Post on 23-Feb-2016
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Geologic Origin of Lakes, Wetlands, & Estuaries(pp.277-287)
Think-Pair-Share
• Take a moment and think about how lakes, wetlands, and estuaries were formed.
• Share this with your partner(S).• Now, let’s discuss your ideas with the class.
Overview
• Glacial Lakes• Volcanic Lakes• Tectonic Lakes• Lakes w/ Other Origins• Origins of Wetlands• Origins of Estuaries
Question
• How did the lakes of North America form?• You may need to do a little research on this
one.• You have 15 minutes to use the internet to
gather information.• Afterwards we will discuss your findings with
the class.
Lakes of Glacial Origin – most important lake-creating force over last few millennia.- Most of the world’s lake basins, including Great lakes, were formed during the Pleistocene era (glaciers covered earth)-The Ice Age-Introduction - Footprints of the Ice Age: part 1 of 14
Terminology
• Glacial Till (drift) –Remnants of the erosive action of glaciers moving across bedrock. Sediments, such as clays, sand, gravel, boulders.
• Moraines – piles of glacial till that often dam up valleys and streams.
Glaciers sometimes expand and push up eroded material called a terminal moraine.
Cirque Lake – “semicircle”-head of glaciated valleys-dammed at the outlet by a low barrier of glacial debris =moraine
Cirque Lake
Recognizing Cirque Lake from Topo Map
Lonesome Lake, NH
Paternoster Lakes – arrangement of lakes in a linear series
• created by terminal moraines, or rock dams, that are formed by the advance and subsequent upstream retreat and melting of the ice
Paternoster Lakes – ex: Glacier National Park, Montana
Kettles on Glacial Outwash Plain
Kettle Lakes/Ponds (plate 9)
Kettle Lakes on Pitted Outwash Plain