Twilight at Rock Creek
Moments before sunrise at Rock Creek in Rock Creek Park, Washington, D.C. I took this photo a little north of Rapids Bridge where the creek consists of fast-flowing water, i.e. rapids. The National Park Service says that this portion of the creek is the "fall zone—the geologic transition zone where the harder rock of the Piedmont Plateau meets the softer, sedimentary rock of the Atlantic Coastal Plain".