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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
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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
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