America's Volcanic Past
|"Though few people in the United States may actually experience an erupting volcano, the evidence for earlier volcanism is preserved in many rocks of North America. Features seen in volcanic rocks only hours old are also present in ancient volcanic rocks, both at the surface and buried beneath younger deposits." -- Excerpt from: Brantley, 1994|
Volcanic Highlights and Features:
|[NOTE: This list is just a sample of various New Mexico features or events and is by no means inclusive. All information presented here was gathered from other online websites and each excerpt is attributed back to the original source. Please use those sources in referencing any information on this webpage, and please visit those websites for more information on the Geology of New Mexico.]|
It seems that each of the Southwestern states has an apparent geologic specialty. If so, and Arizona is the big Canyon state, Utah is the Mesozoic fauna state, and Colorado is the big snow-capped Rocky Mountains state, then what is New Mexico? New Mexicans need only look out their windows for the answer: New Mexico is the Volcano state. New Mexico has one of the greatest concentrations of young, well-exposed, and uneroded volcanoes on the continent. And as a bonus, it is also the Rift Valley state; it has one of only four or five big continental rifts in the world, East Africa being one of the other ones. The fact is, New Mexico is one of the best places to study the natural history of volcanoes. Twenty percent of the U.S. National Parks and Monuments based on volcanic themes are in New Mexico. There are more here than Arizona, Idaho, Oregon, and Washington combined.
Volcanism in New Mexico is not "extinct," but is dormant. The record of volcanism in New Mexico is continuous over tens of millions of years, and there is no reason to think it stopped magically 3000 years ago with the eruption of several cubic kilometers of basalt (McCartys lava flow, El Malpais). New Mexico has one of only three large mid-crustal active magma bodies (Socorro) in the continent. (The others are Long Valley, California and Yellowstone, Wyoming.) The Socorro area is one of the few areas where there is a dearth of young volcanoes, so perhaps the Rift is working on filling out its volcano landscaping.
Every major type of volcanic landform (composite volcano, shield volcano,
volcanic caldera, major ash-flows, pahoehoe and aa lava, maar crater, fissure
eruptions, cinder cones) occurs in New Mexico.
Excerpt from: New Mexico Museum of Natural History and Science Website, 2002
The Interior Plains:
The sculptured beauty and brilliant colors of the Colorado Plateau's sedimentary rock layers have captured the imaginations of countless geologists. This is a vast region of plateaus, mesas, and deep canyons whose walls expose rocks ranging in age from billions to just a few hundred years old. Ancient Precambrian rocks, exposed only in the deepest canyons, make up the basement of the Colorado Plateau. Most are metamorphic rocks formed deep within the Earth while continental collision on a grand scale produced the nucleus of the North American continent well over a billion years ago. Igneous rocks injected millions of years later form a marbled network through parts of the Colorado Plateau's darker metamorphic basement. These deeply-formed rocks were uplifted, eroded, and exposed for eons. By 600 million years ago North America had been beveled off to a remarkably smooth surface. It is on this crystalline rock surface that the younger, more familiar layered rocks of the Colorado Plateau were deposited.
Basin and Range:8
The Basin and Range province has a characteristic topography that is familiar to anyone who is lucky enough to venture across it. Steep climbs up elongate mountain ranges alternate with long treks across flat, dry deserts, over and over and over again! This basic topographic pattern extends from eastern California to central Utah, and from southern Idaho into the state of Sonora in Mexico. Within the Basin and Range Province, the Earth's crust (and upper mantle) has been stretched up to 100% of its original width. The entire region has been subjected to extension that thinned and cracked the crust as it was pulled apart, creating large faults. Along these roughly north-south-trending faults mountains were uplifted and valleys down-dropped, producing the distinctive alternating pattern of linear mountain ranges and valleys of the Basin and Range province.
