Last updated: April 17, 2023
Article
Volcanic Resources Summary—Capulin Volcano National Monument
[Site Under Development]
Photo courtesy of Allyson C. Mathis.
Introduction
Capulin Volcano National Monument preserves the Capulin Mountain—one of the finest examples of a cinder cone volcano in the United States. Capulin Volcano is also one of the most accessible cinder cones in the world with a paved road spiraling the rim and paved trails into and around the crater. The National Park Service has managed Capulin Volcano since 1916.
Significance
Capulin Mountain has a long reputation as being one of the “most perfect specimens of extinct volcanoes in North America.” It was described as such in an 1890 letter by the Land Inspector Harlan, stationed in Folsom, to the Commissioner of the General Land Office. This letter was forwarded to the Secretary of the Interior who withdrew Capulin from lands available for settlement, entry, or disposition in 1891.
Inspector Harlan’s letter referred to Professor James D. Dana, then America’s foremost expert on minerals and volcanoes. It is not known how Professor Dana learned of Capulin Mountain. But somehow Capulin Mountain caught his attention, as it has always caught people’s attention. Today, Capulin Volcano still has special meaning to geologists, students, local residents, national park supporters, and travelers through the High Plains of northeastern New Mexico.
Why does Capulin Volcano capture so many people’s imagination? Is it simply the beauty of the forested mountain as it stately stands above the surrounding plains and its natural environment, outstanding views, and relative solitude it provides? Or perhaps it is because, with its classic cone shape and well-preserved crater, it is easy to imagine the fiery eruption that created it. Or is it because not only is it a type example of a cinder cone, it is also archetypal; that is, bigger and more perfectly formed than most cinder cones?
Enabling Legislation
Protection was first provided to what is now known as Capulin Volcano National Monument (NM) on January 16, 1891, when it was “…withdrawn from settlement, entry or other disposition under any of the public land laws, until such time as Congress may see fit to take action or until otherwise ordered by competent authority….”.
President Woodrow Wilson set Capulin Volcano National Monument aside by Presidential Proclamation No. 1340 August 9, 1916, to preserve “…a striking example of recent extinct volcanoes …” which “…is of great scientific and especially geologic interest” (Presidential Proclamation No. 1340 [39 Stat. 1792]).
Public Law 87-635 passed by the 87th Congress on September 5, 1962, amended the proclamation to “…preserve the scenic and scientific integrity of Capulin Mountain National Monument…” because of the significance of Capulin Volcano.
On December 31, 1987, Congress changed the Monument’s name from, “Capulin Mountain National Monument” to “Capulin Volcano National Monument,” by Public Law 100-225 (101 Stat. 1547) (NPS 2010).
Capulin Volcano
Quick Summary
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Capulin Volcano is a cinder cone volcano. Lava was erupted from its boca, the vent area at its base.
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Capulin Volcano is between 1,200 and 1,400 feet (365 and 425 m) tall (depending on what the base elevation is estimated to be before the eruption began). Capulin Volcano stands almost 1,000 feet (300 m) above the Visitor Center.
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Capulin’s four lava flows cover almost 16 (15.7) square miles (41 square km).
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Capulin Volcano erupted 54,200 years ago. It was built in a single eruption that probably only lasted a few years or less. Capulin Volcano will not erupt again since cinder cones are monogenetic, meaning that they almost always have only one period of activity.
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Capulin eruption occurred during the Ice Ages. At the time, the plains were probably covered with woodlands of juniper and pinyon and occasional grassy meadows. Ponderosa pines grew on the hills. Giant bison, short-faced bear, camels, horses, and Colombian mammoths probably inhabited the area.
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Capulin Volcano is part of the Raton-Clayton Volcanic Field, the easternmost Cenozoic volcanic field in North America.
Not only is Capulin Volcano a classic example of a cinder cone volcano, it is archetypal; e.g., bigger and more perfectly formed than most cinder cones. It is an exceptionally large cinder cone, being roughly equal in size to the younger Sunset Crater that erupted in 1085 CE and is now preserved in Sunset Crater Volcano National Monument in Arizona.
Capulin Volcano is one of the most accessible cinder cones in the country with a paved road to the rim of the mountain. Only two other cinders cones (Lava Butte and Pilot Butt, both near Bend, Oregon) have paved roads to the top. Both are considerably smaller than Capulin Volcano.
Volcanic Features and Resources
Capulin Volcano is a great place to see and learn about the features of cinder cone volcanoes and basaltic lava flows.
