A compilation of gas emission-rate data from 

volcanoes of Cook Inlet (Spurr, Crater Peak, 

Redoubt, Iliamna, and Augustine) and Alaska 

Peninsula (Douglas, Fourpeaked, Griggs, 

Mageik, Martin, Peulik, Ukinrek Maars, and 

Veniaminof), Alaska, from 1995-2006 

By Michael P. Doukas and Kenneth A. McGee 

U.S. Geological Survey 

Open-File Report 2007–1400 

2007 

U.S. Department of the Interior 

U.S. Geological Survey 
U.S. Department of the Interior 

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

Mark D. Myers, Director 

U.S. Geological Survey, Reston, Virginia 200x 

Revised and reprinted: 200x 

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ii
Contents 

Introduction ...................................................................................................................................1

Instrumentation .............................................................................................................................2

Procedure .....................................................................................................................................2

Results..........................................................................................................................................3

Acknowledgments.........................................................................................................................6

References Cited ..........................................................................................................................6

List of Figures 

1. Location map of Cook Inlet area and upper Alaska Peninsula. 

List of Tables 

1. Spurr volcano gas emission rates. 

2. Crater Peak vent on Spurr volcano gas emission rates. 

3. Redoubt volcano gas emission rates. 

4. Iliamna volcano gas emission rates. 

5. Augustine volcano gas emission rates. 

6. Douglas volcano gas emission rates. 

7. Fourpeaked volcano gas emission rates. 

8. Griggs volcano gas emission rates. 

9. Mageik volcano gas emission rates. 

10. Martin volcano gas emission rates. 

11. Peulik volcano gas emission rates. 

12. Uninrek Maars gas emission rates. 

13. Veniaminof volcano gas emission rates. 

iii
A compilation of gas emission-rate data from 

volcanoes of Cook Inlet (Spurr, Crater Peak, 

Redoubt, Iliamna, Augustine and Douglas) and 

Alaska Peninsula (Fourpeaked, Griggs, Mageik, 

Martin, Peulik, Ukinrek Maars, and Veniaminof), 

Alaska, from 1995-2006 

By Michael P. Doukas and Kenneth A. McGee 

Introduction 

This report presents gas emission rates from data collected during numerous airborne plumemeasurement flights at Alaskan volcanoes since 1995. These flights began in about 1990 as means to 

establish baseline values of volcanic gas emissions during periods of quiescence and to identify 

anomalous levels of degassing that might signal the beginning of unrest. The primary goal was to make 

systematic measurements at the major volcanic centers around the Cook Inlet on at least an annual basis, 

and more frequently during periods of unrest and eruption. A secondary goal was to measure emissions 

at selected volcanoes on the Alaska Peninsula. While the goals were not necessarily met in all cases due 

to weather, funding, or the availability of suitable aircraft, a rich dataset of quality measurements is the 

legacy of this continuing effort. An earlier report (Doukas, 1995) presented data for the period from 

1990 through 1994 and the current report provides data through 2006. 

1
This report contains all of the available measurements for SO2, CO2, and H2S emission rates in 

Alaska determined by the U. S. Geological Survey from 1995 through 2006; airborne measurements for 

H2S began in Alaska in 2001. 

The results presented here are from Cook Inlet volcanoes at Spurr, Crater Peak, Redoubt, 

Iliamna, and Augustine and cover periods of unrest at Iliamna (1996) and Spurr (2004-2006) as well as 

the 2006 eruption of Augustine. Additional sporadic measurements at volcanoes on the Alaska 

Peninsula (Douglas, Martin, Mageik, Griggs, Veniaminof, Ukinrek Maars, Peulik, and Fourpeaked 

during its 2006 unrest) are also reported here. 

Instrumentation 

For the airborne study of volcanic plumes, we used a Barringer correlation spectrometer 

(COSPEC V) to measure SO2 column abundance. This venerable instrument was originally designed 

more than three decades ago for measuring emissions from power plants and other industrial sources, 

but its subsequent application for the study of SO2 degassing from volcanoes has been described in 

detail by many authors (Malinconico, 1979; Casadevall and others, 1981; Stoiber and others, 1983). 

