National Research Program | Aleutian Arc Geothermal Fluids

Aleutian Arc Geothermal Fluids: Chemical Analyses of Water and Gas Samples Collected During Volcano Hazards Investigations

Map showing Aleutian Arc volcanoes (triangles).  Red triangles with labels are volcanoes discussed in this report.

Figure 1. Map showing Aleutian Arc volcanoes (triangles). Red triangles with labels are volcanoes discussed in this report.

Introduction

As part of ongoing efforts by the Alaska Volcano Observatory (AVO) to study and monitor volcanoes of the Aleutian Arc, samples of water and gas are occasionally collected from thermal springs, fumaroles, gas vents, and other features. These samples are analyzed in one or more laboratories at the U.S. Geological Survey (USGS). Some of the analytical results are eventually included in publications that summarize the field work or present major conclusions, but some data remains unpublished, especially results from single "grab" samples that are collected during the performance of other work. Such data could be useful for purposes such as constraining the strength of magmatic degassing, evaluating geothermal resources, or simply establishing baseline hydrologic conditions at remote volcanoes that are seldom visited. This report contains the chemical and isotopic data from thermal waters and gases collected from the Aleutian Arc (Figure 1) over the past 20 years, where such data remain unpublished or only published in part. We discuss some interesting features in the data, and offer brief overviews on what the data indicate about subsurface conditions. We emphasize however, that the datasets are small and the inferences drawn from them are preliminary and should not be considered as peer reviewed. One main goal in providing these overviews is to stimulate future research.

For completeness, this report also summarizes the focused investigations of thermal fluids and gases carried out in the past 20 years at Aleutian Arc volcanoes where the data have already been published (e.g., Chiginagak, Akutan, Ukinrek Maars). Results from ongoing investigations focused on the Katmai area (Lopez and others, in prep.) are not included. Brief statements about the volcanoes and their recent eruptive histories are mostly taken from the Alaska Volcano Observatory website (AVO, 2015) as of 1 April 2015, but derive in many cases from Miller and others (1998) or Wood and Kienle (1990).

Methods

A general summary of collection and analytical protocols was given by Bergfeld and others (2013). Gas samples discussed herein were collected in evacuated glass sample bottles without added caustic. Bubbling gases were collected from springs using an inverted funnel and water displacement. Fumarole gases were collected through a metal tube into a T-handle glass bottle with a downstream pinch clamp. Samples for dissolved inorganic carbon (DIC) and its isotopes were collected by injecting water into a septum-equipped evacuated glass bottle using a syringe. Helium isotope samples were collected in copper tubes sealed with refrigeration clamps.

Some water samples were collected according to established field protocols, including: on-site measurement of pH; filtration of water for chemical analysis through 0.45 μm membrane filters; acidification of cation samples; collection of isotope and alkalinity samples in tightly sealed glass bottles (Bergfeld and others, 2013). However, for some of the water samples, field measurements were minimal and consist of temperature and location, and only raw (unfiltered) water samples were collected. Unless otherwise specified, the pH, specific conductance, and alkalinity values presented in the tables are laboratory measurements, and filtration as needed prior to chemical analysis was performed in the laboratory. Lack of field processing probably has minimal negative impact on conservative species like Na, Cl and most major ions, but trace and redox-sensitive species like Fe or nutrients like NO3 and PO4 may have large uncertainties. A few samples were collected raw and acidified, which allows suspended particles to dissolve after collection and can greatly increase the concentrations of many of the metal species.

Chemical analyses of gas and water samples were carried out at USGS laboratories in Menlo Park, California, using methods described in Bergfeld and others (2013). Gases were analyzed by using gas chromatographs equipped with a thermal-conductivity detector. Water samples were analyzed for anions by ion chromatography except for HCO3, which was analyzed by titration and should be considered as "total alkalinity as HCO3" in all tables attached to this report. Cations were analyzed by argon plasma optical-emission spectrometry, and the results given in mg/L and μg/L. For some samples, major cation and trace element concentrations were determined at the USGS Minerals Program laboratories in Denver, Colorado, by inductively coupled plasma mass spectrometry (ICP-MS) using procedures described by Lamothe and others (1999). These results are usually given in ppm and ppb. Analytical results presented herein preserve the units of the reporting laboratory. For low salinity waters (dissolved solids <5000 mg/L), mg/L nearly equals ppm, and μg/L nearly equals ppb. Stable isotope analyses of waters, steam, DIC, CO2, and CH4 were performed by mass spectrometry at the USGS Stable Isotope Laboratory in Reston, Virginia, and are reported in per mil (Revesz and others, 2008a,b). Noble-gas ratios were determined by mass spectrometry at the USGS Noble Gas Laboratory in Denver, Colorado, using methods described in Hunt and others (2013). Reported 3He/4He ratios are corrected for air contamination and are given as RC/RA values, where RA is the 3He/4He ratio in air.

