THE LAURENTIDE ICE SHEET:
The story of US-5 could go back to a time before the last Ice Age. It could attempt to explain the geologic and topographical features of our area. We could have begun by examining the birth of the region's valleys, rivers, and mountains... the fabric upon all that followed was painted. But, time constraints dictate a line had to be drawn somewhere.
You may have difficulty imagining that a mere 20,000 years ago, a blink of the eye in geologic time, your home, neighborhood, town, entire state, in fact all of New England, were all buried beneath the grinding, oppressive weight of nearly two miles of ice.
Because such a vast amount of the earth's water was tied up in these North American glaciers as well as ice sheets elsewhere on the rest of the planet, the worldwide sea level dropped nearly 300 feet. In the process, huge sections of the usually submerged continental shelves around the world's landmasses were left high and dry. In the process a landbridge was formed Bering Straits connecting Asia and North America. Most anthropologists believe it was during this window of opportunity, which lasted several thousands of years, humans first migrated from Asia to North America. If true, then no humans ever set foot in today's New England until some time after the retreat of the last glacial ice sheet. If, as some believe, there was human habitation of the Americas prior to the last ice age then we will probably never know, at least not here in New England. The ice sheet scoured the landscape down to the bedrock and then some. Nothing short of a nuclear war could do more to destroy any potential archaeological evidence of human habitation.
THE GLACIAL MELTBACK:
In New England the end of glacial age began some 18,000 years ago. At this time the Laurentide Ice Sheet began what is called a “meltback”. Though no other single event has shaped our Valley more, it is difficult to imagine by merely looking around us the immeasurable influence the glacial age had on our landscape. How is one to envision to what lofty heights the mountains that surround our Valley would now rise if they had not been ground down to mere hills? How is one to envision how the Valley’s floor was gouged and scoured clean only now to be filled with debris and sediment, in places hundreds of feet deep?
But, if we look elsewhere, there are a couple indications of the ice sheet's immense power. Just look at Long Island and Cape Cod. Both form the terminal regions of the ice sheet. Here the melting of the ice equaled its southern advance. Unlike the rest of New England there is no bedrock just beneath the surface of these two landforms. Long Island and Cape Cod are literally sand castles on a glacial scale. It may strain credulity to comprehend the unimaginable volume of material, mere sand, clay, gravel, and other glacial debris needed to make up these landforms. Yet, all of this material, once the soil and pulverized bedrock of New England and Quebec, was deposited there by the conveyor belt action of the last glaciers. Yet, in true sand castle style, these huge landforms themselves may not be permanent. They are slowly eroding, their sands constantly being redistributed by the forces of nature. For example, it is believed the eastern shoreline of the Cape Cod's outer arm once extended several more miles to the east. Much of that material was distributed northwards creating all the land north of the Truro highlands. Some few thousand years ago, that distinctive sandy hook that encompasses all of Provincetown, did not exist.
The eventual retreat of the ice sheet took thousands of years and left a barren moonscape in its wake. Tundra vegetation, lichen, grass and sedges, made the first forays back into this region and were dominate for several thousand years. As the regional climate continued to warm and this early vegetation made the soil more fertile, forests eventually made a comeback. Yet, these trees were not the species we would today recognize as native to our region. Species, such as spruce, we now expect to find only in more northern climes. As for animal species, there is evidence that herds of caribou, and even the now extinct woolly mammoth, lived in the region. Some speculate that animals created the first trails in the Valley... trails that may have been used by early Natives some several thousand years later. But first the story of Lake Hitchcock.
"US-5: A Highway to History" © Robb Strycharz, 1996-2006
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