Valles Caldera Research Articles

Wildfires and water chemistry: effect of metals associated with wood ash.

The reactivity of metals associated with ash from wood collected from the Valles Caldera National Preserve, Jemez Mountains, New Mexico, was assessed through a series of laboratory experiments. Microscopy, spectroscopy, diffraction, and aqueous chemistry measurements were integrated to determine the chemical composition of wood ash and its effect on water chemistry. Climate change has caused dramatic impacts and stresses that have resulted in large-scale increases in wildfire activity in semi-arid areas of the world. Metals and other constituents associated with wildfire ash can be transported by storm event runoff and negatively affect the water quality in streams and rivers. Differences among ash from six tree species based on total concentrations of metals such as Ca, Al, Mg, Fe, and Mn were identified using non-metric multidimensional analysis. Metal-bearing carbonate and oxide phases were quantified by X-ray diffraction analyses and X-ray spectroscopy analyses. These metal-bearing carbonate phases were readily dissolved in the first 30 minutes of reaction with 18 MΩ water and 10 mM HCO3(-) in laboratory batch experiments which resulted in the release of metals and carbonates in the ash, causing water alkalinity to increase. However, metal concentrations decreased over the course of the experiment, suggesting that metals re-adsorb to ash. Our results suggest that the dissolution of metal-bearing carbonate and oxide phases in ash and metal re-adsorption to ash are relevant processes affecting water chemistry after wildfire events. These results have important implications to better understand the impact of wildfire events on water quality.

The eruptive and magmatic history of the youngest pulse of volcanism at the Valles caldera: Implications for successfully dating late Quaternary eruptions

New 40Ar/39Ar and U/Th ages provide insight into the youngest eruptions at the Valles caldera and also reveal previously unknown pulses of magmatism. The youngest eruptive units, collectively termed the East Fork Member of the Valles Rhyolite, include the El Cajete pyroclastic beds and co-erupted Battleship Rock ignimbrite, and the disconformably overlying Banco Bonito lava flow. Previous attempts to date these units using a variety of techniques yielded ages ranging from <40ka to >1Ma. New 40Ar/39Ar ages were generated using the high-sensitivity, multi-collector ARGUS VI mass spectrometer, which provides more than an order of magnitude increase in precision compared to most single-detector mass spectrometers. 40Ar/39Ar dating of single crystals yields a range of ages, of which the youngest populations are interpreted to represent the eruption age. Sanidine ages indicate that the El Cajete pyroclastic beds and Battleship Rock ignimbrite erupted at 74.4±1.3ka, whereas the Banco Bonito lava erupted at 68.3±1.5ka. Populations of older crystals represent variably degassed xenocrysts, explaining why previous 40Ar/39Ar bulk step-heating analyses yielded spuriously old and irreproducible results. U/Th dating of unpolished zircon surfaces also yield multiple age populations, which range from the eruption age to >350ka, indicating protracted magmatism during the 453-ka-long eruptive hiatus prior to the eruption of the East Fork Member. 40Ar/39Ar and U/Th ages indicate that the East Fork Member represents a short (6.1±2.8ka) eruptive cycle, from a longer-lived magmatic system beneath the southern caldera. Equally short repose periods, similar to the interval between the El Cajete–Battleship Rock and Banco Bonito eruptions, are possible during future volcanism at the Valles caldera. Results demonstrate that detailed geochronology using single-crystal and in-situ techniques is necessary for understanding the eruptive history and magmatic evolution at some young volcanic systems.

Valles Caldera: Preserving the “Yellowstone of the Southwest”