The Rockies form a majestic mountain barrier that stretches from Canada through central New Mexico. Although formidable, a look at the topography reveals a discontinuous series of mountain ranges with distinct geological origins. The Rocky Mountains took shape during a period of intense plate tectonic activity that formed much of the rugged landscape of the western United States. Three major mountain-building episodes reshaped the west from about 170 to 40 million years ago (Jurassic to Cenozoic Periods). The last mountain building event, the Laramide orogeny, (about 70-40 million years ago) the last of the three episodes, is responsible for raising the Rocky Mountains.
|New Mexico's Volcano Types|
The type example and one of the largest young calderas in the world (Valles Caldera) is in New Mexico. Yellowstone is a caldera, but it is a less visually obvious example of this type of volcanic landform.
Several of the largest concentrations of young cinder cones (exemplified by the Raton-Clayton, Zuni-Bandera, and Potrillo fields for starters) are in New Mexico.
Best young examples of a fissure eruption (Albuquerque Volcanoes).
Two of the largest young basaltic lava flows in the world (Carrizozo and McCartys) are in New Mexico. Some of the geological terms for surface features on lava flows were first defined here in New Mexico, not Hawaii.
Maars - Steam Explosion Craters:10
One of the greatest concentrations of young volcanic steam explosion craters (referred to as "maars" by geologists), occur in New Mexico. Zuni Salt Lake Crater and Kilbourne Hole Crater are two maars in New Mexico often used as type examples in textbooks. The remains of maars literally fill White Rock Canyon and they pepper the surfaces of many of the other volcanic fields, like the Mount Taylor and Potrillo fields. They are more abundant, better preserved, and more diversely exposed than those in the type area (Eifel district of Germany). European geologists come here to learn about maars.
The Datil-Mogollon region of New Mexico is one of the largest concentrations of resurgent calderas. These are more eroded than the Valles Caldera, but they are in the same state of exposure as the San Juan Mountains of Colorado, another collection of mid-Tertiary resurgent calderas. You would have to go to the Sierra Madre of Mexico, the Valley of Ten Thousand Smokes in Alaska, or even Armenia to see something similar.
The greatest diversity of young volcanic rock types and classic suites of volcanic rocks (for example, the Mount Taylor and the Raton-Clayton volcanic fields) occur in New Mexico.
The greatest concentration and best-exposed examples of young volcanic necks in the world are in New Mexico (Rio Puerco Valley).
|New Mexico's Volcanic Gemstone|
Gem-quality peridot can be found in deposits at three different locations in New Mexico. The deposits are in the Buell Park area in McKinley County in the northwestern part of the State and in Kilbourne Hole and Potrillo Maar depression, both near the Mexican border in the southeastern part of the State. The color of the material is brown, greenish-brown, yellowish-green, and the desirable peridot green. Some people believe the material from the Kilbourne Hole area is superior to the material from the famous Arizona location on the San Carlos Reservation. Currently, there is no commercial production of material from any of the deposits in New Mexico, but "rockhounds" and other mineral collectors gather materials from these locations for their own use.
Few large cities in the United States have young volcanoes near them like the Albuquerque Volcanoes. They are also an excellent example of volcanoes that occur in a line that geologists call a "fissure eruption." The Albuquerque Volcanoes are also geologically young (as young as 140,000 years). Fissure eruptions like the Albuquerque Volcanoes are common in many parts of the world. Fissure eruptions form because molten rock (or "magma") from many miles within the Earth tends to rise along vertical cracks. When the cracks reach the surface, they cause long surface cracks. Lava and ash then erupts from the crack. Magma quickly cools and solidifies along most of the crack and only a few spots continue to erupt. As these spots continue, small cones of ash, spatter, and lava are built. The Albuquerque Volcanoes we see today are the result of this type of eruption.
|Bandelier National Monument|
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.
