Geologic Tour of New Mexico

Jemez State Monument is in scenic Cañon de San Diego, which is located to the southwest of the Toledo and Valles calderas, large collapse features that formed during voluminous volcanic eruptions 1.6 and 1.25 million years ago in the Jemez Mountains. The monument lies near the mouth of Church Canyon, a tributary to the Jemez River within Cañon de San Diego. Two main rock units, the Pennsylvanian Madera Group and Permian Abo Formation, are exposed in and adjacent to the monument (Figures 3 and 4). Both limestone from the Madera Group and sandstone from the Abo Formation were incorporated into the walls of the 15th century pueblo and the 17th century Spanish mission at Jemez State Monument. Large rounded boulders of early Jemez volcanic field basalt and andesite lavas that were eroded from the high cliffs of Cañon de San Diego and carried by the Jemez River and flash floods in Church Canyon to the vicinity of the monument are also included in the walls of the structures.

Lake Valley was a silver-manganese mining district during the late 19th century. Silver was discovered in 1876, and the area was extensively mined until the silver crash in 1893. The Lake Valley district includes the famed Bridal Chamber, which was found in 1881. The Bridal Chamber was among the richest silver deposits ever mined. The spectacular Bridal Chamber ore body composed of silver chlorides and silver bromides was nearly two hundred feet long and 25 feet thick. Chlorargyrite (cerargyrite; AgCl), the main high-grade ore taken from the Bridal Chamber, was mined out by the late 1880s. Manganese minerals, mainly manganite and pyrolusite, were mined in the Lake Valley district during and after World War II. No significant mining activity has occurred in the area since 1959.

Apache Hill, located about 1.5 miles north of the ghost town of Lake Valley on the east side of New Mexico Highway 27, is one of the best fossil collecting sites in southern New Mexico. The fossils are in the Mississippian Lake Valley Limestone. Good outcrops are located just below the top of the hill. Intact fossils, including brachipods, bryozoans, crinoid plates and calyxes, and horn corals, weather out of the shaly limestone in this particular area. Other fossils that can be found include gastropods, pelecypods, cephalopods, and trilobites.

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.

Bluewater Lake State Park lies at an elevation of 7,400 ft in Las Tuces Valley near the Continental Divide in the Zuni Mountains. The park is between Gallup and Grants along I–40, 7 mi southwest of Prewitt via NM-412. A forest of cottonwoods, piñon, and juniper surrounds the lake. The Navajos knew the area as “large cottonwood trees where water flows out” (Julyan, 1996). It became a state park in 1955. Bluewater and Cottonwood (Azul) Creeks feed the lake. The lake itself is formed by an arched dam 90 ft high and 500 ft long (Robinson, 1994) that impounds 38,500 acre-ft of water. The last time water spilled over the dam was in 1941. The dam is convex in the upstream direction for increased strength, and it is at the mouth of Bluewater Creek in a steep-walled canyon. An overlook at the end of the road through the park facilities offers an excellent view of the dam and canyon. A primitive hiking trail leads down into the canyon below the dam.

The New Mexico Department of Game and Fish maintains a permanent pool of water for fish and periodically stocks the lake with rainbow trout and channel catfish. Indeed, the lake is blue, as the name implies. It is well known to ice-fishermen during the winter. Power and sail boating, hiking, water skiing, wind surfing, and swimming are possible recreational activities in addition to fishing, camping, picnicking. Care should be taken driving in wet weather along the north side of the lake because of muddy conditions. Not all 25 mi of shoreline belong to the state park; some land surrounding the lake belongs to private individuals, Indian tribes, and U.S. National Forest. All water, however, is open to the public.

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.

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.

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.

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.

Villanueva State Park lies in the western portion of San Miguel County and straddles the Pecos River where it enters a narrow canyon one mile south of the village of Villanueva. At the park, reddish-yellow and tan cliffs of sandstone tower up to 300 feet above the park and the river. The rocks in these cliffs tell a geologic story of ancient landscapes and seas. Younger gravels on benches along the river and the topography of canyon itself carry this narrative to the present day.

The Living Desert Zoo and Gardens State Park was established in 1971 to preserve and display the wide variety of animals, plants, and natural environments found in the Chihuahuan Desert. Located north of Carlsbad on US–285, Living Desert Zoo and Gardens State Park offers a variety of outdoor and indoor exhibits depicting the natural, geologic, archaeological, historical, and mineral wealth of the area.