To determine volcanic CO2, we used a LI-COR Model LI-6252 nondispersive infrared analyzer 

and a Model LI-670 flow control unit. This instrument and its use for measuring CO2 in volcanic 

plumes have been described in detail elsewhere (Gerlach and others, 1997; Gerlach and others, 1999). 

We also used an Interscan Model 4170 analyzer with a 0-1 ppm range for measuring H2S and an 

Interscan Model 4240 analyzer with a 0-2 ppm range for direct measurements of SO2 in the volcanic 

plumes. These instruments consist of an electrochemical voltametric sensor coupled to a 1 liter-perminute sample-draw pump. Gas concentrations are recorded from the calibrated analog output of the 

instruments. Because the Interscan sensors have some cross-sensitivity to other gases, outboard scrubber 

tubes connected to the sensor inputs were used to remove the interfering gases. The use of the Interscan 

for measuring H2S and SO2 in volcanic plumes is described in detail by McGee and others (2001) and 

Werner and others (2006). 

Complementing the gas-sensing instrumentation, a pressure transducer mounted within the LICOR analyzer measured atmospheric pressure in the unpressurized aircraft cabin and a GPS receiver 

recorded the precise location of each measurement. A type T thermocouple shielded from wind and 

direct sunlight measured ambient air temperature. Data from all the instruments were recorded on a 

common 1-s time base, and gas readings were corrected for the actual pressure and temperature at the 

altitude where the measurements were taken. 

Procedure 

Two instrument configurations were utilized for the airborne measurements reported here. In one 

case, only the COSPEC and a GPS receiver were used to determine SO2 emission rates. For most of the 

measurements reported here, a twin-engine Piper Navajo aircraft, modified for mounting the COSPEC 

telescope through portals in either the front passenger side window or through the rear cargo door, was 

utilized. Typically, four to six traverses were flown under the downwind plume perpendicular to the 

direction of plume travel with the upward-looking COSPEC to measure an average column abundance 

of SO2. Wind circles at the elevation of the plume were then flown to calculate the velocity of plume 

travel so that a SO2 emission rate could be computed (Doukas, 2002). 

2
In the other configuration, the full instrument package for measuring CO2, SO2, and H2S was 

mounted in the twin-engine aircraft configured for open-flow sampling of external air upstream of 

engine exhaust as described in Gerlach and others (1997) and Gerlach and others (1999). In addition to 

the traverses flown under the plume for the COSPEC measurements described above, a series of 

additional traverses were flown through the plume at successively different altitudes from top to bottom 

of the plume all at the same distance downwind of the vent to record a vertical cross section of the 

plume for each gas present. 

The ambient CO2 background measured on each traverse on either side of the CO2 anomaly was 

fit using routines in PeakFit (v. 4.0) and subtracted from each peak and zeroed to obtain the CO2 due 

only to the volcanic source. A similar procedure was used for H2S and SO2 although no H2S and SO2

were present in the background air. Plume traverses through a vertical slice of the plume were flown 

either in an orbital fashion, where all traverses run in the same direction, or in a back-and-forth fashion 

where each traverse travels the opposite direction from the one above it and the one below it. At those 

volcanoes where traverses were flown in a back-and-forth fashion in a vertical plane through the plume, 

alternate traverses were inverted prior to processing so that all traverses start from a common latitude 

and longitude and extend in the same direction across the plume. This eliminates introducing potential 

offsets between traverses due to the travel time of gas in the sample tubing from intake to analyzer when 

importing the data into contouring and mapping software (Surfer v. 8). Emission rates were then 

calculated from the average plume pressure and temperature, wind speed, and the volcanic gas 

concentration anomaly in cross-section as explained in detail in Gerlach and others (1997) and McGee 

and others (2001). 

Results 

From January 1995 through the end of 2006, more than 135 airborne volcano plume 

measurements were made by the USGS to characterize baseline gas emissions and assess the extent of 

unrest at volcanoes in Cook Inlet and Alaska Peninsula (fig. 1). Sulfur dioxide measurements were 

attempted in every case whereas CO2 and H2S measurements were attempted less frequently. 

