Geologic Tour of New Mexico — Physiographic Provinces

The Chino mine, an open-pit porphyry copper mine, is 15 miles east of Silver City near the village of Hanover in southwestern New Mexico). An overlook of the pit, complete with educational displays, is located on the south side of New Mexico Highway 152 east of Hanover. The excavation is also known as the Santa Rita Mine or Santa Rita del Cobre, named for the former village of Santa Rita, which was removed in the 1950s as mining operations in the area expanded. Concern has been expressed about the stability of the famed landmark on the southeast side of the mine, the spire known as the Kneeling Nun, as the modern-day mining operation moves to the southeast. The Chino mine is the largest porphyry copper deposit in New Mexico. The pit is currently ~1.75 miles across and 1,350 feet deep. The Apaches were the first to notice native copper lying on the ground in a valley northwest of Santa Rita Mountain. The open-pit mining operation began in 1910. The mine became part of Freeport-McMoRan in 2007.

The Valles Caldera National Preserve is one of the most geologically unique and significant areas in North America. The preserve encompasses much of the Valles caldera, a huge volcanic crater that formed 1.2 million years ago during an enormous volcanic eruption that spread ash over large parts of New Mexico. The caldera is located near the summit of the Jemez Mountains, a large volcanic complex in north-central New Mexico. The Valles caldera exhibits world-class examples of the landforms produced by a very large, explosive volcano, and the preservation and exposure of geological features within the Valles is spectacular. Much of what geologists know about large-scale explosive volcanism began with detailed studies of the rocks in the Valles caldera and Jemez Mountains, and the area continues to draw geologists from around the world. Since the eruption 1.2 million years ago, there has been uplift of the crater floor, followed by the eruption of smaller, younger volcanoes called “domes” within the crater left by the large eruption. Since then, the caldera has from time to time been home to a series of large lakes. This dynamic geological history is responsible for the beautiful and unique landscape that we see in the region today.

Mount Taylor volcano, a prominent landmark that can be seen on the skyline west of Albuquerque, is located about 15 miles northwest of the town of Grants, New Mexico. Mount Taylor Peak, at an elevation of 11,301 feet, stands approximately one mile above the Rio San Jose 12 miles to the south. Mount Taylor volcano is part of a larger, northeast-trending volcanic field that includes Mesa Chivato, a broad plateau located northeast of the cone, and Grants Ridge, located southwest of the cone. Basalt that caps Mesa Chivato and other mesas surrounding Mount Taylor makes up about 80% of the volume of the volcanic field. The Mount Taylor volcanic field lies on the southern flank of the San Juan Basin on the Colorado Plateau and straddles the extensional transition zone between the Colorado Plateau and the Rio Grande rift. The Mount Taylor volcanic field is considered to be part of the Jemez Lineament, a zone of young (< 5 million years old) volcanism aligned along an ancient suture in the 1.7 to 1.6 billion year old Proterozoic basement.

Carlsbad Caverns National Park (CCNP) is located in southeastern New Mexico about 20 miles south of Carlsbad. It was initially designated a national monument in 1923, was elevated to a national park in 1930, and was recognized by United Nations Educational, Scientific and Cultural Organization as a World Heritage Site in 1995. Its 46,766 acres include 120 known caves, the two largest of which are Carlsbad Cavern and Lechuguilla Cave, with total passage lengths of 32 miles and 143 miles, respectively, which places them among the world’s longest. Lechuguilla (open only to experienced researchers) is the second deepest limestone cave in the United States at 1,604 feet. More importantly than cave size is the great variety and beauty of the formations and the complexity of the processes that formed them.

Cimarron is Spanish for wild and untamed and originally was used in New Mexico to refer to the wild bighorn sheep, and later to the wild horses and cattle that once roamed throughout the north-central mountains (Pearce, 1965). Today, the sparsely populated Cimarron country in western Colfax County can still be described as wild and untamed with its rugged, timbered mountains (the Cimarron Range), towering cliffs, and the previously unpredictable Cimarron River. The Cimarron River has been tamed somewhat by the Eagle Nest Dam, which controls flooding in the canyon.

Pecos National Historical Park lies in the extreme western portion of San Miguel County, in the broad valley of the Pecos River where the river leaves its deep canyon in the Sangre de Cristo Mountains. The timeless cycles of geologic history are on display in the ancient and modern river deposits in the park. The spectacular cliffs of sedimentary rocks on Glorieta Mesa to the south and the rugged mountains to the north provide a beautiful geologic setting for the ruins and contain rocks that record shifting shorelines and the birth and erosion of mountains.

The site is of enormous cultural and historical significance. The pueblo here was occupied at least as early as 1450. The Coronado Expedition passed through here in 1541 en route to the Great Plains. Spanish missionaries followed soon thereafter. In 1621 the Franciscans built the adobe church whose ruins tower over the park today. In 1680 the Pueblo Revolt put an end to the efforts of the church throughout northern New Mexico; the priest at Pecos was killed and the church laid waste. The site was occupied by the Pecos Indians until 1838.

Sugarite Canyon State Park, once the site of a thriving coal-mining camp, was established as a state park in 1985, but the canyon has been a recreational attraction in northeastern New Mexico for decades. Sugarite Canyon State Park is located about 5 miles northeast of Raton via NM-72 and NM-526 (paved). The elevation in the park ranges from about 6,900 ft to 8,400 ft. This heavily wooded mountain park has something for everyone year round. Trails are maintained through the ruins of the settlement and past coal dumps and mines.

Pancho Villa State Park in Columbus, New Mexico, was established in 1959 “in interest of preservation of the memory of the unique, historical occasion of the last hostile action by foreign troops within the continental United States”. It became the only park in the United States to be named after a foreign invader. The creation of the 60-acre park was a gesture of good will between the United States and Mexico. The town of Columbus has been designated a National Historic Site. Across the street from the park is the privately owned Pancho Villa Museum.

Fenton Lake State Park is in the Jemez Mountains on the west side of the Valles and Toledo calderas, large collapse features that formed during voluminous volcanic eruptions 1.6 and 1.25 million years ago. The landscape around Fenton Lake is characterized by broad, grass-covered valley bottoms that lie between dissected orange-brown to white mesas that are bound by imposing cliffs. The cliffs are formed by the 1.6 to 1.25 million year old outflow sheets of Bandelier Tuff that erupted from the calderas. The south-flowing Rio Cebolla (Spanish word for onion), which feeds Fenton Lake, cut one of the broad valleys after 1.25 million years ago.

Percha Dam and Caballo Lake State Parks, located south of the town of Truth or Consequences, offer striking views of the Caballo Mountains and Red Hills, prominent uplifts in the southern Rio Grande rift. The Percha and Caballo dams were built for the Bureau of Reclamation’s Rio Grande Project in 1918 and 1936–38, respectively. Percha Dam, although only 18.5 feet tall, diverts water into the Rincon Valley, irrigating farmland where much of New Mexico’s famous green chile is grown, along with many other crops. Two miles upstream, the 96-foot-tall and 4,590-feet-wide earth-fill Caballo Dam stores water released from hydroelectric- power generation at Elephant Butte Dam and regulates delivery of that water to downstream users during irrigation season.