Maps of the Niagara Escarpment
The original source maps on which File:Niagara Escarpment map.png and File:Approximate area of the Niagara Escarpment 2.PNG were based have gone 404.
It appears File:Niagara Escarpment map.png and File:Approximate area of the Niagara Escarpment 2.PNG were based on different data. I suspect the underlying data in the older, cruder of our two maps is correct, as there was a dome centered in Michigan, and the escarpment was created when the upper layers in Michigan were scraped off. The escarpment is where one of the harder of those original layers was exposed, and it is my understanding that the southern edges of the dome are detectable too.
The File:Onondaga Formation.jpg is worth mentioning as it runs parallel to a portion of the Niagara Escarpment.
Alternate source maps here: