Geologic Tour of New Mexico

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.

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.

The Valles Caldera National Preserve is one of the most geologically unique and significant areas in North America. The preserve encompasses much of the Valles caldera, a huge volcanic crater that formed 1.2 million years ago during an enormous volcanic eruption that spread ash over large parts of New Mexico. The caldera is located near the summit of the Jemez Mountains, a large volcanic complex in north-central New Mexico. The Valles caldera exhibits world-class examples of the landforms produced by a very large, explosive volcano, and the preservation and exposure of geological features within the Valles is spectacular. Much of what geologists know about large-scale explosive volcanism began with detailed studies of the rocks in the Valles caldera and Jemez Mountains, and the area continues to draw geologists from around the world. Since the eruption 1.2 million years ago, there has been uplift of the crater floor, followed by the eruption of smaller, younger volcanoes called “domes” within the crater left by the large eruption. Since then, the caldera has from time to time been home to a series of large lakes. This dynamic geological history is responsible for the beautiful and unique landscape that we see in the region today.

Storrie Lake State Park is located four miles north of Las Vegas, New Mexico, and can be reached via New Mexico Highway 518. The 1400-foot long earthen dam that retains the water in Storrie Lake was built under the direction of Robert C. Storrie starting in 1916. Water from the Gallinas River, a southeasterly-flowing river with its headwaters in the Sangre de Cristo Mountains and the main water supply for the community of Las Vegas, is diverted for storage in Storrie Lake. The park offers camping, boating, fishing, beaches, and other water-related activities.

Storrie Lake State Park lies on the boundary between two important physiographic provinces, the Southern High Plains and the Southern Rocky Mountains. The lake is on the High Plains just east of the Rincon Range portion of the Sangre de Cristo Mountains, a sub-province of the Southern Rocky Mountains.

City of Rocks State Park is truly a geologic monument; it is formed by large sculptured rock columns (pinnacles) or boulders rising as high as 40 ft and separated by paths or lanes resembling city streets. About 34.9 million years ago a large volcano erupted, forming the rocks in an instant (geologically speaking); then erosion over millions of years slowly formed the sculptured columns that now provide a natural playground for children and adults alike. City of Rocks State Park was established in May 1952 to preserve this geologic wonder.

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?

Ute Lake State Park was established in 1964 at a cost of approximately $5 million and was named after Ute Creek, one of the tributaries of the Canadian River that is impounded by a dam. The small town of Logan is on the east side of the lake, and the lake extends upstream in both the Ute and Canadian Rivers. It is 25 miles northeast of Tucumcari on US–54, NM–39, and NM–540 and is approximately 20 miles west of the Texas–New Mexico state line. Most of the land surrounding Ute Lake is private. All the water is open to the public. The park is in the Pecos Valley section of the Great Plains physiographic province. It lies on the north edge of the Llano Estacado or “staked plains.”

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.

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.

The craggy gray granodiorite spire of Cookes Peak, the highest point in the Cookes Range at 8,404 feet, is a prominent landmark in southwestern New Mexico. Cookes Spring on the southeast side of the range is one of just a few perennial springs in this part of New Mexico; consequently, this peak was an important marker of water for Native American, Spanish, and American travelers through the region during the 19th century. The peak was named for Captain Phillip St. George Cooke, who led the Mormon Battalion through southern New Mexico during the winter of 1846 while scouting an overland wagon route for the U.S. Army. Later, a Pony Express mail station was established near the spring. Fort Cummings was built nearby in 1863 to protect travelers from Apache attacks; the fort was manned by the U.S. Army off and on until Geronimo surrendered in 1886. Ruins of the Cookes Spring Station of the Butterfield Trail and Fort Cummings are located about a mile south of the present-day Hyatt Ranch.