NPS Geodiversity Atlas—El Malpais National Monument, New Mexico

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.

el malpais gri report cover with rock outcrop image
In-depth geologic information is contained in the baseline inventory products of the Geologic Resources Inventory, see table below.


El Malpais National Monument was established to preserve and protect the volcanic wilderness of the Zuni-Bandera Volcanic Field. The monument includes the McCartys flow which was erupted 3,900 years ago and is the youngest lava flow in the state of New Mexico. The monument encompasses cinder cones and basaltic lava flows mostly erupted in the most recent phase of volcanism in the Zuni-Bandera field, and includes lava tubes, lava flow surface features, tree mold fossils, kīpukas, and other volcanic features found in young monogenetic fields.

To learn more about the volcanic resources of El Malpais National Monument, visit the El Malpais Volcanic Resources Summary within the Volcanoes, Craters, and Lava Flows subject website on

Geologic Significance & Geodiversity Highlights

El Malpais National Monument encompasses much of the Zuni-Bandera Volcanic Field, particularly the area covered by lava flows erupted during its most recent phase of activity.

The Zuni-Bandera Volcanic Field contains outstanding examples of basaltic cinder cones and young basaltic lava flows, with both pāhoehoe and ‘a‘ā forms. The McCartys flow is of particular scientific importance. It is one of the longest basaltic lava flows in New Mexico and has been extensively studied to understand inflation processes that occur during lava flow emplacement and as an analog for lava flows on Mars.

El Malpais National Monument contains one of the longest lava tube systems in the world. Extensive lava tube systems in the monument include a wide variety of features formed during eruptions, rare minerals, and unique habitats at their openings and at skylights. Some are ice caves indicating that they contain perennial ice.

The monument’s name, El Malpais (the “badlands”), dates back to the Spanish exploration period and reflects the extremely rugged terrain of the area’s young lava flows. National monument status for the area was first proposed in the 1930s. El Malpais National Monument and the adjacent El Malpais National Conservation Area, comanaged by the National Park Service and the Bureau of Land Management, were established in 1987.

El Malpais National Monument is one of 19 units of the National Park System set aside primarily for their volcanic resources.

El Malpais National Monument is one of 33 units of the National Park System containing at least one volcano.

El Malpais National Monument is one of 17 units of the National Park System that contains a volcano that experienced a historic or prehistoric eruption. The most recent eruption took place 3,900 years ago.

Geologic Setting

El Malpais National Monument mostly encompasses the five young lava flows and their vents of the most recent phase of activity of the Zuni-Bandera Volcanic Field, which occurred in the last 60,000 years. Activity in the field began much earlier, approximately 700,000 years ago.

The young basaltic lava flows of El Malpais mostly buried a terrain of older volcanic rocks and Pennsylvanian to Cretaceous sedimentary rocks. The monument lies at the southern edge of the Zuni Uplift and Precambrian rocks exposed in the core of the uplift are present along the northern monument boundary.

The Zuni-Bandera Volcanic Field is located near the southern margin of the Colorado Plateau and west of the Rio Grande Rift, both areas that have experienced recent basaltic volcanism. The field is in the transition zone between the stable Colorado Plateau with thick crust and the Basin and Range/Rio Grande Rift, where the crust has thinned.

The field is also located on the Jemez lineament, an alignment of young volcanic fields that extends to the northeast.

Jemez Lineament

The Jemez lineament is an alignment of ten young volcanic fields or centers stretching from southeastern Arizona to northeastern New Mexico/southeastern Colorado. It includes a wide variety of volcanic landforms and types including monogenetic volcanic fields, Mount Tayler, a composite volcano north of the Zuni-Bandera Volcanic Field, and the Jemez caldera, where the Valles Caldera National Preserve is located, and the Raton-Clayton Volcanic Field in northeastern New Mexico that includes Capulin Volcano National Monument.

Monogenetic Volcanic Field

The Zuni-Bandera Volcanic Field is a monogenetic volcanic field. Monogenetic volcanic fields are clusters of volcanoes or areas covered by volcanic rocks where each of the volcanic vents experienced one period of activity. They may contain hundreds of individual volcanoes and typically include cinder cones, fissure volcanoes, and other monogenetic volcanoes. Monogenetic volcanic fields usually form in areas of low magma supply.

