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Deborah Bergfeld

Publications and source records attributed to Deborah Bergfeld.

16 recordsLinked to original sources
USGS2025

Gas chemistry and isotope data for volcano monitoring at the Lassen Volcanic Center, Lassen Volcanic National Park

This report presents chemical and isotopic compositions of volcanic gases collected from thermal areas within Lassen Volcanic National Park in northern California from 1974 through 2019. As the southernmost volcano in the Cascade Range and designated a very-high-threat volcano by the U.S. Geological Survey, the Lassen Volcanic Center (LVC) requires consistent monitoring to assess potential volcanic hazards. In 2014, the California Volcano Observatory established a gas geochemical monitoring program at LVC to provide baseline data to evaluate future changes.</p> Results demonstrate consistent spatial patterns in bulk gas chemistry that support a two-circulation-cell hydrothermal model previously established for LVC. Gas samples from circulation cell 1 thermal areas have higher helium isotope ratios (6.59–7.50 times the air value) than those from circulation cell 2 (5.86–6.52 times the air value), indicating a stronger magmatic signature. The Sulphur Works and Pilot Pinnacle thermal areas within circulation cell 1 consistently emit gases with the highest magmatic helium contents, suggesting gas at these areas best represents conditions in the underlying volcanic system. A slight decrease in helium isotope values since 1974 may indicate progressive dilution of magmatic helium-3 (3He) by radiogenic helium-4 (4He) in the absence of recent magma intrusion. Carbon isotope compositions of carbon dioxide across all thermal areas are relatively uniform (−9.7–−7.3 per mil), falling within the range observed at other Cascade Range volcanoes. Based on gas geochemical characteristics and site accessibility, the Sulphur Works and Pilot Pinnacle thermal areas represent optimal targets for continued monitoring of the LVC magmatic-hydrothermal system. This study includes the most comprehensive helium isotope dataset collected at LVC currently available and establishes critical baseline data for future volcanic monitoring efforts.</p>

Open-File Report↗
USGS2023

Tracking carbon from subduction to outgassing along the Aleutian-Alaska Volcanic Arc

Subduction transports volatiles between Earth’s mantle, crust, and atmosphere, ultimately creating a habitable Earth. We use isotopes to track carbon from subduction to outgassing along the Aleutian-Alaska Arc. We find substantial along-strike variations in the isotopic composition of volcanic gases, explained by different recycling efficiencies of subducting carbon to the atmosphere via arc volcanism and modulated by subduction character. Fast and cool subduction facilitates recycling of ~43 to 61% sediment-derived organic carbon to the atmosphere through degassing of central Aleutian volcanoes, while slow and warm subduction favors forearc sediment removal, leading to recycling of ~6 to 9% altered oceanic crust carbon to the atmosphere through degassing of western Aleutian volcanoes. These results indicate that less carbon is returned to the deep mantle than previously thought and that subducting organic carbon is not a reliable atmospheric carbon sink over subduction time scales.

