Time Travel on the Winooski

Deep in a hemlock forest, on a slope overlooking the North Branch River Valley, I close my eyes. If I concentrate hard enough I can almost hear the waves lapping against the shore, smell the sediment-laden tributaries, and feel the icy waters against my skin and the sand beneath my feet. While this isn’t true today, you wouldn’t have to go back too far — in geological time that is — for this to be the reality for much of Central Vermont. That’s because roughly 14,000 years ago the Winooski River Valley was home to an enormous freshwater lake called Glacial Lake Winooski.

As the Laurentide Ice Sheet retreated northwards at the end of the last Ice Age, its last vestiges dammed up river valleys. No longer able to flow to the Champlain Valley, the Winooski River created a lake hundreds of feet deep. Tributaries flowing across the newly emerged landscape carried immense loads of sediment. As these tributaries entered the slow-moving waters of Glacial Lake Winooski, they dropped their heavy loads. Sands first, creating sprawling deltas, and then eventually the silts and clays in the calm depths of the lake bottom.

How do we know this? If you explore the hillsides in Central Vermont, you’ll see clues all around you. At the Vermont Master Naturalist for Educators course at NBNC this past August, I learned to read these kinds of clues on the landscape everywhere I go!

During our week together, our group of teachers learned how the different layers of the landscape tell the history of a place. From the current North Branch River channel, we worked our way upwards through the Northern Hardwood Seepage Forest. Home to Black Ash
and maples, these wet forests were a sign that we were in what once was the bottom of Glacial Lake Winooski, where clays and silts accumulated.

Continuing up the hillside to around 900 feet elevation, we entered a 300-year-old hemlock stand, a clue we had transitioned into well-drained soils. Scanning the hillside I saw an unusually flat feature — another clue! Scrambling up to this feature, we used a shovel to reveal what lay beneath the hemlocks. A sandy delta deposit! We were standing in a place where a tributary once entered Glacial Lake Winooski. I was instantly transported to the past, and to what this place must have looked like 14,000 years ago.

Not many of these Glacial Lake Winooski deltas remain across the Vermont landscape. Many have been modified by human hands or eroded down slope. I like to think that this one escaped erasure because of its location in a centuries old hemlock forest, the roots of the trees helping to hold the clues of our glacial past firmly in place.

The next time you’re on a hillside in central Vermont I encourage you to look for these clues and imagine how time has changed the landscape around you.