The Cinder Cone
Like most cinder cones, Capulin Volcano is a simple volcano that consists of accumulations of ash and cinders around a central vent which was where the summit crater is located. It is made of layers of cinders and ash. Larger volcanic bombs and blocks may also be present.
The overall slope of a cinder cone like Capulin Volcano is determined by the angle of repose, which is between 25 and 32° for ash and cinders. Cinders piling up around the vent periodically avalanche down the sides of the cone and into the crater to reestablish a slope at the angle of repose and forming much the layering present in cinder cones.
The cone probably grew quickly in height early in the eruption, then more slowly as it enlarged. As the base of a cinder cone increases in circumference, a larger volume of material is required for each measure of additional height.
Approximately 100 feet (30 m) of erosion has occurred since the end of the eruption based on the shape of a spatter cliff on the crater rim.
Soil has developed in the approximately 54,000 years since the eruption. Today much of the cone is covered by Pinyon-Juniper Woodland. Pinyon pines and juniper trees grow in rocky soils.
Features:
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Layering of the cone can be seen in the roadcut near the top of the Volcano Road.
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Capulin Volcano has spatter deposits along the rim and crater that accumulated near the end of the eruption as it waned and the eruption column decreased in height. This less vigorous part of the erupt emitted larger bombs that did not cool much during their flight. They were still molten when they landed and fused or welded together to form a solid coating of rock known as spatter. The spatter deposits on the rim and in the crater of Capulin have slowed erosion helping preserve the cinder cone.
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The rim of the Capulin Volcano 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 (basal vent) on the west flank of the cone may have undermined the cone on that side, further lowering that side.
The Crater
Capulin Volcano’s crater has a bowl shape with a diameter of approximately 1450 feet (440 m) and a maximum depth of about 415 feet (125 m). The shape of the crater contributes to Capulin’s classic cinder cone form. The vent area for the cone-building eruption, located at the bottom of the crater, is now plugged and covered by blocks produced during erosion of the crater.
The Boca
The boca is the vent area at the base of the Capulin cinder cone where three lava flows were emitted following the main eruption that built the cinder cone. Most cinder cones erupt lava from a flank vent (boca) like Capulin did, but Capulin’s boca is more complex than most, containing at least two vents and a diversity of volcanic features including lava lakes, collapsed lava tubes, spatter deposits, and pieces of rafted cinder cones.
Features:
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The highest elevations within the boca are low hills which are pieces of the cinder cone flank that were rafted out by the erupting lava flows as they emerged at the base of the volcano. They are composed of cinders resting at the angle of repose.
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Lava lakes are recognizable as flat areas within the boca. Spatter deposits are found at lake margins. The lakes formed behind the boca walls. The lakes may have drained either through the boca walls or back into the lava flow through the bottom of the lake to make the topographic lows.
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Fire-fountaining during the eruption formed the irregular low rocky hills and mounds that make up the spatter ramparts. The fire-fountaining was probably in the Hawaiian eruption style.
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Collapsed lava tubes are topographic low spots filled with broken pieces of the lava tube roof.
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Levees and lava cascades appear almost like fluvial features of rivers of stone. Levees formed on the margins of lava flows. Lava cascades formed where lava cascaded through the boca wall.
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The southern and western boca walls formed when lava flows spread out from the vent area as rubbly walls of lava. These walls of rock were left behind when the lava flow either receded, stopped, or was redirected. These walls formed the boca margins that contained the lava lakes, and through which lava cascades flowed.
Lava Flows
The eruption of Capulin Volcano was accompanied by the production of four lava flows. One flow was erupted prior to the cinder cone building phase, and the other three were erupted from the boca after the main eruption waned.
Erosion has removed much of the rough “malpais” (badland) surface of the flows and many of the lava flow surface features, but squeeze ups and tumuli remain as rock outcrops. Outside the park boundary, pressure ridges are still discernible in places on flow surfaces.
Near its vent, the lava probably was pāhoehoe, or ropy, lava. Lava tubes are characteristic of pāhoehoe flows. Near the flow margins, after the lava cooled and became more viscous, the lava changed to a'ā.
Features:
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Squeeze ups or tumuli are common near the visitor center because the gradient of the flows decreased dramatically after the lava flowed down the lava cascades at the boca margins. Squeeze ups formed on lava flow surfaces when the internal pressure of the lava increased causing the hot fluid lava in the interior of the flow to squeeze out through cracks in the cooled lava crust. A change in gradient in the slope, from a steeper to a lower gradient, is a common cause for an increase of internal pressure that may cause squeeze ups to form.
