While knowing the name of the largest lake currently on Earth might win you a couple of points at a pub quiz (spoilers, it's the Caspian Sea), the largest lake ever to exist on Earth puts all the other inland water bodies to shame. So vast was this area that it has now been awarded a Guinness World Record – it's time to talk about megalake Paratethys.
Megalake Paratethys is thought to have formed approximately 12 million years ago. It covered an area of 2.8 million square kilometers (1.08 million square miles) from where the edge of the eastern side of the Alps would be all the way across eastern Europe to reach Kazakhstan in central Asia. So vast was this lake that scientists and researchers reckon it was larger than the current Mediterranean Sea.
The volume of water contained within Paratethys was thought to be more than 1.77 million cubic kilometers (424,645 cubic miles). This is more than ten times the volume of all current salt and freshwater lakes combined. But far from a refreshing place to swim, the water was thought to be brackish and mildly salty.
The lake was thought to have formed when the mountain ranges of Central Europe rose, thereby separating the ancient Paratethys Sea from the ocean and creating the megalake. Parathethys was not a consistently large area though. In a 2021 study, a team determined the size and volume of the lake but also looked back at geological time to discover desiccation periods within the lake's history. In one such period, between 7.65 and 7.9 million years ago, the lake was thought to have lost as much as two-thirds of its surface area and one-third of its volume. However, eventually, the body of water refueled again after connecting with the Mediterranean Sea.
"Our exploration of the Paratethys goes beyond mere curiosity. It unveils an ecosystem acutely responsive to climate fluctuations. By exploring the cataclysms that this ancient megalake endured as a result of climate shifts, we gain invaluable insights that can elucidate the path to addressing current and future crises in toxic seas, such as the Black Sea." said Dr. Dan Palcu and the Paleomagnetic Laboratory Fort Hoofddijk of the Department of Earth Sciences in a statement.
But what of the creatures that called the lake home? According to research, the megalake was home to a whole host of fauna including seals, ancient elephants, and Cetotherium rabinini, the smallest whale ever found in the fossil record.
Eventually, the megalake Paratethys came to an end between 6.7 and 6.89 million years ago when an outlet was formed by erosion on the lake's southwest edge. The water draining from it likely carved "an impressive waterfall" said Palcu in a 2021 statement in Science.