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K.A. McGee

Publications and source records attributed to K.A. McGee.

18 recordsLinked to original sources
USGS2008

Atmospheric contribution of gas emissions from Augustine volcano, Alaska during the 2006 eruption

Airborne surveillance of gas emissions from Augustine for SO 2 , CO 2 and H 2 S showed no evidence of anomalous degassing from 1990 through May 2005. By December 20, 2005, Augustine was degassing 660 td −1 of SO 2 , and ten times that by January 4, 2006. The highest SO 2 emission rate measured during the 2006 eruption was 8650 td −1 (March 1); for CO 2 , 13000 td −1 (March 9), and H 2 S, 8 td −1 (January 19). Thirty‐four SO 2 measurements were made from December 2005 through 2006, with 9 each for CO 2 and H 2 S. Augustine released 1 × 10 6 tonnes of CO 2 to the atmosphere during 2006, a level similar to the output of a medium‐sized natural gas‐fired power plant, and thus was not a significant contributor of greenhouse gas to the atmosphere compared to anthropogenic sources. Augustine released about 5 × 10 5 tonnes of SO 2 during 2006, similar to that released in 1976 and 1986.

Alaska↗
USGS2006

Puhimau thermal area: a window into the upper east rift zone of Kilauea Volcano, Hawaii?

We report the results of two soil CO 2 efflux surveys by the closed chamber circulation method at the Puhimau thermal area in the upper East Rift Zone (ERZ) of Kilauea volcano, Hawaii. The surveys were undertaken in 1996 and 1998 to constrain how much CO 2 might be reaching the ERZ after degassing beneath the summit caldera and whether the Puhimau thermal area might be a significant contributor to the overall CO 2 budget of Kilauea. The area was revisited in 2001 to determine the effects of surface disturbance on efflux values by the collar emplacement technique utilized in the earlier surveys. Utilizing a cutoff value of 50 g m −2 d −1 for the surrounding forest background efflux, the CO 2 emission rates for the anomaly at Puhimau thermal area were 27 t d −1 in 1996 and 17 t d −1 in 1998. Water vapor was removed before analysis in all cases in order to obtain CO 2 values on a dry air basis and mitigate the effect of water vapor dilution on the measurements. It is clear that Puhimau thermal area is not a significant contributor to Kilauea's CO 2 output and that most of Kilauea's CO 2 (8500 t d −1 ) is degassed at the summit, leaving only magma with its remaining stored volatiles, such as SO 2 , for injection down the ERZ. Because of the low CO 2 emission rate and the presence of a shallow water table in the upper ERZ that effectively scrubs SO 2 and other acid gases, Puhimau thermal area currently does not appear to be generally well suited for observing temporal changes in degassing at Kilauea.

Hawaii↗
USGS2002

Carbon dioxide emission rate of Kīlauea Volcano: Implications for primary magma and the summit reservoir

We report a CO 2 emission rate of 8500 metric tons per day (t d −1 ) for the summit of Kīlauea Volcano, several times larger than previous estimates. It is based on three sets of measurements over 4 years of synchronous SO 2 emission rates and volcanic CO 2 /SO 2 concentration ratios for the summit correlation spectrometer (COSPEC) traverse. Volcanic CO 2 /SO 2 for the traverse is representative of the global ratio for summit emissions. The summit CO 2 emission rate is nearly constant, despite large temporal variations in summit CO 2 /SO 2 and SO 2 emission rates. Summit CO 2 emissions comprise most of Kīlauea's total CO 2 output (∼9000 t d −1 ). The bulk CO 2 content of primary magma determined from CO 2 emission and magma supply rate data is ∼0.70 wt %. Most of the CO 2 is present as exsolved vapor at summit reservoir depths, making the primary magma strongly buoyant. Turbulent mixing with resident reservoir magma, however, prevents frequent eruptions of buoyant primary magma in the summit region. CO 2 emissions confirm that the magma supply enters the edifice through the summit reservoir. A persistent several hundred parts per million CO 2 anomaly arises from the entry of magma into the summit reservoir beneath a square kilometer area east of Halemaumau pit crater. Since most of the CO 2 in primary magma is degassed in the summit, the summit CO 2 emission rate is an effective proxy for the magma supply rate. Both scrubbing of SO 2 and solubility controls on CO 2 and S in basaltic melt cause high CO 2 /SO 2 in summit emissions and spatially uncorrelated distributions of CO 2 and SO 2 in the summit plume.