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Pressure ridges formed when the cooler lava flow crust was more viscous than the hotter interior. As the flow interior moved more rapidly than the cooler crust the crust was wrinkled to form low curved ridges known as pressure ridges. Pressure ridges are convex in the direction that the lava was flowing. Pressure ridges are visible on a flow lobe of lava flow 2.
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About 2.5 miles (4 km) east of Capulin on Hwy 64/87, characteristic rubbly a'ā-type flow fronts are evident.
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Pinyon and juniper trees cover the lava flows probably because these species prefer rocky soils. Crevices in the lava surface may also provide additional moisture from rain collecting in them.
The Rocks
Capulin Volcano erupted ash, cinders, and lava with basaltic composition. Almost all the rocks in the park are vesicular. Some rocks are porphyritic with phenocrysts (crystals) (1-3%) of plagioclase and olivine.
Quartz xenocrysts (crystals that didn’t originate from the magma) and sandstone xenoliths (foreign rock fragments) are common in rocks erupted from Capulin Volcano. Quartz will not crystallize from a basaltic magma. The quartz crystals in Capulin samples are also rounded like those found in sandstone. The source of the xenoliths and xenocrysts is probably the Dakota Sandstone which is near the surface in the Capulin area. The sandstone was probably incorporated in the magma not long before eruption. Some xenoliths show that they have been partially melted by the magma, and some xenoliths show a mixed structure as the basaltic liquid was intermingling and mixing with the sandstone.
Capulin rocks are very heterogeneous. They are not uniform in the number and types of phenocrysts present, and the amount of xenoliths and xenocrysts in a particular sample is highly variable. Olivine phenocrysts are common in some samples, and absent in others. Likewise, the sandstone xenoliths and quartz xenoliths may be abundant (up to 10-15%) in some samples, and completely absent in others.
The color of a cinder or bomb erupted from the volcano may be red, black, yellowish brown, or an intermediate color. The basic bulk composition of all rocks erupted from Capulin Volcano is nearly constant, and the color variation is mostly a result of variation in the oxidation state of iron in the rock. Red cinders contain oxidized (rusted) iron, black cinders do not contain oxidized iron. Yellowish brown cinders were oxidized in the presence of water. Cinders were more likely to be oxidized and turn red in areas of the cinder cone where gas vents were active providing additional heat to facilitate the oxidation of the iron in the rock.
The Eruption of Capulin Volcano
The eruption of Capulin Volcano took place in three parts or phases:
Part 1: The eruption of Lava Flow 1. This is a small lava flow that flowed to the east from a east-northeast trending fissure vent.
Part 2: The mildly explosive eruption that built the Capulin cinder cone
Part 3: Boca eruption
Eruption of Lava Flow 1
Lava Flow 1 flowed to the east from a east-northeast trending fissure vent. Eruptions that ultimately build cinder cones frequently begin with fissure eruptions since magma may travel through the cust in linear dikes. The vent for this lava flow cannot be located and most likely it was buried by the later cinder cone. A mantle of cinders covers this lava flow.
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Cone-Building Eruption
The Capulin cone-building eruption was probably predominantly Strombolian in style. Strombolian eruptions produce small eruption column (less than 1000 feet; 330 m) and send incandescent rooster-tails of cinders and bombs into the air.
Cinders, bombs, and ash accumulated around the vent as the eruption proceeded with the volcano growing in both circumference and height. The explosivity of the eruption kept the crater clear. Spatter, which forms when bombs land while still molten and are able to fuse together to form solid rock, was deposited on the rim and crater near the end of the cone- building eruption as the explosivity of the eruption waned.
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Boca Eruption
The boca vents became active after the main cone-building phase had ended or nearly ended. Evidence for the boca eruptions being the final phase of Capulin’s eruption is the fact that cinders were not deposited on top of the boca features or on top of lava flows erupted from the boca.
The boca eruption was predominately Hawaiian in style. Low fire (lava) fountains probably accompanied the eruption of the lava flows. At least two vents were active during the boca eruption. Lava flowed first to the southeast (Lava Flow 2), then to the southwest (Lava Flow 3), and then to the north (Lava Flow 4) before the eruption ended.
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The Age of Capulin Volcano
Capulin Volcano’s eruption occurred 54,200 ±1,800 years before present. The entirety of the eruption, including that of the four lava flows, probably took place over a period of a few months to a few years at most.
