A giant crack has been widening on the Navajo Reservation near the small town of Leupp, Arizona. The crack occurs 12 miles north of Interstate 40 about half way between Flagstaff and Winslow.
The Navajo Post has a photograph and short video of the crack. Arizona State Geologist Lee Allison has two short posts on the crack here and here. Photos and a geologic map are included in those posts.
The crack is along an extensional fault system mapped in 1984 by George Billingsley of the U.S. Geological Survey. Movement on the fault may be related to the numerous small earthquakes in the area (see Arizona is earthquake country) that derive from crustal extension. The 900-foot long crack is parallel to joints in the Kaibab Limestone.
According to the Navajo Post, the crack has gotten so big that it had to be fenced in.
The photo below shows the crack just south of Leupp Road.