Lake

What is a Lake?

A lake is an often naturally occurring body of water on land, surrounded by dry land and part of the Earth’s water cycle. Lakes vary significantly in size and salinity, are typically larger than ponds, and can be formed in mountainous areas or depressed landforms. Have you ever wondered how these vast bodies of water came to exist? From the majestic Lake Baikal to the mysterious Kraken Mare on Titan, lakes come in all shapes and sizes. Let’s dive into the fascinating world of lakes!

The Word ‘Lake’

The word ‘lake’ comes from Middle English, Old English, Proto-Germanic, and Proto-Indo-European roots, with cognates in Dutch, German, Icelandic, and other languages. There is no universally accepted definition of a lake, and both lakes and ponds are often used interchangeably or have ambiguous boundaries.

Types of Lakes

The majority of lakes on Earth are freshwater and most lie in the Northern Hemisphere at higher latitudes. Canada has 31,752 lakes larger than 3 square kilometers and estimated 2 million total lakes. Finland has 168,000 lakes of 500 square meters or larger. Most lakes have a natural outflow, but some are artificial and constructed for various purposes.

Tectonic Lakes

Tectonic activity creates lakes by disrupting drainage networks and forming endorheic basins with salt lakes like Great Salt Lake and Dead Sea. These lakes often form sinkholes that collapse to create karst topography, a landscape characterized by underground drainage systems.

Volcanic Lakes

Volcanic lakes occupy depressions or larger basins created by volcanism, such as calderas and craters. Crater lakes fill up rapidly due to precipitation but slowly empty via evaporation or groundwater discharge. These lakes are often a testament to the geological history of an area.

Glacial Lakes

Glacial lakes are formed by glaciers and continental ice sheets, creating a variety of lake types including direct contact with ice, glacially carved rock basins, morainic and outwash lakes, and glacial drift basins. These lakes often hold stories of past climate conditions and glaciation events.

Fluvial Lakes

Fluvial lakes are produced by running water, forming plunge pool lakes, fluviatile dams, and meander lakes. Oxbow lakes form in river valleys as a result of meandering, with slow-moving rivers eroding away the outer side of bends 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.

Fluviatile Dams

Fluviatile dams form where sediment from a tributary blocks the main river. These structures can create new lakes or alter existing ones, impacting local ecosystems and water flow patterns.

Lake Classification by Thermal Stratification

Lakes can be classified by thermal stratification, oxygen saturation, and other factors. His system of classification was later modified and improved upon by Hutchinson and Löffler. Thermal stratification is an important physical characteristic of a lake that controls the fauna and flora, sedimentation, chemistry, and other aspects of individual lakes.

Thermal Stratification

Lakes are classified as either holomictic or meromictic based on their thermal stratification. Holomictic lakes have layers with uniform temperature and density, while meromictic lakes have layers of water with different temperatures and densities that do not mix.

Changes in Lake Level

Changes in lake level are controlled by input and output sources, including precipitation, runoff, groundwater, and artificial sources. Lakes can be categorized based on nutrient richness, with oligotrophic lakes being clear and nutrient-poor. Mesotrophic lakes have good clarity and average nutrient levels. Eutrophic lakes are enriched with nutrients, while hypertrophic lakes are excessively rich in nutrients due to human activities like fertilizer use.

Lake Zones

There are different lake zones: epilittoral, littoral, littoriprofundal, and profundal. Each zone plays a crucial role in the overall ecosystem of the lake. The littoral zone, for example, is where submerged macrophytic growth occurs, providing habitats for various aquatic species.

Algae Communities

Algae communities can be classified into types, such as epipelic, epilithic, epipsammic, epiphytic, and epizooic. These communities are essential for the health of the lake ecosystem, providing food sources and oxygen.

Lake Succession

Some lakes disappear quickly due to environmental factors or human development. On 3 June 2005, in Nizhny Novgorod Oblast, Russia, a lake called Lake Beloye vanished in a matter of minutes. The presence of ground permafrost may explain the shrinking or disappearance of hundreds of large Arctic lakes across western Siberia.

Notable Lakes

The largest lake by surface area is the Caspian Sea, which is despite its name considered as a lake from the point of view of geography. The second largest lake by surface area and the largest freshwater lake by surface area is Lake Michigan-Huron, which is hydrologically a single lake.

Other Notable Lakes

Lake Baikal is the deepest lake in the world, located in Siberia, with a bottom at 1,637 metres (5,371 ft). Its mean depth is also the greatest in the world (749 metres (2,457 ft)). The world’s oldest lake is Lake Baikal, followed by Lake Tanganyika in Tanzania. Lake Tanganyika is the longest lake with a length of 660 km, the third largest by volume, the second oldest, and the second deepest at 1,470 m.

Conclusion

Lakes are not just bodies of water; they are living ecosystems that tell stories of our planet’s history. From the vast expanses of Lake Baikal to the mysterious Kraken Mare on Titan, each lake holds unique secrets and plays a vital role in our world. Understanding these natural wonders is crucial for preserving them for future generations.