Lakes | Can’t Sleep? Dive Beneath The Surface

Lakes can form in some surprisingly dramatic ways for bodies of water that mostly just sit there. In this episode, you’ll hear how glaciers, shifting tectonic plates, and volcanic activity create lakes of all shapes and sizes. We’ll also get into lake ecosystems, how water moves and circulates beneath the surface, and why some lakes end up unusually salty.
It’s steady and consistent, with no whispering and no sudden changes, just enough to give your mind something to follow as you wind down. Happy sleeping!
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Transcript

Welcome to the I Can't Sleep Podcast, Where I help you drift off one fact at a time. I'm your host, Benjamin Boster, And tonight's episode is about lakes. A lake is often a naturally occurring, Relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from the ocean. Although they may be connected with the ocean by outflowing rivers. Lakes, Like other bodies of water, Are part of the water cycle, The process by which water moves around the Earth. Most lakes are freshwater and account for almost all the world's surface freshwater. But some are salt lakes, With salinities even higher than that of seawater. Lakes vary significantly in surface area and volume of water. But in total cover approximately 2. 5 times 106 square kilometers, Less than 2% of the Earth's surface. Lakes are typically larger and deeper than ponds, Which are also water-filled basins on land. Although there are no official definitions or scientific criteria distinguishing the two. Lakes are also distinct from lagoons, Which are generally shallow tidal pools dammed by sandbars or other material at coastal regions of oceans or large lakes. Most lakes are fed by springs, Precipitation and surface runoff. And both fed and drained by creeks and rivers. But some lakes are endorheic, Without any outflow, While volcanic lakes are filled by precipitation and runoff and do not have any inflow streams. Natural lakes are generally found in mountainous areas, I. E. Alpine lakes, Dormant volcanic craters, Rift zones, And areas with ongoing glaciation. Other lakes are found in depressed landforms or along the courses of mature rivers, Where a river channel has widened over a basin formed by eroded floodplains and wetlands. Some lakes are found in caverns underground. Some parts of the world have many lakes formed by the chaotic drainage patterns left over from the last ice age. On a geologic time scale, All lakes have a finite lifetime as they will eventually fill in with sediments or spill out of the basin containing them. Artificially controlled lakes are known as reservoirs, And are usually constructed for industrial, Agricultural, Or aquacultural use, For hydroelectric power generation, For supplying domestic drinking water, For ecological or recreational purposes, Or for other human activities. The word lake comes from Middle English lake, Lake, Pond, Waterway, From Old English laku, Pond, Pool, Stream, From Proto-Germanic lako, Pond, Ditch, Slow-moving stream, From the Proto-Indo-European root leg, To leek, Drain. Cognates include Dutch lak, Lake, Pond, Ditch. Middle Low German, Lake, Water, Pooled in a riverbed, Puddle. As in De Wolfslake, De Butterlake. Modern Low German, Lake, Pool, Puddle. German lache, Pool, Puddle, And Icelandic lakur, Slow-flowing stream. Also related are the English words leak and leet. The majority of lakes on Earth are freshwater, 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 kilometers or 1. 2 square miles in surface area. The total number of lakes in Canada is unknown, But is estimated to be at least 2 million. Finland has 168, 000 lakes of 500 square meters or 5, 400 square feet in area or larger. Of which 57, 000 are large, 10, 000 square meters, Or 110, 000 square feet, Or larger. Most lakes have at least one natural outflow in the form of a river or stream, Which maintains a lake's average level by draining excess water. Some lakes do not have a natural outflow and lose water solely by evaporation or underground seepage or both. These are termed Andorraic lakes. Many lakes are artificial and are constructed for hydroelectric power generation, Aesthetic purposes, Recreational purposes, Industrial use, Agricultural use, Or domestic water supply. The number of lakes on Earth is undetermined because most lakes and ponds are very small and do not appear on maps or satellite imagery. In 1957, G. Evelyn Hutchinson published a monograph titled, A Treatise on Limnology, Which is regarded as a landmark discussion and classification of all major lake types, Their origin, Morphometric characteristics, And distribution. Hutchinson presented in his publication 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. 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 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 Ponticaspian, Occupy basins that have been separated from the sea by the tectonic uplift of the sea floor above the ocean 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 distribution of pre-existing drainage networks, It also creates within arid regions and oreac basins that contain 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 the Great Salt Lake and the Dead Sea. Another type of tectonic lake caused by faulting his sag ponds. Volcanic lakes are lakes that occupy either local depressions, E. G. Craters in Mars, 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 a 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. Other volcanic lakes are created when either rivers or streams are dammed by lava flows or volcanic lars. The basin, Which is now Malheur Lake, Oregon, Was created when a lava flow dammed the Malheur River. Among all lake types, Volcanic crater lakes most closely approximate a circular shape. 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 been recognized are lakes in different contact with ice, Glacially carved rock basins and depressions, Moranic and outwash lakes, And glacial drift basins. Glacial lakes are the most numerous lakes in the world. Most 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 epishoff 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 Antarctica. Fluvial or riverine lakes are lakes produced by running water. These lakes include Plunge Pool Lakes, Fluviatal 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. Their crescent shape gives oxbow lakes a higher perimeter to area ratios than other lake types. Lakes formed by other processes responsible for floodplain basin creation. During high floods they are flushed with river water. A solution lake is a lake occupying a basin formed by a 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 ground 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. Talyllyn Lake in North Wales is a landslide lake dating back to the last glaciation in Wales some 20, 000 years ago. Aeolian lakes are produced by wind action. These lakes 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 lie between well-oriented sand dunes, And deflation basins formed by wind action under previously arid paleoenvironments. Moses Lake in Washington, United States was originally a shallow natural lake and an example of a lake basin dammed by windblown sand. China's Banjaran Desert is a unique landscape of megadoons and elongated interdunal aeolian lakes, Particularly concentrated in the southeastern margin of the desert. 