A quick review of geologic activity
prior to the “recent” glaciation
By Ruth and Duane Braun
Before 500 million years ago (mya) Maine did not exist. The edge of the Laurentian continent was the Canadian border. Maine was constructed over the next 120 million years (my) by the collisions of slices of crustal material.
480 mya a volcanic arc collided with the border of Canada to form the very NNE part of Maine.
450 mya a slice of South America called the Gander Terrain collided to form most of Maine. (Mount Desert Island (MDI) was on the far, or quiet, side of this collision.)
420 mya another slice called Avalon collided with Gander. MDI was in the collision zone resulting in a line of volcanoes along the present coast line - MDI being the largest - and the Southwest Harbor Granite, Cadillac Mountain Granite, Somesville Granite and other igneous intrusions.)
360 mya the Meguma terrain (Nova Scotia) collided and supplied the energy for the younger igneous intrusions on the island resulting in the Seawall Granite, Northeast Creek Granite, and Baker Island Granite.)
300 mya the supercontinent of Pangaea formed as Europe and North Africa collided with North America. A mountain range like the Rockies was formed. MDI was on the western flank of this range and erosion carried materials into Canada, probably removing one mile or so of rock.
200 mya Pangaea began to break up and the Atlantic Ocean started forming.