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Anancient lake is a lake that has consistently carried water for more than one million years. Twelve of the 20 ancient lakes have existed for more than 2.6 million years[citation needed], the fullQuaternary period. Ancient lakes continue to persist due to plate tectonics in an activerift zone. This active rift zone creates lakes that are extremely deep and difficult to naturally fill with sediment. Due to the prolonged life of ancient lakes, they serve as models for isolated evolutionary traits andspeciation. Most of the world'sbodies of water are less than 18,000 years old. There are only 20 ancient lakes over 1 million years old.[1]
Lake Baikal is often considered the oldest, as clear evidence shows that it is 25–30 million years old.[2][3]Lake Zaysan may be even older, ofCretaceous origin and at least 66 million years old[4] (most likely around 70 million years[5]), but its exact age is controversial and labeled with some uncertainty.[6] Another contender for oldest isLake Maracaibo, estimated to be 20–36 million years old. In ancient times it was indisputably a true lake, but today it is saline and directly connected to the sea, leading many to consider it a largelagoon or bay.[7]
There are six major types of lakes (listed below). The majority of lakes dry up as the result of the filling withlacustrine deposits, sediment deposited from a river into a lake over thousands of years. Factors that influence the water level decreasing includefluvial-lacustrine sediment build-up,evaporation, natural drainage, andgeophysical processes. Ancient lakes have a prolonged life when compared to younger, more ordinary lakes due to the local activerift zones andsubsided sections of land calledgrabens.
For example,Lake Baikal in Russia, the deepest lake in the world, is an ancient lake created by theBaikal Rift Zone which is 25–30 million years old and 5,387 feet (1,642 m) deep. This is compared to the North AmericanGreat Lakes, which were formed by the last glacial period by glacial scouring and the pooling ofmeltwater which are 14,000 years old and have maximum depths ranging from 200–1,300 feet (60–400 m) deep.
Ancient lake formation is similar to that of arift valley. Formation occurs within a graben that is located on an active rift zone. Grabens are sections of land, formed alongdivergent plate boundaries, which have subsided between two parallel plates. The location of the graben above the active rift zone results in a lake bottom that is constantly dropping in-depth and walls increasing in height.
Ancient lakes allow scientists to study the mechanisms of environmental changes over glacial-interglacial timescales. Evolutionary characteristics includingsexual selection,adaptive radiation andpunctuated equilibrium are studied in ancient lakes due to their prolonged existence and general geographic isolation. Most of the research has been associated with the endemic fauna and diatoms that exist in these isolated lakes, concentrating onLake Baikal, theCaspian Sea and theAfrican Great Lakes. Information is derived from the associations of thefluvial-lacustrine,fluctuating profundal andevaporative facies.
These are the 20 ancient lakes in the world that have existed for more than 1 million years.[1]
| Name | Origin | Type | Age | Area (km2) | Volume (km3) | Depth max | Depth average | Countries | Notes |
|---|---|---|---|---|---|---|---|---|---|
| Lake Pingualuk | meteor impact | fresh, permanent, crater | 1.5 million | 8 | 267 | Canada | |||
| Lake Tahoe | tectonic | fresh, permanent | 1–2 million | 499 | 156 | 505 | 313 | United States | |
| Lake Bosumtwi | meteor impact | soda, permanent, crater | 1–2 million | 49 | 2.24 | 81 | 45 | Ghana | |
| Lake Lanao | volcanic | fresh, permanent | 2 million | 375 | 112 | 60.3 | Philippines | ||
| Lake Titicaca | tectonic | fresh, permanent | 3 million | 8372 | 893 | 281 | 107 | Bolivia,Peru | |
| Lake Prespa | tectonic | fresh, permanent | 1.5-5 million | 259 | 4.8 | 54 | 18.7 | Albania,Greece,North Macedonia | |
| Lake Ohrid | tectonic | fresh, permanent | 1.5-5 million | 358.18 | 53.63 | 286.7 | 163.71 | AlbaniaNorth Macedonia | |
| Lake Malawi | tectonic | fresh, permanent | 2–5 million | 29600 | 8400 | 705 | 292 | Malawi,Mozambique,Tanzania | |
| Lake Hovsgol | tectonic | fresh, permanent | 2–5 million | 2770 | 381 | 267 | 138 | Mongolia | |
| Kati Thanda–Lake Eyre | tectonic | saline, intermittent, endorheic | 2.5-5 million | 9690 | 30.1 | 6 | 3 | Australia | |
| Lake Tanganyika | tectonic | fresh, permanent | 3–6 million | 32000 | 17800 | 1471 | 572 | Burundi,Congo,Tanzania,Zambia | |
| Caspian Sea | tectonic | saline, permanent, endorheic | 5.5 million | 374000 | 78200 | 1025 | 182 | Azerbaijan,Iran,Kazakhstan,Russia,Turkmenistan | |
| Aral Sea | tectonic | saline, permanent | 5.5 million | 64500 | 625 | 67 | 16 | Kazakhstan,Uzbekistan | Formerly the fourthlargest lake in the world with an area of 68,000 km2 (26,300 sq mi). By 1997, it had shrunk to 10% of its original size due to water that was diverted in the Soviet Era. It is now split into 4 smaller lakes. As of 2023, the Aral Sea has become mostly desert. |
| Lake Biwa | tectonic | fresh, permanent | 5–6 million | 674 | 27.5 | 104 | 41 | Japan | |
| Lake Tule | tectonic | fresh, permanent | 3–15 million | 53 | 40 | United States | |||
| Lake Maracaibo | tectonic | saline, permanent, coastal bay | 20+ million | 13010 | 280 | 60 | 25.9 | Venezuela | Historically it was an ancient lake. Now, it is a large tidal bay/inlet rather than a lake in the traditional sense. It is saline and directly connected to theCaribbean Sea, leading many to consider it a large lagoon or bay. |
| Lake Baikal | tectonic | fresh, permanent | 25+ million | 31500 | 23000 | 1741 | 740 | Russia | |
| Issyk-Kul | tectonic | saline, permanent | 25 million | 6236 | 1738 | 668 | 270 | Kyrgyzstan | |
| Lake Vostok | subglacial | fresh, permanent, subglacial | 15–35 million | 12500 | 5400 | 510 | 432 | Antarctica | |
| Lake Zaysan | tectonic | fresh, permanent | 65+ million | 5510 | 53 | 10 | 5 | Kazakhstan | The construction of theBukhtarma dam inundated the lake, thus, in some sources, the lake is considered a reservoir.[8] |
Most of the hundreds of thousands of inland water bodies on our planet are less than 18,000 years old, but a few lakes and inland seas have existed continuously for more than 1 million years. I present a database of the 20 ancient lakes of the world.
Situated in south-east Siberia, the 3.15-million-ha Lake Baikal is the oldest (25 million years) and deepest (1,700 m) lake in the world. It contains 20% of the world's total unfrozen freshwater reserve.