Alaska↗
USGS2021

Groundwater dynamics at Kīlauea Volcano and vicinity, Hawaiʻi

Kīlauea Volcano, on the Island of Hawaiʻi, is surrounded and permeated by active groundwater systems that interact dynamically with the volcanic system. A generalized conceptual model of Hawaiian hydrogeology includes high-level dike-impounded groundwater, very permeable perched and basal aquifers, and a transition (mixing) zone between freshwater and saltwater. Most high-level groundwater is associated with the low-permeability intrusive complexes that underlie volcanic rift zones and calderas and also act to compartmentalize the groundwater system. Hydrogeologic studies of Kīlauea in recent decades, accompanied by deep research drilling, have shown that high-level groundwater is more widespread than once understood, that permeability decreases dramatically at depth, particularly in rift zones, and that freshwater can occur at depths of as much as several kilometers below the local water table. Copious groundwater recharge causes near-surface conductive heat flow to be near zero over much of Kīlauea. Approximately 95 percent of groundwater discharge occurs offshore, accompanied by approximately 99 percent of the approximately 6,000 megawatts of heat supplied by magmatic intrusion. Here, we summarize current understanding of the groundwater system of Kīlauea Volcano and describe transient changes during the decade or more preceding the 2018 eruption sequence. The changes in groundwater chemistry and thermal structure beneath Kīlauea summit hold implications for volcanic-volatile transport and the potential for explosive volcanism. Between 2008 and 2018, the magma conduit beneath the lava lake likely created an adjacent zone of very hot rock that significantly delayed liquid groundwater inflow to the draining magma conduit. Sulfate concentrations in groundwater beneath Kīlauea summit, sampled at the National Science Foundation-funded drill hole 1.5 kilometers south-southwest of the lava lake, declined substantially between 2010 and present. This decline likely reflects, at least in part, the decreased effectiveness of volatile condensation and solution into groundwater (scrubbing). The vent opening in 2008 presumably focused volatile flux into the vicinity of the vent, and progressive drying of the surroundings further restricted interaction with the groundwater system. The decrease in sulfate concentrations in the drill hole between 2010 and 2018 likely reflects decreased effectiveness of scrubbing.

Hawaii↗
USGS2020

Hydrothermal activity in the southwest Yellowstone Plateau Volcanic Field

In the past two decades, the U.S. Geological Survey and the National Park Service have studied hydrothermal activity across the Yellowstone Plateau Volcanic Field (YPVF) to improve the understanding of the magmatic-hydrothermal system and to provide a baseline for detecting future anomalous activity. In 2017 and 2018 we sampled water and gas over a large area in the southwest YPVF and used Landsat 8 thermal infrared data to estimate radiative heat flow. Most of the thermal activity in this region is in close proximity to the Yellowstone Caldera boundary. Springs and fumaroles discharge from a variety of lithologies including some of the youngest rhyolites in the YPVF. Gas compositions and helium isotope ratios of most samples resemble those in other parts of the YPVF. The waters have meteoric origins and tritium was detected in several samples. Thermal waters from some areas have compositions that plot along a line connecting thermal and non-thermal water endmember compositions. The thermal water endmember equilibrated at 160-170 °C, lower than waters in Yellowstone’s geyser basins. Heat discharged by springs and fumaroles originates from within the Yellowstone Caldera and is transported laterally by advection, mainly along the base of rhyolite flows that cover the inferred caldera boundaries.

Yellowstone National Park↗
USGS2020

A post-eruption study of gases and thermal waters at Okmok Volcano, Alaska

We report here on the first focused study of gas discharges and thermal spring waters at Okmok Volcano since the 2008 phreatomagmatic eruptions. Results include the first compositional gas data from Okmok with minimal air contamination and the first data on magmatic carbon in Okmok spring waters. Chemical and isotopic analyses of the waters and gases are used to assess the character of Okmok fluids eight years after the eruptions ceased. Gases from vents on intracaldera Cone C have high concentrations of H2 and contain H2S rather than SO2, demonstrating the influence of a hydrothermal system, while isotope values of carbon ( 10.2 to 8.9‰) and helium (~8 RA) confirm the presence of magma-derived volatiles. Estimates of equilibrium temperatures for the Cone C gas are ~230 ± 30 ºC. A much cooler reservoir with a maximum temperature of ~55 ºC feeds the intracaldera warm springs. Based on discharge measurements of creeks draining the caldera, the total heat output of the warm springs is estimated to be about 32 MW. Gas data from a single location of steaming ground at the Geyser Bight geothermal area southwest of the Okmok Caldera are given. The gas is typical of geothermal gases with high concentrations of H2S and an air-corrected helium isotope ratio of 7.15 RA.

Alaska↗
USGS2018

Hot water in the Long Valley Caldera—The benefits and hazards of this large natural resource

The volcanic processes that have shaped the Long Valley Caldera in eastern California have also created an abundant supply of natural hot water. This natural resource provides benefits to many users, including power generation at the Casa Diablo Geothermal Plant, warm water for a state fish hatchery, and beautiful scenic areas such as Hot Creek gorge for visitors. However, some features can be dangerous because of sudden and unpredictable changes in the location and flow rate of boiling water. The U.S. Geological Survey monitors several aspects of the hydrothermal system in the Long Valley Caldera including temperature, flow rate, and water chemistry.

