Geologic Tour of New Mexico — Federal Parks, Monuments, & Refuges

Angel Peak, a 7000-foot pinnacle capped by sandstone, is a prominent landmark near Bloomfield in northwestern New Mexico. It is in the northern part of the San Juan Basin, a large structural depression that formed starting about 75 million years ago during compressional Laramide deformation. The San Juan Basin was surrounded by mountainous uplifts to the north (now buried by the 35 to 20 Ma San Juan volcanic field in southwestern Colorado) and to the east that also formed by Laramide-related compression. The sediments that can be seen at Angel Peak National Recreation area were eroded off of the old Laramide highlands and deposited in the basin 50 to 65 million years ago. More recently, over the course of the last 5 million years (or less), the westward-draining San Juan River, a tributary to the Colorado River, has eroded the rocks of the San Juan Basin. Drainages feeding into the San Juan River have carved the scenic landscape we see today.

Aztec Ruins National Monument was established in 1923 to preserve the remarkable remains of an ancestral Puebloan farming community, including a twelfth-century Chacoan great house. The settlement flourished from A.D. 1050–1150, at which time it was one of the largest Puebloan settlements in the Southwest, strategically situated between Mesa Verde to the north and Chaco Canyon to the south. Culturally it is considered a Chacoan outlier, at the northern terminus of one of the prehistoric roads that emanated from Chaco. Later occupants (in the 1200s) are thought to have had closer ties to Mesa Verde.

One of the earliest written eyewitness accounts of Aztec Ruins was provided by geologist John Newberry in 1859, who reported at that time that the walls stood 25 feet high. Both the ruins and the setting are spectacular, but the park is perhaps best known for the reconstructed Great Kiva, which was excavated in 1921 and reconstructed by Earl Morris in the 1930s. It is the only restored great kiva in the Southwest and is accessible to visitors; stepping inside provides a unique glimpse of what these ceremonial structures might have been like when they were intact. The park is now a World Heritage Site.

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.

The Bitter Lake National Wildlife Refuge covers about 38 square miles in central Chaves County, east and northeast of Roswell. Situated on the Pecos River where the Chihuahuan Desert meets the Great Plains, the refuge supports an amazing diversity of flora and fauna, including numerous migratory waterfowl in the winter months. Established in 1937, the refuge includes the new Joseph R. Skeen Visitor Center, which sits on the Orchard Park terrace overlooking floodplain wetlands and the redbed escarpment on the eastern skyline.

Beginning at the Visitor Center are a bike trail, a short walking trail, and an 8-mile auto-tour loop. The loop traverses a Pecos Valley terrace overlooking the floodplain for the first 4 miles. The remainder explores floodplain environments, from an abandoned Pecos River meander oxbow lake to the low-lying wetlands. The more adventuresome visitors can explore the refuge’s north tract, which includes the Salt Creek Wilderness. Here, one can hike to the mouth of Salt Creek at the Pecos River and continue onto some of the refuge’s many sinkholes, including the scenic Ink Pot.

West of the flocks of birds and birdwatchers along the wetlands of the Rio Grande, a story of cataclysmic volcanic eruptions, ancient dune fields, and long-gone towering mountains lie quietly awaiting visitors to the Bosque del Apache National Wildlife Refuge. The Chupadera Wilderness Trail and the Canyon Trail traverse this geologic record in the contemplative solitude of a wilderness setting, affording “rockwatchers” a quick trip through millions of years of Earth history.

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.

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.

Visitors to Chaco Canyon, having crossed corrugated expanses of the San Juan Basin to get there, wonder that such a striking canyon exists at all in a landscape otherwise dominated by rolling sand-covered uplands, small mesas, bluffs, and badland-bordered shallow valleys. The canyon’s size (500 feet deep, 2,100 feet wide, 15 miles long), elevation (6,100 feet), orientation (northwest), and noticeable differences in layered rock sequences and landforms on either side arouse further curiosity. How could the current tiny ephemeral stream cut such a canyon unless past climate was different from present semiarid conditions? Moreover, how could prehistoric peoples, let alone park visitors and personnel, live in this remote area with few obvious resources?

El Malpais National Monument is part of the Zuni–Bandera volcanic field in west-central New Mexico. It is one of the best places in the lower forty-eight United States to view young, Hawaiian-style volcanic deposits. There are over one hundred individual volcanoes in this volcanic field, as well as the many associated lava flows, cinder cones, shield volcanoes, and lava tubes. The young age of the volcanism (the youngest eruption occurred just 3,000–4,000 years ago) along with the dry local climate means that the rocks and their volcanic features are beautifully preserved.

The name El Malpais comes from early Spanish explorers and translates literally to “the bad country,” so named because of the extreme roughness of the lava flow surfaces. The Zuni–Bandera volcanic field was recognized as an important geological feature as early as the 1930s, when the area was first proposed as a national monument. However, El Malpais National Monument and the associated El Malpais National Conservation Area weren’t formally established until 1987.