Valles Caldera: Preserving the “Yellowstone of the Southwest” Jeffrey M. Widener (bio) Located northwest of Santa Fe, New Mexico, are the majestic Jemez Mountains—a volcanic mountain range that began forming around 20 million years ago (figure 1) (Wolff et al. 2005). This range sits atop the western edge of the Rio Grande rift, an area of extreme volcanic activity, and is part of the Jemez lineament stretching from southeast Arizona to southern Colorado (Heiken et al. 1990). Recurrent tectonic activity formed and re-formed the Jemez Mountains into a range of lava domes, eroded cones, and incised canyons. Of particular interest to researchers are the eruptions of two small vents around 1.5 million years ago. These explosions left the surface unsupported and, as a result, the Toledo Caldera formed. Around 300,000 years later, another eruption, which was about 100 times stronger than the 1980 Mount St. Helens explosion in Washington, demolished the majority of the Toledo Caldera but formed a new one, the Valles Caldera, which measures almost 15 miles in diameter (Wolff and Gardner 1995; Valles Caldera Trust [VCT] 2003). Click for larger view View full resolution Figure 1. The Valles Caldera National Preserve is located in the volcanic Jemez Mountain range (in the distance)—taken from Santa Fe, NM (photo by author). [End Page 583] After a collapse that forms a caldera, resurgent domes can begin to form if uplift occurs owing to pressure pushing molten rock in the magma chamber below the caldera upward. In the Valles Caldera, this started over 70,000 years ago (Martin 2003, 6). Redondo Peak, at 11,254 feet, is the Valles Caldera National Preserve’s only resurgent dome. This resurgence drained the lakes, created rivers, and formed the Cañon de San Diego, where the Jemez settled in the 1700s. Geographers, geologists, and other researchers recognize the Valles Caldera as an exceptional example of an exposed caldera formation, and, indeed, some call it the “Yellowstone of the Southwest” (VCT 2003, 18; Solomon 2004). Like Yellowstone, it is a place worthy of preservation for its beautiful landscapes. It is also of great importance culturally and ecologically to several indigenous groups, particularly the Towa-speaking Jemez Pueblo. The government continues to seek ways to best preserve such areas for posterity. Over the past few decades, United States (US) government officials have tried using new methods of acquiring and paying for publicly owned land. In 1996, Congress placed the Presidio, a historic military base in San Francisco, under the direction of the Presidio Trust—the first charter land management program. Congress implemented this trust not only to “preserve the Presidio’s natural, scenic, cultural, and recreational resources” but also to help it pay for its own upkeep (Presidio Trust [PT] 2010; Fairfax, Gwin, and Huntsinger 2004). Thus, they established a difference between setting aside public land to be government supported and placing public land under a trust that would become self-supporting. In this case, the Presidio Trust manages 80 percent and the National Park Service (NPS) oversees 20 percent (PT 2010). The Valles Caldera National Preserve, established in 2000, is the second site placed in a trust program—the Valles Caldera Trust—but this region has a historical cultural geography much richer than and different from that of the Presidio (figure 2). While several authors have described the history and the problems associated with the land management practices of the NPS and the United States Department of Agriculture Forest Service (USFS) (Foresta 1984; Dilsaver 1994; Spence 1999; Burnham 2000; Williams 2006; Sellers 2009; Runte 2010), only a handful of scholars have researched the land management system of public land trusts (Benton 1998; Fairfax, Gwin, and Huntsinger 2004; Little, Berrens, and Champ 2005; DeBuys and Usner 2006; Sullivan 2008). On the surface, public land trusts are similar to the NPS and USFS models, but the unique trust model focuses more on actual land use and management for sustainability and resilience than the more familiar NPS [End Page 584] Click for larger view View full resolution Figure 2. The Valles Caldera National Preserve (cartography by author). and USFS models do. Both land management models, however, have a number of important roles in...

Shifting Public Land Paradigms: Lessons from the Valles Caldera National Preserve

The Valles Caldera National Preserve is the largest and most ambitious public land management experiment in the United States’ history. Congress created the Preserve in 2000 as a wholly owned Government Corporation managed not by a federal agency, but instead by a Board of Trustees. The management paradigm was unique. In addition to the familiar requirements of multiple use and sustained yield, the Act included a mandate that the Preserve become financially self-sustaining. This experiment ended in December of 2014 when Congress passed a law transferring management to the National Park Service. The creation of this experiment, along with its subsequent unfolding over 14 years, provides a fascinating window into the challenges associated with public land management generally and a financially driven trust model specifically. This Article examines the Preserve’s experiment and attempts to answer the question — what did we learn? Lessons include: (1) the challenges of having a corporate identity while also complying with laws pertaining to federal agencies, (2) the ways in which NEPA can inform management via iterative processes, (3) successes in science-based of adaptive management, (4) the challenges of running a “working ranch” in the American West, and (5) opportunities to protect cultural resources and honor the religious and cultural practices of living native communities. Absent among these lessons is a clear answer regarding whether public lands can be made financially self-sustaining. The Preserve’s neoliberal charge was thwarted for many reasons, including our cultural beliefs about public lands and the role they play within the American imaginary.

Months between rejuvenation and volcanic eruption at Yellowstone caldera, Wyoming

