DESCRIPTION:
New Mexico Volcanoes and Volcanics

The most unusual feature in the Potrillo Volcanic Field is Aden Crater, a beautifully preserved small shield volcano.

SEE: Potrillo Volcanic Field

Beginning about 30 million years ago, tension caused by movement in the earth's mantle created a huge valley, and immense tear that runs across New Mexico from Colorado to northern Mexico. Now known as the Rio Grande Rift, this pulling apart of the earth's crust resulted from separation along two parallel fault zones. ... Bandelier National Monument is located in north-central New Mexico on the eastern side of the geologically young Jemez Mountains. Situated on the gently sloping Pajarito Plateau, Bandelier is bordered on the south by the Rio Grande and to the west by the San Miguel Mountains.

Capulin Volcano, a nearly perfectly-shaped cinder cone, stands more than 1,200 feet above the surrounding High Plains of northeastern New Mexico. The volcano is long extinct, and today the forested slopes provide habitat for mule deer, wild turkey, black bear and other wildlife. Abundant displays of wildflowers bloom on the mountain each summer. A 2-mile paved road spiraling to the volcano rim makes Capulin Volcano one of the most accessible volcanoes in the world. Trails leading around the rim and to the bottom of the crater allow a rare opportunity to easily explore a volcano.

Capulin Cinder Cone Menu

Kilbourne Hole, the best known of the Potrillo maar volcanoes, sits astride the north-south-trending Fitzgerald fault, surrounded by the late Cenozoic Afton basalt flow. The maar was formed by steam explosions due to the heating of water-saturated sand and silt strata by rising basaltic magma. From the bottom of the crater to the top of the rim the following units are exposed: (1) Santa Fe Group sediments, (2) olivine basalt (Afton basalt), (3) bedded hydroclastic tuffs (base surge and air fall) and vent breccia, and (4) Holocene wind-blown sand.

Four other explosion craters occur in the Potrillo basalt field. Hunt's Hole is a shallower and smaller (1,385 meters wide) version of Kilbourne Hole. Further south on the Mexican border is Potrillo Maar, a 4,920 x 3,385-meter elliptical crater with several cinder cones and basalt flows on its floor. Malpais is a circular tuff ring approximately 1,230 meters in diameter, 25 kilometers west of the Potrillo Maar in the West Potrillo Mountains. The ring is made of well-bedded ash, lapilli tuff, and lapilli breccia. Post-explosion activity constructed a cinder cone and basalt dikes and flows. Riley is a circular tuff cone, 925 meters wide, approximately 12 kilometers north of Malpais. Riley's rim is made of poorly bedded hydroclastic lapilli tuff and tuff breccia, and the floor of the crater contains a basalt flow.

The explosion craters are 55 to 75 kilometers west and west-northwest of El Paso, Texas.

The Ocate (or Mora) volcanic field consists of numerous basaltic to dacitic flows and approximately 50 cinder cones exposed over a broad region of the southern Rocky Mountains (Sangre de Cristo Range) and western Great Plains, on the uplifted eastern flank of the Rio Grande rift. The total volume of volcanic rocks presently exposed is approximately 90 cubic kilometers. The physiographic expressions of flows reflect their relative ages. The oldest flows cap the highest mesas, up to 600 meters above the modern drainage, and successively younger lava flows cap correspondingly lower mesas. The youngest, 10-30 meters above the present drainage, were erupted onto surfaces reflecting the modern stream network. Geomorphic surfaces preserved beneath flows 5.7 million years in age and older are warped and locally displaced across reactivated Laramide fault zones. This tectonic deformation is broadly correlative with renewed rifting and with uplift of adjacent ranges of the southern Rocky Mountains. ...

The Ocate volcanic field is on the east side of the Rio Grande rift in northern New Mexico. Volcanic cones and flows partially surround the Turkey Mountains feature, which looks like a resurgent caldera, but is actually a laccolith. Highways 3 and 85 (U.S.25), north of Las Vegas, New Mexico, enclose most of the Ocate field, and secondary Highways 120 and 121 cross the field.

The Potrillo volcanic field is a typical monogenetic volcanic field lying along the west margin of the Rio Grande rift in southern New Mexico. The Potrillo field can be divided into three volcanic regions: the West Potrillo field consists of more than 150 cinder cones, two maar volcanoes, and associated flows, all covering approximately 1,250 square kilometers. The Aden-Afton field (approximately 230 square kilometers) includes predominantly young flows, three cinder cones, 3 maar volcanoes (including Kilbourne Hole), and Aden Crater, a small shield cone. The Black Mountain - Santo Tomas basalt (40 square kilometers) consists of four eruptive centers in a north-south line near the Rio Grande River. The West Potrillo field is apparently the oldest part of the entire Potrillo volcanic field, but radiometric ages up to 2.65 million years have been obtained from Santo Thomas.

The most unusual feature in the volcanic field is Aden Crater, a beautifully preserved small shield volcano, formed in five stages:

1. extrusion of thin lava flows to build a shield;
2. construction of a spatter rampart around a lava lake dated at 530,000 years;
3. collapse of the western portion of the solidified lava lake;
4. construction of small spatter mounds on the flanks and within the cone; and
5. persisting fumaroles.

To Get there: drive 68 kilometers northwest of El Paso, Texas, or 38 kilometers southwest of as Cruces, New Mexico.