Cerros Del Rio Volcanic Field:2
Across White Rock Canyon, the monument's southern boundary, lies the exposed portion of the Cerros Del Rio Volcanic Field. Active one to three million years ago, this volcanic field features cinder cones, basaltic lava flows, and maar cones. Maar cones form when rising magma encounters water. The resulting steam produces violent eruptions which blow out rock fragments that settle into thin layers. This creates a cone characterized by having many thin layers, a low rim, and a large diameter.
The Pajarito Plateau is of interest geologically as well as archaeologically. It is constituted largely of tuff (consolidated volcanic ash) and basaltic lava ejected thousands of years ago by a great volcano. The caldera (saucer-shaped depression) created by the collapsed summit of the volcano is among the world's largest calderas; its rim forms the Jemez Mountains. Through this highland, running water has cut many steep-walled canyons down to the Rio Grande.
St. Peter's Dome and Boundary Peak:2
Bandelier is bordered on the west by St. Peter's Dome and Boundary Peak. These peaks, part of the San Miguel Mountains, are the eroded remains of a group of 8 to 13 million-year-old volcanoes.
|Capulin Volcano National Monument|
Barella, Raton, and Johnson Mesas:3
To the northwest of Capulin are a number of mesas that are capped with lava, the three largest of which are Barella, Raton, and Johnson mesas.
Just yesterday, on the clock of geological time, the scene near Capulin would have been one of fire, ash, glowing lava, and ear-shattering explosions, for Capulin Mountain is the cone of a volcano that was active only 62,000 years ago. This cinder cone represents the last stage of a great period of volcanism that had begun about eight million years earlier. Capulin's conical form rises more than 1,300 feet above the plains to 8,182 feet above sea level. The mountain consists chiefly of loose cinders, ash, and other rock debris. These materials were spewed out by successive eruptions and fell back upon the vent, piling up to form the conical mound. 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.
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. Sierra Grande rises some 2,200 feet above the surrounding plain, about 10 miles to the southeast of Capulin Cone.
|Carrizozo Malpais (Lava Flow)|
Carrizozo Lava Flow:11
The Carrizozo lava flow, also known as the "Valley of Fires" region, is an excellent example of a large volume lava flow. It is readily visible in most satellite images of the southwestern U.S. both because of its size and obvious "lava flow shape" and because of its dark albedo. Contrasted with the extremely white albedo of the White Sands at its southern extremity, the Carrizozo lava flow is one of the most recognizable features on the face of the planet.
The Carrizozo Malpais are one of the youngest volcanic features in the state of New Mexico. The Malpais, are basaltic lava flows (75 kilometer-long), such as are being erupted today in Hawaii. State highway 380 traverses the Carrizozo Malpais, and this road provides good access to people who want to view, or visit the lava flows. The "Valley of Fires" Recreation Area is located on the Carrizozo Malpais. The Carrizozo Malpais are a lava flow that formed by magma (molten rock) pouring out of a small crack in the earth's surface. The Carrizozo Malpais were formed by an "Hawaiian-style" volcanic eruption. This type of eruption is ongoing in Hawaii today. The Hawaiian-style eruption is very passive, and is typically characterized by magma pouring from a small vent in the earth's surface, and then traveling either across the earth's surface or through a series of lava tubes until it cools and solidifies. Geologists estimate that the entire Carrizozo eruption would have taken between 2 to 3 decades and that the eruption would have proceeded at a slow, steady rate. The Carrizozo Malpais consist of two basaltic lava flows that erupted from within the Tularosa Basin, in south-central New Mexico. The vent area for the lava flows, Little Black Peak, falls on the Capitan lineament, a zone of crustal weakness that extends across eastern New Mexico. The Capitan lineament is defined by a number of igneous features, including the Capitan Pluton, the Carrizozo lava flow, Broken Back Crater and associated lava flow. The Capitan lineament is interpreted as a deeply penetrating zone of crustal weakness along which magmas have been able to rise and erupt. The Carrizozo Malpais have been recently dated, using cosmogenic techniques, at around 5,000 years old. This age is quite a bit older than previous estimates of around 1,500 years that were based on observations of the appearance of the flow surface.
|Cimarron Canyon State Park|
Crenelated granite formations make up sheer palisade cliffs that dominate the park's scenery. From the main canyon, day hikes and cross-country skiing are popular.
|City of Rocks State Park|
City of Rocks State Park:12
The rock formations at the park are so unique that they are only known to exist in six other places in the world. Imaginative visitors may see the rock formations as a small city, complete with houses, chimneys, courtyards, and streets.
