Nearly 700 million years ago, Vermont was located on the equator and was completely under the ocean.  As organisms died in the ocean, they settled down creating a layer which eventually created a limestone base.  About 15 thousand years ago, glaciers covered the area with ice more than a mile deep. Mount Mansfield was completely covered with ice and only the tall peak of Mount Washington was visible.  These glaciers first spread over the area, the scoured the ground of all its soil all the way down to the bedrock.  As these glaciers retreated, they left the ground covered with a layer of rocks and boulders.

      The glaciers began to retreat, they left behind a massive amount of water.  This water filled the area with an enormous historic lake called Lake Vermont.  This lake filled all the valleys between the Green Mountains in Vermont and the Adirondacks in New York with a lake 600 feet deeper than our current Lake Champlain.  The piece of land containing Centennial Woods was completely covered with water.  All of the sediment which was contained in this lake gradually began to settle out of suspension creating a thick layer of silt on the lake bottom which remained behind even after the lake level retreated.

     Feeding into the lake was the Winooski River.  As the Winooski neared its final destination in the lake, the grade at which it was traveling drastically decreased.  This flattening allowed for the river to widen and spread out in a triangle shape over the surrounding land.  This area, called a delta, included the current area of Centennial Woods.  The water in this area traveled at a substantially slower rate compared to the flow above allowing for larger sand particles to begin settling out.  This sand covered the entire delta area burying the silt deep below.

     Over time, subsequent streams and brooks, including the ones currently located in Centennial Woods, began to gradually erode away this top sand level.  Valleys began to form creating low areas and steep slopes.  As these valleys worked progressively deeper, they made their way through the layer of sand down into the previously buried layer of silt.  At the same time, the ridges in between the valleys remained intact with only the deep layer of sand visible.  These variations are very apparent today.  Soil samples taken from valleys contain many differing layers of silt deposits while soil samples only 100 feet away but on top of a ridge reveal seemingly endless amounts of sand.