There are not too many places on earth, where two fault lines come together. A detachment fault (first) and a San Andreas type, right-lateral strike-slip fault (second) meet.
The hike goes into powder dump wash. (explosives used for the highway constructions in 1930, where stored here, right on the fault.)
There should be a booklet that explains the geology of the area.
Some of the oldest rock in the park, can be found in this area, 500 million year meta sedimentary rock, mud and sand metamorphic rock.