An ancient lake is a lake that has consistently carried water for more than one million years. Many have existed for more than 2.6 million years, the full

Quaternary period The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

. Ancient lakes continue to persist due to plate tectonics in an active

rift zone A rift zone is a feature of some volcanoes, especially shield volcanoes, in which a set of linear cracks (or rifts) develops in a volcanic edifice, typically forming into two or three well-defined regions along the flanks of the vent. Believed t ...

. 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 and speciation. Most of the world's bodies of water are less than 18,000 years old. There are only 20 ancient lakes over 1 million years old. Lake Baikal is often considered the oldest, as clear evidence shows that it is 25–30 million years old.

Lake Zaysan Lake Zaysan (, ''Zaısan kóli'', زايسان كؤلئ, ; , ''Zaisan nuur'', en: ''Noble lake''; , ''Ozero Zajsan''; , Xiao'erjing: جَىْصْا پْ; dng, Җэсонпә) is a freshwater lake, ca. 1,810 km² (700 mi²), in eastern Ka ...

may be even older, of

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

origin and at least 66 million years old (most likely around 70 million years), but its exact age is controversial and labelled with some uncertainty. Another contender for oldest is Lake 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 large

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') ...

or bay.

Ancient lakes vs. younger lakes

There are six major types of lakes (Listed below). The majority of lakes dry up as the result of the filling with

lacustrine deposits Lacustrine deposits are sedimentary rock formations which formed in the bottom of ancient lakes. A common characteristic of lacustrine deposits is that a river or stream channel has carried sediment into the basin. Lacustrine deposits form in all ...

, sediment deposited from a river into a lake over thousands of years. Factors that influence the water level decreasing includes fluvial-lacustrine sediment build up, evaporation, natural drainage and

geophysical Geophysics () is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term ''geophysics'' some ...

processes. Ancient Lakes have a prolonged life when compared to younger more ordinary lakes due to the local active

rift zones A rift zone is a feature of some volcanoes, especially shield volcanoes, in which a set of linear cracks (or rifts) develops in a volcanic edifice, typically forming into two or three well-defined regions along the flanks of the vent. Believed t ...

and subsided sections of land called grabens. For example, Lake Baikal in Russia, the deepest lake in the world, is an ancient lake created by the Baikal Rift Zone which is 25–30 million years old and deep. This is compared to the North American

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lak ...

, which were formed by the last glacial period by glacial scouring and the pooling of meltwater which are 14,000 years old, and have maximum depths ranging from deep. *

Rift lake A rift lake is a lake formed as a result of subsidence related to movement on faults within a rift zone, an area of extensional tectonics in the continental crust. They are often found within rift valleys and may be very deep. Rift lakes may be ...

s * Landslide and ice dam lakes * Salt lakes * Oxbow lakes *

Crater lake Crater Lake ( Klamath: ''Giiwas'') is a volcanic crater lake in south-central Oregon in the western United States. It is the main feature of Crater Lake National Park and is famous for its deep blue color and water clarity. The lake partly fill ...

s *

Glacial lake A glacial lake is a body of water with origins from glacier activity. They are formed when a glacier erodes the land and then melts, filling the depression created by the glacier. Formation Near the end of the last glacial period, roughly 10,0 ...

s *

Subglacial lake A subglacial lake is a lake that is found under a glacier, typically beneath an ice cap or ice sheet. Subglacial lakes form at the boundary between ice and the underlying bedrock, where gravitational pressure decreases the pressure melting point ...

Formation of ancient lakes

Ancient lake formation is similar to that of a

rift valley A rift valley is a linear shaped lowland between several highlands or mountain ranges created by the action of a geologic rift. Rifts are formed as a result of the pulling apart of the lithosphere due to extensional tectonics. The linear d ...

. Formation occurs within a graben that is located on an active rift zone. Grabens are sections of land, formed along divergent 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.

Importance to evolution

Ancient lakes allow scientists to study the mechanisms of environmental changes over glacial-interglacial timescales. Evolutionary characteristics including

sexual selection Sexual selection is a mode of natural selection in which members of one biological sex mate choice, choose mates of the other sex to mating, mate with (intersexual selection), and compete with members of the same sex for access to members of t ...

adaptive radiation In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic int ...

and

punctuated equilibrium In evolutionary biology, punctuated equilibrium (also called punctuated equilibria) is a Scientific theory, theory that proposes that once a species appears in the fossil record, the population will become stable, showing little evolution, evol ...

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 on Lake Baikal, the

Caspian Sea The Caspian Sea is the world's largest inland body of water, often described as the world's largest lake or a full-fledged sea. An endorheic basin, it lies between Europe and Asia; east of the Caucasus, west of the broad steppe of Central Asia ...

and the

African Great Lakes The African Great Lakes ( sw, Maziwa Makuu; rw, Ibiyaga bigari) are a series of lakes constituting the part of the Rift Valley lakes in and around the East African Rift. They include Lake Victoria, the second-largest fresh water lake in the ...

. Information is derived from the associations of the fluvial-lacustrine, fluctuating profundal and evaporative facies.

List of ancient lakes

These are the 20 ancient lakes in the world that have existed for more than 1 million years.

References

* Stoermer, Eugene F., and J. P. Smol. "11.1–11.2." ''The Diatoms: Applications for the Environmental and Earth Sciences''. Cambridge, UK: Cambridge UP, 2001. 209–12. Print. * Wilke, Thomas, Risto Väinölä, and F. Riedel. ''Patterns and Processes of Speciation in Ancient Lakes: Proceedings of the Fourth Symposium on Speciation in Ancient Lakes, Berlin, Germany, September 4–8, 2006''. Dordrecht, the Netherlands: Springer, 2009. 126–28. Print. * Vaillant, J. J., G. D. Haffner, and M. E. Cristescu. "The Ancient Lakes of Indonesia: Towards Integrated Research on Speciation." ''Integrative and Comparative Biology'' 51.4 (2011): 634–43. Web. Nov. 2015 * Carroll, Alan R., and Kevin M. Bohacs. "Stratigraphic Classification of Ancient Lakes: Balancing Tectonic and Climatic Controls." ''Geol Geology'' 27.2 (1999): 99. Web * Hoffmann, N., K. Reicherter, T. Fernández-Steeger, and C. Grützner. "Evolution of Ancient Lake Ohrid: A Tectonic Perspective." ''Biogeosciences'' 7.10 (2010): 3377–386. Web. Nov. 2015.

External links

{{portal, Lakes
Species in Ancient Lakes (SIAL)
Limnology Lakes by type Ancient lakes