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Home , Bandelier Tuff, Caldera, Pyroclastic flow, Supervolcano, Valles Caldera

Winter 2010

Th e V a l l e s Ca l d e r a : Ne w Me x i c o ’s Su p e r v o l c a n o New contains one of the three larg- viscous, high-temperature foam. Much like near the vent and smaller ash far from the est young volcanoes in the : a shaken champagne bottle when the cork vent. Pyroclastic-fall deposits can be found the Valles , in the central Jemez is removed, rapid formation of free gas, throughout the Jemez but are Mountains west of Santa Fe. are mostly steam, eventually causes a violent best exposed in the southern large volcanic depressions, more or less explosion, but at eruption temperatures of area along NM–4 between the junctions circular, the diameter of which is many roughly 1,700° F. When the bubble-rich with NM–501 and NM–126. times greater than that of subsequent, post- fragments are blasted into the cold When supervolcanoes explode, they caldera vents. The other two large calderas atmosphere, they “freeze,” forming pum- form huge, hot clouds of , ash, crys- are Yellowstone, , and Long ice. Pumice is nothing more than solidified tals, and hot gas, called pyroclastic flows, Valley, . Of the three, the Valles magmatic foam. which radiate outward from the caldera caldera is both the oldest and at speeds of 50 to 200 miles per the smallest. But when it formed hour. Depending on volume, 1.25 million ago, the distance from the volcanic vent, explosions were anything but and other factors, temperatures small. Approximately 95 cubic may easily exceed 1,000° F when miles of high-viscosity molten the flows come to rest. In recent rock (magma) was blasted years pyroclastic flows have into the stratosphere and onto become known to the general the surrounding landscape, public through movies such as forming what is arguably New Dante’s Peak and a multitude of Mexico’s most famous rock, the documentary films. Geologists call picturesque Tshirege Member of large pyroclastic-flow deposits ash- the Bandelier . As the tuff flow tuffs or . These (consolidated ) was rocks are mixtures of pumice, erupted, the caldera floor col- fine ash, crystal fragments, and lapsed, forming a broad circular pre-eruption rock debris (lithic roughly 12 x 14 miles fragments). The lithics are reamed across. In today’s jargon, caldera- out of the volcanic vents during (11,254 feet) looking west across Valle Grande. This producing eruptions of this size broad is a formed by structural uplift of eruption or picked up as the are called supervolcanoes. over 3,000 feet of intracaldera . Recent research shows pyroclastic flows race over the of the Bandelier type, that Redondo grew during the 30,000- period after the caldera countryside. called , are exceptionally formed, an average uplift rate of about one inch per year. Although If emplacement temperatures hot, viscous liquids rich in sili- uplift is caused by upwelling magma at depth, Redondo Peak is not are hot enough, the ash-flow a volcanic dome. con, aluminum, potassium, and deposits may “weld,” a process sodium. The explosive power of in which enough heat is retained such magma derives from its high content If pumice and ash rain out of the in the deposit to flatten pumice and glass of dissolved water and other volatile com- atmosphere during volcanic explosions, shards and fuse them together. In most ponents, as much as 5 to 6 percent water distinctive beds called pyroclastic-fall deposits viewed outside the Valles caldera by weight. As this magma rises toward the deposits accumulate on the landscape. (e.g., at Bandelier National Monument), surface of the earth, a depth is reached at Such beds are typically composed of the Tshirege (or upper) Member of the which the pressure of overlying cold rocks light-colored, well-sorted layers of pumice. Bandelier Tuff is a nonwelded to moder- is exceeded by the pressure of dissolved The layers display uniform bed thickness ately welded ash-flow tuff. However, some volatiles in the magma. The magma is then and mantle existing topography. Fragment deposits of Tshirege inside the caldera are a mixture of melt, crystals, and bubbles, sizes are generally dependent on distance so densely welded they have formed glassy which can be thought of as an extremely from the volcanic vent, with larger pumice layers of rock resembling . Glassy,