Other monogenetic volcanic fields in the lower 48 states include the San Francisco Volcanic Field in northern Arizona where its most recent eruption formed the cinder cone preserved in Sunset Crater Volcano National Monument , the Raton-Clayton Volcanic Field in northeastern New Mexico that contains Capulin Volcano National Monument, and Craters of the Moon National Monument and Preserve which contains three young lava fields on the eastern Snake River Plain.

Geologic History

Rocks exposed in and around El Malpais National Monument include Precambrian igneous and metamorphic rocks, sedimentary rocks deposited between approximately 290 and 90 million years ago, and the young (Pleistocene and Holocene) basaltic rocks of the Zuni-Bandera Volcanic Field.

Precambrian Basement Rocks

Although not exposed within the monument, Precambrian basement rocks are found at the northern boundary in the Zuni uplift. These igneous and metamorphic rocks are approximately 1,400 million years old and formed during tectonic events when terranes (fragments of continental and oceanic crust) accreted to the growing North America continent.

Late Paleozoic and Mesozoic Sedimentary Rocks

Permian to Cretaceous sedimentary rocks are found in and around El Malpais National Monument, but they are relatively rare within the monument boundary. They are exposed in areas beyond the margins of lava flows, or in kīpukas where sedimentary rock outcroppings formed topographic highs that did not get buried by lava during eruptions. Permian and Jurassic rocks are also exposed in the Zuni uplift north of the monument.

Permian Rocks

Permian rocks are present in the northwestern part of the monument where they occur in kīpukas. Four Permian units are present in the monument (from oldest to youngest):

  • Abo Formation: The Abo Formation is the oldest rock unit exposed in the monument. It consists of red beds deposited in a continental setting.

  • Yeso Formation: In El Malpais National Monument, the Yeso Formation consists of sandstone, siltstone, limestone, and gypsum deposited in coastal environments.

  • Glorieta Sandstone: The Glorieta Sandstone was deposited shoreline/coastal environments with off-shore, beach, and coastal dune deposits.

  • San Andres Limestone: The San Andres Limestone was deposited under shallow marine conditions.

Jurassic Rocks

Jurassic rocks are present near the eastern boundary of the monument where they occur as kīpukas and external to the lava flows. Two Jurassic units are present in El Malpais National Monument (from oldest to youngest):

  • Entrada Sandstone: A small outcropping of the eolian Entrada Sandstone is present at the Narrows near the eastern boundary of El Malpais National Monument.

  • Zuni Sandstone: The eolian Zuni Sandstone forms a prominent bluff east of the McCartys Flow. It forms La Ventana Natural Arch in El Malpais National Conservation Area adjacent to the national monument. Inscription Rock in El Morro National Monument is also comprised of the Zuni Sandstone.

Cretaceous Rocks

Cretaceous rocks in El Malpais National Monument were deposited in and along the Western Interior Seaway. They are found in kīpukas and beyond the margins of the McCartys flow near the eastern boundary of the monument. Three Cretaceous units are present in the monument (oldest to youngest)

  • Dakota Sandstone: Several tongues (members) of the Dakota Sandstone have been mapped in and around El Malpais National Monument. In this region, the Dakota Sandstone consists mostly of sandstone with some conglomerate and siltstone. These tongues interfinger with the overlying Mancos Shale and are usually transgressive sandstones.

  • Mancos Shale: The Mancos Shale was deposited in the Western Interior Seaway. The lower part of the Mancos Shale is present in and around the monument.

  • Tres Hermanos Sandstone: The Tres Hermanos Sandstone was deposited during a second transgression of the Western Interior Seaway.

Zuni-Bandera Volcanic Field

Volcanic activity in the Zuni-Bandera Volcanic Field consists of three phases (from oldest to youngest):

  • Old Basalt Flows Phase: Volcanism began in the Zuni-Bandera Volcanic Field approximately 700,000 years ago with the eruptions of the old basalt flows. These lava flows are deeply weathered and largely covered by soil or alluvium.

  • Chain of Craters Phase: occurred mostly west of the national monument approximately 150,000 years ago.

  • El Malpais Phase: The most recent phase of activity took place from 60,000 to 3,900 years with the eruption of five main lava flows from a series of events including cinder cones and a low shield volcano.