Two significant improvements since 1994 have advanced our capability to make high quality 

measurements. First, beginning in 1995, we began using a LI-COR infrared spectrometer for measuring 

CO2 in volcanic plumes. This instrument is vastly superior to the older MIRAN spectrometer used in 

earlier years and provides considerably better resolution and a lower detection limit for CO2. Second, 

the biggest improvement in methodology from the 1990-1994 measurements to the present is the 

adoption of wind circle measurements for more accurate wind speed determinations to estimate plume 

velocity. This technique, begun in Alaska in 1998 and described in detail in Doukas (2002), results in 

wind speed errors of only about ±5%, a considerable improvement over earlier methods, and allows for 

a direct measurement of the wind at the actual altitude of the core of the plume. 

A small number of the COSPEC measurements were made by flying over the top of the plume 

with the telescope directed downward, a possible configuration noted in the manual of operation for the 

COSPEC (Barringer Research Limited, 1981, p. 1 and 45). This was an experiment to determine the 

validity of this strategy so that it might possibly be used in those instances where winds, clouds or 

topography prevented the aircraft from flying beneath the plume. The majority of the down-looking 

measurements were made in conjunction with up-looking measurements on the same flight so that a 

rigorous comparison could be made. Our results indicate that while a few of the down-looking 

measurements agree very well with the traditional up-looking measurements, most of the down-looking 

measurements seem to overestimate SO2 emission rates, often by 50% and sometimes by as much as 

3
 

Figure 1. Map of the Cook Inlet area and upper Alaska Peninsula showing the location of the 

volcanoes included in this report. Crosses designate volcanoes where measurements have 

been made. Veniaminof volcano is off the map to the WSW. 

4
100%, compared to the up-looking measurements during the same flight. We suspect the down-looking 

measurements may be highly susceptible to variation of sun angle and the albedo of the ground surface. 

At some sun angles, sunlight can pass through the plume and reflect off the ground surface beyond the 

edge of the plume, thereby creating an apparent shadow plume. In other cases, sunlight can pass through 

the plume and be reflected upward from the bottom edge of the plume, thereby passing through the 

plume twice before it is measured. Additionally, some sunlight can be reflected upward from the top of 

the plume without ever passing through the plume even once. For light that does reflect off the ground, 

the amount of return will depend on whether the surface is bare ground, water, or snow. Thus the degree 

of agreement between down-looking and up-looking COSPEC measurements is likely a function of sun 

angle, ground surface albedo, and possibly other parameters. It appears that radiative transfer problems 

are too complex for casual use of this mode, so without further rigorous testing, we cannot recommend 

this strategy except in those cases where a measurement from beneath the plume is simply not possible 

and an order-of-magnitude estimate of SO2 emissions is required, or where a determination of the 

presence or absence of SO2 is sufficient. For this compilation, we report only the traditional up-looking 

COSPEC measurements except in three cases, all at Fourpeaked volcano, where there is no 

corresponding up-looking measurement. 

Tables 1 through 13 list the date of measurement with the corresponding gas emission rates 

determined by airborne plume measurements at each volcanic center studied. Gas emission rates are 

usually expressed as td-1 (metric tons per day). One metric ton per day equals 103

 kilograms per day or 1 

megagram per day (Mg/d). Emission rates are not rounded and are listed as we calculated them from the 

measurements without regard for significant figures. We estimate the uncertainty for the measurements 

reported herein to be ±20% or less. A blank space in the table indicates that a measurement for that 

particular gas was not attempted that day. A zero indicates that an attempt was made to measure the gas 

but no gas was detected. A ‘tr’ indicates that the gas was present in the plume but was of either 

insufficient concentration to be quantified or, in the case of CO2, not resolvable due to variations in 

ambient atmospheric CO2. 

Sixteen measurements were made at the summit of Spurr beginning in August 2004 after the 

onset of a series of volcano-tectonic and long-period earthquakes followed by the formation of a summit 

ice cauldron. Similarly, seventeen measurements were made at Crater Peak, with the majority made 

after the fall of 2004, although Crater Peak, unlike the summit of Spurr, has been measured periodically 

since its eruption in 1992. Spurr/Crater Peak continues to exhibit restless behavior but has not erupted as 

of this writing. 

