Lake Baikal, shown here, is a lake between two high-elevation regions in Siberia, Russia. This is the oldest, deepest lake in the world, containing more water than all of the Great Lakes combined. (Credit: W0zny/Wikimedia Commons)

Meet Lake Baikal: Earth’s largest, oldest, and deepest lake

Lake Baikal holds nearly one-fourth of all Earth’s fresh surface water and is the most scientifically interesting lake on our planet.

Although practically all of Earth’s human population lives on dry land, our surface is 71% covered by water. Of that water, almost all of it is in the oceans, with just 2.5% of it in the form of fresh, rather than salt, water. Most of Earth’s fresh water is in glaciers, ice caps, and permafrost, and water and ice beneath the surface. Most of the rest, as you might expect, is in the large reservoirs of liquid water on our land masses: Earth’s lakes.

All told, fresh water lakes make up just 0.007% of the total amount of water on Earth, but comprise the overwhelming majority of liquid fresh water on our surface. Most of Earth’s lakes are relatively young, less than 18,000 years old and having formed during the end of the last ice age. Only 20 lakes, worldwide, are ancient: more than 1 million years old. But Lake Baikal is not only Earth’s oldest lake, at 25–30 million years of age, but also the largest, and the one with the most potential for revealing new discoveries at the frontiers of astroparticle physics. Here’s the fascinating science behind it.