Tuff Canyon Center, Big Bend NP (M)
This is the central part of Tuff Canyon. The upper end is in the distance, where the canyon seems to turn a corner to the left. In the middle distance, on the canyon floor is a dark object. This is a chunk of the same basalt, which forms the floor of the upper end of the canyon.
The stream has cut through some 40 to 50 feet of tuff, a process still going on. There is no basalt on the canyon floor here to impede erosion.
What little I know about Tuff Canyon, I learned from an interesting publication Down to Earth at Tuff Canyon, Big Bend National Park, Texas, by Daniel S. Barker, published by the Bureau of Economic Geology, of the University of Texas at Austin, 2000.