lake
A lake is a body of still water with or without inflow and outflow through flowing water that is completely surrounded by a land area . It represents a largely closed ecosystem .
definition
A lake is an inland body of water that represents a (larger) accumulation of water in a depression in a land area and, in contrast to an inland sea (e.g. the Mediterranean Sea), has no direct connection to the ocean on the 0 meter contour line . This means that it has no inflow and / or outflow caused by ocean currents . The inflow and outflow are usually small compared to the total amount of water in a lake. In contrast to a river, a lake has no gradient.
The term inland lake is used to distinguish inland lakes from coastal lakes (beach lakes, brackish water lakes close to the coast or lakes created by dikes along the coast), but also generally to denote lakes.
A lake in the sense of the limnological definition is usually much deeper than a pond , pond or pond , so that a temperature stratification that is stable over days to months can develop. The frequency of their mixing is used to classify the lakes, as it also has far-reaching ecological consequences (see Lake Ecosystem ). In this respect, the shallow steppe lakes such as Lake Neusiedl or Lake Balaton are not considered "real" lakes.
However, the exact demarcation between lakes and ponds / ponds etc. is fuzzy and always subjective. This is why some limnologists refer to any basin filled with water as a lake. For their categorization it would then be irrelevant whether a lake is constantly, periodically or episodically filled with water and whether it forms a permanent stratification.
Colloquially, the assignment often depends on the salinity , but this is not a criterion. A lake usually contains fresh water , but there are also large salt lakes , such as B. the Caspian Sea (therefore the earlier common name Caspisee is more appropriate ), the Aral Sea and the Dead Sea . There are also lakes containing soda , for example those in the Rift Valley in the East African Rift Valley, such as Lake Nakuru or some of the Lacken around Lake Neusiedl.
A further definition can be made via the size. The minimum size of a lake is about one hectare .
In astronomy , lakes are also used when they contain a liquid other than water, for example in the methane lakes on Titan .
Formation of lakes
Geologically and geomorphologically, a distinction is made between the following types of sea:
- Lakes created naturally.
- Artificial lakes. Depending on the type of installation, it is called a quarry pond or an artificial reservoir . Artificial lakes can also be created by diking sea bays, e.g. B. the IJsselmeer .
Naturally created lakes can be further subdivided according to the way they were created:
- Glacial lakes were created by the erosive or backfilling effect of glaciers or glacier meltwater. This is the most common type of lake worldwide (e.g. the Great Lakes in North America or the numerous lakes in North and South Germany).
- Glacier edge lakes and ice reservoirs are short-lived lakes on active glaciers.
- Tectonic lakes were formed by the expansion of the earth's crust and the resulting cracks and rift breaks , e.g. B. Lake Baikal . A long chain of lakes formed in the East African rift valley, including Lake Tanganyika, which is 1,470 m deep . The tectonic lakes also include most of the end lakes with no drainage in arid areas , as they are usually located within subsidence areas.
- Damming lakes are created by landslides in the mountains, by lava flows or gravel fields and on coasts by the constriction of sea bays. The latter are also known as beach lakes.
- Karst or sinkhole lakes are created by the dissolution (and removal) of carbonate rock or salt deposits ( subrosion ) in the subsurface and subsidence of the earth's surface, for example the Arendsee and the Süße See in Saxony-Anhalt .
- Lakes created by volcanic activity ( crater lake ). Examples in Germany are the maars in the Eifel , including Laacher See .
- Lakes within meteorite craters such as B. the Elgygytgyn .
- Oxygen lakes are created by the natural shifting of rivers. The old river bed then remains as an elongated lake (e.g. Kamernscher See near Havelberg ; however, due to river regulation : Alte Donau in Vienna).
- Thermokarst lakes arise in areas with permafrost , e.g. B. in Alaska or Northern Siberia.
- Lakes with a complex history. For example, Lake Vättern in Sweden is located . B. within a rift valley, but the basin was mainly carved out by glaciers.
Passing of lakes
Apart from the possibility that lakes can disappear as a result of rapid events, for example through the spillage of its basin or the disappearance of its dam, lakes have a typical tendency to fade away from their material balance. Tributaries bring in sediment, which gradually settles in the low-current lake. Rubble cones, avalanches and mudslides slowly coming down from mountains also contribute to the filling of a lake. Even the entry of dust, pollen, leaves and parts of plants to driftwood sinks to a large extent in the water; if material with organic carbon sinks into deep, oxygen-poor layers, it is not oxidized and decomposed, but instead is deposited as carbon-rich sludge. This process depends on the rate of entry with air currents and bank vegetation protruding over the lake. In dry areas or times, lakes without sufficient inflow can also dry out.
use
In addition to their importance for nature, natural and man-made lakes also offer a number of uses for humans.
Most of the lakes are managed by either professional or anglers . Lakes can also be used as bathing lakes for leisure and recreation , swimming and bathing . Larger lakes offer opportunities for water skiing , windsurfing, and sailing . Inland shipping is also used on many large lakes . Reservoirs are often used to generate electricity in hydropower plants . Drinking water is also often obtained from reservoirs and sufficiently clean natural lakes .