Research Article| August 01, 2015 Months between rejuvenation and volcanic eruption at Yellowstone caldera, Wyoming Christy B. Till; Christy B. Till * 1School of Earth and Space Exploration, Arizona State University, 781 Terrace Mall, Tempe, Arizona 85287, USA2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA *E-mail: christy.till@asu.edu Search for other works by this author on: GSW Google Scholar Jorge A. Vazquez; Jorge A. Vazquez 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA Search for other works by this author on: GSW Google Scholar Jeremy W. Boyce Jeremy W. Boyce 3Department of Earth, Planetary and Space Sciences, University of California–Los Angeles, 595 Charles Young Drive East, Los Angeles, California 90095, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Christy B. Till * 1School of Earth and Space Exploration, Arizona State University, 781 Terrace Mall, Tempe, Arizona 85287, USA2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA Jorge A. Vazquez 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA Jeremy W. Boyce 3Department of Earth, Planetary and Space Sciences, University of California–Los Angeles, 595 Charles Young Drive East, Los Angeles, California 90095, USA *E-mail: christy.till@asu.edu Publisher: Geological Society of America Received: 07 Apr 2015 Revision Received: 26 May 2015 Accepted: 28 May 2015 First Online: 09 Mar 2017 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2015 Geological Society of America Geology (2015) 43 (8): 695–698. https://doi.org/10.1130/G36862.1 Article history Received: 07 Apr 2015 Revision Received: 26 May 2015 Accepted: 28 May 2015 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Christy B. Till, Jorge A. Vazquez, Jeremy W. Boyce; Months between rejuvenation and volcanic eruption at Yellowstone caldera, Wyoming. Geology 2015;; 43 (8): 695–698. doi: https://doi.org/10.1130/G36862.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Rejuvenation of previously intruded silicic magma is an important process leading to effusive rhyolite, which is the most common product of volcanism at calderas with protracted histories of eruption and unrest such as Yellowstone caldera (Wyoming), Long Valley caldera (California), and Valles caldera (New Mexico) in the United States. Although orders of magnitude smaller in volume than rare caldera-forming supereruptions, these relatively frequent effusions of rhyolite are comparable to the largest eruptions of the 20th century, and pose a considerable volcanic hazard. However, the physical pathway from rejuvenation to eruption of silicic magma is unclear, particularly because the time between reheating of a subvolcanic intrusion and eruption is poorly quantified. This study uses nanometer-scale trace element diffusion in sanidine crystals to reveal that rejuvenation of a near-solidus or subsolidus silicic intrusion occurred in ∼10 mo or less following a protracted period (220 k.y.) of volcanic repose, and resulted in effusion of ∼3 km3 of high-silica rhyolite lava at the onset of Yellowstone’s last volcanic interval. The future renewal of effusive silicic volcanism at Yellowstone will likely require a comparable energetic intrusion of magma that remelts the shallow subvolcanic reservoir and generates eruptible rhyolite on month to annual time scales. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Months between rejuvenation and volcanic eruption at Yellowstone caldera, Wyoming

Rejuvenation of previously intruded silicic magma is an important process leading to effusive rhyolite, which is the most common product of volcanism at calderas with protracted histories of eruption and unrest such as Yellowstone caldera (Wyoming), Long Valley caldera (California), and Valles caldera (New Mexico) in the United States. Although orders of magnitude smaller in volume than rare caldera-forming supereruptions, these relatively frequent effusions of rhyolite are comparable to the largest eruptions of the 20th century, and pose a considerable volcanic hazard. However, the physical pathway from rejuvenation to eruption of silicic magma is unclear, particularly because the time between reheating of a subvolcanic intrusion and eruption is poorly quantified. This study uses nanometer-scale trace element diffusion in sanidine crystals to reveal that rejuvenation of a near-solidus or subsolidus silicic intrusion occurred in ∼10 mo or less following a protracted period (220 k.y.) of volcanic repose, and resulted in effusion of ∼3 km3 of high-silica rhyolite lava at the onset of Yellowstone’s last volcanic interval. The future renewal of effusive silicic volcanism at Yellowstone will likely require a comparable energetic intrusion of magma that remelts the shallow subvolcanic reservoir and generates eruptible rhyolite on month to annual time scales.

Snowpack-climate manipulation using infrared heaters in subalpine forests of the Southern Rocky Mountains, USA

Effects of infrared heaters on snow accumulation, snowmelt, and snow–atmosphere energy exchange were examined at Niwot Ridge, Colorado (CO) and compared to a naturally warmer, but otherwise similar subalpine site in the Valles Caldera National Preserve, New Mexico (NM). Observed snow accumulation was 30% lower on average and snow melted out 16 days earlier in the heated plots compared to the controls. Soil temperature during snowmelt was 3°C greater on average and soil moisture was 4% lower on average in heated plots compared to controls. In NM, snow accumulation was 23% lower, snow melted 23 days earlier, soil temperature was 0.6°C greater, and soil moisture was 13% lower on average relative to CO controls. In order to estimate differences in energy and mass balance fluxes at the snow–atmosphere interface in control versus warmer plots, the 1-D, physically based snowmelt model, SNOWPACK, was used. Model results indicated that heaters alter radiative, turbulent and mass fluxes by amounts comparable to the differences between CO and NM fluxes. The proportion of the energy flux associated with latent heat exchange during snowmelt was 9–27% of the total energy flux in heated models and 19–22% of NM models compared to 3–7% in control models. Thus, sublimation loss to the atmosphere was greater in both experimentally and naturally warmer cases relative to the control case. We conclude that IR heaters can provide alterations to the timing and magnitude of snow accumulation and snowmelt consistent with conditions observed at a warmer analog site and with climate and hydrology model projections. Impacts of IR heating on energy partitioning and sublimation should be considered when designing manipulations of the snowpack, as reductions in snowmelt water may alter biological or ecological processes.

