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A LAKE is an area of variable size filled with water, localized in a basin , that is surrounded by land, apart from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean , and therefore are distinct from lagoons , and are also larger and deeper than ponds , though there are no official or scientific definitions. Lakes can be contrasted with rivers or streams , which are usually flowing. Most lakes are fed and drained by rivers and streams.

Natural lakes are generally found in mountainous areas, rift zones , and areas with ongoing glaciation . Other lakes are found in endorheic basins or along the courses of mature rivers. In some parts of the world there are many lakes because of chaotic drainage patterns left over from the last Ice Age . All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them.

Many lakes are artificial and are constructed for industrial or agricultural use, for hydro-electric power generation or domestic water supply, or for aesthetic or recreational purposes or even for other activities.

CONTENTS

* 1 Etymology, meaning, and usage of "lake" * 2 Distribution of lakes

* 3 Origin of lakes

* 3.1 Tectonic lakes * 3.2 Volcanic lakes * 3.3 Glacial lakes * 3.4 Fluvial lakes * 3.5 Solution lakes * 3.6 Landslide lakes * 3.7 Aeolian lakes * 3.8 Shoreline lakes * 3.9 Organic lakes * 3.10 Anthropogenic lakes * 3.11 Meteorite (extraterrestrial impact/ crater) lakes

* 4 Other different types of lakes

* 4.1 Types of lakes according to thermal stratification * 4.2 Types of lake according to seasonal variation of lake level and volume * 4.3 Types of lake according to water chemistry * 4.4 Lakes composed of other liquids

* 5 Paleolakes * 6 Characteristics * 7 Limnology * 8 How lakes disappear * 9 Extraterrestrial lakes

* 10 Notable lakes on Earth

* 10.1 Largest by continent

* 11 See also * 12 References * 13 External links

ETYMOLOGY, MEANING, AND USAGE OF "LAKE"

Oeschinen Lake in the Swiss Alps Lake Tahoe on the border of California and Nevada The Caspian Sea is either the world's largest lake or a full-fledged sea.

The word _lake_ comes from Middle English _lake_ ("lake, pond, waterway"), from Old English _lacu_ ("pond, pool, stream"), from Proto-Germanic *_lakō_ ("pond, ditch, slow moving stream"), from the Proto-Indo-European root *_leǵ-_ ("to leak, drain"). Cognates include Dutch _laak_ ("lake, pond, ditch"), Middle Low German _lāke_ ("water pooled in a riverbed, puddle") as in: de:Moorlake, de:Wolfslake, de:Butterlake, German _Lache_ ("pool, puddle"), and Icelandic _lækur_ ("slow flowing stream"). Also related are the English words _leak_ and _leach_.

There is considerable uncertainty about defining the difference between lakes and ponds , and no current internationally accepted definition of either term across scientific disciplines or political boundaries exists. For example, limnologists have defined lakes as water bodies which are simply a larger version of a pond, which can have wave action on the shoreline or where wind-induced turbulence plays a major role in mixing the water column. None of these definitions completely excludes ponds and all are difficult to measure. For this reason, simple size-based definitions are increasingly used to separate ponds and lakes. One definition of _lake_ is a body of water of 2 hectares (5 acres) or more in area; :331 however, others have defined lakes as waterbodies of 5 hectares (12 acres) and above, or 8 hectares (20 acres) and above (see also the definition of "pond" ). Charles Elton , one of the founders of ecology , regarded lakes as waterbodies of 40 hectares (99 acres) or more. The term _lake_ is also used to describe a feature such as Lake Eyre , which is a dry basin most of the time but may become filled under seasonal conditions of heavy rainfall. In common usage, many lakes bear names ending with the word _pond_, and a lesser number of names ending with _lake_ are in quasi-technical fact, ponds. One textbook illustrates this point with the following: "In Newfoundland, for example, almost every lake is called a pond, whereas in Wisconsin, almost every pond is called a lake."

One hydrology book proposes to define the term "lake" as a body of water with the following five characteristics:

* it partially or totally fills one or several basins connected by straits * has essentially the same water level in all parts (except for relatively short-lived variations caused by wind, varying ice cover, large inflows, etc.) * it does not have regular intrusion of seawater * a considerable portion of the sediment suspended in the water is captured by the basins (for this to happen they need to have a sufficiently small inflow-to-volume ratio) * the area measured at the mean water level exceeds an arbitrarily chosen threshold (for instance, one hectare )

With the exception of the seawater intrusion criterion, the others have been accepted or elaborated upon by other hydrology publications.