Location data in all tables is given in decimal degrees. The reference datum was not always recorded but assuming WGS84 seems to match aerial imagery for most features.

Summary

This report presents the first published chemistry data on waters or gases from three Aleutian Arc volcanoes: Semisopochnoi, Little Sitkin, and Tana. Water chemistry at Little Sitkin and Tana shows that the hydrothermal systems are vapor-dominated, and high concentrations of ammonium reveal a significant interaction with buried organic matter. Gas geothermometry implies a reservoir temperature of 235°C at Little Sitkin, which would make this system one of the hottest in Alaska. This report also updates the record of fluid chemistry at several volcanoes; notably, several new gas analyses from Augustine and a new stream sample at Redoubt, or fills in results for constituents not analyzed in previous studies, such as carbon isotopes.

The carbon isotope data presented in the tables here, or in the recent reports cited, can be combined with results from the two major compilations of carbon isotope values of fluids from Aleutian Arc volcanoes in the literature (Motyka and others, 1993; Symonds and others, 2003b) to fill in the pattern for the entire active part of the arc, from Spurr at the eastern end to Kiska at the western end. The combined carbon isotope dataset is given in Table 15 and plotted in Figure 23. For plotting purposes, values from multiple sites were averaged (for example several sites at Makushin; 3 sites at Atka) so that a single value for each volcano is plotted for each set of researchers. Where 2 or 3 groups of researchers give results, the agreement between the groups is generally fair, worst case being Makushin where the one data point from Symonds and others (2003b) is significantly heavier than all 9 values given by Motyka and others (1993). A few widely divergent values were not given in Table 15 or plotted in Figure 23. These include an extremely negative value from Akutan (-18.1‰) and a positive value from Augustine (+2.3‰) in Motyka and others (1993) and values obtained on cold dilute waters at Augustine and Ukinrek Maars.

Graph showing variation in the isotopic composition of inorganic carbon (CO2 and DIC) along arc from Mt. Spurr to Kiska Island.
Figure 23. Variation in the isotopic composition of inorganic carbon (CO2 and DIC) along arc from Mt. Spurr to Kiska Island (see text and Table 15).

Most geoscientists accept the view that much of the carbon emitted by island arc volcanoes derives from subducted sediments and carbonate minerals, and that the mix between them is a controlling factor in the isotopic composition of the emitted CO2 (Sano and Marty, 1995). The relative importance of shallow crustal carbon sources and losses is still debated, but was particularly emphasized by Symonds and others (2003a). Figure 23 suggests that the carbon isotope composition does vary in a systematic way along the arc, shifting from heavier values toward the east (Spurr excepted) to lighter values toward the center. The shift occurs close to the transition zone from a continental to an oceanic arc. However, a shift back to heavier values at the western end is very apparent, especially considering the new data, and this shift does not correspond to an obvious change in geologic setting. The shift begins hundreds of km east of the intersection of the arc with the Bowers Ridge. Thus the cause of the carbon isotope variations along arc remains uncertain. Nevertheless, the pattern is intriguing and worthy of further investigation. Carbon isotope data are still lacking for known geothermal systems on many of the Aleutian Arc volcanoes. Searches for magmatic CO2 in soil gases, as recently found at Kasatochi and Kiska, have rarely been done in the Aleutian Arc.

Work presented or described herein highlights the fact that thermal springs are not necessarily the most useful features in volcano monitoring. Thermal springs such as those at Aniakchak and ELVC often exhibit long-term stability in composition through the years (Tables 2 & 5). Gas samples from acid-sulfate areas and summit fumaroles, such as those at Augustine (Table 3), are more likely to respond quickly to magmatic unrest. Under certain conditions, streams draining the summit areas can provide useful information on magmatic gas flux, as at Chiginagak and Redoubt. Opportunities to monitor similar streams should not be overlooked, especially in cases when direct sampling in the summit area is precluded by inaccessibility or hazard issues.

