly at various times in its history.

        We are told that only humans can affect the planets temperature in this way, so there goes THAT theory! :)

        • robert2365

          “Only”? I don’t know any climate scientist that have espoused that.

          • OWilson

            I agree, but watch CNN or any of the otre alphabet networks!

      • Jenny H

        Dryland salinity is caused by evaporation of ground water. The salt from the lower deposits is brought up to the surface when the water evaporates.
        It does no need to rely on ‘salt water’ evaporation, just rain water or (worse) irrigation of soils in areas with low precipitation rates.

    • Jenny H

      Maybe it was ALL those animals peeing in it??

  • OWilson

    Catasrophic flooding and not a SUV in sight! :)

    • Hassler

      I would have thought you’d claim it was Noah’s flood, but you anti-science morons believe Earth is only 6,000 years old. Too bad for you.

      • OWilson

        You’re wrong about that too! :)

      • Not_that_anyone_cares, but…

        👎 ᠎

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