Shoreline
The Timeline of Glacial Melting and Sea Levels
When the ice sheet reached its maximum extents around 25,000 years ago, you could walk directly to Nova Scotia across the ice sheet that covered the Gulf of Maine. The weight of the ice depressed the land and, when the glacier finally retreated about 14,000 years ago, the sea flooded the interior of Maine submerging areas that are 300 feet above today’s sea level. In a process called isostatic rebound, over the the next 1,000 years the sea retreated enough so that islands began appearing at the start of this trail, 222 feet above current sea levels. It took another 1,000 years for the shoreline to drop to this level which is now 166 feet above sea level. During this time, sea levels were also rising from the injection of water from the melting glacier, but not nearly as fast as the land was rebounding. As the rebound slowed, the sea was able to settle at each level for longer periods.
The Younger Dryas Cooling Period
Further complicating things, a period of cooling period from about 12,900 to 11,700 years ago, slowed the melting of ice and the glacier temporarily advanced. Since Maine was mostly ice-free the rebound continued as rising sea levels slowed.
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Shoreline Project:
During the period of isostatic rebound, it took at least 1,000 years to drop from the high point on this trail to the low point. Judging by the topography and the geological history, it can be inferred that this was a shoreline for a few hundred years. The evidence is this thin layer of topsoil that covers clay and sand, a common formation in nascent post-glacial soils. Hidden in the layers of the clay soil should be the fossilized remains of microscopic marine plants and animals. Discovering and documenting these remains will help confirm the timeline. Digging a strategically located pit is the first step, followed by the examination of soil samples under a high-powered microscope. We are seeking volunteers to participate in this project.
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