Journal of Geophysical Research B: Solid Earth↗
USGS2001

Soil efflux and total emission rates of magmatic CO2 at the horseshoe lake tree kill, mammoth mountain, California, 1995-1999

We report the results of eight soil CO2 efflux surveys by the closed circulation chamber method at the Horseshoe Lake tree kill (HLTK) - the largest tree kill on Mammoth Mountain. The surveys were undertaken from 1995 to 1999 to constrain total HLTK CO2 emissions and to evaluate occasional efflux surveys as a surveillance tool for the tree kills. HLTK effluxes range from 1 to > 10,000 g m -2 day -1 (grams CO2 per square meter per day); they are not normally distributed. Station efflux rates can vary by 7-35% during the course of the 8- to 16-h surveys. Disturbance of the upper 2 cm of ground surface causes effluxes to almost double. Semivariograms of efflux spatial covariance fit exponential or spherical models; they lack nugget effects. Efflux contour maps and total CO2 emission rates based on exponential, spherical, and linear kriging models of survey data are nearly identical; similar results are also obtained with triangulation models, suggesting that the kriging models are not seriously distorted by the lack of normal efflux distributions. In addition, model estimates of total CO2 emission rates are relatively insensitive to the measurement precision of the efflux rates and to the efflux value used to separate magmatic from forest soil sources of CO2. Surveys since 1997 indicate that, contrary to earlier speculations, a termination of elevated CO2 emissions at the HLTK is unlikely anytime soon. The HLTK CO2 efflux anomaly fluctuated greatly in size and intensity throughout the 1995-1999 surveys but maintained a N-S elongation, presumably reflecting fault control of CO2 transport from depth. Total CO2 emission rates also fluctuated greatly, ranging from 46 to 136 t day-1 (metric tons CO2 per day) and averaging 93 t day-1. The large inter-survey variations are caused primarily by external (meteorological) processes operating on time scales of hours to days. The externally caused variations can mask significant changes occurring at depth; a striking example is the masking of a degassing event generated at depth and detected by a soil gas sensor network in September 1997 while an efflux survey was in progress. Thus, occasional efflux surveys are not an altogether effective surveillance tool for the HLTK, and making them effective by greatly increasing their frequency may not be practical. Published by Elsevier Science B.V.

Chemical Geology↗
USGS2001

Quiescent hydrogen sulfide and carbon dioxide degassing from Mount Baker, Washington

Volcanic H2S emission rate data are scant despite their importance in understanding magma degassing. We present results from direct airborne plume measurements of H2S and CO2 on a 21-orbit survey at eleven different altitudes around Mount Baker volcano in September 2000 utilizing instrumentation mounted in a light aircraft. Measured emission rates of H2S and CO2 were 5.5 td-1 and 187 td-1 respectively. Maximum concentrations of H2S and CO2 encountered within the 4-km-wide plume were 75 ppb and 2 ppm respectively. Utilizing the H2S signal as a marker for the plume allows the corresponding CO2 signal to be more easily and accurately distinguished from ambient CO2 background. This technique is sensitive enough for monitoring weakly degassing volcanoes in a pre-eruptive condition when scrubbing by hydrothermal fluid or aquifers might mask the presence of more acid magmatic gases such as SO2.

Geophysical Research Letters↗
USGS2000

Geochemical evidence for a magmatic CO 2 degassing event at Mammoth Mountain, California, September-December 1997

Recent time series soil CO 2 concentration data from monitoring stations in the vicinity of Mammoth Mountain, California, reveal strong evidence for a magmatic degassing event during the fall of 1997 lasting more than 2 months. Two sensors at Horseshoe Lake first recorded the episode on September 23, 1997, followed 10 days later by a sensor on the north flank of Mammoth Mountain. Direct degassing from shallow intruding magma seems an implausible cause of the degassing event, since the gas released at Horseshoe Lake continued to be cold and barren of other magmatic gases, except for He. We suggest that an increase in compressional strain on the area south of Mammoth Mountain driven by movement of major fault blocks in Long Valley caldera may have triggered an episode of increased degassing by squeezing additional accumulated CO 2 from a shallow gas reservoir to the surface along faults and other structures where it could be detected by the CO 2 monitoring network. Recharge of the gas reservoir by CO 2 emanating from the deep intrusions that probably triggered deep long-period earthquakes may also have contributed to the degassing event. The nature of CO 2 discharge at the soil-air interface is influenced by the porous character of High Sierra soils and by meteorological processes. Solar insolation is the primary source of energy for the Earth atmosphere and plays a significant role in most diurnal processes at the Earth surface. Data from this study suggest that external forcing due largely to local orographic winds influences the fine structure of the recorded CO 2 signals.

