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.

Elephant Butte Lake State Park is located approximately 5 miles north of the town of Truth or Consequences. Elephant Butte Reservoir is on the Rio Grande in south-central New Mexico east of Interstate 25 between Socorro and Las Cruces. The 301-feet high and 1,674-feet long concrete dam across the Rio Grande that created Elephant Butte Reservoir is the largest dam in the state of New Mexico. Elephant Butte Reservoir was the largest man-made reservoir in the world when the dam was completed in 1916. The dam is considered a National Historic Civil Engineering Landmark, primarily because the construction of this dam marked the first civil engineering project designed for international distribution of water.

This is a virtual field trip to the classic Permian reef complex and other geologic features of the Guadalupe Mountains, including those in Carlsbad Caverns National Park and Guadalupe National Park in Texas. It contains an introduction to the geology of the Permian reef complex plus several roadlogs with diagrams and photographs, as well as an extensive bibliography in order to provide a balanced presentation for a geology student audience.

Cerro Pedernal, one of the most recognized landmarks in north-central New Mexico, is located in the northern Jemez Mountains . Cerro Pedernal lies in the transition zone between the Colorado Plateau and the Rio Grande rift. Typical, relatively flat-lying, Colorado Plateau Mesozoic stratigraphy is exposed at the base of the mountain, while younger Cenozoic basin fill sediments underlie the shoulders of the peak. The andesite and basalt flows capping Cerro Pedernal, which give the mountain its distinctive flat top, were erupted from the northern Jemez volcanic field about 8 million years ago. The lava flows and underlying rocks on Cerro Pedernal and on mesas to the southeast have since been faulted and down-dropped to the southeast by as much as 1870 feet (570 m) during Rio Grande rift extension in the last 8 million years.

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.

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.

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.

Lincoln State Monument encompasses most of the community of Lincoln, New Mexico and commemorates the lives of many of the key players in the Lincoln County War (1878-1881). Lincoln, which is located in south-central New Mexico, can be access via U.S. Highway 380. The community was originally named La Placita del Rio Bonito (village of the pretty river); the stream that runs along the north side of the village is called the Rio Bonito. The legislature of the territory of New Mexico, encouraged by local citizenry, renamed the village Lincoln in 1869, in honor of President Lincoln, who was assassinated 4 years earlier.

The main visitor’s center for the monument is located near the east end of town on the north side of the highway. The Lincoln County Courthouse Museum, which highlights the escapades and legal troubles of William H. Bonney (Billy the Kid), is the other main attraction associated with the monument. The courthouse is on the west end of town on the south side of the highway. Admission tickets ($5 for adults, children under 16 free) may be purchased at the visitor’s center or at the courthouse. Other buildings that can be visited as part of the tour include the Montaño store, the San Juan mission, the torreon, the post office and Turnstall Museum, and Dr. Wood’s home.

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.

Navajo Lake State Park, which includes the second largest reservoir in the state, is in the Four Corners region of northwestern New Mexico, 25–30 mi east of Bloomfield. Navajo Dam was built in 1958–1962 by the U.S. Bureau of Reclamation for flood control, recreation, sediment control, and to provide water to the Navajo Indian Irrigation Project, one of the many projects of the basin-wide Colorado River Storage Project established in 1956. The Navajo Indian Irrigation Project, founded in 1962, provides water for approximately 110,000 acres of farmland on the Navajo Indian Reservation. The dam traps water from the San Juan, Piedra, and Los Pinos Rivers and Sambrito and La Jara Creeks. The dam consists of an earth- and rock-filled structure that extends 3,648 ft across the San Juan River and is 402 ft high at an elevation of 6,085 ft. In the reservoir area, five cemeteries, 4 miles of Colorado state highway, and 6.5 miles of railroad were relocated. The city of Farmington has operated a 30-megawatt hydroelectric power plant at Navajo Dam since 1987. When full, the reservoir covers 15,590 acres.