A new species of Atheroides Haliday (Hemiptera, Aphididae) native to North America.

We report and describe the first species of Atheroides Haliday presumed to be native to North America, collected at the Valles Caldera National Preserve, New Mexico, USA. We hypothesize its placement among the Siphini based on morphological, phylogenetic analysis and extend the distribution of the genus to the Holoarctic. We expand the key of the known Atheroides to include the new species and discuss the current hypotheses of the geographic distribution of the type species, Atheroides serrulatus Haliday.

Rare earth elements as reactive tracers of biogeochemical weathering in forested rhyolitic terrain

Rare earth elements (REEs) were evaluated as potential tracers of biogeochemical weathering at pedon, hillslope, and catchment scales in the Jemez River Basin Critical Zone Observatory (JRB-CZO), Valles Caldera National Preserve, NM, USA. We investigated time series of REE patterns in precipitation, soil pore water, groundwater, and stream water, and related these data to REE composition of soil, rock and atmospheric dust. REE signatures in stream waters are dynamic, reflecting processes that occur along hydrologic flowpaths during transport to the stream, including organic matter complexation, primary and secondary mineral weathering, water/soil/bedrock interaction, and atmospheric deposition. Strong compositional similarities for the REE between soil waters and stream waters during the initial snowmelt are consistent with shallow subsurface flows to streams. Most (bio)chemical denudation of REE occurred during the snowmelt-derived dissolved organic carbon (DOC) pulse, during which time apparent colloidal mobilization of REE occurred in association with Fe and Al (oxy)hydroxides. The REE and DOC concentrations in stream waters were positively correlated (R2=0.80, p<0.0001) during snowmelt, suggesting REE complexation and mobilization in association with organic ligands during the period of shallow subsurface flow. Positive Eu-anomalies occur in the soil matrix ([Eu/Eu⁎]RT range from 1.79 to 2.52), soil solutions ([Eu/Eu⁎]RT range from 1.89 to 5.98), and stream waters ([Eu/Eu⁎]RT range from 1.01 to 2.27) with respect to the host lithologies—effects attributable to both eolian deposition and preferential feldspar dissolution. Cerium anomalies in soil solids and porewaters indicate seasonally dynamic translocation and oxidative accumulation in subsurface soil horizons (surface horizons: [Ce/Ce⁎]RT range from 0.70 to 1.1; subsurface horizons: [Ce/Ce⁎]RT range from 0.95 to 1.29), consistent with prior research reporting Ce(IV) co-precipitation with Fe- and Mn-oxide minerals.

Survival and Cause-Specific Mortality of Merriam's Wild Turkeys in the Jemez Mountains, New Mexico

Abstract. Merriam's Wild Turkeys (Meleagris gallopavo merriami) is a species of interest for managers and is considered economically valuable through wildlife viewing and hunting. We captured, radio-marked, and monitored 49 turkeys (27 males, 22 females) over a 3-year period (2008–2011) in the Valles Caldera National Preserve, Jemez Mountains, New Mexico. Annual Kaplan-Meier survival estimates varied among years (range 0.33–0.80). Lowest seasonal survival of 0.42 (SE 0.14) occurred during winter 2010 (1 Dec 2009–31 Mar 2010). We observed 20 fatalities of the 49 monitored turkeys. Predation by bobcats (Lynx rufus) and pumas (Puma concolor) accounted for 60% (n = 12) of losses. Hunter harvest (20%), vehicle collision (5%), disease (5%), and unknown causes (10%) accounted for the remaining losses.

Eruption of reverse-zoned upper Tshirege Member, Bandelier Tuff from centralized vents within Valles caldera, New Mexico