California↗
USGS2018

Multi-year high-frequency hydrothermal monitoring of selected high-threat Cascade Range volcanoes

From 2009 to 2015 the U.S. Geological Survey (USGS) systematically monitored hydrothermal behavior at selected Cascade Range volcanoes in order to define baseline hydrothermal and geochemical conditions. Gas and water data were collected regularly at 25 sites on 10 of the highest-risk volcanoes in the Cascade Range. These sites include near-summit fumarole groups and springs/streams that show clear evidence of magmatic influence (high 3 He/ 4 He ratios and/or large fluxes of magmatic CO 2 or heat). Site records consist mainly of hourly temperature and hydrothermal-flux data. Having established baseline conditions during a multiyear quiescent period, the USGS reduced monitoring frequency from 2015 to present. The archived monitoring data are housed at (doi:10.5066/F72N5088). These data (1) are suitable for retrospective comparison with other continuous geophysical monitoring data and (2) will provide context during future episodes of volcanic unrest, such that unrest-related variations at these thoroughly characterized sites will be more clearly recognizable. Relatively high-frequency year-round data are essential to achieve these objectives, because many of the time series reveal significant diurnal, seasonal, and inter-annual variability that would tend to mask unrest signals in the absence of baseline data. Here we characterize normal variability for each site, suggest strategies to detect future volcanic unrest, and explore deviations from background associated with recent unrest.

California, Oregon, Washington↗
USGS2017

Groundwater resources of the Devils Postpile National Monument—Current conditions and future vulnerabilities

This study presents an extensive database on groundwater conditions in and around Devils Postpile National Monument. The database contains chemical analyses of springs and the monument water-supply well, including major-ion chemistry, trace element chemistry, and the first information on a list of organic compounds known as emerging contaminants. Diurnal, seasonal, and annual variations in groundwater discharge and chemistry are evaluated from data collected at five main monitoring sites, where streams carry the aggregate flow from entire groups of springs. These springs drain the Mammoth Mountain area and, during the fall months, contribute a significant fraction of the San Joaquin River flow within the monument. The period of this study, from fall 2012 to fall 2015, includes some of the driest years on record, though the seasonal variability observed in 2013 might have been near normal. The spring-fed streams generally flowed at rates well below those observed during a sequence of wet years in the late 1990s. However, persistence of flow and reasonably stable water chemistry through the recent dry years are indicative of a sizeable groundwater system that should provide a reliable resource during similar droughts in the future. Only a few emerging contaminants were detected at trace levels below 1 microgram per liter (μg/L), suggesting that local human visitation is not degrading groundwater quality. No indication of salt from the ski area on the north side of Mammoth Mountain could be found in any of the groundwaters. Chemical data instead show that natural mineral water, such as that discharged from local soda springs, is the main source of anomalous chloride in the monument supply well and in the San Joaquin River. The results of the study are used to develop a set of recommendations for future monitoring to enable detection of deleterious impacts to groundwater quality and quantity

California↗
USGS2017

Evidence for degassing of fresh magma during the 2004-2008 eruption of Mount St. Helens: Subtle signals from the hydrothermal system