Data

Data tables referenced on this site: aleutian-arc-volcano-data-20150722.xlsx (Microsoft Excel Format, 100 KB)

ScienceBase metadata: http://dx.doi.org/10.5066/F74X55VB

Author Affiliations

  • W. C. Evans
    U.S. Geological Survey, National Research Program
  • D. Bergfeld
    U.S. Geological Survey, Volcano Science Center
  • C. A. Neal
    U.S. Geological Survey, Volcano Science Center
  • R. G. McGimsey
    U.S. Geological Survey, Volcano Science Center
  • C. A. Werner
    U.S. Geological Survey, Volcano Science Center
  • C. F. Waythomas
    U.S. Geological Survey, Volcano Science Center
  • J.L. Lewicki
    U.S. Geological Survey, National Research Program
  • T. Lopez
    University of Alaska Fairbanks Geophysical Institute
  • M. T. Mangan
    U.S. Geological Survey, Volcano Science Center
  • T. P. Miller
    U.S. Geological Survey, Volcano Science Center
  • A. Diefenbach
    U.S. Geological Survey, Volcano Science Center
  • J. Schaefer
    Alaska Division of Geological and Geophysical Surveys
  • M. L. Coombs
    U.S. Geological Survey, Volcano Science Center
  • B. Wang
    U.S. Geological Survey, Alaska Science Center
  • K. Nicolaysen
    Whitman College
  • P. Izbekov
    University of Alaska Fairbanks Geophysical Institute
  • Z. Maharrey
    U.S. Geological Survey, Volcano Science Center
  • M. Huebner
    U.S. Geological Survey, National Research Program
  • A.G. Hunt
    U.S. Geological Survey, Crustal Geophysics and Geochemistry Science Center
  • J. Fitzpatrick
    U.S. Geological Survey, National Research Program
  • G. Freeburg
    Private citizen

Citation

Evans, W.C., Bergfeld, D., Neal, C.A., McGimsey, R.G., Werner, C.A., Waythomas, C.F., Lewicki, J.L., Lopez, T., Mangan, M.T., Miller, T.P., Diefenbach, A., Schaefer, J., Coombs, M.L., Wang, B., Nicolaysen, K., Izbekov, P., Maharrey, Z., Huebner, M., Hunt, A.G., Fitzpatrick, J., and Freeburg, G., 2015, Aleutian Arc geothermal fluids: chemical analyses of waters and gases sampled in association with the Alaska Volcano Observatory, U.S. Geological Survey Data Release, http://dx.doi.org/10.5066/F78G8HR1

Acknowledgements

Support from the Alaska Volcano Observatory in providing the opportunity to visit and sample these remote features and support from the U.S. Geological Survey in providing analytical capabilities were key to the production of this database. Access and sampling on Tana was facilitated through NSF grants PLR-1301925, PLR-1301927, and REU-1358987. We thank Laura Clor and Keith Kirk of USGS for reviewing the product and Chip Orr for help with the posting.

References

AVO (Alaska Volcano Observatory), 2015, https://www.avo.alaska.edu/volcanoes/index.php

Barnes, I., McCoy, G.A., 1979, Possible role of mantle-derived CO2 in causing two ‘‘phreatic” explosions in Alaska: Geology, v. 7, p. 434–435.

Bergfeld, D., Lewicki, J.L., Evans, W.C., Hunt, A.G., Revesz, K., and Huebner, M., 2013, Geochemical investigation of the hydrothermal system on Akutan Island, Alaska, July 2012: U.S. Geological Survey Scientific Investigations Report 2013-5231, 20 p.

Bleick, H.A., Coombs, M.L., Cervelli, P.F., Bull, K.F., Wessels, R.L., 2013, Volcano-ice interactions precursory to the 2009 eruption of Redoubt Volcano, Alaska: Journal of Volcanology and Geothermal Research, v. 259, p. 373-388.

Bond, A. L., Evans, W. C., and Jones, I. L., 2012, Avian mortality associated with a volcanic gas seep at Kiska Island, Aleutian Islands, Alaska: The Wilson Journal of Ornithology, v. 124, p. 146-151.