The 54,200 ±1,800 years before present age for Capulin Volcano was obtained by by Matthew Zimmerer of the New Mexico Bureau of Geology and Mineral Resources and published in 2019. The date was obtained using the 40Ar/39Ar analytical technique which is a high precision geologic dating technique dependent the radiometric decay of potassium-40 present in the rock.
The 54,200 year old age for Capulin Volcano is a significant refinement from the first estimates of when the eruption occurred, and is both more accurate and more precise than the initial estimates and previous applications of geologic dataing techniques.
The first estimates were rather tenuous as they were based on a correlation to a carbon-14 date at the Folsom archeological site. In the 1950s, researchers thought that a layer of alluvium below one of the lava flows erupted from Capulin Volcano was the same as the alluvium at the Folsom site, although it was several miles distant. By the 1970s researchers realized that the correlation was inaccurate.
Two different geological dating techniques were applied to rocks erupted from Capulin Volcano in the 1990s. One determined that amount of time that the rock had been exposed to cosmogenetic radiation, and the other used the 40Ar/39Ar method. Both techniques indicated that there eruption occurred between between 56,000 and 62,000 years ago.
The 54,200 ±1,800 years before present date obtained by Zimmerer used a mass spectrometer which is able to produce dates that are an order of magnitude more precise than the one used
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Raton-Clayton Volcanic Field
Capulin Volcano is located near the center of the Raton-Clayton Volcanic Field, the easternmost Cenozoic volcanic field in North America. The Raton-Clayton Volcanic Field extends from near Trinidad, Colorado to Clayton, New Mexico, and covers approximately 7,700 square miles (20,000 square km).
The Raton-Clayton Volcanic Field is particularly the most compositionally diverse volcanic field in the United States with compositions of eruptive products ranging from ultramafic to silicic (70-36 wt% SiO2). It is located along the Jemez lineament, a southwest-to-northeast alignment of young volcanic centers across northern New Mexico. The Jemez lineament is a long-lived feature in the lithosphere dating back to the Precambrian when the North American continent was being built via tectonic collisions of island chains.
The Raton-Clayton Volcanic Field consists mostly of monogenetic volcanoes such as cinder cones, tuff rings, fissure volcanoes, and lava domes. It also contains a large andesitic shield volcano (Sierra Grande) near the center of the field. Although it mostly contains monogenetic volcanic fields, it differs from most other fields due to the compositional diversity found within it and the presence of the polygenetic Sierra Grande.
Activity in the field began about 9.2 million years ago and the most recent eruption took place 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 Holocene (the standard time period that geologists use to define whether a volcano or volcanic field is active), the Raton-Clayton Volcanic Field’s low eruption frequency (which includes long periods of inactivity) suggests that volcanic activity in the area has not ceased.
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Phases of the Raton-Clayton Volcanic Field
Volcanic activity in the Raton-Clayton Volcanic Field took place in three phases:
Raton Phase:
The earliest phase of activity in the field 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 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.
Eruptions during the Raton phase produced basaltic lava flows and cinder cones, as well as rhyodacite domes. Because of their age, products of the Raton phase are the most eroded part of Raton-Clayton Volcanic Field. Lava flows that once filled in low areas now stand perched about the general elevation of the land surface due to differential erosion and the lava flows’ resistance of erosion. These lava flows hold up low mesas like Johnson Mesa just west of Capulin Volcano in classic examples of inverted topography.
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Clayton Phase:
The Clayton phase occurred between about 3.8 and 1.7 million years ago, mostly in the eastern and central areas of the field. During this time interval, most eruptions took place at fissure volcanoes or from cinder cones. The largest volcano within the Raton-Clayton Volcanic Field, Sierra Grande, was also active during this interval. Sierra Grande dominants Capulin’s viewshed to the southeast where this shield volcano rises approximately 2,200 feet (670 m) above the plains. Sierra Grande is almost exclusively made of andesitic lava flows that were erupted between 3.8 and 2.8 million years ago. It is also the only volcano in the Raton-Clayton Volcanic Field with an andesitic composition.
Capulin Phase:
Capulin Volcano and many of the other volcanoes that are closest to it including Baby Capulin, a small cinder cone, and Mud Hill, a tuff ring, erupted during the Capulin phase during the last 1.7 million years. The Raton Phase included the eruptions of cinder cones and fissure volcanoes. Because of their relative youth, these volcanoes are not as eroded as the older volcanoes in the field, and like Capulin, they retain the shape of their volcanic constructional landforms.