DISTRIBUTION OF LAKES

The Seven Rila Lakes are a group of glacial lakes in the Bulgarian Rila mountains. Wayanad District Kerala India

The majority of lakes on Earth are fresh water , and most lie in the Northern Hemisphere at higher latitudes . Canada , with a deranged drainage system has an estimated 31,752 lakes larger than 3 square kilometres (1.2 sq mi) and an unknown total number of lakes, but is estimated to be at least 2 million. Finland has 187,888 lakes 500 square metres (5,400 sq ft) or larger, of which 56,000 are large (10,000 square metres (110,000 sq ft) or larger).

Most lakes have at least one natural outflow in the form of a river or stream , which maintain a lake's average level by allowing the drainage of excess water. Some lakes do not have a natural outflow and lose water solely by evaporation or underground seepage or both. They are termed endorheic lakes.

Many lakes are artificial and are constructed for hydro-electric power generation, aesthetic purposes, recreational purposes, industrial use, agricultural use or domestic water supply.

Evidence of extraterrestrial lakes exists; "definitive evidence of lakes filled with methane " was announced by NASA as returned by the Cassini Probe observing the moon Titan , which orbits the planet Saturn .

Globally, lakes are greatly outnumbered by ponds: of an estimated 304 million standing water bodies worldwide, 91% are 1 hectare (2.5 acres) or less in area (see definition of ponds ). Small lakes are also much more numerous than large lakes: in terms of area, one-third of the world's standing water is represented by lakes and ponds of 10 hectares (25 acres) or less. However, large lakes account for much of the area of standing water with 122 large lakes of 1,000 square kilometres (390 sq mi, 100,000 ha , 247,000 acres ) or more representing about 29% of the total global area of standing inland water.

ORIGIN OF LAKES

A portion of the Great Salt Lake in Utah , United States A lake in the Andes Mountains A portion of the Great Salt Lake in Utah , United States A lake in the Andes Mountains

Hutchinson in 1957 published a monograph that is regarded as a landmark discussion and classification of all major lake types, their origin, morphometric characteristics, and distribution. As summarized and discussed by these researchers, Hutchinson presented in it a comprehensive analysis of the origin of lakes and proposed what is a widely accepted classification of lakes according to their origin. This classification recognizes 11 major lake types that are divided into 76 subtypes. The 11 major lake types are tectonic lakes, volcanic lakes, landslide lakes, glacial lakes, solution lakes, fluvial lakes, aeolian lakes, shoreline lakes, organic lakes, anthropomorphic lakes, and meteorite (extraterrestrial impact) lakes.

TECTONIC LAKES

Tectonic lakes are lakes formed by the deformation and resulting lateral and vertical movements of the Earth’s crust. These movements include faulting, tilting, folding, and warping. Some of the well-known and largest lakes on Earth are rift lakes occupying rift valleys, e.g. Central African Rift lakes and Lake Baikal . Other well-known tectonic lakes, Caspian Sea , the Sea of Aral , and other lakes from the Pontocaspian occupy basins that have been separated from the sea by the tectonic uplift of the sea floor above sea level.

Often, the tectonic action of crustal extension has created an alternating series of parallel grabens and horsts that form elongate basins alternating with mountain ranges. Not only does this promote the creation of lakes by the disruption of preexisting drainage networks, it also creates within arid regions endorheic basins that containing salt lakes (also called saline lakes). They form where there is no natural outlet, a high evaporation rate and the drainage surface of the water table has a higher-than-normal salt content. Examples of these salt lakes include Great Salt Lake and the Dead Sea . another type of tectonic lake caused by faulting is sag ponds .

VOLCANIC LAKES

Volcanic lakes are lakes that occupy either local depressions, e.g. craters and maars or larger basins, e.g. calderas , created by volcanism . Crater lakes are formed in volcanic craters and calderas, which fill up with precipitation more rapidly than they empty via either evaporation, groundwater discharge, or combination of both. Sometimes the latter are called caldera lakes, although often no distinction is made. An example is Crater Lake in Oregon , in the caldera of Mount Mazama . The caldera was created in a massive volcanic eruption that led to the subsidence of Mount Mazama around 4860 BC. Other volcanic lakes are created when either rivers or streams are dammed by lava flows or volcanic lahars . The basin within which Malheur Lake , Oregon was created when a lava flow dammed the Malheur River .