El Morro, which means "bluff" or "headland" in Spanish, is an imposing cliff made of Middle to Late Jurassic (155 to 165 million years old) Zuni Sandstone capped by Late Cretaceous Dakota (~95 to 96 million years old) sandstone and shale. Travelers, including Native Americans, Spaniards, and citizens of the United States, have carved their symbols, names, messages, and dates of their passage into the soft cross-bedded Zuni Sandstone for centuries.

Fort Union was established in 1851 to provide a much-needed military presence to travelers on the Santa Fe Trail. The trail had been active since 1821, when much of what is now New Mexico became U.S. territory in 1848, at the end of the Mexican War. Fort Union’s spectacular location on the western edge of the Great Plains was a strategic one, sited as it was near the junction of the Mountain Branch of the Santa Fe Trail with the Cimarron Cutoff. Between 1851 and 1891 Fort Union contained the largest American military presence in the Southwest; over 1,600 troops were stationed there in 1861. In 1878 the railroad came to New Mexico over Raton Pass, and by 1891 Fort Union had been abandoned. Visitors to the national monument can see some impressive historic ruins, including the foundations and adobe walls of many of the original buildings, and remnants of the deeply-rutted Santa Fe Trail.

Ghost Ranch is located approximately 38 miles northwest of the town of Española, New Mexico, just north of U.S. Highway 84, and is run by the Presbyterian Church as a conference center. It has facilities for lodging and camping, as well as paleontology and cultural museums. It lies in the Chama Basin, a broad shallow basin along the eastern margin of the Colorado Plateau in the transition between the Plateau and the Rio Grande rift.

Gila Cliff Dwellings National Monument is in the Mogollon Mountains approximately 44 miles north of Silver City, New Mexico. Gila Cliff Dwellings National Monument was established in 1907 and is one of the nation’s oldest monuments. The monument lies within the Mogollon-Datil volcanic field; volcanic eruptions from this field covered 40,000 km2 of southwestern New Mexico and southeastern Arizona with lava and ash flow tuffs 40 to 24 million years ago.

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.

Kasha-Katuwe Tent Rocks National Monument is on the southeast side of the Valles and Toledo calderas, large collapse features that formed during voluminous eruptions in the Jemez Mountain volcanic field 1.61 and 1.25 million years ago. Tent Rocks encompasses a fascinating landscape in the southeastern Jemez Mountains. Kasha-Katuwe means 'white cliffs' in Keresan, the traditional language of the nearby Pueblo de Cochiti. Delicately layered sand, gravel, volcanic ash, and tuff of the Peralta Tuff Member of the Bearhead Rhyolite and sand and gravel of the Cochiti Formation, which are older units (2 to 6 Ma) in the Jemez Mountain volcanic field, have been erodedinto fragile to robust spires with balanced rocks perched on top. The hoodoos, erosional cones, and pedestal rocks that characterize Tent Rocks form as the result of differential erosion.

Organ Mountains–Desert Peaks National Monument is a large, diverse and recently established park. It has four separate geographic areas: the Organ Mountains, the Doña Ana Mountains, the Potrillo Mountains, and the “Desert Peaks." This tour deals only with the Organ Mountains. The geology of the Doña Mountains area is briefly discussed in the tour of Fort Selden–Leasburg Dam. The Potrillo Mountains include the remote Potrillo volcanic field and are covered in the Kilbourne Hole tour. The "Desert Peaks" includes the Robledo Mountains and Sierra de las Uvas. The Robledo region is described in the tour of the "Prehistoric Trackways National Monument" (a separate, but contiguous national monument).

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.

Petroglyph National Monument is located on Ceja Mesa on the west side of Albuquerque. The monument is best known for the estimated 25,000 rock art images carved into basalt erupted from the approximately 200,000-year-old Albuquerque volcanic field. Using stone chisels and hammer stones, the ancestors of the Puebloan Indians cut most of the petroglyphs into the desert varnish coating the basalt between 1300 and 1680 A.D. A few of the markings are much older, dating back to perhaps 2000 B.C. Spaniards and later generations of Albuquerque inhabitants have produced younger petroglyphs with more modern themes. The monument, created in 1990, includes about 17 miles of petroglyph-covered basalt cliffs and five extinct volcanoes.

The Prehistoric Trackways National Monument is located in the Robledo Mountains just northwest of Las Cruces in Dona Ana County, south-central New Mexico. It contains rocks of Permian age, from the Late Paleozoic Era. They are composed of sediments deposited about 280 million years ago, before the age of the dinosaurs. These rocks contain major deposits of fossilized footprints made by numerous amphibians, reptiles, insects, and crustaceans, as well as plants and petrified wood. Some scientists have called these features the most scientifically significant Permian tracksites in the world. These fossils provide important information about animal behavior in this ancient tropical environment on the edge of the supercontinent Pangea.

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.