Valles caldera (New Mexico, USA) is the type example of a resurgent caldera and source of the Tshirege Member, Bandelier Tuff, which has been long recognized as a normally zoned sequence of ignimbrites. In this paper, we present geologic, stratigraphic, chemical, and mineralogical data from upper flow units of the Tshirege Member obtained at multiple sites within and east of Valles caldera showing that the upper part of the Tshirege Member is reverse-zoned in chemistry and mineralogy. The key to deciphering these compositional changes in zoning is recognition of flow unit Qbt4u, which we informally name the high Ti–Ba unit or HTBU. The HTBU is widespread within the resurgent dome area of the caldera, but is only found in a small area outside and east of the caldera. The HTBU is the most “mafic” unit in the Tshirege Member and is identified by chemical maxima in Ti, Ba, Sr, P, V, and Th, and by unusually high contents of anorthoclase, plagioclase, orthopyroxene, ilmenite, apatite and zircon with respect to other flow units. The HTBU also contains small (≤1cm) enclaves of quenched andesitic magma consisting primarily of plagioclase, orthopyroxene, clinopyroxene, glass and vesicles. Later erupted Tshirege flow units Qbt5l and Qbt5u are chemically more evolved and contain less plagioclase, orthopyroxene, ilmenite, apatite and zircon than the HTBU, and they are more evolved than flow units erupted before the HTBU (approximately 90% of the Tshirege Member).The HTBU is the host ignimbrite of a complex vent breccia exposed for over 3km along the NW faulted face of Redondo Peak, the Valles caldera resurgent dome. Breccia clasts consist of angular to subrounded fragments ≤1m in diameter of Permian red beds, Miocene basin fill sediments, Miocene to Pliocene volcanics and Quaternary ignimbrite (Otowi Member, Bandelier Tuff) that underlie Valles caldera. Flow units Qbt5l and Qbt5u overlie the HTBU vent breccia but these later units do not contain unusual quantities of lithic fragments. Significantly, small mudstone lithic fragments (generally ≤200μm in diameter) in the HTBU vent breccia contain reaction rinds of secondary garnet (andradite) along margins with ignimbrite host. We argue that the tiny andradite crystals (≤50μm) formed by reaction of degassing volatiles in the vent area with relatively Fe–Ca-rich vent breccia fragments at temperatures approaching 800°C and pressures less than a few MPa. Geologic relations and the restricted distribution of upper Tshirege flow units Qbt3t to Qtb5u indicate they were erupted in a short period of time (weeks to months) from a centralized vent near Redondo Peak, and from other buried vents as far east as the eastern ring fracture. We also conclude that late injection of andesitic melt into the residual Bandelier magma chamber stimulated the eruption of upper Tshirege Member pyroclastic flows from different locations and depths of the chamber resulting in a small but significant reversal in chemical and mineralogical zonation.

Historical dendroarchaeology of two log structures in the Valles Caldera National Preserve, New Mexico, USA

We used dendroarchaeological techniques to determine the year of construction of two historic structures in the Valles Caldera National Preserve of New Mexico, USA. Historical documents date some structures in the headquarters area of the Preserve, but the Commissary Cabin and Salt Barn were lacking conclusive construction dates. Both structures were originally thought to have been built by the Otero family who bought the property in 1899. We found that the structures were built from two tree species, white fir (Abies concolor (Gordon) Lindl. ex Hildebr.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), surprising given that ponderosa pines are also found in great numbers in the adjacent forest. Tree rings from 20 logs were confidently crossdated both graphically and statistically and provided cutting dates of trees in both structures of 1940 and 1941 when compared against the Fenton Lake reference chronology (Commissary Cabin: r=0.69, t=15.54, p<0.0001, n=263 years; Salt Barn: r=0.77, t=11.7, p<0.0001, n=232 years). By combining the cutting date years and terminal ring attributes, we suggest that both structures were built in the spring or early summer of 1941 using freshly cut logs and logs that had been cut the previous spring (1940, before or during the growing season) and stockpiled. The cutting dates of 1940 and 1941 indicate that these buildings were constructed during the Franklin Bond (1939–1945) era and associated with the transition from sheep ranching to more modern cattle grazing. These new dates provide a more distinct understanding of the cultural resources at the Valles Caldera National Preserve and provide interpretative staff with more accurate information that can be given to the public.

Stream water carbon controls in seasonally snow-covered mountain catchments: impact of inter-annual variability of water fluxes, catchment aspect and seasonal processes