This state park was originally founded to preserve an unusual landscape consisting of monolithic residual blocks of ash flow tuff seemingly congregated like a "city" in the middle of a rolling grassy plain. The blocks are eroded from the Sugarlump Tuff (about 35 million years old), derived from one of the numerous ash flow calderas of the Datil-Mogollon province, one of the largest concentrations of the remains of large calderas in the Southwest. Roads winding through the monoliths and picnic sites invite the visitor to explore the unusual monolithic landforms eroded from the ancient ash flow.
|Elephant Butte State Park|
Although fossils of the stegomastodon (a primitive relative of today's elephant) have been discovered just west of the reservoir, the area was not named for its former and formidable inhabitants, the name "Elephant Butte" was derived from the eroded core of an ancient volcano, now an island in the reservoir, in the shape of an elephant.
|El Malpais National Monument|
El Malpais means "the badlands" in the Spanish language and is most commonly pronounced ell-mal-pie-ees. Its volcanic features include jagged spatter cones, a lava tube cave system extending at least 17 miles, and fragile ice caves. El Malpais includes the McCartys lava flow, New Mexico's youngest volcanic eruption (approximately 3000 years old), which is visible along much of NM 117. Prior to attaining monument status this was one of the most accessible lava flows. [See McCartys Lava Flow below]
|Grants Lava Flow|
Grants Lava Flow - National Natural Landmark:16
Valencia County - A classic example of recent extrusive volcanism. It contains lava flows that appear very fresh and unweathered. Its gigantic pressure ridges, collapse depressions, and lava tubes are outstanding. Owner: Federal, Private. DESIGNATION DATE: July 1969
The Jemez Mountains are located at the junction of the western boundary of the Rio Grande Rift and the Jemez Lineament. The Jemez Mountains are best known for two major volcanic eruptions, the first of which occurred more than 1.4 million years ago, and the second, a little over one million years ago. Together these eruptions were 600 times more powerful than the 1980 eruption of Mount St. Helens. Over 100 cubic miles of material was spewed out, covering over 1,500 square miles with volcanic ash that was up to 1,000 feet deep in some areas.
The area near Bandelier is also crossed by the Jemez Lineament. The lineament is a line of young volcanoes that represent a weakness in the earth's crust running from east-central Arizona to northeastern New Mexico. These volcanoes include Mount Taylor, the Jemez Mountains, and Capulin Volcano.
|Kasha-Katuwe Tent Rocks National Monument|
Tent Rocks is truly a magical area! Delicately layered gravels and volcanic ashes of the Peralta Tuff Member of the Bearhead Rhyolite have been eroded into interesting shapes, including spires with balanced rocks at the top. The deposits are about 6.8 million years old and were shed off volcanic domes of the Jemez volcanic field. This scenic area is located about 5 miles northwest of Cochiti Pueblo in Sandoval County.
Close inspection of the fragile tent rock formations reveals their susceptibility to erosion. Some of the rocks standing farthest away from the cliff have lost their hard caprock and are disintegrating. An examination of the cliff face reveals small ravines leading inward. Wind and water prevail here, scooping holes of all shapes and sizes in the rock and contouring the ends of the ravines into smooth semicircles. As the result of uniform layering of volcanic material, bands of gray are interspersed with beige-colored rock along the cliff face. Kasha-Katuwe Tent Rocks is located 40 miles southwest of Santa Fe and 50 miles north of Albuquerque, New Mexico, with the most direct access from Interstate 25. Take the Cochiti Reservoir exit from I-25 to NM Route 22 and follow the signs to Cochiti Pueblo. Turn right at the pueblo water tower (painted like a drum) onto Tribal Route 92 (connects to Forest Service Road 266). Travel 5 miles on a dirt road to the Tent Rocks parking area, which is marked with a sign. This is the only parking area for Kasha-Katuwe Tent Rocks.
