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#+title: Nature Talk on Erratics

- source :: https://en.wikipedia.org/wiki/Glacial_erratic
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* Overview
** What does erratic mean?
** If a geologist calls a rock "erratic" what do you suppose they mean?
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** Some examples of major erratics
*** Big Rock, Canada
*** Doane Rock, Cape Cod
*** The one we saw the other day
** What can move them?
*** Major paradox for geologists in the 1800s
*** Considered evidence for flooding 10,000 years ago mentioned in the Bible
***
*** Ice rafting
*** Glacier born
** Laurentide Ice Sheet, two miles thick in Northern Canada
[[file:images/laurentide-ice-sheet.png][Laurentide Ice Sheet extent]]
** Thinnest along the coast, where
*** Nunataks would form along the edges of the glacier
*** Blue Hill, Cadillac Mountain and the Camden Hills would have been nunataks, poking out of a sea of ice that led down to the ocean miles and miles from where the shore is now
** What can we learn about them?
** Post glacial rebound
- http://www.antarcticglaciers.org/glaciers-and-climate/sea-level-rise-2/recovering-from-an-ice-age/
** Temporary glacial lakes, filling and flooding
- https://en.wikipedia.org/wiki/Lake_Missoula
- https://en.wikipedia.org/wiki/Lake_Lewis#/media/File:Lake_Lewis_flood_profiles.jpg
*** Wallula Gap in Washington on the Columbia River
** Where did the ice go?
*** Retreated North as the weather warmed
*** Sea levels rose and the earth got warmer
*** Feedback cycle of less ice to reflect sunlight kept warming the earth
*** Barnes Ice Cap on central Baffin Island, 20,000 year old ice still exists
** So we know it used to be much colder, what about climate change?
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