Byers, F.M. Jr., and Brannock, W.W., 1949, Volcanic activity on Umnak and Great Sitkin Islands, 1946-1948: Transactions, American Geophysical Union, v. 30, p. 719-734.

Cameron, W.A., and Larson, G.L., 1992. Baseline inventory of the aquatic resources of Aniakchak National Monument, Alaska. NPS/PNROSU/NRTR-92/03, National Park Service and Cooperative Park Studies Unit, Oregon State University, National Park Service, Pacific Northwest Region.

Clarisse, L., Coheur, P-F., Chefdeville, S., Lacour, J.L., Hurtmans, D., and ClerbauxC., 2011, Infrared satellite observations of hydrogen sulfide in the volcanic plume of the August 2008 Kasatochi eruption: Geophysical Research Letters, v. 398, n. 10, L10804, doi:10.1029/2011GL047402.

Coats, R.R., 1959, Geologic reconnaissance of Semisopochnoi Island, western Aleutian Islands, Alaska: U.S. Geological Survey Bulletin 1028-O, p. 477-519.

Coombs, M.L., Larsen, J.F., and Neal, C.A., (in prep.), Postglacial Eruptive History and Geochemistry of Semisopochnoi Volcano, western Aleutian Islands, Alaska.

Coombs, M.L., Neal, C.A., Wessels, R.L., and McGimsey, R.G., 2008, Geothermal disruption of summit glaciers at Mount Spurr volcano, 2004-2006: an unusual manifestation of volcanic unrest: U.S. Geological Survey Professional Paper 1732-B, 33 p.

D'Amore, F., and Panichi, C., 1980, Evaluation of deep temperature of hydrothermal systems by a new gas-geothermometer: Geochimica et Cosmochimica Acta, v. 44, p. 549–556.

Ehm, Arlen, 1983, Oil and gas basins map of Alaska: Alaska Division of Geological & Geophysical Surveys Special Report 32, 1 sheet, scale 1:2,500,000. doi:10.14509/2631

Evans, W.C., Bergfeld, D., McGimsey, R.G., and Hunt, A.G., 2009, Diffuse gas emissions at the Ukinrek Maars, Alaska: Implications for magmatic degassing and volcanic monitoring: Applied Geochemistry, v. 24, p. 527-535.

Fierstein, J., and Hildreth, W., 2008, Kaguyak dome field and its Holocene caldera, Alaska Peninsula: Journal of Volcanology and Geothermal Research, v. 177, p. 340-366.

Fournier, R.O., 1989, Geochemistry and dynamics of the Yellowstone National Park hydrothermal system: Annual Review of Earth and Planetary Science, v. 17, p. 13-53.

Giggenbach, W.F., 1988, Geothermal solute equilibria. Derivation of Na-K-Mg-Ca geoindicators: Geochimica et Cosmochimica Acta,v. 52, p. 2749-2765.

Herrick, J.A., Neal, C.A., Cameron, C.E., Dixon, J.P., and McGimsey, R.G., 2014, 2012 volcanic activity in Alaska– Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2014–5160, 82 p., http://dx.doi.org/10.3133/sir20145160.

Horita, J., 2001, Carbon isotope exchange in the system CO2-CH4 at elevated temperatures: Geochimica et Cosmochimica Acta, v. 65, p. 1907-1919.

Hunt, A.G., Stern, L., Pohlman, J.W., Ruppel, C., Moscati, R.J., and Landis, G.P., 2013, Mass fractionation of noble gases in synthetic methane hydrate: Implications for naturally occurring gas hydrate dissociation. Chemical Geology, v. 339, p. 242-250. http://dx.doi.org/10.1016/j.chemgeo.2012.09.033

Janik, C.J., and Bergfeld, Deborah, 2010, Analyses of gas, steam and water samples collected in and around Lassen Volcanic National Park, California, 1975-2002: U.S. Geological Survey Open-File Report, 2010-1036, 13 p.

Keith T.E.C., Thompson, J.M., and McGimsey, R.G., 1995, Chemistry of crater lake waters prior to the 1992 eruptions of Crater Peak, Mount Spurr volcano, Alaska: U.S. Geological Survey Bulletin 2139, p. 59-63.