Kilborne Hole - National Natural Landmark:16
26 miles southwest of Las Cruces in Dona Ana County. An uncommon volcanic feature known as a maar, which is a depression caused by volcanic explosion that emits little volcanic material except gas. Owner: Federal. DESIGNATION DATE: May 1975
|Little Black Peak|
Fewer than 1,000 years ago, lava erupted from Little Black Peak, a tiny volcanic center, resulting in a dark, smooth, somewhat linear lava flow. [See Carizozo Malpais (Lava Flow) above]
|McCartys Lava Flow|
McCartys Lava Flow:11
El Malpais and the Zuni-Bandera field encompasses volcanoes and volcanic flows that range in age from 700,000 to yesterday (geologically speaking). El Malpais includes the McCartys lava flow, New Mexico's youngest volcanic eruption (approximately 3,000 years old), which is visible along much of NM 117. Prior to attaining monument status this was one of the most accessible lava flows. Currently many of the more interesting and well-preserved areas are fenced off from NM 117 and require considerable walking to explore properly. Alternatives are to visit the Lava Falls trail near the extreme southern end of the flow, the Zuni-Acoma trail which lies about midway along the length of the flow, or the Sandstone Bluffs overlook for a vista of the valley in which the lava flowed. For reasons that are not clear as yet, the surface of the lava flow along the Lava Falls trail appears much more weathered and eroded than elsewhere, where the flow is backer and glassy surfaces are retained. Nonetheless, many interesting small-scale phenomena of lava flow emplacement are to be found along the trail and adjacent areas of the lava flow. Many of the small-scale textural details of lava flows were defined on the basis of study of the McCartys lava flow. The Chain of Craters Road is another way to explore the region.
Mount Taylor volcano (known as "Turquoise Mountain" to the Diné; "Spinat" to the Acomas) is largely on U. S. Forest Service land and is readily accessible with a network of maintained gravel and unimproved roads. It is the second largest young volcano in New Mexico after the Valles Caldera. It is a classic example of what is known as a composite volcano. Mount Taylor last erupted about 2.5 million years ago in an eruption that was probably similar to that of the 1980 Mount St. Helens eruption.
|Petrified Forest National Park|
The Painted Desert:15
The Painted Desert is an expanse of badland hills, flat-topped mesas and buttes. It is an arid land, sparsely vegetated and heavily eroded. The name Painted Desert refers to the rainbow of colorful sedimentary layers exposed in the austere landscape. It is represented by outcroppings of the Late Triassic Period Chinle Formation.
Most of the Chinle Group strata exposed at the Petrified Forest National Park belong to the Petrified Forest Formation. Three members are present (ascending order): Blue Mesa, Sonsela and Painted Desert.
Painted Desert Member of the Chinle Group:10
The Painted Desert Member of Lucas (1993b) overlies the Sonsela Member conformably. The northern portion of PEFO, the "Painted Desert", is the type area of this unit and is badlands mostly developed in the Painted Desert Member. At Petrified Forest National Park, the Painted Desert Member is as much as 147 meters thick, and 80-90% of its thickness is reddish-brown, calcareous, bentonitic mudstone. Several informally named sandstone beds are present in the lower part of the Painted Desert Member, as is a formally named bed of reworked tuff. The informally named sandstones are the Flattops and Painted Desert sandstones of Roadifer (1966) and Billingsley (1985).
