Geologic Tour of New Mexico

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.

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.

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.

Brantley Lake State Park on the Pecos River was officially opened in November 1989. The park lies 12 mi north of Carlsbad via US–285. Brantley Lake is designed to hold 348,540 acre-ft of water. Although the primary functions of the lake are flood control and water storage for irrigation and water commitments to Texas and Mexico, the lake is best known for its water recreation and fishing. The most common fish stocked by the New Mexico Department of Game and Fish include largemouth bass, walleye, channel catfish, trout, sunfish, white bass, bluegill, and crappie. Brantley Wildlife Management Area lies south of the dam, as well as north of Brantley Lake, in the area once occupied by Lake McMillan. The Pecos River valley is a major waterfowl migration route, and many species of birds are present on and near the lake throughout the year.

Kilbourne Hole in south-central New Mexico is a classic example of a maar crater that formed as a result of the explosive interaction of hot basaltic magma with groundwater during a volcanic eruption. When the steam-saturated eruption column that forms during an explosive event gravitationally collapses, a ring-shaped surge travels radially outward along the ground away from the vent. The stratified, cross-bedded pyroclastic surge deposits around the crater at Kilbourne Hole are spectacular. The surge deposits may have formed as a consequence of a series of steam explosions during the emplacement of the basalt.

Kilbourne Hole is unique because of the remarkable abundance of both crustal and mantle (peridotite/olivine-bearing) xenoliths that are in basalt bombs ejected during the eruption. Xenoliths are inclusions of pre-existing rock derived from country rocks, in this case, pieces of mantle and crust, that were incorporated into the mafic magma as it moved from a depth of about 40 miles (60 km) to the surface.

Cabezon Peak is one of the best-known and most visible landmarks in northwest New Mexico. This giant volcanic plug is visible for tens of miles in all directions, and as far away as Placitas. Cabezon means “big head” in Spanish, and it is aptly named. It is the largest of several dozen widely scattered rocky monoliths, called the Rio Puerco necks. Rising above the Rio Puerco valley floor, they are some of the best-preserved examples of volcanic necks in the world. The craggy black peaks stand in sharp contrast to the sparsely vegetated, buff-colored lowlands from which they emerge. Mt. Taylor looms majestically to the southwest, Mesa Prieta borders the valley to the east, and the Jemez Mountains are visible to the north. This starkly beautiful landscape is unique in New Mexico. At an elevation of 7,786 ft, Cabezon Peak towers more than 1,100 ft above its base, and 2,000 ft above the Rio Puerco nearby.

Smokey Bear Historical Park is in the center of the town of Capitan. In May 1950, a raging forest fire blackened approximately 17,000 acres of the Capitan Mountains in the Lincoln National Forest in central New Mexico. As forest fire fighters brought the blaze under control, a small black bear cub was found clinging to the remains of a charred tree. First aid was administered to the badly burned bear cub and he was sent to Santa Fe for further treatment. Although the fire fighters didn’t realize it then, a national symbol had been born. The story of the bear cub was told in newspapers and on radio throughout the country. The cub, named Smokey Bear, went to the National Zoo in Washington, D. C. and became the living symbol for fire prevention. Through many successful campaigns, Smokey not only was responsible for reducing the number of man-made forest fires but he also raised more than $27 billion through donations in the past 40 years.

The 64-mile stretch of narrow gauge railroad track between Antonito, Colorado and Chama, New Mexico was originally built in 1880 as part of the Denver and Rio Grande Western Railroad. This rail line provided much-needed transportation and freight service between Denver and mining camps in Silverton during the late nineteenth and early twentieth centuries. When the Federal Government discontinued the use of the silver and gold standard to back American currency, the "Silver Panic" in 1893 caused the closure of many of the mines in the Silverton area. The railroad continued to operate with revenues from transportation of livestock, timber, and farm produce. The oil and gas industry in the Four Corners region also utilized the railroad. Demand for rail transportation in this region waned by the mid-twentieth century. Passenger service on the Denver and Rio Grande Western Railroad ended in 1951 and freight service ended in 1968. Railroad enthusiasts and legislative bodies in New Mexico and Colorado recognized the scenic splendor of the train route between Chama and Antonito. Through a joint effort, the Cumbres and Toltec Scenic Railroad, complete with coal-powered steam engines carrying tourists in railcars on refurbished narrow gauge tracks, was created in 1970 to preserve this historic and picturesque section of railroad.

Spectacular exposures of Permian Yeso Group overlain by tilted and faulted late Oligocene to Pleistocene sedimentary and volcanic rocks are preserved at the head of Church Canyon to the east of Jemez Springs in Cañon de San Diego in the southwestern Jemez Mountains. This area is on private land owned by the Catholic Church; therefore, permission must be obtained from the church offices in Jemez Springs before visiting these outcrops.

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.