Monday, January 19, 2015

Rap-Shaw is Built on Fragile Glacial Till

One can see, when the water is at its lowest during the winter, just how thin the soil is on our islands.

To comprehend how the recent geology of this region was shaped, we have to accept the work of glaciers unimaginably deep and more or less permanent in any human terms. Eskers are a remnant of glaciers, and they are found frequently in the Adirondacks and any place where there were glaciers. How many times have we found ourselves on a road called The Hogsback?

Glacial meltwater creates tunnels under or through the glacier. These rivers will carry debris scraped from surrounding higher exposed rock and carried away within the glacier. Such a river is often large and powerful enough to carry debris. Eskers are the tall narrow ridges, created on the glacier's underside by these streams or rivers: river bottom contained within or under the glacier. They are comprised of rocks tumbled along and then left behind and exposed as the glacier melts and releases most of its energy to the sea.

After the last glacier retreated 10,000 years ago or so around here, the North-Western quadrant of what became Stillwater Reservoir contained a river that ripped during the spring run-off and otherwise meandered in meadows through finely stratified glacial till between eskers. Today, the Beaver River is interrupted by a big hydro dam that created Beaver River Flow, or Stillwater Reservoir. Many of these eskers have been stripped of soil by annual level fluctuations and by wind-fired wave action, leaving long bare piles of round boulders. Many of the boulders strewn about the pond are gigantic, straining imagination considering the power of moving water.

This rock jungle is unpredictable to the uninitiated and dangerous to motor boats. Esker sides are steep, so fancy underwater radar warns too late.

The two islands that comprise Rap-Shaw are esker remnants. They are fragile and are gradually, literally, losing ground.

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