Geodiversity refers to the full variety of natural geologic (rocks, minerals, sediments, fossils, landforms, and physical processes) and soil resources and processes that occur in the park. A product of the Geologic Resources Inventory, the NPS Geodiversity Atlas delivers information in support of education, Geoconservation, and integrated management of living (biotic) and non-living (abiotic) components of the ecosystem.
Geologic Features and Processes
Capulin Volcano National Monument (NM) preserves Capulin Volcano, one of the tallest and most perfectly-formed cinder cones in North America. The volcano stands 8,182 ft (2,494 m) above sea level and about 1,300 ft (400 m) above the surrounding plain. Cinder cones are small volcanoes formed by the accumulation of cinders (scoria) around a volcanic vent. Cinder cones form during mildly explosive eruptions of basalt that are rigorous enough to eject lava fragments and ash into the air, but not form large eruptive columns. Lava flows are commonly erupted from the base of cinder cones during eruptions. Four such lava flows were erupted from Capulin Volcano.
Capulin is one of the most accessible cinder cone volcanoes in the country, and is one of only three such volcanoes with paved roads to the top. The 2-mile (3.2 km) road spirals up the mountain to the rim, a 1-mile (1.6 km) trail circles the rim, and a 0.3-mile (0.5 km) trail descends to the bottom of the crater, allowing visitors a unique opportunity to explore this volcanic landscape. The 793-acre national monument contains the Capulin cinder cone, its boca, and parts of the four lava flows formed during the eruption.
A boca is a vent at the base of a cinder cone where lava flows are erupted. Lava is not erupted from s crater at the top of a cinder cone since the mostly-loose pile of cinders that make up a cone are too weak to support the pressure of a rising column of magma.
Capulin Volcano erupted 54,200 years ago during the most recent stages of activity in the Raton-Clayton Volcanic Field. The Raton-Clayton Volcanic Field is a collection of more than 100 volcanic vents and associated lava flows and volcanic edifices mostly located in northeastern New Mexico, although a few vents are in southern Colorado.
Geologic Setting & Regional Geology
The Raton-Clayton Volcanic Field is in the Raton section of the Great Plains physiographic province. The Raton section has substantially more topographic relief than most of the rest of the Great Plains with mesas capped by resistant lava flows and volcanic edifices dominating the landscape. The volcanic rocks of the Raton-Clayton Volcanic Field are found at the surface in much of the Raton section, with Cretaceous or Cenozoic sedimentary rocks otherwise at the surface.
The Raton section extends from southern Colorado where the land surface gradually climbs in elevation from the Arkansas River to the lava-flow-capped mesas that characterize the northern and northwestern portion of the volcanic field. To the southwest, the Raton section includes the Ocate Volcanic Field near Wagon Mound, New Mexico and just north of Fort Union National Monument. The southern boundary of the Raton section is the Canadian escarpment along the Canadian River.
Raton-Clayton Volcanic Field
The Raton-Clayton Volcanic Field is the easternmost young volcanic field in North America. Volcanic fields are areas that are more or less covered by volcanic rocks. Many volcanic fields are clusters of cinder cones, sometimes with a composite cone in the middle of the field. The Raton-Clayton Volcanic Field consists of cinder cones, volcanic domes, and the large andesite shield volcano, Sierra Grande. It covers approximately 7,700 square miles in northeastern New Mexico and southeastern Colorado.
The Raton-Clayton Volcanic Field is located along the Jemez lineament, a southwest-to-northeast alignment of young volcanic centers across northern New Mexico. This alignment is not the result of a hot spot track, such as the one that created the Hawaiian Islands as there is no eruptive age progression along it. The Jemez lineament is a long-lived feature that likely resulted from an intraplate boundary in the lithosphere dating back to the Precambrian when the North American continent was being built via tectonic collisions of island chains with the larger landmass.
Two other national park sites in New Mexico with young volcanic rocks are also located along the Jemez Lineament. El Malpais National Monument features young basaltic lava flows erupted in the Zuni-Bandera Volcanic Field, and Bandelier National Monuments contains ash flow tuffs that were erupted from the Valles Caldera.
Most researchers have recognized three phases of activity in the Raton-Clayton Volcanic Field. The initial phase, generally called the Raton phase, took place between 9.2 and 3.5 million years ago when a variety of eruptive centers were active mostly in the western parts of the field, and on its northern and southern margins. The middle (Clayton) phase occurred between about 3.8 and 1.7 million years ago and took place in the eastern and central areas of the field. The most recent or Capulin phase has been active in the center of the field during the last 1.7 million years.
Raton phase volcanics consist of lava flows that were erupted into topographic lows, along with domes of “pasty” (viscous) lava. The lava flows that now hold up the mesas west of Capulin Volcano are classic examples of inverted topography. As erosion took place since the time of eruption, the previously low areas that were filled with lava became topographic highs because the volcanic rocks are more resistant to erosion than the surrounding sedimentary rocks.
