The Black Mesa landslide is located 2.7 miles (4.3 km) north of Black Canyon City. The slide mass is largely east of I-17 but underlies the north-bound lane for about 3,100 feet (945 m). It appears to be a primarily translational landslide. With a slide mass perimeter of ~2.1 miles (3.4 km) encompassing 0.21 square miles (0.54 square km), this landslide is significantly larger than the Black Canyon City landslide. From the scarp on the upper slope of Black Mesa to the foot of the slide is a distance of ~0.6 miles (1 km). We have not observed physical evidence for recent (i.e., historic) movement of the landslide mass. Nonetheless, the landslide mass is inherently less stable than undisturbed deposits and may be subject to failure along planes of weakness and areas modified by I-17 construction. Because the Black Mesa landslide underlies and includes potentially unstable rock and alluvium in close proximity to I-17, it presents a more serious hazard to the highway than the active Black Canyon City landslide. Photo by B. Gootee; annotation by J. Cook.