Redoubt volcano has not degassed significantly since it erupted in 1989-90 but has been 

measured periodically to check for any anomalous degassing. Similarly, Douglas volcano is not 

producing any significant amount of gas and is visited only occasionally as a precaution. The plume of 

Iliamna has been measured twenty times from 1995 through 2006 with several of those measurements 

occurring in 1996 during a dike emplacement episode (Roman and others, 2004). In recent years, 

Iliamna has consistently degassed a small amount of SO2 with occasional small amounts of H2S. 

Augustine received the most attention of any volcano in Alaska with 54 gas measurements 

during the period covered by this report; more than half of those were made during the eruption that 

occurred between January and April 2006. Peak gas emission rates for Augustine in 2006 were 8650 td-1

(SO2), 13000 td-1 (CO2), and 8 td-1 (H2S). As of late 2007, Augustine was producing less than 100 td-1

SO2 and CO2, and no H2S. 

Fourpeaked volcano became restless in September 2006. An explosion of gas, ash, and steam 

rising from high on the ice-clad northeast flank of the volcano on September 17 signaled the beginning 

of the unrest. Shortly thereafter, a linear series of vigorously degassing vents was observed. Six gas 

5
measurement flights were made from September 23 through the end of the year and recorded peak 

emission rates of 2940 td-1 (SO2), 834 td-1 (CO2), and 140 td-1 (H2S). The gas data suggest an intrusion 

of magma to shallow levels under the summit but, however, no eruption has occurred. The 140 td-1

value for H2S is the largest emission rate we have recorded anywhere for that gas. 

Mageik and Martin volcanoes were measured four and five times respectively from 1998 

through 2006. Interestingly, on the August 2004 flight, significant degassing rates of CO2 and H2S were 

recorded at Mageik, but no SO2, whereas at nearby Martin volcano SO2 and H2S were recorded, but no 

CO2 was detected. The other volcanoes on the Alaska Peninsula that have been measured (Griggs, 

Peulik, Ukinrek Maars, and Veniaminof) were successfully visited only once. This is due primarily to 

the high costs associated with flying to these sites, and also the frequently poor weather. The single 

successful measurement at Ukinrek Maars was at a nearby feature called Gas Rocks. 

Acknowledgments 

We acknowledge the efforts of the numerous individuals who contributed to the USGS airborne 

gas measurement program in Alaska by conducting or participating in the gas flights or facilitating the 

work. We especially want to recognize Game McGimsey for his work in this regard. Funding for this 

work was provided by the USGS Volcano Hazards Program through the Alaska Volcano Observatory 

and the Volcano Emissions Project. 

References Cited 

Barringer Research Limited, 1981, Operation and Maintenance Manual, Correlation Spectrometer, 

COSPEC V: Rexdale, Ontario, Canada, Barringer Research Limited, 96 p., (Revision 6, December 

1996). 

Casadevall, T.J., Johnston, D.A., Harris, D.M., Rose, W.I., Malinconico, L.L., Stoiber, R.E., Bornhorst, 

T.J., Williams, S.N., Woodruff, L. and Thompson, J.M., 1981, SO2 emission rates at Mount St. 

Helens from March 29 through December, 1980, in Lipman, P.W., and Mullineaux, D.L., eds., The 

1980 eruptions of Mount St. Helens, Washington: U.S. Geological Survey Professional Paper 1250, p. 

193-200. 

Doukas, M. P., 1995, A compilation of sulfur dioxide and carbon dioxide emission-rate data from Cook 

Inlet volcanoes (Redoubt, Spurr, Iliamna, and Augustine), Alaska during the period from 1990 to 

1994: U. S. Geological Survey Open-File Report 95-55, 15 p. 

Doukas, M.P., 2002, A new method for GPS-based wind speed determinations during airborne volcanic 

plume measurements: U. S. Geological Survey Open-File Report 02-395, 13 p. 

Gerlach, T. M., Delgado, H., McGee, K. A., Doukas, M. P., Venegas, J. J., and Cardenas, L., 1997, 

Application of the LI-COR CO2 analyzer to volcanic plumes: A case study, Volcán Popocateptl, 

Mexico, June 7 and 10, 1995: Journal of Geophysical Research, v. 102, p. 8005-8019. 

