A Compilation of Sulfur Dioxide and Carbon Dioxide Emission-Rate Data
from Mount St. Helens during 1980-88
- Kenneth A. McGee
- David A. Johnston Cascades Volcano Observatory, U.S. Geological Survey, 5400 MacArthur Boulevard, Vancouver, Washington 98661, (206) 696-7695, kenmcgee@pwavan.wr.usgs.gov
- Thomas J. Casadevall
- Mail Stop 903, U.S. Geological Survey, Box 25046, Denver Federal Center, Denver, CO 80225-0046; (303) 236-1080, tcasadev@usgs.gov
U.S. Geological Survey Open-File Report 94-212
This report is preliminary and has not been reviewed for conformity
with U.S. Geological Survey editorial standards or with the North
American Stratigraphic Code. Any use of trade, product, or firm
names is for descriptive purposes only and does not imply endorsement
by the U.S. Government.
INTRODUCTION
Airborne monitoring of Mount St. Helens by the USGS began in May 1980 for
sulfur dioxide emissions and in July 1980 for carbon dioxide emissions. A
correlation spectrometer, or COSPEC, was used to measure sulfur dioxide in
Mount St. Helens' plume. The upward-looking COSPEC was mounted in a fixed-
wing aircraft and flown below and at right angles to the plume.
Typically, three to six traverses were made underneath the plume to
determine the SO2 burden (concentration x pathlength) within a cross-
section of the plume. Knowing the burden along with the plume width and
plume velocity (assumed to be the same as ambient wind speed), we could
then calculate the emission rate of SO2. The use of correlation
spectroscopy for determining the sulfur dioxide output of volcanoes is
well established and the technique has been discussed in detail by a
number of investigators (Malinconico, 1979; Casadevall and others, 1981;
Stoiber and others, 1983).
Carbon dioxide in the Mount St. Helens plume was measured by an infrared
spectrometer tuned to the 4.26 µm CO2 absorption band. An external sample
tube was attached to the fuselage of a twin-engine aircraft to deliver
outside air to the gas cell of the spectrometer. The aircraft was then
flown at several different elevations through the plume at right angles to
plume trajectory to define plume area and carbon dioxide concentration in
a vertical cross-section of the plume. These two parameters along with
the density of CO2 for the altitude of the plume and the plume velocity
(assumed as above to be equal to ambient wind speed) were then used to
calculate the CO2 emission rate (Harris and others, 1981).
DISCUSSION
From May 1980 to September 1988, more than 1000 fixed-wing aircraft
flights were made by the U.S. Geological Survey in order to measure and
characterize gas emissions from Mount St. Helens. Sulfur dioxide was
detected on the majority of these flights. However, toward the end of
this time period, and particularly during the final two years of
measurements, the sulfur dioxide burden was often below the detection
limit of the COSPEC. On those days, the sulfur dioxide emission rate was
arbitrarily assigned a value of 3 tonnes/day in the database. Carbon
dioxide was routinely measured starting in July 1980. These measurements
were discontinued in August 1981 after CO2 levels had declined to near
background levels.
The data listing in this report contains all of the available daily SO2
and CO2 emission rates determined by the USGS from May 1980 through the
end of the measurements in September 1988. On a few occasions, two gas-
measurement flights were made in a single day. In those cases, two
emission-rate values are listed for that day. Portions of this database
have been presented earlier by Casadevall and others (1981, 1983), Harris
and others (1981), McGee (1992a), and McGee and Sutton (in press). Other
data pertaining to these measurements such as plume dimensions and wind
information were earlier listed in McGee (1992b).
SUMMARY OF RESULTS
Emission rates from Mount St. Helens, 1980-1988 in tab-delimited ASCII format.
Editor's note: I have included graphs of the raw data purely to illustrate
the general pattern they show.
ACKNOWLEDGEMENTS
We would like to acknowledge the efforts of numerous individuals who
contributed to the success of the USGS airborne gas measurement program by
participating in the gas flights. Funding for this work has been provided
by the USGS Volcano Hazards Program and the Global Change and Climate
History Program.
REFERENCES CITED
- Casadevall, T.J., Johnston, D.A., Harris, D.M., Rose, W.I.,
Malinconcio, L.L., Stoiber, R.E., Bornhorst, T.J., Williams, S.N.,
Woodruff, Laurel 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.
- Casadevall, T.J., Rose, W.I., Gerlach, T.M., Greenland, L.P., Ewert,
J., Wunderman, R. and Symonds, R., 1983, Gas emissions and the eruptions
of Mount St. Helens through 1982: Science, v. 221, p. 1383-1385.
- Harris, D.M., Sato, Motoaki, Casadevall, T.J., Rose, W.I. and
Bornhorst, T.J., 1981, Emission rates of CO2 from plume measurements, 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.
201-207.
- Malinconico, L.L., 1979, Fluctuations in SO2 emission during recent
eruptions of Etna: Nature, v. 278, p. 43-45.
- McGee, K.A., 1992a, The structure, dynamics, and chemical composition
of noneruptive plumes from Mount St. Helens, 1980-88: Journal of
Volcanology and Geothermal Research, v. 51, p. 269-282.
- McGee, K.A., 1992b, Volcanic-plume data from Mount St. Helens during
1980-88: U.S. Geological Survey Open-File Report No. 92-361, 24 p.
- McGee, K.A. and Sutton, A.J., in press, Eruptive activity at Mount St.
Helens, Washington, USA, 1984-1988: A gas geochemistry perspective:
Bulletin of Volcanology.
- 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., Forcasting Volcanic Events: Amsterdam, Elsevier, p. 425-444.
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