Stream water carbon (C) export is one important pathway for C loss from seasonally snow-covered mountain ecosystems and an assessment of overarching controls is necessary. However, such assessment is challenging because changes in water fluxes or flow paths, seasonal processes, as well as catchment specific characteristics play a role. For this study we elucidate the impact of: (i) changes in water flux (by comparing years of variable wetness), (ii) catchment aspect [north-facing (NF) vs. south-facing (SF)] and (iii) season (snowmelt vs. summer) on all forms of dissolved stream water C [dissolved organic C (DOC), chromophoric dissolved organic matter (CDOM) and dissolved inorganic C (DIC)] in forested catchments within the Valles Caldera National Preserve, New Mexico. The significant correlation between annual water and C fluxes (e.g. DOC r2 = 0.83, p < 0.02) confirms annual stream water discharge as the overarching control on C efflux, likely from a well-mixed ground water reservoir as indicated by previous research. However, CDOM exhibited a dominantly terrestrial fluorescence signature (59–71 %) year round, signaling a strong riparian and near stream soil control on CDOM composition. During snowmelt, the role of water as C transporter was superimposed on its control as C reservoir, when the NF stream transported significantly more soil C (40 % DOC, 56 % DIC) than the SF stream as a result of hillslope flushing. Inter-annual variations in winter precipitation were paramount in regulating annual stream C effluxes, e.g., reducing C effluxes three-fold after a dry (relative to wet) winter season. During the warmer summer months % dissolved oxygen saturation decreased, δ13CDIC increased and CDOM assumed a more microbial signature, consistent with heterotrophic respiration in the stream and riparian soils. As a result of stream C incubation and soil respiration, \( P_{{{\text{CO}}_{2} }} \) increased up to 12 times atmospheric values leading to substantial degassing.

A GIS-based volcanic hazard and risk assessment of eruptions sourced within Valles Caldera, New Mexico

The objective of this study is to evaluate the spatial extent of a possible future eruption using a GIS-based volcanic hazard tool designed to simulate pyroclastic fallout and density currents (PDCs) as well as lava flows and to assess the social and economic vulnerabilities of the area at risk. Simulated pyroclastic fallout deposits originating from the El Cajete crater within the Valles Caldera, Jemez Mountains volcanic field, New Mexico, are calibrated to isopach and lithic isopleth maps of the Lower and Upper El Cajete as constructed by Wolff et al. (2011). The change in the axial orientation of fallout deposits between the Lower and Upper El Cajete is best matched using seasonal variations in wind speed and direction based on modern atmospheric records. The calibration of PDCs is based on the distribution and run-out of the Battleship Rock Ignimbrite. Once calibrated, hazards are simulated at a second vent location determined from probability distributions of structural features. The resulting hazard simulation maps show the potential distribution of pyroclastic fallout, PDCs and lava flows, indicating areas to the S/SE of Valles Caldera to be at greatest risk.To assess hazard preparedness, social vulnerability is evaluated for all census-designated places (CDPs) within the study site. Based on methods by the Hazards and Vulnerability Research Institute, twenty-four variables were selected as proxies of social vulnerability and a principal component analysis was used to generate eight components, which account for 64% of the total variance. The eight component scores are summed into a final score for each CDP, and the standard deviations from the mean of the scores are mapped with the CDPs, allowing for an easy visualization of areas that are considered more socially vulnerable.Economic vulnerability is evaluated through a multi-criteria evaluation of population, infrastructure, road types and land use. Each variable is categorized and assigned a value representing relative vulnerability based on cost and importance. The variables are assigned weights relative to one another through a pairwise comparison and summed together into a final map showing the distribution of economic vulnerability, which is useful when used with the hazard simulation maps for targeting areas for mitigation to reduce economic loss.In order to evaluate the overall risk, the hazard simulation maps and vulnerability assessments are aggregated through weighted linear combination and pairwise comparison matrices, creating a total of three risk maps. Although the actual maps provide greater detail, overall, based on the criteria chosen, the risk maps show that pyroclastic fallout has the greatest impact, effecting areas up to 50km S/SE of the Valles Caldera, including highly vulnerable cities, such as Los Alamos and White Rock. The PDC and lava flow hazards, however, impact significantly smaller areas, primarily disturbing forested land. The methodology presented in this paper allows for a robust analysis of the risks posed by eruptions sourced from the Valles Caldera and is especially useful in focusing mitigation strategies to reduce the loss from such hazardous events.

Mosses New to New Mexico

A bryophyte inventory was conducted in the Valles Caldera National Preserve (VCNP), New Mexico, from 2009 to 2011. Specimens representing 113 species of bryophytes were collected. Of those bryophytes, seven of the mosses were new to New Mexico: Atrichum tenellum (Röhling) Bruch & Schimper, Dicranum tauricum Sapjegin, Orthotrichum pallens Bridel, Sphagnum girgensohnii Russow, Tortella fragilis (Hooker & Wilson) Limpricht, Tortella tortuosa (Hedwig) Limpricht var. fragilifolia (Juratzska) Limpricht, and Warnstorfia exannulata (Hedwig) Loeske.

