Albuquerque sits in the Middle Rio Grande Valley, which is part of the great Rio Grande Rift. The rift zone begins in Colorado, runs southward through the center of New Mexico, and ends in the state of Chihuahua in Mexico.
About 30 million years ago New Mexico began to pull apart. The rift zone is bounded by two parallel faults that are still in motion. The center of the rift area dropped downward more than 30,000 feet, while the sides uplifted.
Volcanoes also formed along the edge of the rift zone, especially in the Jemez area.

The west side of the Sandias are very rocky, while the east side has a gentle slope. The rock at the top of the Sandia is the same as the rock that lies about 15,000 feet below sea level under Albuquerque.

The western slope, extending east of the crest ridge at the north and south ends of the Sandia Mountains was designated as a wilderness area in 1978. The wilderness area is made up of 37,232 acres that is split in two near its center where the Sandia Peak Tramway sits.