On the rocks: High up, above the Hudson River

My imagination took me back all those years. It was a time of frequent earthquakes. The unstable crust was being compressed and deformed by its collision with Africa. Frequently there were volcanic eruptions far off to the east. Great black clouds of soot rose into the sky during the days; at nighttime the eastern horizon glowed with a soft red.

That was a lot of very good geology but we thought there might be more to see, so we continued walking east. About halfway across the bridge I began to take note of a series of relatively small hills on the east side of the river. One was due east of the bridge, right in the heart of Poughkeepsie. Then there were four more, arrayed as if in a line, extending off to the north.

It would have been easy to have not noticed them at all; none of them are all that big. But I quickly guessed that I was looking at a kind of hill that is common farther north in the Hudson Valley. These appeared to be remnants of ice age hills called drumlins. I have written about drumlins several times before. Woodstock has several of them. The Comeau Hill is one of them and there are a few more just east of town. They are beautiful little hills, sculpted by the ice of passing glaciers. They are perfectly symmetrical with steep slopes dipping east and west. The north slopes are also steep, but the south slopes have much more gentle inclines. Drumlins are shaped just like upside down spoon bowls and they are common — very, very common throughout much of the Hudson Valley.

When we came home I dug out my topographic maps and confirmed that these were drumlins. I even found that Dutchess Community College is built upon one of them. One of their academic buildings is actually called Drumlin Hall.

It all got more interesting when I continued to study the maps. It seems that these are just about the most southern of all the Hudson Valley drumlins. To the south drumlins just disappear; to the north they become very frequent. Everywhere I looked, these drumlins lay atop of other landscape features. They had to be younger than all others. That clinched it; I was looking at the record of the one last final advance of the ice. I had been looking at the last gasp of the Ice Age!

Now, in my mind’s eye, I returned to the Walkway Over the Hudson and gazed east. I watched as that glacier moved south. It wasn’t very large and just barely rose above the horizon. Compared with earlier chapters of glaciation, this one was puny. It was near the end of the Ice Age and this small glacier was all that could be managed. But, all around me, the Hudson Valley was bleak and barren. This was still very much an ice age landscape.

I watched the glacier advance to the center of what would someday be Poughkeepsie and then it slowed down and ground to a complete halt. This last chapter of the Ice Age was running out of steam (or running out of cold?). I continued to watch; it warmed up and then the ice began to melt. It soon vacated this part of the Hudson Valley. As the glacier disappeared the drumlins emerged from the ice and took on the appearance that they still display. The Ice Age was over. ++

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