Sierra Grande is the largest volcano in the Raton-Clayton Volcanic Field. This volcano stands prominently to the southeast of Capulin Volcano and rises approximately 2,200 feet above the plains. The eruptions that formed Sierra Grande took place between 3.8 and 2.8 million years ago. Sierra Grande is an unusual volcano in that it is shaped most like a shield volcano, but is made of a different type of volcanic rock (andesite) that is more “pasty” than lava flows that build more typical basaltic shield volcanoes like Kilauea in Hawaiian Volcanoes National Park.
Most of the volcanism during the Capulin phase has been located in the vicinity of Capulin Volcano. Mud Hill, located just north of Capulin Volcano, is one of the oldest volcanoes of the Capulin phase, with its eruption occurring about 1.7 million years ago. Baby Capulin, a small cinder north of Mud Hill, erupted more recently than Capulin Volcano at 44,800 years ago. The most recent eruptions in the Raton-Clayton Volcano Field took place northeast of Capulin Volcano at Twin Mountain 37,600 years ago and Purvine Hills 36,600 years ago, both located a few miles northeast of Capulin Volcano.
While there have been no eruptions in the past 36,000 years, the field’s eruption frequency along with its periods of inactivity between eruptions suggest that volcanic activity in the area has not ceased. It is likely that any future volcanism will occur at a new vent since cinder cones like Capulin Volcano are monogenetic, meaning that they typically are the product of a single eruptive episode. After a cinder cone’s eruption ends, its plumbing system, or conduit, is blocked by solidified magma.
Most volcanoes located in the Raton-Clayton Volcanic Field, including Capulin, erupted basalt or similar rock types that are low in silica, but a range of compositions are found in the field.
Capulin EruptionThe eruption that led to the construction of Capulin Volcano began with eruption of a lava flow from a fissure or series of small vents. Cinders on top of this first lava flow provide evidence that it was erupted prior to the formation of the Capulin cinder cone.
The cone-building phase of the eruption was characterized by intermittent, discrete explosive bursts that ejected cinders a few hundred feet into the air in firework-like incandescent “rooster-tails” in a Strombolian eruption. The cone grew quickly in height early in the eruption, then more slowly as it enlarged. As the base of a cone grew, a larger volume of material was required for each measure of additional height.
The height of the eruption column decreased as the eruption waned, so that the cinders and volcanic bombs to be still molten when they landed on the rim of the crater. They welded together to form deposits called spatter.
The vents in the boca became active after the main cone-building phase had ended or nearly ended. The eruption style changed to Hawaiian with lower fire fountains, lava lakes, lava tubes and pahoehoe (ropy) lava. Lava flowed initially to the south, and then towards the north in the final stages of the eruption.
Geologic Features of Capulin Volcano
Capulin Volcano has a long reputation as one of the “most perfect specimens of extinct volcanoes in North America” as it was described in an 1890 letter to the Commissioner of the General Land Office that led to the withdrawal of Capulin from the lands available for settlement, entry, or disposition. This significance was echoed when the site was established as a national monument in 1916.
Cinder cones are the most common type of volcanoes on land, but few are as large or as symmetrical as Capulin Volcano, making Capulin an archetype of the form. Cinder cones (also known as scoria cones) are simple volcanic edifices that consist of deposits of scoria that fall down around the vent during moderately explosive eruptions of basaltic (low silica) magma. The slope of a cinder cone is determined by the angle of repose, which for ash and cinders is between 25 and 32°. Periodically during an eruption, the cinders piling up around the vent may exceed the angle of repose. When this happens, the cinders and ash avalanche down the sides of the cone and into the crater, and reestablish a slope equal to the angle of repose. These avalanches play an important role in forming the layers of cinders and ash that make up cinder cones.
The rim of the Capulin cone is higher on the east side than the west side. During the eruption, winds probably blew predominately from west to east and more material accumulated on the east flank. Additionally, eruptions from the boca on the west side of the cone may have undermined that side, lowering its height.
The crater has a bowl shape with a diameter of approximately 1450 feet and a maximum depth of 415 feet. The vent area for the cone-building eruption is located at the bottom of the crater but is plugged by solidified lava and covered by blocks produced during erosion. The spatter deposits on the rim and in the crater of the Capulin cone have slowed erosion, helping preserve the shape of volcano although its height has been slightly reduced.
The lava flow vent area, or boca, at the base of Capulin Volcano is complex, with a variety of features that were produced during the eruption. Collapsed lava tubes, lava lake deposits, and spatter deposits have been mapped in the boca, in addition to two sections of rafted cinder cone that formed when pieces of the cinder cone flank that were carried out by erupting lava as it emerged at the mountain’s base.
Four lava flows that cover 15.7 square miles were erupted at Capulin Volcano, but only small parts of them immediately adjacent to the cinder cone are within the park boundary.
Age of Capulin Volcano
Accurate measurements of the age of rocks erupted at Capulin Volcano were not available until the 1990s. Previously, a correlation of alluvium below a Capulin lava flow to the Folsom archeological site led to an estimation that Capulin Volcano erupted less than 10,000 before present, a value that was reported in the literature for decades.