Published by the Bureau of Geology and Resources • A Division of New Mexico Tech welded ash-flow tuffs are sometimes called collapse into the chamber, forming a vitrophyres. circular caldera depression. Much of the Volcanic ash from explosions exploded pyroclastic material falls back is often carried long distances by wind, into the collapse depression, but much is but it can be distinguished by geochemical dispersed around the caldera and into the composition and by age. Because of our abil- atmosphere. ity to obtain radiometric dates on volcanic After the caldera forms, several events materials, ash layers can provide important take place almost simultaneously: Caldera indicators of age in deposits that are other- walls slough inward forming an apron wise difficult to date. Thus, we know that ash of sediments and adjacent to from the Valles caldera explosion was carried steep slopes; a (or ) develop in by winds as far away as central and the caldera depression from rain and snow eastern Kansas and was rafted by the ancestral melt; small volcanic flows and domes erupt Rio Grande as far south as El Paso. If ash into the lake, becoming interlayered with of known age is found in river, lake, and the sediments; and the caldera floor begins ocean sediments, it can provide accurate time to lift from continued rise of magma from constraints on sedimentation rates and other below. Rapid uplift of the caldera floor earth processes. soon after caldera formation is called resur- gence. After resurgence, more magma erupts along the ring of buried collapse faults, forming domes and flows between the resurgent dome and the caldera walls. These later eruptions, called ring-fracture or moat eruptions, become interlayered with yet more sedi- ments and lake deposits. The interior of a well-developed, mature caldera eventually becomes a complicated maze of uplifted pyroclastic flows, lava flows, and sediments flanked by a ring of younger moat lava domes and sediments. The Valles caldera forms an almost perfect circular depres- sion containing a resurgent Minimum distribution of Valles caldera ash deposits; the prevailing wind direction at the time of the explosion was dome with more than 3,000 generally to the north. Rafts of pumice that floated down feet of central uplift above the the Rio Grande formed deposits still observable as far south caldera floor and a nearly com- as El Paso. plete ring of moat eruptions. It is no wonder that the Valles caldera is the type example of a resurgent Caldera Formation caldera and the place where General model of caldera formation. From research published in the 1960s come to study caldera timing, deposits, earth’s , calderas tend to form in by Robert L. Smith and Roy A. Bailey and morphology. Most other calderas clusters. Thus, the Valles caldera (1.25 mil- of the U.S. Geological Survey, the Valles are not as perfect in form. For example, lion years old) was preceded in this region caldera became famous as the location Yellowstone displays an elongate, elliptical by the comparably sized Toledo caldera where the first model of large caldera shape with two resurgent domes. Ring- (1.62 million years old). Much of Toledo formation was devised: As large volumes fracture eruptions were so voluminous that caldera was obliterated during formation of magma accumulate a few miles beneath one resurgent dome and the west caldera of the Valles caldera. In Wyoming the the earth’s surface, there may be swelling wall are buried in younger lava flows. As a (0.64 million years of the ground surface, rupture of faults result, Yellowstone was not recognized as a old) was preceded by the smaller Henry’s and fractures, seismic activity, and heating resurgent caldera until many years after the Fork caldera (1.3 million years old) and the of overlying ground water. Eventually Valles model was studied, published, and larger Big Bend Ridge caldera (2.1 million gas pressure exceeds confining pressure of applied to other suspected calderas. years old). The San Juan Mountains of overlying rocks, and the magma explodes, Because they commonly occur along southwest contain more than producing immense pyroclastic falls and hot spots, tectonic boundaries, and other fifteen calderas that formed between 24 flows. Emptying of the locations where anomalously large amounts and 30 million years ago, and the Gila destabilizes