Link to the El Malpais Volcanic Resources Summary

El Malpais Phase

Five main basaltic lava flows were erupted during the El Malpais phase of the Zuni-Bandera Volcanic field.
They are (from oldest to youngest):

  • El Calderon Flows (<60,000 years before present): These flows erupted from a cinder cone in the northern part of the monument. The El Calderon flows are approximately 22 miles (35 km) long and have been partially buried by younger lava flows.

  • Twin Craters Flows (18,000 years before present): The Twin Crater lava flows erupted from four main cinder cones and have the shortest length of any of the El Malpais phase lava flows. They consist mostly of tube-fed pāhoehoe, but also contain channelized ‘a‘ā lava.

  • Hoya de Cibola Flows (>11,000 years before present): These pāhoehoe flows were erupted from the Hoya de Cibola shield volcano in the western part of the monument.

  • Bandera Flows (11,000 years before present): The Bandera flows consist mostly of ‘a‘ā, unlike the other flows of the El Malpais phase which are mostly pāhoehoe. These young flows still have most of their surface structure and include tree mold fossils. They also have a network work lava tubes and collapsed tubes.

  • McCartys Flow (3,900 years before present): The McCartys flow was erupted from a small edifice in the southeastern part of the monument. Its glassy rind is well-preserved as a variety of lava flow surface features. The McCartys flow’s inflation structures have been extensively studied to learn more about this process of lava flow emplacement.

Mafic magmas like the basalts in El Malpais National Monument have low viscosity (resistance to flow), and mafic lava flows can travel great distances from their vent. Eruptions of these magmas are usually effusive to mildly explosive, typically ranging from 0 (Effusive) to 2 (Explosive) on the Volcanic Explosivity Index. Eruption styles are typically Hawaiian where low fire fountains are produced to Strombolian eruptions that look like volcanic fireworks.

Geologic Features and Processes

The majority of the significant geologic resources in El Malpais National Monument result from the volcanic eruptions that produced its lava flows, cinder cones, shield volcano and associated volcanic features during the El Malpais phase of the Zuni-Bandera Volcanic Field.

Lava Flows

The stark beauty and rugged terrain of its young lava flows are one of the primary hallmarks of El Malpais National Monument and in fact is responsible for the monument’s name (the “badlands”).

Most of the land surface of El Malpais National Monument is covered by the young lava flows of the El Malpais phase of activity in the Zuni-Bandera Volcanic Field, with lava flows ranging from 60,000 years old to 3,900 years old. The older El Malpais flows have experienced weathering so that some of their features are no longer present, but the McCartys flow is fresh and shows many excellent examples of features of young basaltic lava flows.

Pāhoehoe and ‘A‘ā: Lava Flow Forms

Both pāhoehoe (ropy) and ‘a‘ā (rough and clinker) lava flows are present in El Malpais National Monument, but pāhoehoe is more common. Pāhoehoe lava flows in El Malpais have hummocky, billowy, ropy, rubbly, and/or wrinkled surfaces. ‘A‘ā lavas have rough and clinkery surfaces.

The difference in viscosity (resistance to flow) is the most important characteristic of flowing lava that determines whether it will be pāhoehoe or ‘a‘ā. Pāhoehoe forms in more fluid (less viscous lavas) relative to ones that form ‘a‘ā. Sometimes a pāhoehoe flow converts to ‘a‘ā at greater distances from the vent.

Lava Flow Surface Features

Lava flow surface features are present on lava flows in the monument, especially the McCartys flow which is only 3,900 years old. Surface features include squeeze ups, tumuli, and pāhoehoe toes.

Inflation Structures

Pāhoehoe lava flows can be emplaced through inflation versus flowing either in channels or tubes. Inflation occurs when lava supply is greater than the ability for a flow to spread laterally due to cooling at the flow margins, therefore the lava flow thickens from within producing a uniform uplift of the solidified surface.

The McCartys flow is inflated with lava rise plateaus and inflation pits in the central and southern parts of the flow. Inflation pits are uninflated portions of a plateau typically have steep margins.

Lava Tubes

The lava tube systems in El Malpais National Monument have a cumulative length of more than 60 mi (95 km), making them among the longest in the word. Lava tubes are present in all the El Malpais phase lava flows except for the McCartys flow where they are rare or absent since it was predominantly emplaced through inflation.

The monument contains the southern most ice caves in the United States. Long sections of collapsed tubes are also present in the monument.

El Malpais’ lava tubes are also known for their fragile speleothems and the presence of rare cave minerals.