Kodosky, L.G., and Keskinen, M., 1990, Fumarole distribution, morphology, and encrustation mineralogy associated with the 1986 eruptive deposits of Mount St. Augustine, Alaska: Bulletin of Volcanology, v. 52, p. 175-185.

Kodosky, L.G., Motyka, R.J., and Symonds, R.B., 1991, Fumarolic emissions from Mount St. Augustine, Alaska: 1979-1984 degassing trends, volatile sources and their possible role in eruptive style: Bulletin of Volcanology, v. 53, p. 381-394.

Kolker, A., and Mann, R., 2009, Heating up the economy with geothermal energy—a multi-component sustainable devel¬opment project at Akutan, Alaska: Geothermal Resources Council Transactions, v. 33, p. 7–11.

Kolker, A., Stelling, P., Cumming, W., and Rohrs, D., 2012, Exploration of the Akutan geothermal resource area, in 37th Stanford University Workshop on Geothermal Res¬ervoir Engineering, Stanford, Calif., 2012, Proceedings, SGP-TR-194.

Lamothe, P.J., Meier, A.L., and Wilson, S., 1999, The determination of forty four elements in aqueous samples by inductively coupled plasma - mass spectrometry: U.S. Geological Survey Open-File Report 99-151, 14 p.

Larsen, J.F., Neal, C.A., Schaefer, J.R., Kaufman, A.M., and Lu, Z., 2015, The 2008 phreatomagmatic eruption of Okmok Volcano, Aleutian Islands, Alaska: Chronology, deposits, and landform changes: Alaska Division of Geological & Geophysical Surveys Report of Investigation 2015-2, 53 p. doi:10.14509/29405

Lopez, T., Tassi, F., Rizzo, A., Fiebig, J., Aiuppa, A., Galle, B., Capecchiacci, F., Caliro, S., Guidice, G., and Chiodini, G., (in prep.), Geochemical constraints on the volatile sources and subsurface conditions at Mount Martin, Mount Mageik, and Trident Volcanoes, Katmai Volcanic Cluster, Alaska.

Mangan, M., Miller, T., Waythomas, C., Trusdell, F., Calvert, A., and Layer, P., 2009, Diverse lavas from closely spaced volcanoes drawing from a common parent: Emmons Lake Volcanic Center, eastern Aleutian Arc: Earth and Planetary Science Letters, v. 287, p. 363-372.

Mariner, R.H., Venezky, D.Y., and Hurwitz, S., 2006, Chemical and isotopic database of water and gas from hydrothermal systems with an emphasis for the western United States: U.S. Geological Survey Data Series 169, http://pubs.er.usgs.gov/publication/ds169.

McGee, K.A., Doukas, M.P., McGimsey, R.G., Neal, C. A., and Wessels, R.L., 2010, Emission of SO2, CO2, and H2S from Augustine Volcano, 2002-2008, in, Power, J.A., Coombs, M. L., and Freymueller, J.T., eds., The 2006 eruption of Augustine Volcano, Alaska: U.S. Geological Survey Professional Paper 1769, p. 609-627.

McGimsey, R.G., Neal, C.A., Dixon, J.P., and Ushakov, S., 2008, 2005 volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2007-5269, 94 p.

McGimsey, R.G., Neal, C.A., and Doukas, M.P., 1995, Volcanic activity in Alaska—summary of events and response of the Alaska Volcano Observatory 1992: U.S. Geological Survey Open-File Report 95-83, 26 p.

Miller, T.P., McGimsey, R.G., Richter, D.H., Riehle, J.R., Nye, C.J., Yount, M.E., and Dumolin, J.A., 1998, Catalogue of the historically active volcanoes of Alaska: U.S. Geological Survey Open-File Report 98-0582, 104 p.

Motyka, R.J., Moorman, M.A., and Liss, S.A., 1981, Assessment of thermal spring sites Aleutian Arc, Atka Island to Becherof Lake – preliminary results and evaluation: Alaska Division of Geological and Geophysical Surveys Open-File Report 144, 173 p.

Motyka, R.J., Moorman, M.A., and Poreda, R.J., 1988, Geochemistry of thermal springs and fumaroles, Hot Springs Bay Valley Akutan Island, Alaska, in Motyka, R.J., and Nye, C.J., eds., A geological, geochemical, and geophysical survey of the geothermal resources at Hot Springs Bay valley, Akutan Island, Alaska: Alaska Divi¬sion of Geological & Geophysical Surveys Report of Investigations 883, p. 71–104.

