National Park Service
This small park, established in 1916 by presidential proclamation, offers a close-up view of one of the most perfectly preserved cinder cones in North America. The road to the summit provides access to the summit crater, and if you have ever wanted to walk into a volcano, Capulin Mountain is one of the few places you can do so. A 0.2-mile-long trail from the summit parking lot descends to the vent at the bottom of the crater. The view from the crater rim encompasses all of northeastern New Mexico as well as parts of Texas, Oklahoma, and Colorado.
(WGS 84 or NAD 83)
Capulin Volcano National Monument is located on NM 325 about 3 miles north of US 64/87, between the villages of Capulin and Folsom. It is administered by the National Park Service. There is a fee for admission, but the drive to the summit is well worth it. A small Visitor Center and campground are maintained near the park entrance.
The park is on the western edge of the Great Plains. The Sangre de Cristo Mountains (the southernmost of the Southern Rocky Mountains) are barely visible on the far western horizon. Capulin Mountain is part of the Raton–Clayton volcanic field, which covers over 8,000 square miles. Much of northeastern New Mexico is covered by vast sheets of lava that flowed from more than a hundred now-extinct volcanoes found in this region. The volcanic eruptions started about 9 million years ago and continued intermittently until about 37,000 years ago. The volcanic rocks here are mostly basaltic in composition and consist of lava flows and cinder cones, piles of cinders and volcanic centers from which many of these eruptions issued forth. Capulin Mountain, which erupted about 54,000 years ago, is one of the youngest and most perfectly preserved of these cinder cones.
The Rock Record
The oldest rocks known in northeastern New Mexico are the Precambrian granites, gneisses, and schists exposed in the Sangre de Cristo Mountains, west of Raton. The park itself is entirely composed of Capulin-age basalts, which in general range in age from 1.45 million years old to only 37,000 years old. Capulin itself is 54,000 years old, though there are younger features nearby, including Baby Capulin (45,000 years old). Nearby, in the valley of the Dry Cimarron River, there are impressive exposures of Mesozoic rocks, including the brightly colored shales of the Triassic Dockum Group, dune deposits of the Jurassic Entrada Sandstone, and Cretaceous sandstones of the Dakota Group. It is in Dakota Group sandstones that the dinosaur footprints at Clayton Lake State Park are found. Just outside the city of Raton on Goat Hill, the Cretaceous–Tertiary boundary is visible in exposures of the Raton Formation. The famous iridium-enriched clay layer, which marks the Cretaceous–Tertiary boundary worldwide, is exposed here, and at a few other places in northwestern New Mexico. The Tertiary Ogallala Formation, which holds up the High Plains, is exposed throughout much of this corner of the state.
Recent isotopic age determinations on the volcanic rocks of this region have allowed us to unravel the eruptive history of the Raton–Clayton volcanic field, which consisted of three major phases of eruption. The first major phase of volcanic activity (the Raton-age basalts) began about 9 million years ago, when basalts flooded down broad stream valleys that today are high mesas: Fisher’s Peak, Horse Mesa, Johnson Mesa, and Oak Canyon (Kelleher) Mesa, forming the platform for the younger Emery Peak volcano. These early major eruptions ended about 8 million years ago.
As part of this same phase of volcanic activity, outpourings of basalt 7.3 million years ago produced the linear Larga Mesa and Kiowa Mesa flows, which are tiny in comparison with the earlier eruptions. This was followed 6.5 million years ago by small volume rhyolitic eruptions in a band from Red Mountain and Towndrow Mountain on Johnson Mesa south to Laughlin Peak and Palo Blanco Mountain. These rhyolitic eruptions were followed by more massive floods of basalt that produced Mesa de Maya, mostly in southeastern Colorado, and the Yates flows at the southernmost part of this volcanic field. Both flows erupted about 5 million years ago and are included in the Raton basalts. Colorado’s Mesa de Maya flow extends across the northeast corner of New Mexico into the northwest corner of Oklahoma.