SEE: Red Hill

The Raton-Clayton volcanic field, in the extreme northeastern corner of New Mexico, is Pliocene to Holocene in age. Approximately 120 basaltic to nephelinitic cinder cones, ranging in age from greater than 1 million to 2,300 years old, are distributed throughout the field, with a concentration of feldspathoidal compositions near the town of Des Moines. Many cones have associated lava flows. Perhaps the most impressive cone is the youngest, which is fortunately protected as Capulin National Monument. The rim of this steep-sided cinder cone is approximately 1.7 kilometers in circumference, and stands 305 meters high, with a crater depth of 125 meters. A variety of andesitic and dacitic volcanic necks and domes also occurs throughout the field; Sierra Grande, a large stratovolcano 15 kilometers in diameter and 600 meters in height, is composed of numerous flows of a distinctive and homogeneous andesite.

The Raton-Clayton volcanic field is in northeastern New Mexico and southeastern Colorado. Raton is approximately 125 kilometers east of Taos, New Mexico. U.S. Highway 64 cuts directly through the center of the field and connects the towns of Raton and Clayton.

Very little is known about the Red Hill (also called Quemado) volcanic field. It lies only 24 kilometers east of the large Springerville, Arizona volcanic field and is morphologically and (based on reconnaissance data) petrologically similar to the basaltic volcanism on the eastern side of the Springerville field. The fact that many vents appear morphologically young, as are vents on the eastern edge of the Springerville field, strengthens the impression that the two areas of volcanism are related. ...

The Red Hill cone is a youthful vent consisting of reddish cinders. ... a tentative age assignment of 500,000 years for Red Hill. The associated lava flow is olivine basalt with preserved pressure ridges on its surface, but a moderately thick soil cover is locally present.

Red Hill maar is interesting as an example of a moderately youthful maar associated with faulting and fissure-type eruptive activity. ... Like the Zuni Salt Lake maar to the north, a small cinder cone occurs on the floor of the Red Hill maar, and is offset from the center of the crater. Cinders interbedded with maar deposits suggest that the eruption started with pyroclastic cinder and ash activity, evolved to more explosive maar-type eruptions, and later returned to the eruption of ash and cinders. The late ash blankets most of the crater rim-forming maar deposits, and ash was apparently dispersed by strong southwesterly winds to the northeast where ash covers the countryside for 5 to 10 kilometers along US Highway 60.

Red Hill lies along US Highway 60, approximately 30 kilometers east of Springerville, Arizona, and 37 kilometers west of Quermado, New Mexico.

The Taos Plateau volcanic field is the most voluminous concentration of lavas along the axis of the Rio Grande rift, covering approximately 7,000 square kilometers and ranging from basalt to rhyolite. Despite their location in a well developed rift setting, the lava were erupted from monogenetic central volcanoes, including at least 35 shields and cones clustered within a 30x50-kilometer region of the central Taos Plateau. The larger volcanoes form an imperfect concentric pattern approximately 40 kilometers in diameter: tholeiitic shields are located centrally within the volcanic field, andesite volcanoes at intermediate positions, and dacite farthest out. Two small silicic lava domes are also near the field's center. Individual volcanoes tend to be petrologically uniform. Basaltic rocks are volummetrically dominant, and volumes of rock types decrease as the silica content increases. ...

The Taos Plateau volcanic field fills the northern end of the Rio Grande rift valley, north-northwest of Taos, New Mexico. Highways 285 and 3 skirt the west and east sides of the field, respectively. Secondary roads lead to many of the cones.

The Zuni-Bandera lava field in western New Mexico forms part of the Jemez volcanic lineament. The field occupies a large valley south of Grants, New Mexico, and is bounded to the west by the Zuni uplift. Stretching 90 kilometers long and 1 to 35 kilometers across, it covers an area of 2,460 square kilometers with a composite thickness of 20 to 60 meters of lava. Between 62 and 123 cubic kilometers of lava was erupted from 74 vents that tend to be aligned along faults and fissures. ... Various names have been applied to the field including Malpais, McCartys, Zuni, and Bandera.

The Zuni-Bandera volcanic field provides excellent examples of a variety of vent types and lava flow morphologies. Eruptive centers, and pyroclastic activity, are marked by cinder cones, spatter ramparts and cones, small shields, maars, and collapse pits. Lava flows exhibit pahoehoe, aa, and block surface textures and may be extremely long, as exhibited by the 90-kilometer-long Fence Lake flow to the west and the 60-kilometer-long McCartys flow to the east. Lava tubes up to 28.6 kilometers long form some of the most struking morphological features within the field. These tubes are restricted to pahoehoe flows but are not limited to a specific lava composition. Other surface morphologies indicative of tube-fed lava characterize some of the flows and include pressure ridges, tumuli, linear squeezeups, grooved lava, and collapse pits.

The Zuni-Bandera field is located 112 kilometers west of Albuquerque, New Mexico, and approximately 390 kilometers northwestof El Paso, Texas. Access is provided by I-40 across the northern part of the field, by State Highway 53 along the northwest margin, and by State Highway 117 along the eastern and southern margins. Much of the area is privately owned.

Volcanic maar north of Red Hill Maar.

Also called "tuff cones," maars are shallow, flat-floored craters that scientists interpret have formed above diatremes as a result of a violent expansion of magmatic gas or steam; deep erosion of a maar presumably would expose a diatreme. Maars range in size from 200 to 6,500 feet across and from 30 to 650 feet deep, and most are commonly filled with water to form natural lakes. Most maars have low rims composed of a mixture of loose fragments of volcanic rock and rocks torn from the walls of the diatreme.

Maars occur in the western United States, in the Eifel region of Germany, and in other geologically young volcanic regions of the world. An excellent example of a maar is Zuni Salt Lake in New Mexico, a shallow saline lake that occupies a flat-floored crater about 6,500 feet across and 400 feet deep. Its low rim is composed of loose pieces of basaltic lava and wallrocks (sandstone, shale, limestone) of the underlying diatreme, as well as random chunks of ancient crystalline rocks blasted upward from great depths.

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