Results from chemical and isotopic analyses of water and gas collected between 2002 and 2016 from sites on and around Mount St. Helens are used to assess magmatic degassing related to the 2004-2008 eruption. During 2005 the chemistry of hot springs in The Breach of Mount St. Helens showed no obvious response to the eruption, and over the next few years, changes were subtle, giving only slight indications of perturbations in the system. By 2010 however, water chemistry, temperatures, and isotope compositions (δD and δ 18 O) clearly indicated some inputs of volatiles and heat associated with the eruption, but the changes were such that they could be attributed to a pre-existing, gas depleted magma. An increase of ~ 1.5‰ in the δ 13 C values of dissolved carbon in the springs was noted in 2006 and continued through 2009, a change that was mirrored by a similar shift in δ 13 C-CO 2 in bubble gas emissions. These changes require input of a new source of carbon to the hydrothermal system and provide clear evidence of CO 2 from an undegassed body of magma. Rising trends in 3 He/ 4 He ratios in gas also accompanied the increases in δ 13 C. Since 2011 maximum R C /R A values are ≥ 6.4 and are distinctly higher than 5 samples collected between 1986 and 2002, and provide additional evidence for some involvement of new magma as early as 2006, and possibly earlier, given the unknown time needed for CO 2 and He to traverse the system and arrive at the springs.

Washington↗
USGS2017

Monitoring gas and heat emissions at Norris Geyser Basin, Yellowstone National Park, USA based on a combined eddy covariance and Multi-GAS approach

We quantified gas and heat emissions in an acid-sulfate, vapor-dominated area (0.04-km 2 ) of Norris Geyser Basin, located just north of the 0.63 Ma Yellowstone Caldera and near an area of anomalous uplift. From 14 May to 3 October 2016, an eddy covariance system measured half-hourly CO 2 , H 2 O and sensible ( H ) and latent ( LE ) heat fluxes and a Multi-GAS instrument measured (1 Hz frequency) atmospheric H 2 O, CO 2 and H 2 S volumetric mixing ratios. We also measured soil CO 2 fluxes using the accumulation chamber method and temperature profiles on a grid and collected fumarole gas samples for geochemical analysis. Eddy covariance CO 2 fluxes ranged from − 56 to 885 g m − 2 d − 1 . Using wavelet analysis, average daily eddy covariance CO 2 fluxes were locally correlated with average daily environmental parameters on several-day to monthly time scales. Estimates of CO 2 emission rate from the study area ranged from 8.6 t d − 1 based on eddy covariance measurements to 9.8 t d − 1 based on accumulation chamber measurements. Eddy covariance water vapor fluxes ranged from 1178 to 24,600 g m − 2 d − 1 . Nighttime H and LE were considered representative of hydrothermal heat fluxes and ranged from 4 to 183 and 38 to 504 W m − 2 , respectively. The total hydrothermal heat emission rate ( H + LE + radiant) estimated for the study area was 11.6 MW and LE contributed 69% of the output. The mean ± standard deviation of H 2 O, CO 2 and H 2 S mixing ratios measured by the Multi-GAS system were 9.3 ± 3.1 parts per thousand, 467 ± 61 ppmv, and 0.5 ± 0.6 ppmv, respectively, and variations in the gas compositions were strongly correlated with diurnal variations in environmental parameters (wind speed and direction, atmospheric temperature). After removing ambient H 2 O and CO 2 , the observed variations in the Multi-GAS data could be explained by the mixing of relatively H 2 O-CO 2 -H 2 S-rich fumarole gases with CO 2 -rich and H 2 O-H 2 S-poor soil gases. The fumarole H 2 O/CO 2 and CO 2 /H 2 S end member ratios (101.7 and 27.1, respectively, on average) were invariant during the measurement period and fell within the range of values measured in direct fumarole gas samples. The soil gas H 2 O/CO 2 end member ratios (~ 15–30) were variable and low relative to the fumarole end member, likely resulting from water vapor loss during cooling and condensation in the shallow subsurface, whereas the CO 2 /H 2 S end member ratio was high (~ 160), presumably related to transport of CO 2 -dominated soil gas emissions mixed with trace fumarolic emissions to the Multi-GAS station. Nighttime eddy covariance ratios of H 2 O to CO 2 flux were typically between the soil gas and fumarole end member H 2 O/CO 2 ratios defined by Multi-GAS measurements. Overall, the combined eddy covariance and Multi-GAS approach provides a powerful tool for quasi-continuous measurements of gas and heat emissions for improved volcano-hydrothermal monitoring.