Black Forest Bed of Ash:10
The Black Forest Bed of Ash (1992) (formerly Black Forest tuff: Billingsley, 1985) is a prominent, white, ledge-forming bed of very tuffaceous sandstone and conglomerate as much as 10.6 meters thick. Its base is typically brown-weathering limestone-pebble conglomerate overlain by white-weathering pink to purple reworked tuff. The "Black Forest" is a log and stump field - mostly of Araucarioxylon arizonicum - in the tuff. Ash (1992) reported a K-Ar age of 239 +9 million years from biotite in the upper tuffaceous part of the Black Forest Bed. This is a Middle Triassic age by any timescale and underscores the fact obvious from outcrop examination that the volcanic detritus in the Black Forest Bed has been reworked from an older source. Painted Desert Member strata above the Black Forest Bed are dominantly reddish-brown mudstones and siltstones with some lenticular sandstones.
|Petroglyph National Monument|
Long before Albuquerque spread its lights across the Rio Grande Valley, prehistoric people lived here. Today we find their tools, or scattered ruins of their houses, and sometimes places where they carved petroglyphs into the rocks. The black, volcanic cliffs that stand like a wall on Albuquerque's West Side became a vast outdoor art gallery, or perhaps a holy place. Sometimes for religion, sometimes for a record, the people chipped their ideas and visions into the volcanic boulders.
Petroglyph National Monument:5
The new monument, created in June of 1990, includes the five extinct volcanoes along Albuquerque's western horizon and the entire 17-mile-long dark cliff below, the great rock art gallery.
|Potrillo Volcanic Field|
Potrillo Volcanic Field:1
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.
The most unusual feature in the Potrillo volcanic field is Aden Crater, a beautifully preserved small shield volcano.
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.
Hunt's Hole and Patrillo Maar:1
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.
|Rayton-Clayton Volcanic Field|
Rayton-Clayton Volcanic Field:1
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. 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.
|Rio Grande Rift|
Rio Grande Rift:9
During the Quaternary, the mid-section of the continent was beginning to be pulled apart by extensional forces. Volcanism accompanied this activity. The upper Rio Grande River flowed southward through New Mexico within a long fault-bounded basin, the Rio Grande Rift, where lava from a source deep in the mantle periodically spread across the surface. In the near geologic future, several million years or so, a youthful ocean basin may occupy this area.
|Rockhound State Park|
Rockhound State Park:12
Located on the rugged west slope of the Little Florida Mountains, Rockhound State Park is a favorite for "rockhounds" because of the abundant agates and quartz crystals found there. Hiking trails provide spectacular views of the surrounding landscape. Scattered throughout the park are rock and mineral specimens of volcanic origin. These treasures range from varieties of silica minerals, quartz crystals, chalcedony, Agate, and common opal. Visitors are allowed to take up to 15 pounds of rock for their personal collections.
If a volcano is eroded to its roots, the cooled magma in the exposed conduit and in the feeding cracks is exposed. The eroded remnant of a steep, pipe-like conduit that feeds the central vent is called a volcanic neck. Dikes are formed by magma that has congealed in vertical cracks or tension features. They cut across the structure of adjacent rocks. Shiprock in New Mexico is a volcanic neck with radiating dikes. Erosion has stripped away the volcanic cone, leaving only the hard skeletal remains of the central vent and the vertical dikes. Shiprock is 450 meters high, and its dikes form great walls across the desert.
The Ship Rock landform, located in northwestern New Mexico, is the remnant of an explosive volcanic eruption that occurred around 30 million years ago. The main part of the landform is 600 meters high, and 500 meters in diameter. Ship Rock, known as Tse Bitai, or "the winged rock" in Navajo, is a volcanic neck, or the central feeder pipe of larger volcanic landform which has since eroded away. The neck is composed of fractured volcanic rock, or breccia, crosscut by many thin veins of lava. Ship Rock is composed of an unusual, highly potassic magma composition called a "minette", thought to form by very small degrees of melting of the earth's mantle. Ship Rock was probably 750 to 1,000 meters below the land surface at the time it was formed, and has since gained its prominent form due to erosion of surrounding rocks. Another striking feature of Ship Rock are the dikes, or wall-like sheets of lava that radiate away from the central neck. A total of six dikes have been recognized. These dikes would have been intruded at some depth below the earth's surface at the time that the Ship Rock eruption was occurring. Like the neck, the dikes have since been exposed due to differential weathering through time of the hard lava of the dikes, and the more easily eroded sandstone and shale of the countryrocks.
