Digging back in time to an era of retreating glaciers
By Tom French
Roughly 11,000 years ago, whales were swimming over the foothills of the Adirondacks and St. Lawrence Valley. One of them, a “White Whale,” or Beluga, died over Norfolk. It came to rest in about 60 feet of water and was subsequently buried until it was found in 1989 by Duane V. Pelkey as he was digging with a backhoe. At just over 12 feet long, evidence suggests it was a female between 25 to 30 years old, about the life expectancy for a Beluga.
Whales must have been quite common in the salt-water sea over the North Country and Canada because a number of remains have been uncovered, mostly in Canada. Clusters of five and six have been found near Ottawa and Montreal. The Norfolk Delphinapterus leucas is the only one ever discovered in New York.
I know this because my neighbor, Dr. Brian Carl, Professor of Geology at SUNY Potsdam, asked if I wanted to go search for sand dunes in the DEC’s Brasher State Forest. I think he mentioned the whale in passing, a sleight of hand to perk my curiosity. Then he showed me LIDAR imagery of the North Country.
As most everyone knows, New York state, all the way to Long Island, was once buried beneath a sheet of ice two miles thick with perhaps a few peaks of the Adirondacks sticking out above the fray like islands in a stream. What is often forgotten about this glacial epoch that lasted 2.6 million years is it only ended 12,000 years ago when all that ice melted. At the same time that the city of Jericho, believed to be one of the oldest cities in the world, was being established in the Middle East, New York was essentially uninhabitable with the weight of all that ice pushing the earth’s crust down hundreds of feet in places.
What happened next, over the course of only a couple thousand years, included whales, large vertical canyons, beaches, anticyclonic winds, and sand dunes along with a significant amount of climate change.
As the ice sheet retreated, massive lakes formed, precursors to the Great Lakes with names like Lake Vermont, Lake Algonquin, and Lake Iroquois. They were held in place by the retreating ice sheet, terminal moraines, or depressions in the earth’s crust. Often, ice dams and moraines failed catastrophically. Water hurled out quickly. Imagine Lake Ontario emptying over the course of a few hours or days.
And then the Atlantic Ocean flowed in along with the whales. The Champlain Sea extended up the St. Lawrence Valley reaching south towards Albany, north and west of Ottawa, and over much of Jefferson, St. Lawrence, Franklin, and Clinton counties. Sediments, clays, and sands were deposited. Whales and other sea life flourished.
Over the course of 2,000 years, as the earth rebounded from the weight of the ice, the sea retreated leaving a changed landscape that can still be found today in places like the DEC’s Brasher State Forest.
Brian had recently discovered LIDAR data collected as part of the U.S. Geological Survey’s (USGS) National Map Program, a project to create highly-detailed topographic information of the United States. Sometime in the last few years, a plane traversed the North Country and Adirondacks in a grid pattern while beaming laser light to the ground which when reflected measured the elevation at every point of latitude and longitude to the square meter.
It took Brian a week to download all the data, two terabytes worth, and then more than three months to analyze all the little segments, over 6,000 traces of topography in the St. Lawrence lowlands up into the foothills of the Adirondacks.
When he showed his results to Dave Franzi, a SUNY Plattsburgh professor who has studied beach terraces and glacial lake features on the eastern side of the Adirondacks for several years, Franzi said, “Those are dunes, very similar to ones I’ve discovered in the Champlain Valley.”
Brian showed up at my door with a stack of maps and LIDAR images in October for a drive – just a sortie to discover if anything of interest was noticeable from the road. He’d waited until after the leaves had dropped so he could see through the trees. We entered the Brasher Forest off Route 53, the Brasher Falls-Helena Road, and followed the Wilson Truck Trail. I navigated using a paper map to confirm various turns in the road and landmarks such as trailheads and swamps. At the same time, I held the LIDAR imagery so that I was able to tell Brian when we’d be approaching one of his “dunes.”
The road crossed a swamp and a bridge over a tributary of the St. Regis River. According to the map and data, the road would rise out of the lowlands and cross the structures Brian had found on the map. Right on target, the road rose and cut through a ridge, but not of rock. As we approached, we could see it was a mound of sand.
Brian pulled over and was ecstatic. He jumped out of the car. “It’s sand, Tom! Fine grained sand!” He kicked some loose and scooped a handful. “It’s a dune!” And then he climbed to the top of the cut which was over 10 feet high.
I followed and could see the topography of a small dip to the right before the next dune.
We continued down the road, and every time there was a bump on the LIDAR, there was a line of sand crossing the road.
Two miles of ice is massively heavy. It pushed out at its margins, flowing like a super thick milkshake, scraping the ground, pushing and mixing everything together. But when it melted, the water had a winnowing effect that left behind sand too heavy to be washed away.
Beaches formed at the water’s edge. Over time, as the water levels dropped, a series of beach terraces formed that can also be seen in the LIDAR. Further down the Wilson Truck Trail, near where it intersects with Bush Road, an ATV trail heads into the woods to the north – literally on top of one of the beach terraces. Brian and I hiked into the woods and could see several – smaller and flatter than a dune, terrace-like steps down the hill. The shorelines of a sinking sea.
After all the water receded, the wind blew in an anticyclonic pattern around a high-pressure system centered on the retreating glacier to the north. A brief moment in geologic time when it was also dry enough for dunes to form – large ripples of sand blown by the wind 10,000 years ago and then frozen in time by vegetation as the climate changed again.