6
Gerlach, T. M., Doukas, M. P., McGee, K. A., and Kessler, R., 1999, Airborne detection of diffuse 

carbon dioxide at Mammoth Mountain, California: Geophysical Research Letters, v. 26, p. 3661-

3664. 

Malinconico, L.L., 1979, Fluctuations in SO2 emission during recent eruptions of Etna: Nature, v. 278, 

p. 43-45. 

McGee, K. A., Doukas, M. P., and Gerlach, T. M., 2001, Quiescent hydrogen sulfide and carbon 

dioxide degassing from Mount Baker, Washington: Geophysical Research Letters, v. 28, p. 4479-

4482. 

Roman, D. C., Power, J. A., Moran, S.C., Cashman, K. V., Doukas, M. P., Neal, C. A., and Gerlach, T. 

M., 2004, Evidence for a dike emplacement beneath Iliamna Volcano, Alaska in 1996: Journal of 

Volcanology and Geothermal Research, v. 130, p. 265-284. 

Stoiber, R.E., Malinconico, L.L., and Williams, S.N., 1983, Use of the correlation spectrometer at 

volcanoes, in Tazieff, H. and Sabroux, J.C., eds., Forecasting Volcanic Events: Amsterdam, Elsevier, 

p. 425-444. 

Werner, C. A., Christenson, B. W., Hagerty, M., and Britten, K., 2006, Variability of volcanic gas 

emissions during a crater lake heating cycle at Ruapehu Volcano, New Zealand: Journal of 

Volcanology and Geothermal Research, v. 154, p. 291-302. 

7
Table 1. Spurr volcano gas emission rates. 

Day Month Year SO2 CO2 H2S 

07 August 2004 0 609 0.2 

15 September 2004 0 1300 1.0 

16 September 2004 0 1167 tr 

29 October 2004 0 1400 3.0 

28 February 2005 83 327 0 

02 March 2005 47 536 0 

10 May 2005 110 750 2.0 

11 May 2005 72 760 6.7 

20 September 2005 54 246 0.3 

06 April 2006 184 

23 April 2006 62 184 2.6 

26 April 2006 49 498 2.5 

12 July 2006 100 

28 August 2006 53 

25 September 2006 64 150 1.5 

17 November 2006 390 308 3.9 

Note: Emission rates expressed as metric tons per day (td-1); for this and successive tables, a blank space indicates no 

measurement, a zero indicates gas not detected, and ‘tr’ indicates gas present but not quantifiable. 

Table 2. Crater Peak vent on Spurr volcano gas emission rates

Day Month Year SO2 CO2 H2S 

19 August 1996 0 10 

02 April 1997 0 

24 May 1997 0 1010 

09 August 2000 0 140 0 

10 September 2001 tr 10 tr 

07 August 2003 0 160 0 

15 September 2004 0 1000 0 

16 September 2004 0 10 0 

30 October 2004 0 116 0 

28 February 2005 9 447 0 

02 March 2005 0 812 0 

10 May 2005 3 413 

11 May 2005 tr 10 0 

20 September 2005 59 

23 April 2006 0 722 0 

26 April 2006 0 145 0 

25 September 2006 0 0 0 

Note: Emission rates expressed as metric tons per day (td-1) 

8
Table 3. Redoubt volcano gas emission rates

Day Month Year SO2 CO2 H2S 

02 April 1997 0 0 0 

09 August 2000 0 10 0 

10 September 2001 0 10 1 

10 May 2005 9 52 0 

Note: Emission rates expressed as metric tons per day (td-1) 

Table 4. Iliamna volcano gas emission rates

Day Month Year SO2 CO2 H2S 

11 January 1995 9 

09 August 1996 137 

13 August 1996 120 270 

18 August 1996 70 883 

20 September 1996 282 

08 October 1996 404 

10 October 1996 111 

02 April 1997 0 

24 May 1997 163 130 

25 May 1998 56 72 

09 August 2000 54 44 

10 September 2001 0 1 0 

01 July 2002 0 0 0 

02 July 2002 tr 0 0 

10 September 2002 0 0 0 

01 August 2003 127 0 0 

03 August 2003 tr tr tr 

07 August 2004 29 4 

08 August 2004 20 304 2 

10 May 2005 30 0 0 

Note: Emission rates expressed as metric tons per day (td-1) 

