The right-relayed Rio Grande rift, Taos to Hatch, New Mexico
— Vincent C. Kelley

The Rio Grande rift contains the course of the Rio Grande which heads in southern Colorado and flows southward through New Mexico, eventually emptying into the Gulf of Mexico. The northern end of the rift is bounded by the Colorado Plateau and by the New Mexico and Colorado Rockies and High Plains. The southern part of the rift lies in the Basin and Range province of southern New Mexico. The rift has also been considered to be a part of the orogenic Rockies (Eardley, 1962, p. 390) because of its bordering uplifts. Bryan (1938) was the principal early worker to recognize the rift with his term "Rio Grande depressions." The rift and its borders have been extensively mapped since the work of Bryan and his students. The portion of the rift considered here is about 435 km in length. It consists of a double right echelon (series of parallel right-echelon offsets) of uplifts, ramps, benches, and synclines between faults arranged in overlapping or relay patterns (fig. 1).