Geologic Tour of New Mexico

he Ship Rock landform, located in northwestern New Mexico, is the remnant of an explosive volcanic eruption that occurred around 30 million years ago. The main part of the landform is 600 meters high, and 500 meters in diameter. Ship Rock, known as Tse Bitai, or "the winged rock" in Navajo, is a volcanic neck, or the central feeder pipe of larger volcanic landform which has since eroded away. The neck is composed of fractured volcanic rock, or breccia, crosscut by many thin veins of lava. Ship Rock is composed of an unusual, highly potassic magma composition called a "minette", thought to form by very small degrees of melting of the earth's mantle. Ship Rock was probably 750 to 1000 meters below the land surface at the time it was formed, and has since gained its prominent form due to erosion of surrounding rocks.

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.

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.

Leasburg Dam State Park is adjacent to Fort Selden State Monument 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.

Sumner Lake State Park is approximately 16 miles northwest of Fort Sumner on US-84 and NM-203 at the junction between the Pecos River and Alamogordo Creek. It was established in 1960 as Alamogordo Reservoir; the name was changed in 1974 to avoid confusion with the growing town of Alamogordo in south-central New Mexico. Sumner Lake was named after nearby Fort Sumner, which honors Col. Edmund Vose Sumner, who commanded the 9th Military District and built Forts Craig, Union, Thorn, and Fillmore (Julyan, 1996). Alamogordo (Spanish for big cottonwood) Creek was named after the abundant, large cottonwood trees along the river valleys.

Caballo Lake State Park is located approximately 14 miles south of the town of Truth or Consequences. Caballo Reservoir is on the Rio Grande in south-central New Mexico east of Interstate 25 between Socorro and Las Cruces.

Camping, picnicing, and boating facilities are available at this state park. Caballo Lake State Park is the third largest state park in New Mexico. This park is generally quiet compared to Elephant Butte State Park to the north.

The Gilman Tunnels are on NM 485 along the Rio Guadalupe in the southwestern Jemez Mountains, approximately 5 miles northwest of the intersection of NM 4 and NM 485. Two narrow and unusually high tunnels were cut through Precambrian granite in the 1920s to facilitate passage of logging trains through this particularly rugged and constricted section of Guadalupe Canyon, known as the Guadalupe Box. Logs that were harvested in the western Jemez Mountains in the 1920s were taken by narrow-gauge railroad to a sawmill in Bernalillo. The tunnels were enlarged in the 1930s to accommodate logging trucks. Logs were hauled out of the mountains and then loaded on trains at Gilman logging camp, which was established in 1937 about two miles south of the tunnels. The railroad was shut down by flooding along the Jemez and Guadalupe Rivers in 1941. The highway now occupies the old railroad bed. Aside from providing access to the Guadalupe Box itself, NM 485 provides an unparalleled view of the stratigraphy of Guadalupe Canyon.

Bandelier National Monument, best known for its cultural significance and well-preserved cliff dwellings, also offers visitors a chance to observe the volcanic geology that made the area so well-suited for prehistoric Puebloan civilization. The rock in most of the monument is Bandelier Tuff, a light-colored, soft volcanic rock that formed during two very large, explosive volcanic events that occurred 1.6 and 1.2 million years ago. These two large eruptions, which together produced hundreds of cubic miles of rock, created the thick sheets of white-to-pink volcanic ash and ignimbrite seen in cliffs in many parts of the Jemez Mountains. This rock, composed of pumice, ash, and volcanic crystals, is not very strongly cemented, and, in many places, has a chalky texture. The soft and easily eroded nature of this rock allowed the deep Frijoles Canyon to be incised by Frijoles Creek, and then provided the perfect setting for the prehistoric Puebloan civilization. These people carved cliff dwellings and building blocks for structures from the volcanic rocks. They occupied this idyllic setting until around A.D. 1,100, when climate change or a combination of factors forced them to abandon the dwellings, the remains of which we see today.

This small park, established in 1916 by presidential proclamation, offers a close-up view of one of the most perfectly preserved cinder cones in North America. The road to the summit provides access to the summit crater, and if you have ever wanted to walk into a volcano, Capulin Mountain is one of the few places you can do so. A 0.2-mile-long trail from the summit parking lot descends to the vent at the bottom of the crater. The view from the crater rim encompasses all of northeastern New Mexico as well as parts of Texas, Oklahoma, and Colorado.

The Salinas Pueblo Missions National Monument is located in the westernmost part of the Great Plains province, in Torrance County near Mountainair. The monument consists of three small and widely separated units — Abó, Gran Quivira, and Quarai.

When the Spanish arrived in this area in the late 1500s they found multiple inhabited pueblos, and they referred to this area as the Salinas District. However, because of drought, famine, disease, and Apache raiding, by the late 1600s the entire Salinas District was depopulated of both Native Americans and Spaniards. What remains today are reminders of this earliest contact between Pueblo Indians and Spanish colonists: the ruins of three mission churches and a partially excavated pueblo that Juan de Oñate called Las Humanas or, as it is now known, Gran Quivira Pueblo.