Spatial and temporal trends in pre-caldera Jemez Mountains volcanic and fault activity

New 40Ar/39Ar dates from the Jemez Mountain volcanic field (JMVF) reveal formerly unrecognized shifts in the loci of pre-caldera volcanic centers across the northern Jemez Mountains; these shifts are interpreted to coincide with episodes of Rio Grande rift faulting. Early activity in the field includes two eruptive pulses: 10.8–9.2 Ma basaltic to dacitic volcanism on Lobato Mesa in the northeastern JMVF and 12–9 Ma mafic to silicic volcanism in the southwestern JMVF. While 9–7 Ma eruptions persisted in the southern JMVF, a new eruptive center developed on the La Grulla Plateau in the northwestern JMVF (8.7–7.2 Ma), corresponding with a period of rift widening caused by reactivation of Laramide faults in this area. The older 8.7–7.8 Ma mafic lavas emitted from Encino Point and the younger 7.7–7.2 Ma trachyandesite and dacite erupted on the La Grulla Plateau are assigned to a new unit called the La Grulla Formation. The chemical composition of a 640 m stack of lava flows exposed in the northern margin of the Valles caldera changes from dacite to andesite, then back to dacite upsection, becoming slightly more alkalic upward. The shift to more alkalic compositions occurs across a sedimentary break, marking a subtle change in magma source for the older Paliza Canyon Formation and the younger La Grulla Formation lavas. New age constraints from a rhyolite intrusion in the southern JMVF and pumiceous rhyolite deposits in the northern JMVF suggest an episode of localized, 7.6–7.8 Ma rhyolitic volcanism that occurred in the central part of the JMVF between 12–8 Ma Canovas Canyon Rhyolite and 7–6 Ma peak Bearhead Rhyolite volcanism. Younger Bearhead Rhyolite intrusions (7.1–6.5 Ma) are more widespread than previously documented, extending into the northeastern JMVF. Tschicoma Formation dacite erupted at 5 Ma in the Sierra de los Valles and then erupted throughout the northeastern JMVF 5–2 Ma. The more refined geochronology of the JMVF indicates that pre-caldera volcanic centers were characterized by geographically and chemically distinct, relatively short-lived, episodes of activity. Volcanism generally migrated eastward through time in the southern JMVF, but the pattern in the northern JMVF had a more complex east (10–9 Ma) to west (9–7 Ma) to east (5–2 Ma) pattern that reflects the timing of motion on faults. The new ages, coupled with detailed mapping of both volcanic rocks and the Santa Fe Group, document significant pulses of faulting, erosion, and deposition during middle Miocene time and during late Miocene time across the Cañones fault zone in the northern JMVF.

Magmatic Recharge during the Formation and Resurgence of the Valles Caldera, New Mexico, USA: Evidence from Quartz Compositional Zoning and Geothermometry

The Valles caldera complex in north-central New Mexico, USA, represents the type example of resurgent caldera system, characterised by eruption of two voluminous high-silica rhyolite ignimbrites (the Otowi and Tshirege Members of the Bandelier Tuff) at 1.608 ± 0.010 Ma and 1.256 ± 0.010 Ma, respectively. Refined dating has shown that resurgence occurred shortly after eruption of the Tshirege, or Upper Bandelier Tuff (UBT). Central resurgence of ~1000 m was accompanied by small-volume eruptions of the Deer Canyon Rhyolite, followed closely by the Redondo Creek Rhyodacite. The Cerro del Medio Rhyolite lava dome complex is a product of ring fracture volcanism following resurgence, erupting at 1.229 ± 0.017 Ma. A central aim of this study was to find evidence for magmatic recharge during this geologically short (~ 27 ka) time period. We have combined cathodoluminescence (CL) imaging and titanium-in-quartz geothermometry techniques to individual quartz crystals from 1) different stratigraphic horizons of the UBT ignimbrite, 2) samples of the Deer Canyon Rhyolite and 3) the Cerro del Medio Rhyolite lavas. CL imaging reveals that ~80% of the erupted volume UBT ignimbrite contains unzoned quartz crystals (average concentration = 28 ± 2 ppm Ti), recording relatively isothermal temperatures of 647-696 °C. An abrupt occurrence of compositionally zoned quartz crystals ) within the mid-to-late erupted UBT ignimbrite units 3-5 reveals evidence for interaction with hotter magma. Corresponding titanium-in-quartz measurements of outer, bright CL rims (71 ± 9 ppm Ti) reveal temperature increases of ~100 °C relative to the start of the UBT eruption. We have discovered an interesting heterogeneity within the Deer Canyon Rhyolite lavas, with strong spatial control on eruption of porphyritic lavas containing complexly zoned quartz crystals onto the western regions of the resurgent dome. Conversely, crystal-poor to aphyric lavas containing small, unzoned quartz crystals are conf%%%%Le complexe de caldeiras de Valles au centre-nord du Nouveau-Mexique, Etats-Unis, constitue l'exemple type d'un systeme de caldeira resurgente, caracterise par l'eruption de deux volumineuses ignimbrites rhyolitiques riche en silice (les Membres Otowi et Tshirege de la Bandelier Tuff) a 1.608 ± 0.010 Ma et 1.256 ± 0.010 Ma, respectivement. Des techniques de datation de haute precision ont montre que la resurgence s'est produite rapidement apres l'eruption de la Tshirege ou Upper Bandelier Tuff (UBT). La resurgence du centre de la caldeira d'environ 1000 m s'est accompagnee des eruptions mineures des rhyolites de Deer Canyon, puis de la rhyodacite de Redondo Creek. Le complexe de domes de lave rhyolitiques de Cerro del Medio est le produit de volcanisme de fracture annulaire post-resurgence a 1.229 ± 0.017 Ma. Un point cle de cette etude etait de trouver des evidences de recharge magmatique durant ce court episode ~ 27 ka. Nous avons analyse des cristaux de quartz par imagerie de cathodoluminescence (CL) et geothermometrie du titane dans 1) plusieurs niveaux…

