One of the greatest parts of Las Cruces is the amazing view that we all have of the Organ Mountains! They frame our town to the east, provide lots of camping and hiking opportunities, and are always the centerpiece in some awesome sunrises and sunsets! Even though they’re always in our backyard, how much do you really know about them?
The Organ Mountains originated about 32 million years ago in the middle of the Tertiary Period. At that time, magma began to ooze from great depths, pushing up the overlying layers of rock. Some of the magma was forced to the surface ejecting vast quantities of ash, rock, and lava over an area of 100 square miles. The result of this volcanic activity can be seen today as the dark red rocks of the Organ caldera that forms the southern portion of the range. The magma that did not reach the surface cooled slowly to form the Organ batholiths. The pinnacles of the northern Organs are remnants of this slowly cooled magma. This craggy, light gray rock of granite composition can be easily recognized in the northern section of the range. Along the western side of the pinnacles, the remnant of the sedimentary layers can be seen forced into nearly vertical bedded layers. The interface between the sedimentary rock and batholiths is the location of several historic mines.
Between 15 to 8 million years ago, faulting along the Rio Grande Rift lifted the Organ Mountains on the east and tilted the region down the west. The Rio Grande became a central conduit for many small streams, carrying Organ Mountain silt to the Gulf of Mexico. The faulting along the Rio Grande Rift is still active. Occasionally, small earthquakes are felt in Las Cruces. Windblown rock and sand, rains, and changing temperature continue to erode away the Organ Mountains and the age-old cycle continues.
Source: National Park Service