The other Alligator Rock. (photo by Johanna Titus)
We have been exploring the ice age history of the North-South Lake State Park. Specifically we have been following the trails of glaciers as they entered the park and flowed across the landscapes there. Our saga began several issues ago when we followed a branch of the Hudson Valley glacier as it entered Kaaterskill Clove. That glacier sculpted much of the landscape that the Blue Trail follows as it traces the north rim of the great canyon. It carved such scenic spots as Inspiration Point and Sunset Rock.
In our next column we followed the ice another long distance. It turned north when it reached the canyon just below Kaaterskill Falls. We followed it up that canyon and then across the top of the falls and on into the basin of South Lake. All along the way we were, very literally, following in the trail of a glacier that had passed this way perhaps 14,000 years ago. It left a trail of scratches, called glacial striations, in the bedrock.
Sometime later we crossed over to the Mountain House parking lot, just east of North Lake. There we picked up the trail of another mass of ice that we followed westward to the boundary of North and South Lakes. We stood on a point of rock lying between the two lakes and, in our mind’s eyes, we saw one glacier coming from the southwest and another from the northeast. They were about to collide with each other and we stood in between.
Just try to imagine how much fun this sort of “science” is for us to do. We spend our time outdoors, hiking about on some of the most scenic lands east of the Rocky Mountain Front. We follow those striations and we follow the glaciers that left them. We plot it all up on a map and come to document and understand what happened here during the closing chapters of the Ice Age.
Our next goal was to find the line along which those two glaciers collided. Our working hypothesis was that it lay on the peninsula that separates the two lakes so we went off to explore that location. Fortunately for us there is an old trail that takes hikers such as us, first west, along the shore of North Lake, and then turns around to go east, towards the South Lake Pavilion. It was the east bound trail where we started finding some very interesting evidence.
Many of you have probably done this trail and, if so, then you will remember the famed “Alligator Rock” that lies alongside it. Alligator rock is a massive boulder; it must be 25 feet from one end to the other. It is composed of stratified sandstones, commonly known as Catskill bluestone. It’s the stratification that led to it becoming famous. Those strata are potential weak levels within such rocks. The whole of Alligator Rock was, long ago, tilted into a gentle incline. The strata slope upwards and to the east. Well, somewhere along the line, a mass of sandstone broke loose along one of those stratified planes and a lump of rock fell down. That left what looks exactly like the lower jaw of an open mouth: an alligator’s mouth.
Probably millennia later, some long forgotten visitors came along and thought it would be fun to put a bunch of rocks into the “mouth” of the alligator. They became the teeth. That’s pretty much been the case ever since. For one or perhaps two centuries, our alligator has been armed with teeth. Some people come along and remove them, others replace them and still more people come along and rearrange them to suit their whims. But most of the time our alligator has a big toothy grin on his face.
The two of us have long known this friendly alligator, but last summer, while exploring the area for this article, we encountered still another one of these stone reptiles. It was only about 100 feet off to the west of the first one, but we had just never seen it before. It too, had an open mouth, armed with more large teeth.
We were looking around and soon we noticed that there were a lot of rather large boulders which were strewn about all over the peninsula between North and South Lakes. And, pretty much all of them, like Alligator Rock, were lying there on an angle. We knew we were on to something of some geological importance. We had found the crash site where those two glaciers collided! A landscape, littered with large boulders, all lying askew, is very typical of what geologists call a glacial moraine. The boulders and the heaps of earth here were bulldozed to this site, by the advance of the two glaciers.
This is thus a double moraine. Some of the moraine’s earth came from the southwest; the rest came from the northeast. All of it was carried by one glacier or the other. That makes it something special; it is certainly just not an ordinary moraine. We need a better name for this surprising landscape feature. We have decided to call it a “crash moraine.” It really is something remarkable and it does deserve its own nomenclature.
With our coming to understand the nature of these colliding glaciers, we have taken another big step forward towards documenting the ice age history of North/South Lake State Park. But, in fact, we still have some more to learn.
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