pre-existing rock masses, which of heat rise from the mantle through the Wilderness–Black Range region of south- new mexico earth matters 2 winter 2010 west New Mexico contains another ten (albedo) causing climatic cooling. calderas that formed between 25 and Such eruptions would presumably 35 million years ago. affect oscillatory climate patterns such as El Niño. Climate disruptions Predicting the Next Eruption could continue for decades while the People often ask if the Valles caldera ash blanket is slowly eroded. Many is dormant or extinct. The youngest researchers also have concluded that eruption within the caldera is the such eruptions have detrimental effects Banco Bonito lava flow dated at on animal populations; thus, forma- roughly 40,000 years ago, which is tion of the Toba caldera, partially traversed by NM–4 in the (74,000 years ago), produced a huge southern caldera. Roughly twenty-five outpouring of ash that bottlenecked eruptions have occurred since the human and animal migration and Valles caldera formed 1.25 million evolution. On the other hand, some years ago, about one eruption every of the world’s most fertile regions 50,000 years. Thus, on this crude sta- are areas where deposits of volcanic tistical basis, we might expect the next ash accumulated, and marine life can eruption in another 10,000 years or so. benefit from the infusion of iron and But the length of time between these silica from volcanic ash. Fortunately, twenty-five eruptions is highly irregu- gigantic caldera eruptions occur at Digital elevation model of Valles caldera. Blue outline an estimated frequency of only two lar, so predicting the next eruption shows maximum extent of lakes in Valle San Antonio and on eruption frequency is not realistic. Valle Grande approximately 500,000 years ago. The lakes to four events per million years. However, an eruption sometime in the formed when San Antonio Mountain and South Mountain Nonetheless, it is impossible to predict lava domes erupted, blocking San Antonio Creek and East when the next supervolcano will blow Fork . (making great fodder for “act of God” movies). Resources The immense heat associated with caldera magma chambers and their erup- tion products creates hot springs, fuma- roles, and underground reservoirs of hot water. In younger calderas these features are collectively called active hydrothermal systems or geothermal systems. The geothermal system of Yellowstone caldera, which includes Old Faithful, is world- renowned, but the Valles caldera also contains an active geothermal system with distinctive thermal features and a small, but hot (650° F), underground reservoir. Baca Land and Co. and Union Oil of California unsuccessfully explored the Valles reservoir for electricity generation potential between 1962 and 1984. Hydrothermal fluids dissolve metals from Flow test of well VC-2a, May 1987, Sulphur adjacent rocks and may form ore deposits Springs, Valles caldera, from a single fracture in favorable underground horizons. In in Bandelier Tuff at 1,607 feet, 410° F. The older, eroded calderas, such as Creede, geothermal “reservoir” underlies a thin Colorado, or Questa, New Mexico (26.9 Photo of Tshirege Member (upper member) of the Bandelier Tuff, produced during cap of acid hot springs, fumaroles, and gas and 25.7 million years old, respectively), vents surrounded by rocks containing sulfur, the Valles caldera eruption (1.25 million kaolin, and other acid-stable . Author these ore deposits are economically signifi- years ago). It overlies the Otowi Member photo. cant. Gold, silver, copper, lead, zinc, and (lower member) of Bandelier Tuff from the molybdenum are commonly mined from comparably sized but earlier Toledo caldera hydrothermal deposits in eroded calderas. event (1.62 million years ago). The Guaje future is likely; the Jemez has pyroclastic-fall deposit underlies the lower Bandelier Tuff. Author photo. produced hundreds of eruptions during its 14-million-year history, and the Valles The Impact on Climate caldera still retains immense quantities of Recently much attention has been paid to Because calderas form collapse depres- heat within its interior. Most volcanologists the impact that supervolcanoes have on cli- sions, the resulting basins collect water would probably classify Valles as dormant. mate. A continent-sized ash blanket would that form lakes. of caldera