Ship Rock - National Natural Landmark:16
San Juan County - Ship Rock is an outstanding example of an exposed volcanic neck accompanied by radiating dikes; it towers 1,400 feet above the surrounding plain. Owner: Indian trust (Navajo Tribe). DESIGNATION DATE: May 1975
Chuska Volcanic Field:10
Ship Rock is a spectacular volcanic neck located within the Colorado Plateaus province in the northwestern ("Four Corners") region of New Mexico and in the middle of Navajo country. It is part of what is known as the Chuska volcanic field, a diffuse group of small intrusions, dikes, and some extrusive rocks scattered between Gallup, New Mexico and Farmington, New Mexico. Intrusive rocks in the field, like most Colorado Plateaus province intrusives, include some unusual petrologies: minette, vogesite, basaltic tuff, and tuff breccia. The Buell Park diatreme, which consists of kimberlite, is also part of the field. Ship rock is thought to represent the interior of a maar-type eruption. The intrusion is 500 meters in diameter at its greatest width, and rises 600 meters above the surrounding plains. It consists of tuff breccia and fractured and comminuted host rocks with thin, sheet-like intrusions of minette locally cutting through the entire mass. The intrusion is estimated to have been emplaced at a minimum of 750 and a maximum depth of 1000 meters below the original surface. Host rocks at the current level of erosion are late Cretaceous, marine origin Mancos Shale.
|Sierra Blanca Volcano|
Sierra Blanca Volcano:10
Sierra is an older volcanic pile consisting of intrusive stocks and dikes and contemporaneous ash, breccia, and flows. Sierra Blanca is not a modern volcano like Mount Taylor or the Valles Caldera, but is an old one that has been greatly eroded. It is estimated to have been originally on the order of 3,000 feet high and 20 miles in diameter and consisting of about 185 cubic miles of volcanic material. Estimates of the age of the initial volcano is 38 to 26 million years. This means that it erupted at about the same time that the volcanoes of the Gila and Mogollon Ranges in western New Mexico were erupting. There was considerable volcanism in the Southwest during this interval of time, most of which just preceded the formation of the Basin and Range Province. Volcanism of this age is often referred to as "mid-Tertiary" volcanism, which in the lingo of southwestern volcanology means "old". It is a testament to the original great size of the volcano, together with later block-faulting that it remains as a significant mountain even today. Sierra Blanca is said to be the eastern-most mountain associated with the Basin and Range Province, and the southern-most mountain in the U.S. with relief that extends upward into the Arctic-Alpine life zone.
|Sugarite Canyon State Park|
Sugarite Canyon State Park:12
An extended cliff of basaltic rock columns, often referred to as "caprock" is the dominant geologic feature at the park. About 12 million years ago, broad sheets of molten lava erupted from a nearby volcano, forming layers of basalt rock 10-100 feet thick. Rock climbing is allowed on the caprock.
|Taos Volcanic Field|
Taos Volcanic Field:10
The Taos Volcanic Field is the largest volcanic field within the Rio Grande Rift. It is also petrologically and volcanologically diverse, including compositions from tholeiite to rhyolite, and vent morphologies from cinder cones to steep-sided domical volcanoes. The field covers over 7,000 km2 and shares the broad valley floor with the Rio Grande which cuts through extensive sheets of thick lavas, the Serviellta basalts, to form the Rio Grande Gorge. It is bounded on the east side by the Sangre de Cristo Mountains and on the west by the Tusas Mountains. On the north it terminates near the Colorado border and on the south squeezes into the narrow constriction between the Taos basin and the Espanola basin.