Kīpukas are areas that are surrounded by younger lava flows. Kīpukas of varying sizes in El Malpais National Monument have substrates of older volcanic rocks, sedimentary rocks, or eolian deposits.

Volcano Types

El Malpais National Monument contains a variety of volcano types that are typical of monogenetic volcanic fields like the Zuni-Bandera Field. Volcano types in the national monument include cinder cones and shield volcano.

Cinder Cones

There are at least 11 cinder cones in El Malpais National Monument. Most of these cinder cones were vents for the El Malpais phase lava flows, except for the Hoya de Cibola flow whose vent was a shield volcano.

Cinder cones are accumulations of volcanic cinders (scoria) and ash accumulated around a central vent. Their steep slopes average approximately 30 degrees, close to the angle of repose for volcanic cinders. The Bandera Crater cinder cone is breached.

Several cinder cones in El Malpais National Monument are also associated with cinder fields which are accumulations of lose cinders around a cinder cone and are fallout deposits.

Cinder cone eruptions are usually mildly explosive and at a 1 (Severe) or 2 (Explosive) on the Volcanic Explosivity Index, with a Strombolian eruption style that looks like volcanic fireworks. Their eruptions typically last a short period of time (from months to a few years), and lava flows may be emitted from vents at the base of the cinder cone, particularly during the waning stages of an eruption.

Shield Volcano

The only shield volcano in El Malpais National Monument is Hoya de Cibola. Shield volcanoes are broad volcanoes with gentle slopes and are usually constructed almost exclusively of basaltic and/or andesitic lava flows.

This small shield is approximately 1.5 mi (2.4 km) in diameter and 300 ft (90 m) high with a vent located at the summit

Paleontological Resources

The paleontological resources of El Malpais National Monument include marine invertebrate fossils in sedimentary rock units, tree mold fossils in the young lava flows of the Zuni-Bandera Volcanic Field, and Pleistocene fossils in lava tube caves.

Fossils in Sedimentary Rocks

Fossils are only known from three sedimentary units in El Malpais National Monument: the San Andres Limestone, Oak Canyon Member of the Dakota Formation, and the Tres Hermanos Sandstone. These units contain marine invertebrates.

Tree Molds

Tree molds are known from several locations in the El Calderon, Bandera, and McCartys flows.
Tree molds form when a lava flow surrounds a tree and forms an impression of it before the tree is burnt away by the hot lava. Sometimes the lava knocks down the tree as it moves. It is also possible for the tree remains standing as it is engulfed by flames and surrounded by lava.

El Malpais National Monument is one of five units of the National Park System that has been identified as having tree mold fossils.

Fossils in Lava Tube Caves

The lava tube caves in El Malpais contain a variety of vertebrate skeletal remains and packrat middens that may be fossils, but they have not been dated so it is not known whether they are modern or prehistoric. It is likely that the lava tubes contain significant Holocene fossils given their excellent preservation capability.

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

More than 400 lava tube caves have been documented in El Malpais National Monument. The monument contains the southernmost ice caves in North America.

Cave resources in the park include ice deposits, fossils, archeological sites, and important habitat for bats and other wildlife.

Volcanic landscapes where lava flows are present are considered a type of pseudokarst. Pseudokarst is formed through geological processes that do not involve dissolution of rock, which occurs in true karst. The lava tubes and collapsed tubes in El Malpais are volcanic pseudokarstic. Based on the presence of volcanic bedrock, 93% of El Malpais National Monument was identified as containing pseudokarst.

Four percent of monument was identified as containing karst due to the presence of limestone or other karstic bedrock in those areas.

All NPS cave resources are protected under the Federal Cave Resources Protection Act of 1988 (FCRPA)(16 U.S.C. § 4301 et seq.).

Related Links

Other Geodiversity Values

The boundary of El Malpais National Monument was designed to incorporate most of the young lava flows of the El Malpais phase of activity in the Zuni-Bandera Volcanic Field. Most of the geoheritage values of the monument, including its geodiversity, tie back to its volcanic resources and processes that formed them.

El Malpais contains outstanding examples of lava flow surface features as well as other features of a monogenetic volcanic field. The monument is also has great scientific importance due to the extensive lava tube systems and the inflation features of the McCartys flow.

Other geodiversity highlights of El Malpais National Monument include rare plants and plant communities and the Zuni-Acoma Trail.