Wyoming↗
USGS2016

The Lassen hydrothermal system

The active Lassen hydrothermal system includes a central vapor-dominated zone or zones beneath the Lassen highlands underlain by ~240 &deg;C high-chloride waters that discharge at lower elevations. It is the best-exposed and largest hydrothermal system in the Cascade Range, discharging 41 &plusmn; 10 kg/s of steam (~115 MW) and 23 &plusmn; 2 kg/s of high-chloride waters (~27 MW). The Lassen system accounts for a full 1/3 of the total high-temperature hydrothermal heat discharge in the U.S. Cascades (140/400 MW). Hydrothermal heat discharge of ~140 MW can be supported by crystallization and cooling of silicic magma at a rate of ~2400 km 3 /Ma, and the ongoing rates of heat and magmatic CO 2 discharge are broadly consistent with a petrologic model for basalt-driven magmatic evolution. The clustering of observed seismicity at ~4&ndash;5 km depth may define zones of thermal cracking where the hydrothermal system mines heat from near-plastic rock. If so, the combined areal extent of the primary heat-transfer zones is ~5 km 2 , the average conductive heat flux over that area is >25 W/m 2 , and the conductive-boundary length <50 m. Observational records of hydrothermal discharge are likely too short to document long-term transients, whether they are intrinsic to the system or owe to various geologic events such as the eruption of Lassen Peak at 27 ka, deglaciation beginning ~18 ka, the eruptions of Chaos Crags at 1.1 ka, or the minor 1914&ndash;1917 eruption at the summit of Lassen Peak. However, there is a rich record of intermittent hydrothermal measurement over the past several decades and more-frequent measurement 2009&ndash;present. These data reveal sensitivity to climate and weather conditions, seasonal variability that owes to interaction with the shallow hydrologic system, and a transient 1.5- to twofold increase in high-chloride discharge in response to an earthquake swarm in mid-November 2014.

California↗
USGS2015

Origins of geothermal gases at Yellowstone

Gas emissions at the Yellowstone Plateau Volcanic Field (YPVF) reflect open-system mixing of gas species originating from diverse rock types, magmas, and crustal fluids, all combined in varying proportions at different thermal areas. Gases are not necessarily in chemical equilibrium with the waters through which they vent, especially in acid sulfate terrain where bubbles stream through stagnant acid water. Gases in adjacent thermal areas often can be differentiated by isotopic and gas ratios, and cannot be tied to one another solely by shallow processes such as boiling-induced fractionation of a parent liquid. Instead, they inherit unique gas ratios (e.g., CH 4 /He) from the dominant rock reservoirs where they originate, some of which underlie the Quaternary volcanic rocks. Steam/gas ratios (essentially H 2 O/CO 2 ) of Yellowstone fumaroles correlate with Ar/He and N 2 /CO 2 , strongly suggesting that H 2 O/CO 2 is controlled by addition of steam boiled from water rich in atmospheric gases. Moreover, H 2 O/CO 2 varies systematically with geographic location, such that boiling is more enhanced in some areas than others. The &delta; 13 C and 3 He/CO 2 of gases reflect a dominant mantle origin for CO 2 in Yellowstone gas. The mantle signature is most evident at Mud Volcano, which hosts gases with the lowest H 2 O/CO 2 , lowest CH 4 concentrations and highest He isotope ratios (~16Ra), consistent with either a young subsurface intrusion or less input of crustal and meteoric gas than any other location at Yellowstone. Across the YPVF, He isotope ratios ( 3 He/ 4 He) inversely vary with He concentrations, and reflect varied amounts of long- stored, radiogenic He added to the magmatic endmember within the crust. Similarly, addition of CH4 from organic-rich sediments is common in the eastern thermal areas at Yellowstone. Overall, Yellowstone gases reflect addition of deep, high-temperature magmatic gas (CO 2 -rich), lower-temperatures crustal gases ( 4 He- and CH 4 -bearing), and those gases (N 2 , Ne, Ar) added principally through boiling of the meteoric-water-derived geothermal liquid found in the upper few kilometers. We also briefly explore the pathways by which Cl, F, and S, move through the crust.

