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