THE CATSKILL GEOLOGISTS BY PROFESSORS ROBERT AND JOHANNA TITUS - A landslide in Catskill Part One -The Slide

Did you hear about the recent landslide on Cauterskill Road in the Village of Catskill? See our first photo. That was on May 7th. It made the local TV newscasts for at least for one night and then faded from the news. It wrecked one house; but otherwise, was not all that large an event. That makes it a family tragedy and we certainly cannot lose sight of that. But we think that it was an important event for other reasons. There is much to learn from it. One thing that the local news reports stated was that people did not know the cause of the slide. We would like to fix that. And we would like to make people aware of this particular type of geohazard. If you live in our region, especially in the lower Hudson Valley, then your home might be next; you need to know about this.

The story actually started about 14,000 years ago. At that time much of this part of Catskill was under the waters of a glacial lake. Catskill Creek flowed into that lake and deposited sandy sediments that made a delta. Those waters drained away long ago but the delta and its sands are still there and, centuries ago, people started to move into the area and began building homes atop the old delta sediments. Delta tops are usually flat, and their soft sediments make it easy to dig basements, so they make attractive places to build houses. People also constructed roads, one of the being Cauterskill Road. The problem was that there were also a series of small streams that had long been eroding small valleys and canyons into those same delta sands. One of those, a small unnamed creek, had eroded its way almost to today’s Cauterskill Road. Streams, large and small, all look as if they have always been where you see them and always will be. But that simply is not true; that’s Nature being deceptive. You see, all streams are constantly changing. They are typically deepening and widening their valleys. They are often also elongating them. One way of doing that is by what geologists call headward erosion. The upper reaches of any creek will cut into the landscape at the stream’s top, its head. It’s not unusual for that head of the stream to have steep slopes. All of this was going on at the top of this creek and that was setting up Cauterskill Road for a landslide.

It’s been a rainy spring so far and a lot of water has been soaking into the ground. We are always alert for this sort of thing, because, especially in the spring, that generates what we like to call a “landslide season.” When the earth gets too waterlogged then gravity stresses build up and that goes on to generate multiple curved fractures. This is especially the case with lake sediments. See our second illustration, courtesy of the U.S. Geological Survey. Eventually masses of earth begin sliding down along these fractures. That, we think, is what happened along Cauterskill Road. But there is a lot more to the story. We will be back next week to continue.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.” Read their blogs at “thecatslillgeologist.com.”