Geologic Tour of New Mexico

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.

Rockhound State Park lies in the Little Florida Mountains southeast of Deming, New Mexico. It was established in 1966 as the first park in the United States that allowed collecting of rocks and minerals for personal use. Each visitor is allowed to collect as much as 15 lb of rocks and minerals from the 1,100-acre park; mineral dealers are not allowed to collect for sale. Rockhound State Park actually consists of two separate units, the main park and Spring Canyon Recreation Area. Spring Canyon lies in the northern Florida Mountains, south of the main park, and is open for day use only from Easter through November.

Sevilleta National Wildlife Refuge (NWR) is located in central New Mexico about 15 miles north of Socorro. The refuge spans the Rio Grande valley from the Sierra Ladrones on the west to the Los Pinos Mountains on the east, an area of approximately 30 miles by 15 miles, encompassing 230,000 acres. The area was designated a Spanish land grant, Sevilleta de la Joya, in 1819. The land grant was sold in 1928 to Socorro County and then, in 1936, to General Thomas D. Campbell, under whom it became a ranch for sheep and cattle. The Campbell Family Foundation donated the land to the Nature Conservancy in 1973, which then passed it on to the U.S. Fish & Wildlife Service to become a national wildlife refuge dedicated to preservation and enhancement of the integrity and natural character of the land. The transfer stipulated that the land should undergo natural processes of succession, including floods and fires, without human interference. Thus, most of the refuge has very limited public access, but the Mesa View Trail west of the Visitor Center is open for hiking at least five days per week.

The Zuni-Bandera volcanic field, in northwest New Mexico, has had many episodes of basaltic eruptions over the last million years. The youngest lava flow in the field is the McCartys flow, which is only 3000 years old, one of the youngest volcanic features in the 48 contiguous United States! The Zuni-Bandera volcanic field has produced many basaltic lava flows, some with a-a characteristics, and some that are paheohoe. There are also a number of well-preserved cinder cones that can be visited, as well as many lava tubes, some of which contain perennial ice. The Zuni-Bandera volcanic field is an excellent site for studying physical volcanology of basaltic magmatic systems.

The Tyrone mining district, the second largest porphyry copper deposit in New Mexico, is located 10 miles southwest of Silver City in the Burro Mountains of southwestern New Mexico. Native Americans initially mined turquoise from the area around 600 AD. Underground mining was established in the early 1860s and the current mode of mining, open-pit stripping, began in 1968. The mine became part of Freeport-McMoRan in 2007. Parts of the pit are currently being reclaimed.

The country in northwestern New Mexico between Cuba and Farmington is a land of contrast. Flat grassy plains are cut by valleys that expose the multi-colored moonscapes that we call badlands. The largest area of badlands in the region that is readily accessible to the public is the Bisti/De-Na-Zin Wilderness, popularly known as the Bisti Badlands. The badlands are generally exposed in a series of east to west-trending valleys formed by the tributaries that feed to the south to the north-flowing Chaco River.

The many fossils preserved in this region make this one of the best places on Earth to study the fascinating story of the end of the age of dinosaurs and the beginning of the age of mammals. These fossils will not be obvious to casual visitors, but visitors will be instantly struck by the spectacular scenery of this area, which has been featured in books, magazines, calendars, and websites.

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.

Fort Selden State Monument is adjacent to Leasburg Dam State Park on NM–157 (Fort Selden Road) at the Radium Springs exit on I–25, north of Las Cruces. It is an area rich in both geologic and human history. The location was an ancient Indian campground and a crossing point for Spanish caravans headed across the Jornada del Muerto. Living-history demonstrations of 19th century military life at Fort Selden highlight many weekends during the summer. Wildlife viewing, especially bird watching, is popular at the state park. A bird list is available from the park office. In the winter months many species of ducks, teals, snow geese, cranes, herons, egrets, swans, and pelicans migrate through the southern Rio Grande valley and can be seen at the state park. Numerous raptors, including owls, turkey vultures, eagles, and hawks, can be seen hunting in the area. Small mammals common to the park include rabbits, squirrels, chipmunks, rodents, coyotes, and foxes.

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.

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.