The Guinness Book of World Records has recognized a lake as the largest in the world, but the body of water dried up millions of years ago.
The Parathetys once covered the current Black and Caspian Seas and blanketed parts of the surrounding European and Asian countries: Kazakhstan, Georgia, Azerbaijan, Romania, Hungary, and Serbia.
At its largest, scientists suspect Paratethys covered about 1.08 million square miles.
But it also went through several periods of drying out between 7.65 and 7.9 million years ago, which eventually shrank its borders.
And once it reconnected with the Mediterranean between 6.7 and 6.9 million years ago, it was no longer an independent lake.
The new world record is based on a 2021 study that mapped the megalake’s historical boundaries and volume.
The Megalake Paratethys once covered the area now occupied by the Black and Caspian Seas. Some of the only remaining evidence of its existence can be found in these cliffs overlooking the Black Sea
These proportions were published in the journal Scientific Reports.
Part of the reason for the delay was that the lake dried up a long time ago.
But thanks to advanced geological research tools, it took its rightful place in the world record books this month.
The Parathetys was home to unique wildlife, including giant elephants, tiny whales, and rich communities of single-celled organisms that formed the base of the food chain.
Cycles of drying out and refilling left their marks in the rocks that ringed the lake. By analyzing the magnetic signatures in these rocks, scientists could propose a timeline for the lake’s rise and fall.
The Parathetys had a tumultuous history, thanks to the actively shifting continental plates in the region.
It initially formed as a sea about 34 million years ago, spanning from the Balkans to Kazakhstan and Turkmenistan – overlapping the modern-day coasts of both sides.
The Parathetys once encompassed the Black Sea and the Caspian Sea. It also covered much of modern-day Georgia, Azerbaijan, Hungary, Romania, and Serbia
Around 11 million years ago, the smashing together of plates in the Earth’s crust gave rise to Central Europe’s mountain ranges – the Balkans, Alps, and Carpathians.
These changes cut the Paratethys from the rest of the open ocean, turning it from a sea into a lake.
Over millions of years, the marine species trapped when the mountains went up either adapted or died off.
Soon, a thriving ecosystem developed in the Paratethys.
Riabinini, the world’s smallest baleen whale species, made its home there. This tiny mammal is fed by filtering out microorganisms living in the mud at the bottom of the lake.
And in the swamps and lowlands surrounding the megalake lived the deinotherium, a vast species of elephant whose backward-curving tusks may have been used to excavate food.
Unique wildlife made its home in and around the Eurasian megalake Parathetys. But a series of drying-out events devastated these communities, and eventually, it reconnected with the open ocean
Between 9.75 and 7.65 million years ago, a series of drying-out events meant the lake lost more than two-thirds of its surface area and one-third of its volume. In some places, the water level decreased by 250 meters (820 feet).
These fluctuations killed off much of the lake’s wildlife. As the Parathetys lost water, its salt concentration went up too much for its residents to adapt.
The timeline of these events is recorded in the rock itself, and scientists can read these records with a technique known as magnetostratigraphy.
Every 100,000 to 1 million years, the Earth’s magnetic polarity has reversed. When each of these events occurred, it left its mark in volcanic rocks that hardened with the signature of the current direction.
So if there is a rock whose direction matches a known polarity flip, then the surrounding soil and rock can be presumed to be from that same time period.
Comparing samples from the areas surrounding the lake to the dates of these reversals, scientists could reconstruct the Parathetys’s dimensions.
Around 6.7 and 6.9 million years ago, after one of these drying cycles, the Parathetys refilled so much that it was reconnected with the Mediterranean Sea.
At this point, it was no longer a distinct body of water and lost its status as a lake.
But it still qualified as the largest lake the world has ever seen, cementing its place in the Guinness Book of World Records.