GLACIAL LAKES

Glacial lakes are lakes created by the direct action of glaciers and continental ice sheets. A wide variety of glacial processes create enclosed basins. As a result, there are a wide variety of different types of glacial lakes and it is often difficult to define clear-cut distinctions between different types of glacial lakes and lakes influenced by other activities. The general types of glacial lakes that have recognized are lakes in direct contact with ice; glacially carved rock basins and depressions; morainic and outwash lakes; and glacial drift basins. Glacial lakes are the numerous lakes in the world. Most the lakes in northern Europe and North America have been either influenced or created by the latest, but not last, glaciation, to have covered the region. Glacial lakes include proglacial lakes , subglacial lakes , finger lakes , and epishelf lakes. Epishelf lakes are highly stratified lakes in which a layer of freshwater, derived from ice and snow melt, is dammed behind an ice shelf that is attached to the coastline. They are mostly found in the Antarctica.

FLUVIAL LAKES

Fluvial lakes are lakes produced by running water. These lakes include plunge pool lakes, fluviatile dams and meander lakes. The most common type of fluvial lake is a crescent-shaped lake called an _oxbow lake _ due to the distinctive curved shape. They can form in river valleys as a result of meandering. The slow-moving river forms a sinuous shape as the outer side of bends are eroded away more rapidly than the inner side. Eventually a horseshoe bend is formed and the river cuts through the narrow neck. This new passage then forms the main passage for the river and the ends of the bend become silted up, thus forming a bow-shaped lake.

SOLUTION LAKES

A solution lake is a lake occupying a basin formed by surface dissolution of bedrock. In areas underlain by soluble bedrock, its solution by precipitation and percolating water commonly produce cavities. These cavities frequently collapse to form sinkholes that form part of the local karst topography . Where groundwater lies near the grounds surface, a sinkhole will be filled water as a solution lake. If such a lake consists of a large area of standing water that occupies an extensive closed depression in limestone, it is also called a _karst lake_. Smaller solution lakes that consist of a body of standing water in a closed depression within a karst region are known as _karst ponds._ Limestone caves often contain pools of standing water, which are known as _underground lakes ._ Classic examples of solution lakes are abundant in the karst regions at the Dalmatian coast of Croatia and within large parts of Florida .

LANDSLIDE LAKES

Landslide lakes are lakes created by the blockage of a valley by either mudflows, rockslides, or screes. Such lakes are common in mountainous regions. Although landslide lakes may be large and quite deep, they are typically short-lived. An example of a landslide lake is Quake Lake , which formed as a result of the 1959 Hebgen Lake earthquake .

AEOLIAN LAKES

Aeolian lakes are lakes produced by wind action. They are found mainly in arid environments although some aeolian lakes are relict landforms indicative of arid paleoclimates. Aeolian lakes consist of lake basins dammed by wind-blown sand; interdunal lakes that lies between well-oriented sand dunes; and deflation basins formed by wind action under previously arid paleoenvironments. Moses Lake, Washington , is an example of a lake basins dammed by wind-blown sand.

SHORELINE LAKES

Shoreline lakes are generally lakes created by blockage of estuaries or by the uneven accretion of beach ridges by longshore and other currents. They include maritime coastal lakes, ordinarily in drowned estuaries; lakes enclosed by two tombolos or spits connecting an island to the mainland; lakes cut off from larger lakes by a bar; or lakes divided by the meeting of two spits.

ORGANIC LAKES

Organic lakes are lakes created by the action of plants and animals. on the whole they are relatively rare in occurrence and quite small in size. in addition, they typically ephemeral features relative to the other types of lakes. The basins in which organic lakes occur are associated with beaver dams, coral lakes, or dams formed by vegetation.

ANTHROPOGENIC LAKES

Anthropogenic lakes are artificially created lakes formed by human activity. They can be the result of intentional damming of rivers and streams or subsequent filling of abandon excavations by either ground water, precipitation, or a combination of both.

METEORITE (EXTRATERRESTRIAL IMPACT/ CRATER) LAKES

Meteorite lakes, which are also known as crater lakes, are lakes created by catastrophic extraterrestrial impacts by either meteorites or asteroids . Examples of meteorite lakes are Lonar crater lake , India , Lake Elgygytgyn , and Pingualuit crater lake, Quebec, Canada, As in case of Lake El'gygytgyn and Pingualuit crater lake, meteorite (extraterrestrial impact/ crater) lakes can contain unique and scientifically valuable sedimentary deposits aasociated with long records of paleoclimatic changes.

