Mention U.S. volcanoes and most Americans think of Yellowstone, the Pacific Northwest, Alaska and Hawaii. But there is a wealth of volcanic terrain in other parts of the country, especially in the Southwest; New Mexico is rich in Tertiary and Quaternary volcanics.
Perhaps most famous is Shiprock, a volcanic neck that towers 1400 feet above the plains of northwest New Mexico; it is the remnant of a volcano that formed 30 million years ago. The largest volcanic region in the State is the Dantil-Mogollon Field of the southwest quadrant; like the San Juans of Colorado, its ranges were formed from recurrent volcanic eruptions over an extended period of time (in this case, 40-20 million years ago). Sierra Blanca, rising between White Sands National Monument and the city of Roswell, also formed during that period; just northwest of Sierra Blanca is the Carrizozo Lava Flow which developed 5000 years ago and stands out as an elongated, black lake on satellite photos of the State.
Young volcanoes, calderas and lava flows sculpt the landscape of north-central and northeastern New Mexico. Mt. Taylor, a prominant massif northeast of Grants, is a composite volcano of the late Teritary Period, which last erupted 2.5 million years ago. The Taos Plateau, just south of Colorado's San Luis Valley, formed between 5 and 2 million years ago as the Rio Grande Rift began to open; the domes of Mt. San Antonio and Ute Mountain developed during this rifting process and the Rio Grande River has cut a deep gorge through the volcanic plateau, just west of Taos. The Valles Caldera, northwest of Santa Fe, is one of the largest intact calderas on the planet; 10-15 miles wide and up to 2000 feet deep, it is the remnant of a massive volcanic explosion that occured about 1 million years ago.
In northeast New Mexico, the Raton-Clayton volcanic field harbors a mix of cinder cones, lava-topped mesas and shield volcanoes; most prominant is Sierra Grande, a stratovolcano that rises over 2000 feet above the surrounding plains. Northwest of Sierra Grande is Capulin Mountain National Monument, a classic cinder cone which formed 60,000 years ago; a 2-mile toll road takes you to the summit of this young volcano.