Mud Hill is a tuff ring formed when magma encountered water at or near the surface during the eruption. Tuff rings are produced by these highly explosive phreatomagmatic (hydrovolcanic) eruptions.
Geoheritage Values
The volcanic origin of Capulin Mountain and the surrounding volcanic terrain of the Raton-Clayton Volcanic Field has shaped nearly every aspect of the monument’s natural and cultural history.
Geologic resources are literally the bedrock of units in the National Park System, but their relationship to other park resources are especially evident at a small monument like Capulin Volcano where the boundary was drawn to encompass most of the cinder cone. The higher elevation and rocky soils have favored the growth of pinyon pine and juniper trees, and even the volcano gets its name from the Spanish word for chokecherry which is found growing on the volcano and in its crater. The monument also hosts a wide variety of wildlife including mountain lions, bobcats, black bear, mule deer, and wild turkeys, all species that are not common on the surrounding plains.
Geologic resources make up our geoheritage. The National Park Service defines geoheritage as “the significant geologic features, landforms, and landscapes characteristic of our nation which are preserved for the full range of values that society places on them, including scientific, aesthetic, cultural, ecosystem, educational, recreational, tourism, and other values” (NPS 2013).
Capulin Alberta Arctic Butterfly
Capulin Volcano provides habitat for the Capulin Alberta Arctic Butterfly. The Capulin Alberta Arctic Butterfly was first found on Capulin’s rim in 1969 and was identified as a new subspecies. It utilizes grassland found along the rim. The species is only found at Capulin and a few nearby areas such on Raton Mesa. The New Mexico Department of Game and Fish includes this butterful as a Species of Greatest Conservation Need in their Comprehensive Wildlife Conservation Strategy.
Capulin Goldenrod
Capulin Goldenrod is a rare endemic plant first collected at Capulin Volcano in 1930, and identified as a new species in 1936. It was found again in the monument in 2010 when its type area was resurveyed.
Capulin Goldenrod grows among basalt boulders near the base of the cinder cone. This species of goldenrod has been found in a few other sites in northeastern New Mexico and southeastern Colorado and little information about the potential distribution and abundance of this plant elsewhere is available.
Paricutin Volcano
The link to Paricutin, the “volcano born in a cornfield” that erupted in central Mexico from 1943 until 1952, is one of the geoheritage values of Capulin Volcano. Paricutin is one of the relatively few cinder cones whose entire eruption was witnessed and documented, and so it has great scientific importance. Geologists think that the eruption of Paricutin volcano is a good analog for the eruption of Capulin Volcano.
Like Capulin Paricutin Volcano is cinder cone. Paricutin’s eruption lasted nine years. Precursors to its eruption began about a month before the eruption itself began when the residents of nearby villages began to feel numerous small earthquakes and hear subterranean noises caused by magma rising towards the surface in the crust. These earthquakes and noises increased in frequency and intensity so that by the time the eruption began, they were almost continuous. The eruption began at approximately 4:30 p.m. on February 20, 1943. A fissure had opened in a cornfield and began spewing gasses, ash, and small rock fragments. Farmer Dionisio Pulido, his wife, and a field worker, were in the cornfield when the eruption began, and they all safely escaped.
After 24 hours, the new volcano was almost 100 feet (30 m) tall. On the second. day, lava flows began to be erupted from vents on the flanks of the cone. Lavas were erupted continuously throughout the rest of the eruption. Two nearby villages eventually were completely buried by lava flows. Virtually all plant life, including crops, weve killed within a 5-mile radius of the volcano, and wild fruits and berries, bees, and wild game disappeared from a much larger area.
Geologic Issues
There are several geological issues at Capulin Volcano National Monument including erosional along the Volcano Road, cinder mining of cinder cones outside of the monument but visible from the rim, and the presence of geohazards.
Erosion along the Volcano Road
One of the greatest geologic issues facing Capulin Volcano is erosion along the Volcano Road. The road was first constructed in 1925, and paved in 1986. It is eligible for inclusion in the National Register of Historic Places.
The road has been a maintenance challenge from the start, with frequent washouts after several rain storms. The road is cut into the natural slope, creating erosion on the uphill side of the road, and downslope erosion especially at the culverts is greater than that on the uphill side.
In 2019, a major washout of the road required that the road be closed for five months while repairs were made.
Related Links
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Capulin Volcano National Monument (CAVO), New Mexico—[CAVO Geodiversity Atlas] [CAVO Park Home ] [CAVO npshistory.com]