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 and 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 legs are legs created by the actions of plants and animals. On the whole, They are relatively rare in occurrence and quite small in size. In addition, They typically have 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. Peat lakes are a form of organic lake. They form where a buildup of partly decomposed plant material in a wet environment leaves a vegetated surface below the water table for a sustained period of time. They are often low in nutrients and mildly acidic, With bottom waters low in dissolved oxygen. Artificial lakes, Or anthropogenic lakes, Are lake water bodies created by human activity. They can be formed by the intentional damming of rivers and streams, Rerouting of water to inundate a previously dry basin, Or the deliberate filling of abandoned excavation pits by either precipitation runoff, Groundwater, Or a combination of both. Artificial lakes may be used as storage reservoirs that provide drinking water for nearby settlements, To generate hydroelectricity, For flood management, For supplying agriculture or aquaculture, Or to provide an aquatic sanctuary for parks and nature reserves. The Upper Silesian region of southern Poland contains an anthropogenic lake district consisting of more than 4, 000 water bodies created by human activity. The diverse origins of these lakes include reservoirs retained by dams, Flooded mines, Water bodies formed in subsidence basins and hollows, Levee ponds, And residual water bodies following river regulation. Same for the Lusatian Lake District, Germany. In India, Sudarshana Lake is a historical artificial lake located in the semi-arid region of Girnar, Gujarat, Originally constructed during the reign of Chandragupta Maurya. Meteorite lakes, Also known as crater lakes, Not to be confused with volcanic crater lakes, Are created by catastrophic impacts with the Earth by extraterrestrial objects, Either meteorites or asteroids. Examples of meteorite lakes are Lonar Lake in India, Lake El Geigetgen in southeast Siberia, And the Pingualuit Crater Lake in Quebec, Canada. As in the cases of El Gaigetkin and Pinguiluot, Meteorite lakes can contain unique and scientifically valuable sedimentary deposits associated with long records of paleoclimatic changes. In addition to the mode of origin, Lakes have been named and classified according to various other important factors, Such as thermal stratification, Oxygen saturation, Seasonal variations in lake volume and water level, Salinity of the water mass, Relative seasonal permanence, Degree of outflow, And so on. The names used by the lay public and in the scientific community for different types of lakes are often informally derived from the morphology of the lake's physical characteristics or other factors. Also, Different cultures and regions of the world have their own popular nomenclature. One important method of lake classification is on the basis of thermal stratification, Which has a major influence on the animal and plant life inhabiting a lake, And the fate and distribution of dissolved and suspended material in the lake. For example, The thermal stratification, As well as the degree and frequency of mixing, Has a strong control over the distribution of oxygen within the lake. Based upon their thermal stratification, Lakes are classified as either holomictic, With a uniform temperature and density from top to bottom at a given time of year, Or meromictic, With layers of water of different temperature and density that do not intermix. The deepest layer of water in a merimictic lake does not contain any dissolved oxygen, So there are no living aerobic organisms. Consequently, The layers of sediment at the bottom of a meromectic lake remain relatively undisturbed, Which allows for the development of lacustrine deposits. In a holomictic lake, The uniformity of temperature and density allows the lake waters to completely mix. Based upon thermal stratification and frequency of turnover, Polymictic lakes are divided into amictic lakes, Cold monomictic lakes, Dimictic lakes, Warm monomictic lakes, Polymictic lakes, And oligomictic lakes. A salt lake, Also known as a saline lake or brine lake, Is an inland body of water situated in an arid or semi-arid region, With no outlet to the sea, Containing a high concentration of dissolved neutral salts, Principally sodium chloride. Examples include the Great Salt Lake in Utah and the Dead Sea in southwestern Asia. An alkali sink, Also known as an alkali flat or salt flat, Is a shallow saline feature that can be found in low-lying areas of arid regions and in groundwater discharge zones. These features are typically classified as dry lakes or playas because they are periodically flooded by rain or flood events and then dry up during drier intervals, Leaving accumulations of brines and evaporatic minerals. A salt pan is a small shallow natural depression in which water accumulates and evaporates, Leaving a salt deposit, Or the shallow lake of brackish water that occupies a salt pan. The term salt pan comes from open pan salt making, A method of extracting salt from brine using large open pans. A saline pan is another name for an ephemeral acid saline lake, Which precipitates a bottom crust that is subsequently modified during subaerial exposure. Lava Lake is a large volume of molten lava, Usually basaltic, Contained in a volcanic vent, Crater, Or broad depression. Hydrocarbon lakes are bodies of liquid ethane and methane that occupy depressions on the surface of titans. They were detected by the Cassini-Huygens space probe. Lakes have numerous features in addition to lake type, Such as drainage basin, Also known as catchment area, Inflow and outflow, Nutrient content, Dissolved oxygen, Pollutants, PH, And sedimentation. Changes in the level of a lake are controlled by the difference between the input and output compared to the total volume of the lake. Significant input sources or precipitation onto the lake, Runoff carried by streams and channels from the lake's catchment area, Groundwater channels and aquifers, And artificial sources from outside the catchment area. Output sources are evaporation from the lake, Surface and groundwater flows, And any extraction of lake water by humans. As climate conditions and human water requirements vary, These will create fluctuations in the lake level.

Reviews

Never knew there were so many lakes! Interesting story to fall asleep to. I've never heard the Dutch word for lake that you said. In Dutch a lake is called "meer". A sea is called "zee".

In German it is the opposite. A sea is called "meer", and a lake is called "see" 🤔

Boy, Benjamin - That was an exhaustive list of lake types!! 😅 Thanks!