Ancient ‘megalake’ covered more than a million square miles 10 million years ago

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Less than 10 million years ago, the largest lake to ever exist on Earth — Lake Paratethys — suffered a “disaster” that killed most of its life forms, a new study says.

At its largest, Paratethys covered an area of ​​more than a million square miles (2.8 million square km) — slightly larger than today’s Mediterranean, according to a team led by experts from Utrecht University, the Netherlands.

For a modern comparison, Paratethys would extend from the Eastern Alps to what is now Kazakhstan in Central Asia.

It also contained a volume of water of more than 1.77 million km3 – more than a third of the volume of the Mediterranean Sea today.

But between 9.75 and 7.65 million years ago, up to a third of the megalake water was lost to evaporation, the lake fragmented and the central basin, now the Black Sea, became extremely toxic and barren.

Most life forms in the lake — including miniature dolphins and seals — became extinct, and those that survived were sick and disfigured, the study authors say.

Location of the Paratethys mega lake.  The current geography is shown for comparison (this is not what Europe looked like at the time)

Location of the Paratethys mega lake. The current geography is shown for comparison (this is not what Europe looked like at the time)

THE PARATETHYS MEGALAKE

Paratethys is the largest lake the world has ever known.

At its largest, Paratethys covered an area of ​​more than a million square miles (2.8 million square kilometers) — larger than the present-day Mediterranean.

It was initially located in the Paratethys Sea before being closed off by moving tectonic plates about 12 million years ago.

Paratethys succumbed to disasters that turned the region into a ‘toxic waste world’ driven by climate change.

The researchers based their estimates on geological and fossil records in the Black Sea, where the Paratethys originally existed.

Besides the Black Sea are the Caspian Sea, the Aral Sea, Lake Urmia, Lake Namak and other remnants of the Paratethys.

‘It must have been a post-apocalyptic prehistoric world – an aquatic version of the wasteland of Mad Max,’ says study author Wout Krijgsman of Utrecht University.

Paratethys formed as a lake about 12 million years ago, after a giant sea was disconnected from the ocean, and life evolved there over 5 million years – cut off from the rest of the world.

Paratethys used to be a sea, connected to the rest of the world’s waters until 34 million years ago, but the moving tectonic plates closed it off.

It contained more water than 10 times the volume of all modern lakes combined.

The megalake’s unique array of creatures included dolphins and whales — including the smallest in Earth’s history — as well as crustaceans and algae.

Comparison of water volume between Lake Paratethys mega-lake and other water bodies (lakes and ice sheets).  Paratethys contained more water than 10 times the volume of all modern lakes combined

Comparison of water volume between Lake Paratethys mega-lake and other water bodies (lakes and ice sheets). Paratethys contained more water than 10 times the volume of all modern lakes combined

The three-meter-long Cetotherium riabinini is the best known of these dolphin-sized dwarf baleen whales, researchers say.

But the fauna was later almost completely obliterated by disasters that turned the region into a salty waste world.

Over its five-million-year lifespan, climate changes have made the lake shrink as it went through “dehydration” — extreme dehydration and removal of moisture.

Artist's impression of the extinct pygmy whale Cetotherium riabinini compared to a 6-foot-long human

Artist’s impression of the extinct pygmy whale Cetotherium riabinini compared to a 6-foot-long human

A final period of desiccation — between 7.65 million and 7.9 million years ago — sounded the death knell for the megalake.

During this ‘most severe’ drying period, called the Great Chersonian Drying, the water level dropped by as much as 250 meters.

Paratethys lost a third of its water and 70 percent of its surface area during this latest drying period, researchers reveal.

As a result, the remaining water was stored in a central, highly saline lake, surrounded by smaller ‘minimers’ unsuitable for the life forms within it.

Besides the Black Sea are the Caspian Sea, the Aral Sea, Lake Urmia, Lake Namak and other remnants of the Paratethys.  Pictured, cliffs on the promontory of Cape Kaliakra on the Black Sea, Bulgaria

Besides the Black Sea are the Caspian Sea, the Aral Sea, Lake Urmia, Lake Namak and other remnants of the Paratethys. Pictured, cliffs on the promontory of Cape Kaliakra on the Black Sea, Bulgaria

“These crises were similar to the desiccation of the Aral Sea, but hundreds of times larger in magnitude,” said lead study author Dan Palcu of the University of São Paulo.

Once the fourth largest inland body of water in the world, Aral once covered an area of ​​26,000 square miles — larger than the state of West Virginia — but it had largely dried up by the 2010s.

The demise of Paratethys had its advantages anyway: the ancestors of today’s giraffes and elephants would have been forced to migrate to today’s African savanna.

According to Nature, the megalake probably also formed a spectacular waterfall when it drained into the Mediterranean between 6.7 million and 6.9 million years ago.

The study, titled “Late Miocene megalake regressions in Eurasia,” is published by Nature in Scientific Reports.

The Earth moves beneath our feet: Tectonic plates move through the mantel, producing earthquakes as they rub against each other

Tectonic plates are composed of the Earth’s crust and the upper part of the mantle.

Below is the asthenosphere: the warm, viscous conveyor belt of rock on which tectonic plates ride.

The Earth has fifteen tectonic plates (pictured) that together have shaped the landscape we see around us today

The Earth has fifteen tectonic plates (pictured) that together have shaped the landscape we see around us today

Earthquakes usually occur at the boundaries of tectonic plates, where one plate dives under another, pushes another up, or where plate edges scrape against each other.

Earthquakes rarely occur in the middle of plates, but they can occur when old fractures or fissures are reactivated far below the surface.

These areas are relatively weak compared to the surrounding plate and can easily slip and cause an earthquake.

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