California↗
USGS1998

Airborne volcanic plume measurements using a FTIR spectrometer, Kilauea volcano, Hawaii

A prototype closed-path Fourier transform infrared spectrometer system (FTIR), operating from battery power and with a Stirling engine microcooler for detector cooling, was successfully used for airborne measurements of sulfur dioxide at Kilauea volcano. Airborne profiles of the volcanic plume emanating from the erupting Pu′u′O′o vent on the East Rift of Kilauea revealed levels of nearly 3 ppm SO 2 in the core of the plume. An emission rate of 2,160 metric tons per day of sulfur dioxide was calculated from the FTIR data, which agrees closely with simultaneous measurements by a correlation spectrometer (COSPEC). The rapid spatial sampling possible from an airborne platform distinguishes the methodology described here from previous FTIR measurements.

Geophysical Research Letters↗
USGS1998

Three-year decline of magmatic CO2 emissions from soils of a Mammoth Mountain tree kill: Horseshoe Lake, CA, 1995-1997

We used the closed chamber method to measure soil CO 2 efflux over a three-year period at the Horseshoe Lake tree kill (HLTK)—the largest tree kill on Mammoth Mountain in central eastern California. Efflux contour maps show a significant decline in the areas and rates of CO 2 emission from 1995 to 1997. The emission rate fell from 350 t d −1 (metric tons per day) in 1995 to 130 t d −1 in 1997. The trend suggests a return to background soil CO 2 efflux levels by early to mid 1999 and may reflect exhaustion of CO 2 in a deep reservoir of accumulated gas and/or mechanical closure or sealing of fault conduits transmitting gas to the surface. However, emissions rose to 220 t d −1 on 23 September 1997 at the onset of a degassing event that lasted until 5 December 1997. Recent reservoir recharge and/or extension-enhanced gas flow may have caused the degassing event.

Geophysical Research Letters↗
USGS1998

Annual cycle of magmatic CO2 in a tree-kill soil at Mammoth Mountain, California: Implications for soil acidification

Time-series sensor data reveal significant short-term and seasonal variations of magmatic CO 2 in soil over a 12 month period in 1995–1996 at the largest tree-kill site on Mammoth Mountain, central-eastern California. Short-term variations leading to ground-level soil CO 2 concentrations hazardous and lethal to humans were triggered by shallow faulting in the absence of increased seismicity or intrusion, consistent with tapping a reservoir of accumulated CO 2 , rather than direct magma degassing. Hydrologic processes closely modulated seasonal variations in CO 2 concentrations, which rose to 65%–100% in soil gas under winter snowpack and plunged more than 25% in just days as the CO 2 dissolved in spring snowmelt. The high efflux of CO 2 through the tree-kill soils acts as an open-system CO 2 buffer causing infiltration of waters with pH values commonly of <4.2, acid loading of up to 7 keq H+ ṁha −1 ṁyr −1 , mobilization of toxic Al 3+ , and long-term decline of soil fertility.

Geology↗
USGS1994

Eruptive activity at Mount St Helens, Washington, USA, 1984-1988: a gas geochemistry perspective

The results from two different types of gas measurement, telemetered in situ monitoring of reducing gases on the dome and airborne measurements of sulfur dioxide emission rates in the plume by correlation spectrometry, suggest that the combination of these two methods is particularly effective in detecting periods of enhanced degassing that intermittently punctuate the normal background leakage of gaseous effluent from Mount St Helens to the atmosphere. Gas events were recorded before lava extrusion for each of the four dome-building episodes at Mount St Helens since mid-1984. For two of the episodes, precursory reducing gas peaks were detected, whereas during three of the episodes, COSPEC measurements recorded precursory degassing of sulfur dioxide. During one episode (October 1986), both reducing gas monitoring and SO2 emission rate measurements simultaneously detected a large gas release several hours before lava extrusion. Had both types of gas measurements been operational during each of the dome-building episodes, it is thought that both would have recorded precursory signals for all four episodes. Evidence from the data presented herein suggests that increased degassing at Mount St Helens becomes detectable when fresh upward-moving magma is between 2 km and a few hundred meters below the base of the dome and between about 60 and 12 hours before the surface extrusion of lava. ?? 1994 Springer-Verlag.

