Michael,
I appreciate your geological comments. Understanding the roadside geology is up there with understanding and appreciating the roadside history and architecture.
Looking at the area you note in Google Earth, it looks like the road from the NW (going SE) follows along the edge of the flow, climb it and then crosses the bridge. An older road seems to climb the flow just a little bit to the west.
In street view you can see the edge of the flow readily.....but all this is conjecture as I have little to no expertise.
Dave
Keep the Show on the Road