Time Travel at Ausable Chasm November 23, 2012
Posted by Jill S. Schneiderman in geologic time.
Today I traveled back to a time 500 million years ago. At Ausable Chasm I descended 150 feet through layer upon layer of sandstone. Carved by glacial meltwater a mere few thousand years ago, the Ausable river now flows along the bottom of this slot canyon into Lake Champlain.
Known to some as the “Grand Canyon of the East” it really is a remarkable geological site. One drops beneath the rim that’s populated by tall spruce, fir, pine and hemlock trees and immediately steps into another time–a time when the Iapetus Ocean, ancestor of today’s Atlantic, encroached on the shore of a North American continent whose remnants we see in the high peaks of the Adirondack mountains.
It was a sandy shore. We know this because the Potsdam sandstone exposed in the walls of Ausable Chasm is composed of tiny quartz (SiO2) grains that are held together by quartz cement. This very hard, compact and weather-resistant rock contains few fossils because beds of sand, unlike mud, are ill-suited for the preservation of organisms. But traces of the one-time presence of life 500million years ago are abundant in the form of tracks and trails and vertical burrows dug by animals feeding on microorganisms and detritus in the sands.