Motyka, R.J., Liss, S.A., Nye, C.J., and Moorman, M.A., 1993, Geothermal resources of the Aleutian Arc: Alaska Division of Geological and Geophysical Surveys Profes¬sional Report 0114, 17 p., 4 sheets, scale 1:1,000,000.

Neal, C.A., McGimsey, R.G., Miller, T.P., Riehle, J.R., and Waythomas, C.F., 2001, Preliminary volcano-hazard assessment for Aniakchak Volcano, Alaska: U.S. Geological Survey Open-File Report 00-519, 35 p.

Neal, C.A., McGimsey, R.G., Dixon, J.P., Manevich, A., and Rybin, A., 2008, 2006 volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2008-5214, 102 p.

Neal, C.A., McGimsey, R.G., Dixon, J.P., Cameron, C.E., Nuzhdaev, A.A., and Chibisova, M., 2010, 2008 volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2010-5243, 94 p.

Nye, C. J., Hammond, W. R., Tytgat, G. C., and Dorava, J. M., 1995, June 29, 1993, outburst flood from Kidazgeni Glacier, Mount Spurr volcano, Alaska: U.S. Geological Survey Bulletin 2139, p. 199-204.

Pfeffer, M.A., Doukas, M.P., Werner, C.A., and Evans, W.C., 2013, Airborne filter pack measurements of S and Cl in the plume of Redoubt Volcano, Alaska February-May 2009: Journal of Volcanology and Geothermal Research, v. 259, p. 285-289.

Power, J.A., Coombs, M. L., and Freymueller, J.T., eds., 2010, The 2006 eruption of Augustine Volcano, Alaska: U.S. Geological Survey Professional Paper 1769, 667 p.

Revesz, K. and Coplen T.B., 2008a, Determination of the delta (2H/1H) of water: RSIL lab code 1574. In Methods of the Reston Stable Isotope Laboratory (eds. Revesz, K., and Coplen, T.B.), Chap. C1. U.S. Geological Survey Techniques and Methods 10–C1, 27 p. Available from: http://pubs.water.usgs.gov/tm10C1/

Revesz, K. and Coplen, T. B., 2008b, Determination of the delta (18O/16O) of water: RSIL lab code 489. In Methods of the Reston Stable Isotope Laboratory (eds. Revesz, K., and Coplen, T.B.), chap. C2. U.S. Geological Survey Techniques and Methods, 10–C2, 28 p. Available from: http://pubs.water.usgs.gov/tm10C2/

Sano, Y., and Marty, B., 1995, Origin of carbon in fumarolic gas from island arcs: Chemical Geology, v. 119, p. 265-274.

Schaefer, J.R., Scott, W.E., Evans, W.C., Jorgenson, J., McGimsey, R.G., and Wang, B., 2008, The 2005 catastrophic acid crater lake drainage, lahar, and acidic aerosol formation at Mount Chiginagak volcano, Alaska, USA: Field observations and preliminary water and vegetation chemistry results: Geochemistry, Geophysics, Geosystems, v. 9, doi:10.1029/2007GC001900.

Schaefer, J. R., Scott, W. E., Evans, W. C., Wang, B., and McGimsey, R. G., 2013, Summit crater lake observations, and the location, chemistry, and pH of water samples near Mount Chiginagak Volcano, Alaska: 2004-2012: Alaska Division of Geological and Geophysical Surveys Report of Investigations 2011-6, 25 p.

Scott, W.E., Nye, C.J., Waythomas, C.F., and Neal, C.A., 2010, August 2008 eruption of Kasatochi Volcano, Aleutian Islands, Alaska – Resetting an island landscape: Arctic, Antarctic, and Alpine Research, v. 42, p. 250-259.

Simons, F.S., and Mathewson, D.E., 1955, Geology of Great Sitkin Island, Alaska: U.S. Geological Survey Bulletin 1028-B, p. 21-43.

Snyder, G. L., 1959, Geology of Little Sitkin Island, Alaska: in Investigations of Alaskan volcanoes, U.S. Geological Survey Bulletin B 1028-H, p. 169-210, 1 plate, scale 1:20,000.