This was followed by the eruption of two very different and distinct types of magma. At 4 million years ago, Bellisle Mountain (Dale Mountain on some recent maps) erupted lava that flowed off Johnson Mesa and down the Dry Cimarron River to a few miles past Folsom. Other vents of this composition are found near Capulin Mountain and, although not dated, are presumed to be about the same age. The last of the Raton-age basalts erupted 3.6 million years ago and cap Bartlett Mesa above the city of Raton.
Then the largest eruptions of the region began. The Clayton-age basalts constitute the second of three major periods of eruption. The first eruption of this Clayton-age sequence was of Sierra Grande, which covers 43 square miles and rises 2,100 feet above the surrounding plain. Dates from five different locations on the mountain (including the summit crater) range from 2.63 to 3.85 million years. The huge Clayton Basalt flows then poured forth; today they extend eastward from Sierra Grande for 40 miles. They cover 295 square miles and occupy many ancient drainages that reflect the trends of the earlier Ogallala drainages. The Clayton basalts range in age from 2.3 to 2.4 million years. Rabbit Ear Peak, west of the city of Clayton, is one of a line of east-southeast-trending vents for this episode of eruption.
The Capulin basalts represent the third and final phase of volcanism in this region; they range in age from 1.45 million years old to only 37,000 years old—practically yesterday, geologically speaking. Gaylord (Carr) Mountain and Yankee Volcano basalts erupted 1.45 and 1.1 million years ago, respectively. Capulin Mountain, the most prominent cinder cone from this phase of volcanism, erupted 54,000 years ago.
Road to the Summit — The road to the summit of Capulin includes several pullouts where one can stop and examine the inclined layers of cinders that make up the volcano. The view from the summit is quite spectacular, offering a glimpse of portions of four states, and of the many volcanic features surrounding Capulin Mountain. Below the parking area, near the base of Capulin Mountain, is the vent out of which the basaltic lava flowed. The tree-covered rim that surrounds the vent is part of the wall that formerly enclosed the lava pool. Turning around, one can look into the crater from which the gases escaped and blew the molten lava into the air, where it cooled and fell back to Earth, forming the present cone.
Crater Rims — An interesting feature of many of the cinder cones in the area is the asymmetry of the crater rims, which tend to be lower on the southwest or west sides. This breaching of the craters suggests that when the volcanoes were active, the prevailing winds from the southwest to west caused the cinders to accumulate on the opposite downwind flank of the cone. The rim of Capulin is higher on the far side because that was the downwind side at the time of eruption. A trail around the rim of the crater gives spectacular views in all directions, as well as an opportunity to see birds and other wildlife. Another trail leads to the floor of the crater, about 415 feet below the highest point on the rim. Both trails are fairly short and well worth the walk.
Pressure Ridges— The lava flow southwest of the base of Capulin Mountain has prominent pressure ridges, which formed at the time of eruption. These features formed when the upper surface of the flows cooled, becoming rigid while the liquid lava below the surface continued to flow, creating folds or ridges in the upper surface.
Sierra Grande — The large mountain to the south is Sierra Grande, by far the largest and most imposing volcano in this region. It is 8 miles in diameter and rises nearly 2,100 feet above the plains. Volcanic breccias are present around the crest, but no true crater remains from its eruption about 2.5 million years ago. At an altitude of 8,720 feet above sea level, Sierra Grande is high enough to intercept the summer rain clouds, so that the grass on it is wet and green, even when the surrounding plains are dry and brown.
Mud Hill and Baby Capulin— The big volcano about one mile to the north (with trees on far side) is Mud Hill. Behind it, another mile, is Baby Capulin Mountain (bare cone into its crater we can see). Baby Capulin is 45,000 years old.
High Plains of Northeastern New Mexico: A Guide to Geology and Culture by William R. Muehlberger, Sally J. Muehlberger, and L. Greer Price, Scenic Trip # 19, New Mexico Bureau of Geology and Mineral Resources, 2005.
Capulin Volcano National Monument — U.S. National Park Service website