The photograph shows the field exposure of a normal dip-slip fault near Abiquiu, New Mexico, on the western side of the Río Grande Rift, an intracontinental zone of Cenozoic crustal extension, subsidence, and volcanism. The rocks on the left are part of the Abiquiu Formation of Oligocene age, and those on the right are Santa Fé Group, of Miocene age. The reddish-yellow and black staining of the rocks along the fault indicate the presence of manganese and iron oxide minerals that were deposited by fluids flowing along the fracture.

What is not readily apparent from the photograph is that the right side of the fault is actually the downdropped side (the "hanging wall"). It is topographically higher because the Santa Fé Group here is more heavily mineralized (note the thick black coating) than the Abiquiu Formation, and thus more resistant to weathering and erosion. The illustration on the right shows the actual tectonic relationship of the two fault blocks prior to formation of the present surface by erosion.