Records and data
Worldwide there are 1.4 million lakes with surfaces larger than ten hectares. The country with the most lakes is Canada with over 900,000 lakes. Finland has 187,888 lakes. The entire water of all lakes would cover the entire land surface 1.30 meters high. On average, the water in a lake changes completely every five years. The ten largest lakes in the world contain 85 percent of the water of all lakes. The Lake Baikal alone contains one fifth of all the fresh water on earth.
Largest area
| lake | surface | depth | location | Water type |
|---|---|---|---|---|
| Caspian Sea | 393,898 km² | 995 m |
Russia , Kazakhstan , Azerbaijan , Iran , Turkmenistan |
Salt water |
| Lake Superior | 82,414 km² | 405 m | USA , Canada | Freshwater |
| Lake Victoria | 68,870 km² | 81/85 m | Tanzania , Kenya , Uganda | Freshwater |
| Lake Huron | 59,596 km² | 229 m | USA, Canada | Freshwater |
| Lake Michigan | 58,016 km² | 281 m | United States | Freshwater |
| Lake Tanganyika | 32,893 km² | 1,470 m | Democratic Republic of the Congo , Tanzania, Zambia , Burundi | Freshwater |
| Big Bear Lake | 31,792 km² | 446 m | Canada | Freshwater |
| Baikal lake | 31,492 km² | 1,642 m | Russia | Freshwater |
| Lake Malawi | 29,600 km² | 706 m | Malawi , Tanzania, Mozambique | Freshwater |
| Great slave lake | 28,438 km² | 614 m | Canada | Freshwater |
| Lake Erie | 25,745 km² | 64 m | USA, Canada | Freshwater |
| Winnipeg Lake | 24,341 km² | 18 m | Canada | Freshwater |
| Lake Ontario | 19,259 km² | 244 m | USA, Canada | Freshwater |
| Lake Balkhash | 18,428 km² | 26 m | Kazakhstan | Brackish water |
| Lake Ladoga | 17,703 km² | 255 m | Russia | Freshwater |
Deepest lakes
Highest lake
The Lhagba Pool in Tibet was 6,368 m high, but its classification as a lake (instead of a meltwater pool ) was controversial. The lake no longer exists today. According to this, the crater lake of the 5920 m high Licancabur volcano on the border between Bolivia and Chile is the highest lake on earth.
The Lake Titicaca is located 3,810 m above sea level and is the highest commercially navigable waters of the earth.
Deepest lake
- The Dead Sea is 420 m below sea level .
- The Vostok Sea lies 3700 to 4000 meters below the ice surface of the Antarctic .
Lake with the clearest water
The Blue Lake in the Tasman region of New Zealand has the highest visibility of all natural freshwater bodies of 70–80 meters. Distilled water for laboratory use has a visibility of about 80 m.
Underground lakes
There are lakes hidden under glacial ice in Greenland and Antarctica .
Caves and underground mines can have lakes. A higher-lying water-filled chamber in the mountain is called a water sac in the mountain world .
The (artificial) Seegrotte in Lower Austria was created by opening a water bag through a man-made blast . The (natural) Lac Souterrain de Saint-Léonard in Switzerland is also used by boats with tourists.
ecology
The rise in the CO 2 concentration in the earth's atmosphere in the Anthropocene leads not only to acidification of the world's oceans but also to acidification of lakes.
Lakes outside the earth
Images from the Cassini space probe showed that there are lakes of liquid methane and ethane on Saturn's moon Titan , which are fed by rivers. The average temperature of titanium is –179 ° C, which means that the methane remains liquid. The largest lake of Titan is the Kraken Mare with around 400,000 square kilometers .
Under the ice cap at the south pole of Mars , a lake containing salt water with a horizontal extension of 20 km was discovered using the radar of the Mars Express 2018 probe . Underground lakes are also conceivable on the icy moons of Jupiter and Saturn (planet) .
Lake and sea in Low German
In Low German (and also in Dutch ) the word meanings of “sea” and “lake” are interchanged in relation to High German: The seas bordering northern Germany are called the North Sea and the Baltic Sea (both the sea); in the interior are z. B. the Steinhuder Sea , the Zwischenahner Sea , the Great Sea and others; in the Netherlands the Zuiderzee was renamed the IJsselmeer after it was dyed .
Rough or high seas (the ...) means high swell, so high waves at the sea.
See also
- Earth / dates and numbers
- List of lakes in Germany
- List of lakes in Bavaria
- List of lakes in Austria
- List of the largest lakes in Switzerland
Web links
- Lake ecosystem (information from the Nuremberg Education Center)
- World Lake Database of the ILEC International Lake Environment Committee
supporting documents
- ↑ Rüdiger Mauersberger: Classification of the lakes for natural space exploration of the northeast German lowlands. Templin, 2006.
- ↑ From the water. In: Süddeutsche Zeitung , December 16, 2016, p. 14.
- ↑ a b Nelson’s Blue Lake - The clearest freshwater ever reported. In: NIWA. Retrieved December 20, 2011 .
- ↑ Nelson's Blue Lake clearest. In: New Zealand Herald. December 20, 2011, accessed December 20, 2011 .
- ↑ Discovered underground lake on Mars orf.at, July 25, 2018, accessed on July 25, 2018.
- ↑ CO2 in air and water - acidification also affects freshwater animals . In: Deutschlandfunk . ( deutschlandfunk.de [accessed on February 4, 2018]).
- ↑ Discovered underground lake on Mars orf.at, July 25, 2018, accessed on July 25, 2018.