Cathedral Cliff, Volcanic plug in San Juan County, United States.

Cathedral Cliff is a 5,810-foot volcanic plug on Navajo Nation land in San Juan County, New Mexico, rising 400 feet above the high-desert plain beside U.S. Route 491, about 13 miles south of Shiprock. It is an eroded diatreme of the Navajo Volcanic Field, with intact and broken beds of pyroclastic rock exposed in its pipe.

Cathedral Cliff is the eroded remnant of a maar-diatreme volcano that formed when rising magma met groundwater-saturated country rock, probably around 30 million years ago during the Oligocene, in the Navajo Volcanic Field. Later erosion stripped 500 to 1,000 metres of overlying sediment, exposing the diatreme and its rarely preserved transition zone to the maar.

Cathedral Cliff stands on Navajo Nation land in San Juan County, where the formation is a landmark beside U.S. Route 491 about 13 miles south of Shiprock. The cliff takes its name from its shape, a tall rock tower with vertical joints that resemble a cathedral front. The nearest higher neighbour is Table Mesa, one mile southwest, and Barber Peak lies 1.5 miles southeast.

The site sits about 13 miles south of Shiprock and is easily viewed from the roadside. Photography works best during early morning or late afternoon when light angles highlight the rock formation.

The formation displays a rare transition between two different types of volcanic activity where rising magma met water-saturated rock. This unusual combination of geological processes is rarely preserved in such clear form at other locations.