Bulletin of Volcanology↗
USGS1992

The structure, dynamics, and chemical composition of noneruptive plumes from Mount St. Helens, 1980-1988

From May 1980 to September 1988, more than 1000 fixed-wing aircraft flights were made with a correlation spectrometer to measure the sulfur dioxide flux from Mount St. Helens volcano. These flights also provided valuable data on the structure and dynamics of noneruptive plumes emanating from Mount St. Helens. During 1980 and part of 1981, an infrared spectrometer was also used to measure carbon dioxide emission rates. At distances up to 25 km from Mount St. Helens, plume widths can range up to 20 km or more, with width/thickness ratios from 3 to about 30. Maximum sulfur dioxide concentrations in these plumes depend on wind speed and are typically under 5 ppm and usually 1 ppm or less. Close examination of the plume data reveals that the characteristics of quiescent plumes from Mount St. Helens are strongly affected by certain meteorological conditions such as thermal and wind stratification in the troposphere, as well as by the topography of the volcano. ?? 1992.

Journal of Volcanology and Geothermal Research↗
USGS1980

Annotated bibliography of spectrophotometric studies in the system U-Fe-Se-S-O-H, 1967-78

Preparation of this bibliography was originally begun to supply background information on previous ultraviolet and visible spectrophotometric studies on various chemical species thought to be important in the formation of sedimentary uranium deposits; we also thought that preparing the bibliography would help direct experimental efforts to determine the association of iron and uranium with several metastable sulfur species. In compiling these references, however, we found that much work had been done on the chemical species of interest by using types of spectroscopy other than ultraviolet and visible spectrophotometry. The dimensions of the bibliography were therefore broadened to include a wide variety of spectral-measuring techniques to make this report useful to a larger audience.

Open-File Report↗
USGS1977

A thermostatic water bath for experimental studies in aqueous solutions

A temperature-controlled water bath for the study of ion-pairing equilibria and mineral solubility in aqueous solutions below 100&deg;C is described. The bath is similar to a previously described system (P. B. Hostetler and C. L. Christ, 1968, U.S. Geol. Survey Prof. Paper 600-D, p. D217-D221) but incorporates several significant improvements. Included among these are a more efficient stirring mechanism, a potentially larger solid-to-solution ratio, and improved equilibration of the gas phase with the solution.

Journal of Research of the U.S. Geological Survey↗
USGS1977

Activity-product constants of brucite from 10 degrees to 90 degrees C

The activity-product constant of brucite, K B = [Mg 2+ ][OH - ] 2 (where the brackets denote activities), was determined experimentally at 10°, 25°, 40°, 55°, 70°, and 90°C. The values obtained for -log K B are 10.89±0.16 (10°), 10.88±0.10 (25°), 10.90±0.10 (40°), 10.90±0.10 (55°), 10.99±0.14 (70°), and 11.10±0.14 (90°). Using National Bureau of Standards Technical Note 270 data for the ions, the free energy of formation (Δ G ° t ) at 25° for brucite is 831.486 joules per mole ( 198,730 cal mol -1 ). Using data compiled by R. A. Robie and D. R. Waldbaum in 1968 for the ions, this Δ G ° t is -823,323 J mol -1 (-198,930 cal mol -1 ). Values of log KB are also calculated for the temperature range 0° to 200°C, by using thermochemical data listed by V. B. Parker, D. D. Wagman, and W. H. Evans in 1971 and E. G. King, M. J. Ferrante, and L. B. Pankratz in 1975 and the partial molal heat capacities estimated by C. M. Criss and J. W. Cobble in 1965. The experimental values are similar to the calculated values, especially at lower temperatures.

Journal of Research of the U.S. Geological Survey↗