Ancient lake
An ancient lake is a lake that has held water for more than a million years. There are about 20 of these lakes, and more than half have existed for over 2.6 million years.
Notable ancient lakes include Lake Baikal in Russia, often considered the oldest at about 25–30 million years old and up to 1,642 meters deep. Lake Zaysan may be even older—around 66–70 million years old—but its exact age is debated. Lake Maracaibo in Venezuela is estimated at 20–36 million years old; it used to be a true lake, but today it is salty and connected to the sea, so some people call it a large lagoon.
Ancient lakes last so long because they sit in active rift zones where tectonic plates pull apart, creating very deep lakes that are hard to fill with sediment. Their long life makes them useful for studying how environments change over time and how species evolve in isolation.
Most lakes today are much younger—often less than 18,000 years old. By contrast, ancient lakes are much older and often deeper. For example, Lake Baikal’s depth is linked to its rift-zone origin, while the nearby Great Lakes in North America formed much more recently, about 14,000 years ago.
Scientists study ancient lakes to understand past climate changes and evolutionary processes, such as how organisms adapt and diversify. Much research focuses on Lake Baikal, the Caspian Sea region, and Africa’s Great Lakes, especially their unique animals and microscopic life like diatoms.
There are ancient lakes that are more than 1 million years old, though some very old subglacial lakes have ages that aren’t yet clear.
This page was last edited on 2 February 2026, at 06:04 (CET).