Gas Emissions and the Eruptions of Mount St. Helens Through 1982

Abstract

The monitoring of gas emissions from Mount St. Helens includes daily airborne measurements of sulfur dioxide in the volcanic plume and monthly sampling of gases from crater fumaroles. The composition of the fumarolic gases has changed slightly since 1980: the water content increased from 90 to 98 percent, and the carbon dioxide concentrations decreased from about 10 to 1 percent. The emission rates of sulfur dioxide and carbon dioxide were at their peak during July and August 1980, decreased rapidly in late 1980, and have remained low and decreased slightly through 1981 and 1982. These patterns suggest steady outgassing of a single batch of magma (with a volume of not less than 0.3 cubic kilometer) to which no significant new magma has been added since mid-1980. The gas data were useful in predicting eruptions in August 1980 and June 1981.

Measurements of volcanic SO2 and CO2 fluxes by combined DOAS, Multi-GAS and FTIR observations: a case study from Turrialba and Telica volcanoes

“…Casadevall et al 1983;Burton et al 2007;Symonds et al 1994). Water vapour, CO 2 and SO 2 are the most abundant volcanic gases (Symonds et al 1994).…”

Characterization and modeling of the complete volcanic gas phase.

“…St Helens. (Le Guern et al, 1980 b;Casadevall 1983;Varekamp and Busek, 1981;Phelan et al, 1982). Discrimination of magmatic activity from phreatic activity would be possible at the initial stage of an eruption by sampling the plume from the distance.…”

“…St Helens was extensively studied using the best set of geophysical and geochemical methods (Casadevall and Greenland, 1981;. Predic tion of some small explosions following the May 18 th 1980 big burst were successfully made using the main components of the gas phase: carbon and sulfur (Casadevall et al, 1983). Calculation on thermodynamic equilibria showed the mixing between magmatic volatiles and hydrothermal fluids (Gerlach and Casadevall, 1986).…”

A rapid deployment instrument network for temporarily monitoring volcanic SO<sub>2</sub> emissions – a case study from Telica volcano

“…In particular, increases in SO 2 emissions have been largely associated with magmatic inputs to shallower levels; this process plays an important role in controlling eruptive events, as demonstrated by studies conducted during periods of enhanced volcanic activity (e.g. Casadevall et al, 1983;Olmos et al, 2007;Malinconico Jr., 1979;Zapata et al, 1997).…”