Montana, Wyoming↗
USGS2014

Hydrothermal monitoring in a quiescent volcanic arc: Cascade Range, northwestern United States

Ongoing (1996–present) volcanic unrest near South Sister, Oregon, is accompanied by a striking set of hydrothermal anomalies, including elevated temperatures, elevated major ion concentrations, and 3 He/ 4 He ratios as large as 8.6 R A in slightly thermal springs. These observations prompted the US Geological Survey to begin a systematic hydrothermal-monitoring effort encompassing 25 sites and 10 of the highest-risk volcanoes in the Cascade volcanic arc, from Mount Baker near the Canadian border to Lassen Peak in northern California. A concerted effort was made to develop hourly, multiyear records of temperature and/or hydrothermal solute flux, suitable for retrospective comparison with other continuous geophysical monitoring data. Targets included summit fumarole groups and springs/streams that show clear evidence of magmatic influence in the form of high 3 He/ 4 He ratios and/or anomalous fluxes of magmatic CO 2 or heat. As of 2009–2012, summit fumarole temperatures in the Cascade Range were generally near or below the local pure water boiling point; the maximum observed superheat was <2.5°C at Mount Baker. Variability in ground temperature records from the summit fumarole sites is temperature-dependent, with the hottest sites tending to show less variability. Seasonal variability in the hydrothermal solute flux from magmatically influenced springs varied from essentially undetectable to a factor of 5–10. This range of observed behavior owes mainly to the local climate regime, with strongly snowmelt-influenced springs and streams exhibiting more variability. As of the end of the 2012 field season, there had been 87 occurrences of local seismic energy densities approximately ≥ 0.001 J/m 3 during periods of hourly record. Hydrothermal responses to these small seismic stimuli were generally undetectable or ambiguous. Evaluation of multiyear to multidecadal trends indicates that whereas the hydrothermal system at Mount St. Helens is still fast-evolving in response to the 1980–present eruptive cycle, there is no clear evidence of ongoing long-term trends in hydrothermal activity at other Cascade Range volcanoes that have been active or restless during the past century (Baker, South Sister, and Lassen). Experience gained during the Cascade Range hydrothermal-monitoring experiment informs ongoing efforts to capture entire unrest cycles at more active but generally less accessible volcanoes such as those in the Aleutian arc.

California;Oregon;Washington↗
USGS2005

Comparative soil CO2 flux measurements and geostatistical estimation methods on Masaya volcano, Nicaragua

We present a comparative study of soil CO 2 flux ( F C O 2 "> F C O 2 ) measured by five groups (Groups 1–5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1–5 measured F C O 2 using the accumulation chamber method at 5-m spacing within a 900 m 2 grid during a morning (AM) period. These measurements were repeated by Groups 1–3 during an afternoon (PM) period. Measured F C O 2 ranged from 218 to 14,719 g m −2 day −1 . The variability of the five measurements made at each grid point ranged from ±5 to 167%. However, the arithmetic means of fluxes measured over the entire grid and associated total CO 2 emission rate estimates varied between groups by only ±22%. All three groups that made PM measurements reported an 8–19% increase in total emissions over the AM results. Based on a comparison of measurements made during AM and PM times, we argue that this change is due in large part to natural temporal variability of gas flow, rather than to measurement error. In order to estimate the mean and associated CO 2 emission rate of one data set and to map the spatial F C O 2 distribution, we compared six geostatistical methods: arithmetic and minimum variance unbiased estimator means of uninterpolated data, and arithmetic means of data interpolated by the multiquadric radial basis function, ordinary kriging, multi-Gaussian kriging, and sequential Gaussian simulation methods. While the total CO 2 emission rates estimated using the different techniques only varied by ±4.4%, the F C O 2 maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of F C O 2 , but a variety of geostatistical methods are appropriate to estimate the total CO 2 emission rate from a study area, which is a primary goal in volcano monitoring research.

Masaya↗