THE CATSKILL GEOLOGISTS BY PROFESSORS ROBERT AND JOHANNA TITUS - An Ice Age landscape at the Mountain Top Arboretum

CATSKILL - Why on earth would anyone visit an arboretum in the middle of the winter? The leaves have all fallen down and blown away. The branches are bare, and you can hardly tell one type of tree from another. Let’s make it worse: let’s go there on a rainy day, a cold rainy day! Yep, that’s what we did recently. Why on earth would we do that? Well, we had been thinking about the West Meadow. That’s the field, just to your left as you drive onto the grounds. We have been there many times, and we have written about it several times. We know that there are number of locations there that display exposed bedrock and that ice age glaciers had scoured those outcrops. But we were thinking about all the material that overlies that bedrock. What was that stuff? How did it get there? Who else but a couple of geologists even think of asking such questions?

We walked through the gate to the West Meadow and saw one very fine exposure of that bedrock. See our first photo. As we had picked a rainy day, we knew that this rock would be shiny and that that would make any structures exposed on that surface very clear to see. Sure enough, there they were – glacial striations. If you have been reading our columns long enough then you will look at our photo and see those striations for yourself. They are those right-to-left scratches on the surface. Each one was etched onto that surface by a rock being dragged along by an advancing glacier. We had brought a compass and found that they were all oriented exactly north-to-south. Glaciers are really good at moving from the polar north to the warmer south and that is what we were looking at.

We stood upon that scoured surface, turned north and then were transported into a distant past. It was about 25,000 years ago and the main ice sheet of the most recent glaciation was adancing across this site. About 2,000 feet of ice rose above us and so it was totally black down here. But we were the mind’s eyes;  we could see everything around us, near and far. All across the North Meadow it was the same. The ice was pressed against the bedrock and it was scraping up and carrying away everything above that scoured surface.

Centuries passed by and we stood there; the mind’s eyes are patient, they can do such things. Then the climate warmed and we saw that the ice was melting away. Slowly the glacier above us was disappearing. This had been dirty ice; it had picked up a lot of earth, rocks and even boulders as it had descended from the north. As it melted, all of the meltwater flowed off to the south. That carried off a lot of earth with it. But most of the sediment that had been in this “dirty” ice settled onto all the arboretum grounds. Then the ice was all gone. We looked around and saw bare earth. It looked a lot like the North Meadow but with no plants of any sort. These lands were dotted with cobbles and boulders. We had solved our problem.

This was what glacial geologists call a “ground moraine.” It was a foot or two of rocky earth, all lying upon that scoured surface. Over the next 14,000 years or so it would slowly begin turning into something of a real soil. Foliage would invade this site and someday people would plant the trees of an arboretum here. See our second photo. Nice, isn’t it?

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.” Read their blogs at “thecatskillgeologist.com.” Visit the arboreum webpage at mtarboretum.org.