walls produce significant sunlight reflectivity and eruption of ring-fracture can new mexico earth matters 3 winter 2010 cause repeated cycles of lake drainage and renewed lake formation. Lake deposits from the Valles caldera are dated by determining the age of interlayered volcanic deposits; thus, we know that a large lake occupied Valles soon after the caldera formed (1.25 million years ago) but that subsequent lakes occupied parts of the caldera roughly 800,000, 500,000, and 55,000 years ago. The South Mountain lake formed when eruption of the South Mountain rhyolite dome and flow complex blocked the ancestral drainage of the East Fork Jemez River roughly 520,000 years ago. Drilling of South Mountain lake deposits in Valle Grande produced cores that revealed a 200,000-year history of sediment accumulation, the longest mid- lake record in the southwestern U.S. Presently these cores are being studied to document climate cycles during this geo- logically “not-too-ancient” climate period. Similarities between our present climate A–Bandelier pumice, an example of “frozen” magmatic foam; B–Nonwelded Bandelier Tuff and portions of the South Mountain (note the lithic and pumice fragments); C–Moderately welded Bandelier Tuff with large partially collapsed pumice; D–Densely welded Bandelier Tuff, so welded that it resembles obsidian. Author climate cycles have been noted by several photos. groups of researchers. These records may be useful in developing future climate pyroclastic deposits, the “global model Fraser Goff has spent 32 years working in the models and predictions of future climate of caldera resurgence,” a classic, high- and Valles caldera. He was variations. temperature geothermal system with ana- employed by Los Alamos National Laboratory logs to fossil ore deposits, and a sequence from 1978 to 2004 to conduct geothermal energy The Valles Caldera National of lake deposits recording late Pleistocene and research and now works with Preserve climate cycles. The Valles caldera is truly the New Mexico Bureau of Geology on the STATEMAP Program. He received his B.S. in In 2000 the U.S. government purchased New Mexico’s “State ,” a geologic chemistry from San Jose State College (1971) and the Baca Land and Cattle Co. and created treasure and one of the most famous his Ph.D. in earth science from the University of the 88,900-acre Valles Caldera National calderas in the world. California, Santa Cruz (1977). Preserve. The preserve is managed by the —Fraser Goff Valles Caldera Trust, whose mandate is to “protect and preserve the scientific, scenic, I give particular thanks to my colleague Additional Reading geologic, watershed, fish, wildlife, historic, Jamie N. Gardner and my wife Cathy cultural, and recreational values of the J. Goff (Janik) for their geologic and Valles Caldera – A Geologic History by Preserve, and to provide for multiple use geothermal insight and unwavering Fraser Goff. University of New Mexico and sustained yield of renewable resources support during my many years of Valles Press, 2009. within the Preserve.” Detailed geologic research. I also offer many, many thanks to maps of every 7.5-minute topographic the host of geoscientists who have worked Valles Caldera: Map and Geologic History quadrangle covered by the preserve are on the Valles caldera since the turn of the of the Southwest’s Youngest Caldera by Kirt among the many multi-institutional sci- last century. Long-term financial support Kempter and Dick Huelster. High Desert entific activities funded since 2000. These from Los Alamos National Laboratory, Field Guides, 2007. maps may be obtained from the New the Valles Caldera , the Mexico Bureau of Geology and Mineral U.S. Forest Service, the U.S. Geological Encyclopedia of Volcanoes, Haraldur Sig- Resources at: http://geoinfo.nmt.edu/ Survey, and the New Mexico Bureau of urdsson, editor-in-chief. Academic Press, publications/maps/geologic/ofgm/home. Geology and Mineral Resources is grate- 2000. cfm. In 2010 the bureau will release a fully acknowledged. Thanks also to Nelia 1:50,000-scale color compilation as a single Dunbar for reviewing the manuscript. When Yellowstone Explodes by J. Achen- Valles caldera geologic map. Its appearance bach. In National Geographic, v. 216, pp. will no doubt spawn a new wave of geo 56–69, 2009. science research on the caldera. The Valles caldera will forever be a