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At over 1600 meters deep and some 25 million years old,. Lake Baikal in Russia is the world’s deepest and oldest lake.

And you know what that means:. Since time immemorial, we’ve been curious about what lies at the bottom of it. According to the Buryat, the indigenous people of Siberia, the lake is home to a giant fishy dragon monster called Lusud-Khan.

Sort of like the Loch Ness Monster of Russia. Others say the water hides sunken train cars full of a Russian admiral’s gold. And some claim to have seen aliens or mysterious lights in its depths.

Of course, those stories have yet to be proven, but the true story of Lake Baikal might be almost as strange. The lake is what’s known as a rift valley. It formed as two tectonic structures (the Siberian platform and the Amurian/North China plate) moved away from each other.

And its geography is still evolving today. As many as 2000 mini-earthquakes (or tremors) occur at the lake every year, and it gets about 2 cm wider annually. The exact details of how and when these processes started is still debated, but one thing’s for sure:.

It began a long time ago. Most lakes are only about 20,000 years old, but Baikal is ancient — at least 25 million years old, if not older. Because of that, scientists have been able to learn a lot about the past by studying it.

For example, by analyzing the types of pollen found in its sediment, researchers discovered what kinds of plants lived there over 10,000 years ago. They’ve also found fossil evidence of everything from sponges to an ancient parrot to small mammals from the Miocene epoch more than 5 million years ago. So clearly, Lake Baikal used to be the place to be.

But there’s plenty of interesting stuff there today, too. These days, the lake supports a really bizarre collection of life. The majority of its species are found nowhere else on Earth!

Part of that diversity is thanks to its hydrothermal vents. These are places where cold lake water enters cracks in the Earth’s crust and heats up as it gets close to the magma deep beneath the surface. Then, the heated water emerges, usually laden with minerals.

Lake Baikal is actually one of the only lakes in the world that has these structures at its bottom; they’re much more commonly found in oceans. But that helps make it unique. In Baikal, the warmth and minerals surrounding the vents support a strange array of creatures that manage to live without ever seeing the light of the sun.

Scientists have found giant mats made of bacteria, as well as sponges, limpets, fish, and small shrimp-like creatures called amphipods living at the very bottom of the lake. They’re not dragon monsters or anything, but they are adapted to total darkness and to living under the pressure of thousands of meters of water. Which is at least almost as cool.

The lake’s community is also supported by the water’s especially high levels of dissolved oxygen, even at those extreme depths. It’s likely circulated, at least in part, thanks to convection: a process that cycles water from the surface, down to the bottom of the lake and back up again. This process may be influenced by all kinds of things, including those vents, wind, water density, and salinity.

Even animals that live underwater need oxygen to survive, so high oxygen levels help keep them flourishing. It may even help some of them grow to unusual sizes. For example, many of Baikal’s more than 350 amphipod species are much larger than average, potentially thanks to all that oxygen.

Lake Baikal is definitely one of the most diverse places on the planet, but its story isn’t just limited to the water. Once you break the surface and come up for air, you’ll also find the nerpa hanging out on the lake’s shores. These are the only exclusively freshwater seals in the world, and it’s estimated that about 100,000 of these adorable, gloriously rotund creatures live at the lake.

Although how they got there is a bit of a mystery, considering Lake Baikal is hundreds of kilometers from the ocean. Either way, we’re glad they’re around. Unfortunately, though, there’s a chance they might not always be.

Like many places around the world, Lake Baikal and all the amazing creatures in it are currently being threatened by pollution and climate change. In the past 70 years, the lake has warmed by more than 1.2°C. And by 2100, the surface waters are expected to warm by another 4.5°.

Those temperatures, along with pollution, have likely contributed to massive algal blooms on the surface: huge growths of algae which are toxic to animals like fish and crustaceans. Earlier ice melts could also spell disaster for the nerpa, which need plenty of spring ice so they have a place to mate and give birth to their pups. And if the lake warms too much, it could deplete the water of oxygen, effectively suffocating amphipods and other creatures that live in the deeper waters.

Lake Baikal is a treasure trove of biodiversity and natural beauty, but it won’t stay that way forever if we continue down our current path. The good news is, we still have some time to give this story a happy ending. Thanks for watching this episode of SciShow!

If you’d like to learn more about the weird places on this planet, and there are a lot of them, you can watch our episode about the lava lake in Antarctica. [♩OUTRO].