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

speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution withi ...

. Most of the world's

bodies of water A body of water or waterbody (often spelled water body) is any significant accumulation of water on the surface of Earth or another planet. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as p ...

are less than 18,000 years old. There are only 20 ancient lakes over 1 million years old.

Lake Baikal Lake Baikal (, russian: Oзеро Байкал, Ozero Baykal ); mn, Байгал нуур, Baigal nuur) is a rift lake in Russia. It is situated in southern Siberia, between the federal subjects of Irkutsk Oblast to the northwest and the ...

is often considered the oldest, as clear evidence shows that it is 25–30 million years old. Lake Zaysan 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 Lake Maracaibo ( Spanish: Lago de Maracaibo; Anu: Coquivacoa) is a lagoon in northwestern Venezuela, the largest lake in South America and one of the oldest on Earth, formed 36 million years ago in the Andes Mountains. The fault in the northern se ...

, 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 Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when h ...

, natural drainage and geophysical processes. Ancient Lakes have a prolonged life when compared to younger more ordinary lakes due to the local active rift zones and subsided sections of land called

graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic conte ...

s. For example,

in Russia, the deepest lake in the world, is an ancient lake created by the

Baikal Rift Zone The Baikal Rift Zone is a series of continental rifts centered beneath Lake Baikal in southeastern Russia. Current strain in the rifts tends to be extending with some shear movement. A series of basins form along the zone for more than , creatin ...

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 lakes ...

, which were formed by the last glacial period by glacial scouring and the pooling of

meltwater Meltwater is water released by the melting of snow or ice, including glacial ice, tabular icebergs and ice shelves over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing. Meltwater ca ...

which are 14,000 years old, and have maximum depths ranging from deep. * Rift lakes * Landslide and ice dam lakes *

Salt lake A salt lake or saline lake is a landlocked body of water that has a concentration of salts (typically sodium chloride) and other dissolved minerals significantly higher than most lakes (often defined as at least three grams of salt per litre) ...

s *

Oxbow lake An oxbow lake is a U-shaped lake or pool that forms when a wide meander of a river is cut off, creating a free-standing body of water. In South Texas, oxbows left by the Rio Grande are called '' resacas''. In Australia, oxbow lakes are call ...

s * Crater lakes *

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, ...

s * Subglacial lakes

Formation of ancient lakes

Ancient lake formation is similar to that of a rift valley. 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 choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (in ...

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 in ...

and

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

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

, 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 A ...

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 th ...

. 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