Thousands of volcanoes erupted throughout the western U.S. in the last 60 million years. Among the larger volcanoes is Valles Caldera in the northwest Rio Grande Rift. The Valles Caldera lies within the Jemez Volcanic Field, a large complex of basaltic through rhyolitic volcanism accumulated over the last 13 million years, culminating in ash flow eruptions and caldera collapse. The Valles Caldera is the type area for resurgent ash flow calderas. This type of caldera is characterized by post-collapse upward bulging, or resurgence, of the caldera floor and eruptions of late silicic domes along the interior ring fracture.
Valles Caldera - National Natural Landmark:16
Mainly located in Rio Arriba and extends into Sandoval County -30 miles northwest of Santa Fe. A large circular depression, 12 to 15 miles in diameter, with scalloped walls rising from a few hundred to more than 2,000 feet above the present floor. It is one of the largest calderas in the world. Owner: Federal. DESIGNATION DATE: May 1975
|Zuni-Bandera Volcanic Field|
Zuni-Bandera Volcanic Field:6
The Zuni-Bandera volcanic field, in northwest New Mexico, has had many episodes of basaltic eruptions over the last million years. The youngest lava flow in the field is the McCartys flow, which is only 3,000 years old, one of the youngest volcanic features in the 48 contiguous United States! The Zuni-Bandera volcanic field has produced many basaltic lava flows, some with aa characteristics, and some that are pahoehoe. There are also a number of well-preserved cinder cones that can be visited, as well as many lava tubes, some of which contain perennial ice. The Zuni-Bandera volcanic field is an excellent site for studying physical volcanology of basaltic magmatic systems.
The Bandera flows originated from Bandera Crater, a double cinder cone about 150 meters high and 1 kilometer in diameter. The eruption of Bandera Crater and its associated flows was the second youngest volcanic event in the Zuni-Bandera Volcanic Field. Like many other cinder cones in the volcanic field, Bandera Crater is breached to the southwest, probably due in part to local prevailing winds. A large lava tube, intermittently collapsed, extends about 29 kilometers south from the breach in the crater wall and a commercial ice cave is located in a collapsed portion of the tube near the Candelaria Trading Post. Causey (1970) recognized seven stages in the development of Bandera Crater and its associated flows, culminating in the eruption of the black cinders that cap the cinder cone and blanket the hills to the north. Two small commercial cinder pits have been opened in the cinders covering the hills to the north of NM Highway 53 where the cinder blanket is thickest. Both aa and pahoehoe surfaces are common on the flows.
McCartys flow is the youngest basalt flow within the Zuni-Bandera volcanic field. Its source is a low shield volcano located about 40 kilometers south of the intersection of I-40 and NM-117. A small cinder cone about 8 meters high sits on top of this broad shield. Although some of the lava flowed southwestward 8 to 9 kilometers, most followed the preexisting drainage and flowed northward about 40 kilometers before turning to flow eastward 10 kilometers down the Rio San Jose valley. The McCartys flow overlies older basalts of the Zuni-Bandera volcanic field and Holocene alluvium.
Zuni-Bandera, Mount Taylor, Jemez Volcanic Fields:6
The Zuni-Bandera volcanic field volcanism occurs along the Jemez linament, a zone of apparent crustal weakness defined by a concentration of late-Cenozoic volcanism. The Zuni Bandera volcanic field also occurs in a "transition zone" between the Colorado Plateau, with crustal thicknesses of over 40 kilometers to the Rio Grande Rift where the crust is much thinner. The Jemez linament trends north-northeast, and includes the Zuni-Bandera volcanic field, the Mount Taylor volcanic field, and the Jemez volcanic field. The Jemez linament apparently has been a long-lasting tectonic feature that penetrates the lithosphere to great depth, and the basaltic lavas of the Zuni-Bandera volcanic field appear to be mantle-derived melts.
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