location of focused geoscientific research because it has so much to offer: well- characterized “supervolcano” features and new mexico earth matters 4 winter 2010 Bu r e a u Ne w s Earth Science Achievement Upcoming Retirements Awards It is with regret that we announce the On February 4 the 2010 New Mexico retirement this summer of four bureau Earth Science Achievement Awards were researchers with over a century of combined presented to Dr. Gary King, for outstand- service. Three of them will remain on staff ing contributions advancing the role of one-quarter time. Richard Chamberlin earth science in areas of public service and began his 30-year career at the bureau as a public policy in New Mexico, and to Dr. uranium economic geologist. Since 1990 Bruce Thomson, for outstanding contribu- he has concentrated on geologic mapping tions advancing the role of earth science in volcanic terranes of central New Mexico. in areas of applied science and education Research includes his work on domino-style in New Mexico. These awards are co- crustal extension in the , Volume 10, Number 1 sponsored by the New Mexico Bureau of a detailed eruptive history of the Socorro Published twice annually by the Geology and Mineral Resources, a division caldera, and an ongoing study of mafic dikes New Mexico Bureau of Geology and Mineral Resources of New Mexico Tech in Socorro, and the that radiate outward from the caldera cluster Peter A. Scholle Energy, Minerals and Natural Resources southwest of Socorro. Former director Frank Director and State Geologist Department (EMNRD) in Santa Fe. They Kottlowski once referred to Richard as “my a division of were initiated in 2003 to honor those often idea man.” Richard is well known for his New Mexico Institute of unrecognized champions of earth science work on the tectonics and thermal history Mining and Technology issues vital to the future of New Mexico. of central and southwestern New Mexico. Daniel H. López President Selections were made following a statewide Robert Eveleth, the bureau’s mining 801 Leroy Place nomination process. engineer, has spent 33 years keeping track of Socorro, New Mexico 87801-4750 Gary King has long been a champion New Mexico’s mineral production activities. (575) 835-5420 of natural resource protection and Bob has probably answered every conceiv- Albuquerque Office environmental issues. A native New able question on New Mexico mining 2808 Central SE Mexican from Stanley, Gary King holds history, mining law, and mining claims and Albuquerque, New Mexico 87106 (505) 366-2530 a Ph.D. in organic chemistry from the has explained every aspect of the mineral Visit our main Web site University of Colorado and a law degree extraction industry. Bob has been associate geoinfo.nmt.edu from the University of New Mexico. He curator of the bureau’s mineral museum for Board of Regents was assistant secretary for environmental years and participated in the Abandoned Ex Officio management at the U.S. Department of Mines Program on underground metal Bill Richardson Energy and served for twelve years in the mines. He is the creator and manager of Governor of New Mexico New Mexico State Legislature. During the bureau’s mining archives and database, Viola Florez this time, he sponsored a bill that would which include more than 5,000 historic Secretary of Higher Education establish a mining reclamation law in and irreplaceable photographs. Ibrahim Appointed New Mexico for the first time. Dr. King Gundiler has served New Mexico Tech as a Ann Murphy Daily served as a commissioner and chairman of professor in the Department of Metallurgy President 2005–2011, Santa Fe the Mining Commission. In 2006 he was and as a researcher. Since becoming the elected Attorney General of New Mexico, bureau’s extractive metallurgist in 1989 Abe Jerry A. Armijo Secretary/Treasurer where he continues his efforts. has been involved in countless projects— 2009–2015, Socorro Bruce Thomson is director of the researching noncyanide extraction of gold Richard N. Carpenter University of New Mexico Water and silver, solving corrosion problems in oil 2009–2015, Santa Fe Resources program and a professor in the and gas wells, improving the processing of potash ores, and reprocessing mine tailings, Abe Silver, Jr. Department of Civil Engineering, where 2007–2013, Santa Fe he now serves as Regents Professor. His to name a