Geologic Tour of New Mexico

Cimarron is Spanish for wild and untamed and originally was used in New Mexico to refer to the wild bighorn sheep, and later to the wild horses and cattle that once roamed throughout the north-central mountains (Pearce, 1965). Today, the sparsely populated Cimarron country in western Colfax County can still be described as wild and untamed with its rugged, timbered mountains (the Cimarron Range), towering cliffs, and the previously unpredictable Cimarron River. The Cimarron River has been tamed somewhat by the Eagle Nest Dam, which controls flooding in the canyon.

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.

A spectacular, eroded anticline and syncline pair lies between the Ojito Wilderness and the village of San Ysidro in north-central New Mexico. The San Ysidro area lies near the intersection of four significant geologic features, including the mildly deformed Colorado Plateau to the west, the Laramide-age (75 to 55 million years old) Sierra Nacimiento uplift to the north, and the late Oligocene to Miocene Rio Grande rift to east. The northeast-trending Jemez lineament, characterized by young volcanism, cuts across all three geologic provinces. The <15 million year old Jemez volcanic field is visible to the northeast, the 2 to 3 million year old Puerco Necks, including Cabezon Peak, are located just to the west, and the 1.5 to 3.3 million year old Mount Taylor volcano can be seen on the skyline to the west.

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 Carrizozo Malpais are one of the youngest volcanic features in the state of New Mexico. The Malpais, which are the 75 km-long black feature in the satellite image, are basaltic lava flows, such as are being erupted today in Hawaii. State highway 380 traverses the Carrizozo Malpais, and this road provides good access to people who want to view, or visit the lava flows. The Valley of Fires Recreation Area is located on the Carrizozo Malpais.

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 country in northwestern New Mexico between Cuba and Farmington is a land of contrast. Flat grassy plains are cut by valleys that expose the multi-colored moonscapes that we call badlands. The largest area of badlands in the region that is readily accessible to the public is the Bisti/De-Na-Zin Wilderness, popularly known as the Bisti Badlands. The badlands are generally exposed in a series of east to west-trending valleys formed by the tributaries that feed to the south to the north-flowing Chaco River.

The many fossils preserved in this region make this one of the best places on Earth to study the fascinating story of the end of the age of dinosaurs and the beginning of the age of mammals. These fossils will not be obvious to casual visitors, but visitors will be instantly struck by the spectacular scenery of this area, which has been featured in books, magazines, calendars, and websites.

Mount Taylor volcano, a prominent landmark that can be seen on the skyline west of Albuquerque, is located about 15 miles northwest of the town of Grants, New Mexico. Mount Taylor Peak, at an elevation of 11,301 feet, stands approximately one mile above the Rio San Jose 12 miles to the south. Mount Taylor volcano is part of a larger, northeast-trending volcanic field that includes Mesa Chivato, a broad plateau located northeast of the cone, and Grants Ridge, located southwest of the cone. Basalt that caps Mesa Chivato and other mesas surrounding Mount Taylor makes up about 80% of the volume of the volcanic field. The Mount Taylor volcanic field lies on the southern flank of the San Juan Basin on the Colorado Plateau and straddles the extensional transition zone between the Colorado Plateau and the Rio Grande rift. The Mount Taylor volcanic field is considered to be part of the Jemez Lineament, a zone of young (< 5 million years old) volcanism aligned along an ancient suture in the 1.7 to 1.6 billion year old Proterozoic basement.

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.

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.