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AGS Meeting
June 29, 2021 @ 6:45 pm - 8:00 pm
June Presentation: A Fall Line Overview: Brooklyn to Texas, asthenosphere to alluvium, Cambrian to Anthropocene
The Fall Line is the landward edge of the Mesozoic and younger sediments of the Atlantic and Gulf Coastal Plains. Shoals and rapids upstream of the boundary, caused by exposure of older, harder rocks, localized many cities founded in pre-railroad times, by impeding river navigation and providing waterpower. The sinuous course of the Fall Line from Texas to New York City is traceable to tectonic events from the Cambrian Period down to the present, including the following (approximate ages in millions of years ago): separation of ancestral North America from the supercontinent Rodinia (570), collision of continents to make Pangaea (320), collapse of the mid-Pangaea mountains and subsequent rifting (280), opening of the Atlantic Ocean (170), Southern Appalachian present uplift (15). The history of uplift and erosion down to the present accounts for the fact that some parts of the Piedmont (Upper Flint River basin) are flatter than parts of the Coastal Plain (Fall Line Hills). Human land use may have widened floodplains downstream of the Fall Line.
Speaker Bio: Bill Witherspoon is co-author (with Pamela Gore) of Roadside Geology of Georgia, which has sold more than 8,000 copies. Since the book appeared in 2013, Bill has presented more than 100 walks, talks, and workshops throughout the state. From 1997 until his retirement in 2014, he was an instructor at Fernbank Science Center, part of DeKalb County Schools. In 2007, the National Association of Geoscience Teachers named him Georgia Outstanding Earth Science Teacher. He has worked as a research geologist for Shell Oil and taught at UT Chattanooga. His Ph.D. research at UT Knoxville concerned the structure of Blue Ridge front in Tennessee. Bill provides an events e-newsletter sign-up, event calendar, teacher resources, digital maps, and signed books at the web site georgiarocks.us.
Join the presentation via WebEx: https://gsumeetings.webex.com/gsumeetings/j.php?MTID=m2de9a0f59d882cbeea9229311d11bca5
Join by phone 415-655-0002
Access code: 120 591 9826