We have visited a lot of long-gone glacial lakes throughout the Catskills during our years of writing for the Mountain Eagle. Most of the Schoharie Creek Valley was once, for example, lake bottom. But there is something much bigger that we would like to spend some time on. That’s a bit of geology that you really should know about. It’s Glacial Lake Albany. Did you know that at the very end of the Ice Age much of the lower Hudson Valley was flooded with the waters of a substantial lake? Take a look at our first illustration, courtesy of the New York State Museum. That’s Lake Albany in blue. It extended from well north of Albany, south almost to New York City. That’s a large lake. It wasn’t all that deep, but it was big. Have you ever visited Lake Champlain? That’s another post glacial lake, a virtual twin of Lake Albany but it’s one that has not yet drained away. Lake Albany formed while the Hudson Valley glacier was melting and retreating to the north. The enormous weight of the ice had depressed the crust by several hundred feet. That depression left space for the lake waters. As the ice melted back to the north all that weight was removed and the crust rebounded, and then those waters drained away. See the arrows on our second illustration. The down arrows reflect the weight of the ice; the up arrows show the rebound.
So, in a way, you can think of Lake Albany as following in the footsteps of a melting glacier. During that retreat, the lake bottom filled in with sediments, mostly dark silt and clay. Again, see our second illustration. The blue on that map view is, essentially, a map of those sediments. Lake bottoms tend to be flat, and so too are the sediments of Lake Albany. The two of us have trained our eyes to look for flat landscapes at the bottom of the Hudson Valley. The next time you are headed south on the Thruway we would like it is you watched for these flat areas, left and right of the highway. They are common features up and down the valley. But there are only limited numbers of them in our region. The shores of the Hudson River in eastern Greene County show several good locations. And starting next week we will go see one very good example.
Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.” Read their blogs at “thecatskillgeologist.”
Remember to Subscribe!
No comments:
Post a Comment