You might be wondering, since I keep mentioning it, what the Potomac gorge is.  It’s an interesting geological/hydrological feature of the Potomac River: a 15 mile stretch from Great Falls to Theodore Roosevelt Island in Washington, DC, in which the river drops about 130 feet.  Great Falls itself is a plunge of 76 feet over about two thirds of a mile.  This is one of the longest and most dramatic fall zones of any watercourse on the Atlantic seaboard.  It’s the area where the hard metamorphic rock of the piedmont meets the sediments of the coastal plain, and as a transitional area supports a large diversity of life, including over 200 rare communities and species.

One of the interesting geological features of the gorge is the bedrock terraces. These very hard rock formations are quite erosion resistant, and are swept by frequent floods, resulting in micro-habitats where you can find unusual species of plants.  Sometimes you can find plants growing next to each other that wouldn’t co-exist anywhere else in the world.  And there are species found in the gorge that are otherwise rare east of the Appalachians, like racemose goldenrod and Coville’s phacelia.

More rare plants can be found in the Potomac gorge than in any other part of Maryland.

There’s more.  A lot more.  When I started researching for this post I discovered some really nice articles, and spent hours reading, and decided I couldn’t do the topic justice on my little blog.  Most of what’s written here I found in the following sources:

“The Wildest Urban River: Potomac River Gorge”  –Jeffrey P. Cohn, Oxford Journals

Potomac Gorge Field Guide  –National Park Service

Potomac Gorge Site Conservation Plan  –Nature Conservancy

Potomac Gorge –Michael Kircher, Burn Magazine

Geologic Map of the Potomac River Gorge  –USGS