Navajo Nation Reservation
Monument Valley lies on the border of Utah and Arizona within the Navajo Nation Reservation.
The valley was carved out of the Colorado Plateau by ancient rivers which left the majestic buttes rising above the valley floor.
The red color of the valley is due to iron oxide in the siltstone sand.
The buttes have three layers or strata from bottom to top: shale, sandstone and siltstone.
Since Monument Valley is on tribal land, it is not part of the U.S. National park system.