few. However, when asked what research is focused on the chemistry and a metallurgist does, Abe defers to the defini- William Villanueva Regent-Designate treatment of inorganic contaminants tion of his professor Terkel Rosenqvist: “A 2009–2010, Socorro in ground water, especially arsenic and metallurgist should be a jack of many trades uranium. Recent research projects have and a master of some.” Marshall Reiter Editors been directed toward issues associated with joined New Mexico Tech in 1970, first L. Greer Price Jane C. Love reuse of treated waste water. He has served teaching in the geology department for five Layout and Graphics on several local, state, and national com- years, then moving to the bureau where Gina D’Ambrosio mittees dealing with water issues, including he pursued geothermal studies in New Leo Gabaldon ten years of service on the Water Quality Mexico and neighboring areas. He and his Phil Miller Protection Advisory Board, which reports students have identified the high heat flow Earth Matters is a free publication. to the City of Albuquerque, Bernalillo of the Rio Grande rift and the San Juan For subscription information please call County, and the Albuquerque Bernalillo Mountains and have used measurements of (575) 835-5490, or e-mail us at County Water Utility Authority. subsurface temperature gradients to study [email protected] ground water flow. Cover photo of Ship Rock, New Mexico © Gary Rasmussen new mexico earth matters 5 winter 2010 New Mexico Institute of Mining & Technology NONPROFIT ORGANIZATION New Mexico Bureau of Geology and Mineral Resources U.S. Postage 801 Leroy Place Socorro, New Mexico 87801-4750 PAID Return service requested p e r m i t n o . 1888 Al b u q u e r q u e , NM

Pu b l i c a t i o n s Coming Soon We are currently working on a new Geologic Map of the Valles Caldera, Jemez Mountains, New Mexico, by Fraser Goff, Jamie N. Gardner, Steven L. Reneau, Shari A. Kelley, Kirt A. Kempter, and John R. Lawrence. This detailed map, which will be printed at a scale of 1:50,000, has been compiled from detailed larger-scale maps of nine 7.5-minute topographic quadrangles completed as part of the federally funded STATEMAP program. The new map compilation encompasses the Valles Caldera National Preserve and includes the westernmost parts of Bandelier National Monument and Santa Clara Pueblo. This is the first geologic map of the Valles caldera to be published since 1970 when the U.S. Geological Survey released its 1:125,000-scale geologic map of the Jemez Mountains, New Mexico, by Robert L. Smith, Roy A. Bailey, and Clarence S. Ross. Since 1970 four decades of new geologic studies and mapping and new geochronologic data have added to our understanding of the relations of stratigraphic units in and around the Valles caldera. The new map and its accompanying cross sections, unit descriptions, and The Geology of Northern New Mexico’s Parks, correlation chart represent the collective work of dozens of researchers, Monuments, and Public Lands, L. Greer Price, editor, mappers, and lab technicians. We hope to have it out by the end of 2010. 380 pp. Available May 1. ISBN: 978-1-883905-25-5. $24.95 Few places in the U.S. boast as rich a diversity of landscape and public lands as northern New Mexico. Here in one volume is an For more information about this and other bureau publications: authoritative overview of the geology of these parks, monuments, • Visit our Web site at http://geoinfo.nmt.edu and public lands, with information on the regional setting, the rock record, and the most prominent geologic features. The book includes • Write or visit our Publications Office on the campus of New chapters on nine national parks and monuments, seventeen state Mexico Tech, 801 Leroy Place, Socorro, New Mexico 87801 parks, and many of the most popular Bureau of Land Management • Call (575) 835-5490 or e-mail us at [email protected] and U.S. Forest Service units in this part of the state. Also included • Publication prices do not include shipping and handling or taxes are chapters on two of our newer units, the Valles Caldera National where applicable. Preserve and Kashe-Katuwe Tent Rocks National Monument. With nearly 300 full-color geologic maps, graphics, and photographs, the book is a perfect introduction to some of New Mexico’s most significant geologic landscapes. new mexico earth matters winter 2010