Lakes: Origins and Morphometry 4 October, 2011 Why does lake distribution of lakes look like 45º 0º 45º That is how precipitation follows Lakes form from 11 processes: Tectonic Cause depravations or brakes in the earth continental crust Graben feature: drop of one piece of crust and high on both sides Lake Tahoe is an example Warping and uptilting African Rift Valley Lakes formed by the crust separating crust (will eventually break away from Africa which will create a new sea! Volcanic activity Crater Lake, OR water comes from rain fall and overflows creating outflow (freshwater lake) Landslides Glacial Lakes: 4 types glacial lakes are the most common type of lake worldwide Lakes held by ice Dammed rivers by ice growth creating lake Glacial rock basins Formed from erosion Moraines and outwash dams Basins formed in glacial drift Kettle lakes Geochemical Solution Lakes Result from chemical erosion Fluviatile Processes Form from rivers that bend and eventually create oxbow lakes (Taieri River & Amazon) Wind Shoreline Processes Organic Accumulatoin Behavior of Higher Organisms Meteroic Impact Round, flat landscape, looks like volcanic lake but because flat land you know it?s not, tend to be very old Ex. Lake Drummond Not positive it?s a meteoric impact High levels of peat so it could have been from a massive peat burn Morphometry Measuring lake dimensions Types of measurements Horizontal Maximum length: Maximum effective breadth: measurements without island in they way Vertical Synthetic (calculated) Shoreline Length DL = Minimum DL = 1.0 (means lake is a perfect circle) Measures degree of irregularity of shore Contour Length Length of basin as you go down water column Mean Depth = Volume (m3)/Area (m2) = m Depth lake would have if lake had same depth everywhere Deeper the lake the lower productivity Light Amount of nutrients getting recycled Volume: sum of all stratum volumes Skipped Development of volume and depth ratio slides All this is used to create a bathymetric map of the lake Maps of depth contours Inverted topographical map On a Bathymetric map: Name Location Standard Geographic reference Geographic orientation (north) Depth contour lines drawn at regular intervals Statement of contour interval Inlets and outlets Name of makers of map and date Oxygen in Paul Lake Increases as you get deeper because it?s a source due to phytoplankton then decreases around 5m Fluctuations in Lake Morphometry Ex. Aral Sea ? lake has decreased due to a lot of evaporation and demand for water for irrigation Ex. Lake Chad
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