The Potomac Above Natural Navigation Limits

While searching for some topic photos for the blog tonight I came across this picture, which I think I took at Chain Bridge, which connects Washington with Virginia.

In an earlier post, we got to take a look at the Great Falls of the Potomac, another rocky, somewhat dramatic area for a river that is otherwise usually depicted as serene, flat, and just a nice scenic portion of a larger capital scene.  Like many east coast rivers, the Potomac is indeed a nice, flat, boat-worthy river until it hits the toes of the Appalachian rise.  Like the Nile pinching at its "cataracts", these rivers then narrow into rather rocky affairs that feature little rapids.

Yes, I know this is not the Potomac.  What we see here is the Susquehanna river just north of Harrisburg, Pennsylvania. This was taken from US 22 northbound, looking west.  

As seen above, in places where the navigation head is closer to the first great ridges of the Appalachians, the whole affair gets pinched into this sort of scene framed by enclosing mountains.  These features are known as "water gaps".  For the Potomac, this occurs much further upstream than this scene in Washington at Harper's Ferry, where Virginia, Maryland, and West Virginia converge.  Here we have a double gap, where the Shenandoah joins the Potomac.

US 340 looking north upstream the Shenandoah to its confluence, between the mountains, with the Potomac.  The white steeple rising from the left shore is the only sign of Harper's Ferry, WV, that can be seen through the rather dense riparian forests of cottonwoods, ashes, and willows.  

The water gaps and river-worn sections of the Appalachians are excellent places to see the exposed underbelly of eastern North America.  While our vegetated and softened landscape here has nothing on the "naked geology" of the western lands and Mexico, it is far from boring as far as geologists and rockhounds are concerned.  Yeah, we have the classic riverboat scenes, but we also have rougher and swifter patches like this right around the corner.  In some places, they have allowed for dams and mills to be constructed that were responsible for powering and watering the foundations of American industrialization.