Symonds, R.B., Rose, W.I., Gerlach, T.M., Briggs, P.H., and Harmon, R.S., 1990, Evaluation of gases, condensates, and SO2 emissions from Augustine volcano, Alaska: the degassing of a Cl-rich volcanic system: Bulletin of Volcanology, v. 52, p. 355-374.

Symonds, R.B., Ritchie, B.E., McGimsey, R.G., Ort, M.H., Poreda, R.J., Evans, W.C., and Janik, C.J., 1997, Investigations of gas seeps and springs in the vicinity of The Gas Rocks, South shore Becharof Lake, Alaska: U.S. Geological Survey Open-File Report 97–127, 27p.

Symonds, R.B., Janik, C.J., Evans, W.C., Ritchie, B.E., Counce, D., Poreda, R.J., and Iven, M., 2003a, Scrubbing masks magmatic degassing during repose at Cascade-Range and Aleutian-Arc volcanoes: U.S. Geological Survey Open-File Report 03–435, 22 p.

Symonds, R.B., Poreda, R.J., Evans, W.C., Janik, C.J., and Ritchie, B.E, 2003b, Mantle and crustal sources of carbon, nitrogen, and noble gases in Cascade-Range and Aleutian-Arc volcanic gases: U.S. Geological Survey Open-File Report 03–436, 26 p.

Viglino, J.A., Harmon, R.S., Borthwick, J., Nehring, N.L., Motyka, R.J., White, L.D., and Johnston D.A., 1985, Stable-isotope evidence for a magmatic component in fumarole condensates from Augustine volcano, Cook Inlet, Alaska, U.S.A.: Chemical Geology, v. 49, p. 141-157.

Waitt, R.B., and Begét, J.E., 2009, Volcanic processes and geology of Augustine Volcano, Alaska: U.S. Geological Survey Professional Paper 1762, 78 p.

Waythomas, C.F., Power, J.A., Richter, D.H., and McGimsey, R.G., 1998, Preliminary volcano-hazard assessment for Akutan Volcano, east-central Aleutian Islands, Alaska: U.S. Geological Survey OpenFile Report 98–0360, 36 p.

Waythomas, C.F., Miller, T.P., and Mangan, M.T., 2006, Preliminary volcano hazard assessment for the Emmons Lake Volcanic Center, Alaska: U.S. Geological Survey Scientific Investigations Report 2006-5248, 33 p.

Webster, J.D., Mandeville, C.W., Goldoff, B., Coombs, M.L., and Tappen, C., 2010, Augustine Volcano – the influence of volatile components in magmas erupted A.D. 2006 to 2,100 years before present, in, Power, J.A., Coombs, M. L., and Freymueller, J.T., eds., The 2006 eruption of Augustine Volcano, Alaska: U.S. Geological Survey Professional Paper 1769, p. 383-420.

Werner, C.A., Doukas, M.P., and Kelly, P.J., 2011, Gas emissions from failed and actual eruptions from Cook Inlet volcanoes, Alaska, 1989-2006: Bulletin of Volcanology, v. 73, p. 155-173.

Werner, C., Evans, W.C., Kelly, P.J., McGimsey, R., Pfeffer, M., Doukas, M., and Neal, C., 2012, Deep magmatic degassing versus scrubbing: Elevated CO2 emissions and C/S in the lead-up to the 2009 eruption of Redoubt Volcano, Alaska: Geochemistry, Geophysics, Geosystems, v. 13, n. 3, Q03015, doi:10.1029/2011GC003794

Werner, C., Kelly, P.J., Doukas, M., Lopez, T., Pfeffer, M., McGimsey, R., and Neal, C., 2013, Degassing of CO2, SO2, and H2S associated with the 2009 eruption of Redoubt Volcano, Alaska: Journal of Volcanology and Geothermal Research, v. 259, p. 270-284.

Wescott, E.M., Turner, D.L., Nye, C.J., Beget, J.E., and Motyka, R.J., 1985, Preliminary report on geothermal resource investigations at Mt. Spurr, Alaska: Alaska Division of Geological & Geophysical Surveys Public Data File 85-65, 22 p.

Wood, C.A., and Kienle, (eds.), 1990, Volcanoes of North America: United States and Canada: New York, Cambridge University Press, 354 p.