Lake Origins - Lake Origins Lecture 2 Fall 2011 BIOL/EVPP...

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Lake Origins Lecture 2 Fall 2011 BIOL/EVPP 350 Freshwater Ecosystems Dr. Kim de Mutsert
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Lake Basins The lake basin is the “bowl” or depression that contains the water Lake basins are formed by numerous processes, the principal being: 1.Glacial activity 2.Tectonic/Crustal movement 3.Volcanic action 4.Solution processes 5.Fluviatile/riverine processes 6.Animal/human activity
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1.Lakes formed by Glacial Processes Glaciation is a major geological process that forms lakes Continental glaciers are slowly moving and melting ice masses as deep as 3000 (!) meters: this weight enables them to rework the earth’s surface Glaciers create basins for lakes by: - dropping sediments - leaving icebergs in sediments - scouring and depressing the earth’s surface
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1.Lakes formed by Glacial Processes Glacial activity has resulted in the greatest number of lakes and some of the largest lakes in area Glacial lakes are found in areas of steep terrain where scour has been the mechanism Lake in contact with a glacier The lakes of Minnesota (“Land of 10,000 Lakes”), the Adirondacks in New York and The Great Lakes are attributable to glacial activity
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Alpine Glaciation Small mountain glaciers advanced as recently as the “little ice age” (1570-1860) Deepening basins or producing new ones When filled with water, “tarns” are created Photos: Kim de Mutsert, 2006
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Piles of remnants of glacial erosive action (clay, sand, gravel, boulders) are called moraines Moraines can dam up valleys or rivers, thereby creating lakes Castle Lake, CA: cirque lake formed by glacier scour
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Lake Origins - Lake Origins Lecture 2 Fall 2011 BIOL/EVPP...

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