Brazos Mountains to 55 million years ago during the Laramide orogeny. To the east and northeast lie the Sangre de Cristo Mountains which share a similar geological history. The Brazos Cliffs, which form a dramatic backdrop to Tierra Amarilla, are formed of Precambrian quartzite. Brazos Mountains The Brazos Mountains is a range in far northern Rio Arriba County, in northern New Mexico in the southwestern United States. A high crest runs from the border with Colorado for over in a south-southeasterly direction. The high point of the range at is on Grouse Mesa, at the Brazos Benchmark. Two miles (3 km) to
Roan Cliffs In addition, the name Book Cliffs is often applied to both landforms, with Roan Cliffs being an alternate name. Moreover, because of the how far they are spread between Utah and Colorado, they are sometimes mistakenly believed to be separate landforms of the same name within each state. The Roan Cliffs are situated north of (in back of) and above, but run roughly parallel to, the Book Cliffs. Stretching nearly from west to east, the Roan Cliffs begin on southern edge of the West Tavaputs Plateau, on the eastern edge of the Willow Creek (and the US‑191 corridor), north of