Global Trade Tradeoff: Rickettsial Disease in Taiwan

Global Trade Tradeoff: Rickettsial Disease in Taiwan

Linkages Between Riparian Characteristics, Ungulate Grazing, and Geomorphology and Nutrient Cycling in Montane Grassland Streams

Abstract Catchment characteristics and disturbances control the conditions and processes found in stream ecosystems. We examined nutrient cycling linkages between riparian soils and adjacent streams and the impacts of the removal of ungulate grazing on these ecosystems and processes at six grazing exclosure sites in the Valles Caldera National Preserve, NM, USA. The exclusion of native and domestic ungulate grazers for 3 yr significantly increased the riparian aboveground biomass of standing vegetation (273 ± 155 in grazed vs. 400 ± 178 g . m -2 in exclosures) and litter (58 ± 75 in grazed vs. 110 ± 76 g . m -2 in exclosures) ( P = 0.003 and 0.006, respectively). Except for an increase in total soil phosphorous (P) at three of the six sites, soil nutrient values were minimally affected by grazing after five growing seasons. Within the six sites studied, no connection was found between 0–15-cm depth soils, which were P-limited based on stoichiometric ratios, and stream nutrient availability or limitation, which were nitrogen limited. Stream geomorphology was not significantly altered by 5 yr of grazing exclusion. The elimination of grazing suppressed instream nutrient processing with significantly longer NH 4 uptake lengths ( P = 0.003). These results suggest the exclusion of ungulate grazing impacts terrestrial characteristics (increased standing vegetative biomass) that are linked to ecosystem services provided by adjacent aquatic ecosystems (reduced N-uptake). Management plans should carefully balance the positive effect of grazing on stream nutrient processing and retention reported here with the well-documented grazing-related loss of other ecosystem services such as decreased fish and aquatic invertebrate habitat and effects on water-quality parameters such as turbidity and water temperature.

Caldera resurgence during magma replenishment and rejuvenation at Valles and Lake City calderas

A key question in volcanology is the driving mechanisms of resurgence at active, recently active, and ancient calderas. Valles caldera in New Mexico and Lake City caldera in Colorado are well-studied resurgent structures which provide three crucial clues for understanding the resurgence process. (1) Within the limits of 40Ar/39Ar dating techniques, resurgence and hydrothermal alteration at both calderas occurred very quickly after the caldera-forming eruptions (tens of thousands of years or less). (2) Immediately before and during resurgence, dacite magma was intruded and/or erupted into each system; this magma is chemically distinct from rhyolite magma which was resident in each system. (3) At least 1 km of structural uplift occurred along regional and subsidence faults which were closely associated with shallow intrusions or lava domes of dacite magma. These observations demonstrate that resurgence at these two volcanoes is temporally linked to caldera subsidence, with the upward migration of dacite magma as the driver of resurgence. Recharge of dacite magma occurs as a response to loss of lithostatic load during the caldera-forming eruption. Flow of dacite into the shallow magmatic system is facilitated by regional fault systems which provide pathways for magma ascent. Once the dacite enters the system, it is able to heat, remobilize, and mingle with residual crystal-rich rhyolite remaining in the shallow magma chamber. Dacite and remobilized rhyolite rise buoyantly to form laccoliths by lifting the chamber roof and producing surface resurgent uplift. The resurgent deformation caused by magma ascent fractures the chamber roof, increasing its structural permeability and allowing both rhyolite and dacite magmas to intrude and/or erupt together. This sequence of events also promotes the development of magmatic–hydrothermal systems and ore deposits. Injection of dacite magma into the shallow rhyolite magma chamber provides a source of heat and magmatic volatiles, while resurgent deformation and fracturing increase the permeability of the system. These changes allow magmatic volatiles to rise and meteoric fluids to percolate downward, favouring the development of hydrothermal convection cells which are driven by hot magma. The end result is a vigorous hydrothermal system which is driven by magma recharge.