The Maine Geological Survey says that “glaciers similar to today’s Antarctic Ice Sheet probably extended across Maine several times during the Pleistocene Epoch, which lasted from about 2.5 million to 10,000 years ago.”
Like Antarctica! It was Maine, but it wasn’t Maine at all. No moose, no pine trees, no Irving Stations — everything potentially recognizable about the state was crushed under hundreds or thousands of feet of snow and ice. Flat, featureless and friggin’ freezing.
And when I say “crushed,” I really mean crushed. Glaciers are solid ice but they also move, flowing downhill like a creeping river. But they’re so heavy that they scrape and scour and deform everything below them, and glacially-scarred granite and other bedrock is still visible at points all over the state.
Those scrapes were caused by large continental ice sheets, but other glaciers were also at work shaping the landscape. Alpine glaciers formed on our tallest peaks and eroded them away or cut them into sharp bowls — like the famous cirques below the summit of Mt. Katahdin.
The weight of glaciers affected the state in other ways, too, including literally sinking the ground. The Laurentide Ice Sheet was the most recent glacier to cover Maine, between about 35,000 and 11,000 years ago, and it was so heavy under its thousands of feet of ice that it pushed the land underneath it down several hundred feet.
The land was so squashed that Maine’s coastline looked very different than it does today when the glaciers finally retreated. Seawater rushed in to fill the low-lying areas, and the ocean extended far up into the Kennebec and Penobscot river valleys. Geologists think that everything up to about 420 feet of elevation in central Maine was covered by the sea.
There was lots of freshwater, too, of course. As the glaciers receded they left a whole mess in their wake: tons of freshwater, huge boulders, silt and dirt. All that stuff mixed with the seawater that was lapping against the face of the glacier. It was like the worst mud season possible, and it lasted for thousands of years.
All that junk left in the wake of the receding glaciers — the ocean sediments, the sand and gravel and silt and clay — built up into odd piles called moraines that are still visible in many parts of Maine, running like furrowed brows across the landscape. Elsewhere, the glacial sediments built up as parts of streams running below the glaciers. When the ice retreated these deposits remained as sharp ridges called eskers, found in places like Katahdin Woods and Waters National Monument.
Finally, some time around 11,000 years ago, Maine was glacier-free. The landscape sighed and lifted up to its present elevations. Vegetation began to appear, first in the form of tundra grasses, shrubs, moss, and lichen, probably similar to the landscape in northern Canada. Were there Musk Oxen here then? Were there Polar Bears and Tundra Swans and Lapland Longspurs and other creatures only found on the tundra? I don’t know! I can’t find anything about that! Let me ask around, and check in next time.
Nick Lund of Cumberland is outreach and network manager at Maine Audubon. He has written about nature for the National Audubon Society, Down East, National Parks Magazine, The Washington Post, and others. He can be found online at TheBirdist.com and on Twitter @TheBirdist.