9
Table 5. Augustine volcano gas emission rates 

Day Month Year SO

2 CO2

H

2S 

11 January 1995 0 0 

09 August 1996 0 0 

13 August 1996 0 0 

18 August 1996 0 0 

20 September 1996 0 0 

08 October 1996 0 0 

10 October 1996 0 0 

02 April 1997 0 0 

24 May 1997 0 30 

25 May 1998 0 0 

09 August 2000 0 0 

10 September 2001 0 0 0 

01 July 2002 0 tr tr 

02 July 2002 0 tr tr 

10

1 September 2002 0 0 0 

10

2 September 2002 0 0 0 

01 August 2003 0 0 0 

03 August 2003 0 0 0 

07 August 2004 0 0 0 

10 May 2005 0 0 0 

20 December 2005 660 

04 January 2006 6560 

09 January 2006 2800 

10 January 2006 5500 

16 January 2006 2780 4980 tr 

19 January 2006 3020 5970 8.2 

24 January 2006 914 1480 4.9 

08 February 2006 3960 

13 February 2006 3384 

16 February 2006 7800 

24 February 2006 7830 

01 March 2006 8650 

09 March 2006 1020 13000 0 

10 March 2006 3110 9100 0 

16 March 2006 4260 

22 March 2006 1070 

29 March 2006 1270 

06 April 2006 1965 

11 April 2006 1220 

19 April 2006 1440 

27 April 2006 751 626 1.3 

12 May 2006 400 

23 May 2006 223 

02 June 2006 430 

12 July 2006 495 

28 August 2006 450 

24 September 2006 283 289 1.3 

25 September 2006 266 0 0 

10
12 October 2006 953 

23 October 2006 100 

04 November 2006 160 

16 November 2006 225 tr 0 

17 November 2006 220 300 0 

18 November 2006 211 400 0 

Note: Emission rates expressed as metric tons per day (td-1), 1Morning measurement, 2Afternoon measurement 

Table 6. Douglas volcano gas emission rates

Day Month Year SO2 CO2 H2S 

10 August 2000 0 tr 

02 July 2002 tr tr 0 

10 September 2002 tr tr tr 

18 November 2006 tr tr tr 

Note: Emission rates expressed as metric tons per day (td-1) 

Table 7. Fourpeaked volcano gas emission rates 

Day Month Year SO2 CO2 H2S 

23 September 2006 2353 834 140 

24 September 2006 1620 340 74 

30 September 2006 2207 

12 October 2006 22641

23 October 2006 29401

04 November 2006 820 

17 November 2006 16501

18 November 2006 1000 595 27 

Note: Emission rates expressed as metric tons per day (td-1), 1COSPEC measurement with down-looking telescope 

Table 8. Griggs volcano gas emission rates 

Day Month Year SO2 CO2 H2S 

01 July 2002 0 0 0 

Note: Emission rates expressed as metric tons per day (td-1) 

11
Table 9. Mageik volcano gas emission rates 

Day Month Year SO2 CO2 H2S 

10 August 2000 tr tr 

01 September 2002 tr tr 

07 August 2004 0 1365 69 

24 September 2006 tr tr tr 

Note: Emission rates expressed as metric tons per day (td-1) 

 

Table 10. Martin volcano gas emission rates 

Day Month Year SO2 CO2 H2S 

24 May 1998 114 280 

10 August 2000 tr tr 

01 September 2002 0 0 0 

07 August 2004 73 0 43 

24 September 2006 24 tr tr 

Note: Emission rates expressed as metric tons per day (td-1) 

Table 11. Peulik volcano gas emission rates 

Day Month Year SO2 CO2 H2S 

24 May 1998 0 0 

Note: Emission rates expressed as metric tons per day (td-1) 

Table 12. Ukinrek Maars gas emission rates 

Day Month Year SO2 CO2 H2S 

24 May 1998 0 187 

Note: Emission rates expressed as metric tons per day (td-1) 

12
Table 13. Veniaminof volcano gas emission rates 

Day Month Year SO2 CO2 H2S 

02 August 2003 0 0 0 

Note: Emission rates expressed as metric tons per day (td-1) 

13