OTHER DIFFERENT TYPES OF LAKES

One of the many artificial lakes in Arizona at sunset. Lake Parramatta , an artificial lake in Sydney , Australia . A naturalized former gravel pit lake in northern Croatia . The crater lake of Volcán Irazú , Costa Rica . These kettle lakes in Alaska were formed by a retreating glacier. Ephemeral 'Lake Badwater', a lake only noted after heavy winter and spring rainfall, Badwater Basin , Death Valley National Park . Ice Melting on Lake Balaton

In addition to mode of origin, lakes have been named and classified in various other ways according to their thermal stratification, salinity, relative seasonal permanence, degree of outflow, and other factors. Also, different cultures and regional of the world have their popular nomenclature

TYPES OF LAKES ACCORDING TO THERMAL STRATIFICATION

In addition to their origin, there are various other ways of either naming or defining types of lakes. One major way of classification lakes in on the basis of thermal stratification because it is a major control on animal and plant life inhabiting a lake and the fate and distribution of dissolved and suspended material in a lake. For example, the thermal stratification and the degree and frequency of mixing exerts a strong control on the distribution of oxygen within it. In addition, lake can be classified according important factors such as seasonal variations in lake volume and level, oxygen saturation, and salinity of its water mass. Finally, the names of types of lakes that are used by the lay public and in the scientific for different types of lakes are often informally derived from either from their morphology of other aspects or their physical characteristics.

F.A. Forel, who is also referred to as the father of limnology, was the first scientist to classify lakes according to their thermal stratification . His system of classification was later modified and improved upon by Hutchinson and Laffler. Because the density of water varies with temperature, with a maximum at +4 DC, thermal stratification is an important physical characteristic of lakes that controls the fauna and flora, sedimentation, chemistry, and other aspects of individual lakes. First, the colder, heavier water typically forms a layer near the bottom, which called the _hypolimnion _. Second, normally overlying it is a transition zone known as the _metalimnion _. Finally, overlying the metalimnion is a surface layer of a warmer, lighter water is called the _epilimnion _. However, this _typical_ stratification sequence can vary widely depending either on the specific lake, the time of season, or combination of both.

Based upon thermal stratification, lakes are classified as either holomictic lakes or meromictic lakes . A meromictic lake is a lake which has layers of water which do not intermix. The deepest layer of water in such a lake does not contain any dissolved oxygen. In addition, the layers of sediment at the bottom of a meromictic lake remain relatively undisturbed because there are no living aerobic organisms . The lack of disturbance allows for the development of lacustrine varves . A Holomictic lake is a lake that has a uniform temperature and density from top to bottom at a specific time during the year. This uniformity temperature and density in allows the lake waters to completely mix. Holomictic lakes are non-meromictic lakes. Based upon thermal stratification and frequency of turnover, holomictic lakes are divided into amictic lakes , cold monomictic lakes , dimictic lakes , warm monomictic lakes , polymictic lakes , and oligomictic lakes. The classification of lakes by thermal stratification presupposes lakes with sufficient depth to form a hypolimnion. As a results, very shallow lakes are excluded this classification system.

The stratification in a lake is not always the result of variation to density because of thermal gradients. Stratification within a lake can also be the result of differences in density resulting from gradients in salinity . In case of a difference in salinity, the hypolimnion and epilimnion are separated not by a thermocline but by a halocline , which is sometimes referred to as a _chemocline _.

TYPES OF LAKE ACCORDING TO SEASONAL VARIATION OF LAKE LEVEL AND VOLUME

Lakes are informally classified and named according to the seasonal variation in their lake level and volume. Some of the names include:

* Ephemeral lake is a short-lived lake or pond. If it fills with water and dries up (disappears) seasonally it is known as an _intermittent lake._

* Dry lake is a popular name for an ephemeral lake that contains water only intermediately at irregular and infrequent intervals.

* Perennial lake is a lake that has water in its basin throughout the year and is not subject to extreme fluctuations in level.

* Playa lake is a typically shallow, intermittent lake that covers or occupies a playa either in wet seasons or in especially wet years but subsequently drying up in an arid or semiarid region.

* Vlei is a name used in South Africa for a shallow lake which varies considerably in level with the seasons.

TYPES OF LAKE ACCORDING TO WATER CHEMISTRY

Lakes are also informally classified and named according to the general chemistry of their water mass. Some of the types of lakes include:

* An acid lake is a lake that has a pH is below neutral