Paleogeology

I don't know why, but I just find this stuff fascinating.

I usually like to do things the hard way, but I must be going at it backward this time. I'm surfing Google Earth, like always, and I come across the most puzzling things. I'm looking off New York's Long Island and right there at the continental shelf, I see this sharp gash eroded away by what can only be an ancient Hudson River way back when the ice shelf covered North America. Then there's a smooth indentation connecting the present-day Hudson with the gash in the shelf. Interesting.

What might have caused this? Maybe this:

Catastrophic Flooding From Ancient Lake May Have Triggered Cold Period