A lake is a mass of silent water that is delimited by land from a river, stream or any moving water it however has an inlet that serves it with water. Lakes exist nearly at every part of the universe; however, areas with ample rainfall host the larger number of lakes.
In arid and semi-arid areas, lakes exist as well but seasonally as a result of the small rainfall experienced in these areas. Lake Chad, a lake near the famous Sahara desert in Africa, for instance, is one lake that exists on a very dry area; however, its size usually changes according to the dryness or wetness of the Sahara (Likens, 2010).
Igneous rocks form from the solidification of pumice either underneath or above the Earth’s surface. Metamorphic rocks result from pre-existing rocks that have been altered chemically or physically without melting the agents of these changes include intense heat and pressure actions of hot fluids.
These rocks form through a solid-state transformation an instance when intrusive igneous rock granite is subjected to high pressures and temperatures, the original granite texture will transform to a new texture consisting of alternating light and dark mineral bands.
When magma erupts from the Earth’s surface either as a result of volcanic activity or the Earth’s movement, a large mass of land is displaced causing the formation of creators.
Volcanic activity also has been a key determinant on the size and shape of lakes available since an eruption may create a new lake as well as terminating an already existing lake or dividing the lake in to several basins. The basins are relatively smaller as compared to real lakes and eventually end up drying up or being swamps.
When a creator is formed and rainfall is experienced, the creator will trap rain water and result in a creator lake, though this lake does not necessary have inlet or outlet, therefore, most creator are saline lakes. Lakes are formed in various methods, through depression instigated by faulting of the Earth’s surface.
The world’s deepest lake, Lake Baikal in Russia, was formed through this method. The famous Great Rift Valley lakes from Jordan River valley to South-eastern Africa also exist as a result of the Earth’s faulting or fracturing (Cushing, Cummins, & Minshall, 2006).
The Rift region constitutes of such lakes as the Lake Baringo in Kenya , Lake Tanganyika in Tanzania, the Dead sea, Reelfoot lake in Tennessee near the Mississippi River were formed as result of the earthquake.
Most lakes in the world, however, are formed by Glaciers and by washing depressions and leaving remains that block water drainage and hence forming a large mass of water. Such lakes as the Great lakes, Great bear and Great Slaves lakes in Canada are formed through glacial origin (Likens. 2010).
The last major glacier was called Laurentide began to form around 100,000 years ago. Around 18,000 years ago, the Laurentide covered all of Canada and extended to the United States of America to the South around Illinois and Chicago Ordinarily, the nonstop evolutionary change that lakes do undergo basically takes place in the watershed.
The bits and pieces of the lake made up of silt, soil gnarled by rainwater and streams as well as living organisms are the slow but sure alterations that lakes go through. This culminates into changes in both the physical and chemical constituents of a lake. Nonetheless, the same distress the progression and enlargement of the animal community and plants as a whole.
Close to 10000 to 20000 years ago, the vast lake-dotted and marshy landscapes in North America were formed by glacier. The formation of lakes is through the extortion of holes present in the bedrock (Likens. 2010). This is known for leaving behind covered up portions of ice whose melting moulded in the form of basins and dumping material across stream beds (Likens. 2010).
However, human activity like channelling of sewerage systems to the rivers and streams that drain in to a lake, fertilizers, poor methods of waste disposal among other human activities has dramatically changed the lake forming process from the natural process of thousands of years to more or the same a shorter duration process.
The Mississippi River is one famous world world’s Rivers and it was formed through the earthquake. It is one river that has a very wound flow and oxbow shapes (u-shaped). This nature has led to formation of lakes for example the Salton Sea which is on the lower course of this river.
Lakes are grouped according to the nature of the water in that lake. A lake can be a fresh water lake or salt (saline) water lake. The amount of water that enters a fresh water lake through inlets such as rivers, streams and precipitations is equivalent to the amount of water that is given out through evaporation and outlets. These waters will obtain a smaller amount of soluble salts hence the name fresh water lakes.
Salty lakes, on the other hand, contain a larger percentage of salt content and are mostly found in dry areas. Saline lakes similarly can also exist as a remnant of fresh water lake that existed prior to it. Great Salt Lake is an example of the few remaining segments of glacial Lake Bonneville. These lakes are slowly but surely decreasing as a result of too much evaporation (Likens, 2010).
The hydrologic Cycle explains the concept of how water goes and comes through evaporation by the solar energy and transpiration from the Plantae kingdom respectively. It also explains the variance in water level in a lake. Precipitation is the main cause of the lake level flux in that if rainfall increases, the lake level increases and similarly if rainfall decreases, the lake level fluctuation falls respectively.
The size of a lake varies due to different factors: they grow small and, at the end, turn into swamps, marshes and even dry lake. This is due to the accumulation of sediments on the bottom and along the lake edges (Likens, 2010). The sediment that accumulates on the bottom of the lake consists of some nutrient such as phosphorus and nitrogen.
Phosphorous is the smallest available nutrient in the lakes and thus its copiousness or paucity controls the extent to which algae grows. Phosphorous mainly increases in a lake as a result of sewerage treatment, fertilizers and septic tanks or even from other phosphorous- rich wastes. Therefore, as phosphorous increases, it will be food for the algae which will engulf the lake.
When these algae increase, they form a layer that protects the sunlight to penetrate to the bottom of the lake. The lake will have a high percentage of nutrients and hence it becomes eutrophic. A eutrophic lake will be green as a result to the algae growth and will have limited oxygen in the hypolimnion.
A lake that has less percentage of nutrients or not at all will be oligotrophic and it will be clear and has enough dissolved oxygen in the hypolimnion. It is also important to note that there are some lakes that tend to portray a fifty per cent trait where half of the water contains nutrients while the other half is nutrient poor such a lake is said to be mesotrophic.
The bouncing back of the Earth’s crust, changes in climate and erosion continue to alter the shapes and sizes of the lakes in the world as a whole. The sizes and shapes of lakes in the world will therefore keep on changing with reference to the climatic conditions and human activities.
Those lakes that will receive the largest percentage of nutrients, such as phosphorus (which is one of the major nutrients) ,support the growth of algae. When the algae population increases, it will engulf the lake in question and this will result in lakes becoming smaller and smaller (Cushing, Cummins, & Minshall, 2006). Nearly all the lakes in the world are formed as a result of Geologic and Human events.
The rivers or streams that originate from lakes are the main suppliers of both nutrients and salts to a certain lake. A lake that has fewer inlets as compared to outlets will tend to be saline in nature since the concentration of the salts in the lake is high as compared to the water that enters the lake.
On the other hand, a lake that has enough inlets as well as outlets will tend to have fresh water since there is free entry and exist of any soluble salts. Lakes are natural features that support the ecosystem of nearly every member of any of the seven major kingdoms constitutes the Earth’s population.
However, lakes are facing a possible threat to become a rare resource due human activities as well as the mutual symbiosis that exists to all ecosystems where every member has their own niche (Likens, 2010).
References
Cushing, C. E., Cummins, K. W., & Minshall, G. W. (2006). Rivers and Stream Ecosystems of the World. USA: University of California Press
Likens, G. E. (2010). Lake Ecosystem Ecology: A Global Perspective. USA: Academic Press