Geology and Plants

The plant life of El Malpais National Monument has been shaped by its geology. Unique plant associations including stands of exceptionally old trees are present in the monument where they are shaped by the unusual habitats present in the monument. Kīpukas with sedimentary substrates generally host different plant communities than those growing on volcanic bedrock. Cinders phacelia (Phacelia serrate) is an endemic species that grows on volcanic cinders only in El Malpais National Monument and the San Francisco Volcanic Field in Arizona, in and around Sunset Crater Volcano National Monument.

Zuni-Acoma trail

The Zuni-Acoma Trail in El Malpais National Monument is a 7.5-mile (12-km) long trail that mostly traverses the McCartys lava flow. This rough trail travels on top of the uneven lava flow surface and is marked by piles of rocks known as cairns. The trail is part of the ancient route connecting the pueblo of Zuni, west to El Malpais to the pueblo Acoma, east of El Malpais and has been used by tribal peoples for at least hundreds of years, if not longer.


Geohazards in El Malpais National Monument range from those associated with rock fall and slope stability, caves, and abandoned mineral lands to seismic and volcanic hazards.

Volcanic Hazards

Although individual vents within the Zuni-Bandera Volcanic Field should not erupt again as cinder cones and fissure volcanoes generally have only one period of volcanic activity, future eruptions may take place. Monogenetic volcanic fields have low magma supply rates so there may be long intervals between subsequent eruptions.

The US Geologic Survey’s 2018 update to the national volcanic threat assessment places the Zuni-Bandera Volcanic Field into the very low threat category. Threat rankings are assigned to one of five categories ranging from very high to very low. The threat assessment is not a forecast of future eruption, but an evaluation of the potential severity of impacts that may result from future eruptions at a given volcano.

The assessment consists of two parts: an evaluation of volcanic hazards and the exposure of people and human infrastructure to those hazards. Both the volcanic hazard part of the ranking and the human exposure part are low for the Zuni-Bandera Volcanic Field, leading to an overall threat score of 5.4. El Malpais National Monument is one of 17 units of the National Park System containing volcanoes evaluated in the threat assessment.

Seismic Hazards

El Malpais National Monument has a moderate seismic hazard. The USGS 2014 Seismic Hazard Map indicates that the El Malpais area has a 2% chance that earthquake peak ground acceleration of between 12 and 14 %g (percent of gravity) being exceeded in 50 years. This peak ground acceleration is roughly equivalent to VI on the Modified Mercalli Intensity Scale. The expected number of damaging earthquake shaking in the vicinity of El Malpais National Monument in 10,000 years is between 4 and 10.

Abandoned Mineral Lands

Six abandoned mineral lands sites are in El Malpais National Monument containing a total of 28 features. The Geologic Resources Inventory indicated that there are four additional sites within the monument that are not part of the NPS AML database.

The six AML sites are all quarries. Five of the sites were mined for cinders or “lava rock,” and the other site, which is off of New Mexico 117, was quarried for sandstone.

NPS AML sites can be important cultural resources and habitat, but many pose risks to park visitors and wildlife, and degrade water quality, park landscapes, and physical and biological resources. Be safe near AML sites—Stay Out and Stay Alive!

Related Link

Burghardt, J. E., E. S. Norby, and H. S. Pranger, II. 2014. Abandoned mineral lands in the National Park System—comprehensive inventory and assessment. Natural Resource Technical Report NPS/NRSS/GRD/NRTR—2014/906. National Park Service, Fort Collins, Colorado. [PDF]

Regional Geology

El Malpais National Monument is a part of the Colorado Plateaus Physiographic Province and shares its geologic history and some characteristic geologic formations with a region that extends well beyond park boundaries.

Maps and Reports

The Geologic Resources Inventory produces digital geologic maps and reports for more than 270 natural resource parks. The products listed below are currently available for this park, check back often for updates as many maps, reports, and posters are still in progress.
  • 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.

Source: Data Store Saved Search 2817. To search for additional information, visit the Data Store.

NPS Soil Resources Inventory project has not been completed for El Malpais National Monument. General information can be found on the NPS Data Store.

Source: Data Store Saved Search 2822. To search for additional information, visit the Data Store.

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El Malpais National Monument

National Park Service Geodiversity Atlas

The 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.

El Malpais National Monument

Last updated: March 21, 2024