ID

30fc8992-516a-4d41-9198-d67de9a921fc

Nature Talk on Erratics

- source :: https://en.wikipedia.org/wiki/Glacial_erratic

- tags ::

Overview

What does erratic mean?

If a geologist calls a rock "erratic" what do you suppose they mean?

ID

b7e1a61b-fd05-11ea-9fe2-e86a64ecc701

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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f471bdc8-fdc9-11ea-9fe2-e86a64ecc701