Advances in dating techniques and application of a new technique in the mid-1990s led to a determination that the Capulin eruption occurred between 56,000 and 62,000 years ago, although the eruption itself probably only lasted a few years or less.
More recent refinements in the argon-argon dating technique have yielded a much more precise age determination for the eruption age of Capulin Volcano: 54,200 ±1,800 years before present.
No fossils have been found in Capulin Volcano NM, and fossils are not likely to be present.
The Folsom site, the type site for the Folsom tradition (Paleo-Indian), is located approximately 8 miles northwest of Capulin Volcano. The Folsom site was the first location to show that now-extinct Pleistocene mammals coexisted with humans in North America. The site has been dated at approximately 10,500 years before present.
All NPS fossil resources are protected under the Paleontological Resources Preservation Act of 2009 (Public Law 111-11, Title VI, Subtitle D; 16 U.S.C. §§ 470aaa - 470aaa-11).
Caves and Karst
Areas with basaltic lava flows and features such as the Capulin boca may contain collapsed lava tubes and other types of cave openings or overhangs. A number of collapsed lava tubes have been mapped in the Capulin boca, but no caves have been documented to date.
All NPS cave resources are protected under the Federal Cave Resources Protection Act of 1988 (FCRPA)(16 U.S.C. § 4301 et seq.).
Natural geologic processes continue to occur in and around Capulin Volcano on time scales ranging from seconds to years. Visitors should be cautious and alert to geohazards that may be present. Rock fall and slope movements along the flanks of the volcano may present a potential hazard, especially along the Volcano Road.
Because cinder cones typically only have one period of activity (e.g., they are monogenetic), potential volcanic hazards at Capulin Volcano NM itself are minimal. However, given the eruption interval and periods of interactivity of the Raton-Clayton Volcanic Field throughout its history, future eruptions may occur in the vicinity of the national monument. Relative to other types of volcanic activity, eruptions of basaltic magmas like what was erupted Capulin Volcano tend to be low explosively, although lava flows may cover large areas. The Raton-Clayton Volcanic Field is not monitored for volcanic activity as the most recent eruption occurred more than 36,000 years ago. Volcanic areas are considered active only if they have had eruptions within the last 10,000 years. However, precursors such as earthquakes, gas emissions and other signs of unrest usually occur before an eruption. For example, at Paricutin Volcano that erupted in central Mexico from 1953 to 1952 and that is considered a good modern analog for Capulin Volcano, earthquakes and subterranean noises were reported prior to the eruption.
Northeastern New Mexico has a relatively low seismic hazard. The USGS 2014 Seismic Hazard Map indicates that the Capulin area has a 2% chance that an earthquake peak ground acceleration of between 8 and 10 %g (percent of gravity) being exceeded in 50 years due to earthquakes. Peak ground acceleration between 8 and 10 %g is roughly equivalent to V to VI on the Modified Mercalli Intensity Scale. The expected number of damaging earthquake shaking in northeastern New Mexico in 10,000 years is between 2 and 4.
USGS Earthquakes Hazard Program Information by Region-New Mexico
Geology Field Notes
Students and teachers of college-level (or AP) introductory geology or earth science teaching courses will find that each park's Geologic Resource Inventory report includes the Geologic History, Geologic Setting, and Geologic Features & Processes for the park which provides a useful summary of their overall geologic story. See Baseline Inventories, below.
Capulin Volcano National Monument is a part of the Great Plains Physiographic Province and shares its geologic history and some characteristic geologic formations with a region that extends well beyond park boundaries.
Geologic Resources Inventory
- Scoping summaries are records of scoping meetings where NPS staff and local geologists determined the park’s geologic mapping plan and what content should be included in the report.
- Digital geologic maps include files for viewing in GIS software, a guide to using the data, and a document with ancillary map information. Newer products also include data viewable in Google Earth and online map services.
- Reports use the maps to discuss the park’s setting and significance, notable geologic features and processes, geologic resource management issues, and geologic history.
- Posters are a static view of the GIS data in PDF format. Newer posters include aerial imagery or shaded relief and other park information. They are also included with the reports.
- Projects list basic information about the program and all products available for a park.
- Capulin Volcano—Natural Features and Ecosystems
- Capulin Volcano—Volcano Formation
- Capulin Volcano—Volcanic Fields
- Capulin Volcano—Park Home
- NPS—Volcanic Landforms: Extrusive Igneous
- NPS—Geologic Time
- NPS—Explore Regional Geology
Related ArticlesCapulin Volcano National Monument
National Park Service Geodiversity AtlasThe servicewide Geodiversity Atlas provides information on geoheritage and geodiversity resources and values within the National Park System. This information supports science-based geoconservation and interpretation in the NPS, as well as STEM education in schools, museums, and field camps. The NPS Geologic Resources Division and many parks work with National and International geoconservation communities to ensure that NPS abiotic resources are managed using the highest standards and best practices available.
For more information on the NPS Geodiversity Atlas, contact us.