EVALUATION OF SULFUR-DIOXIDE EMISSIONS FROM EXPLOSIVE VOLCANISM - THE1982-1983 ERUPTIONS OF GALUNGGUNG, JAVA, INDONESIA

Galunggung volcano, Java, awoke from a 63-year quiescence in April 198 2, and erupted sporadically through January 1983. During its most viol ent period from April to October, the Cikasasah Volcano Observatory re ported 32 large and 56 moderate to small eruptions. From April 5 throu gh September 19 the Total Ozone Mapping Spectrometer (TOMS), carried o n NASA's Nimbus-7 satellite, detected and measured 24 different sulfur dioxide clouds; an estimated 1730 kilotons (kt) of SO2 were outgassed by these explosive eruptions. The trajectories, and rapid dispersion rates, of the SO2 clouds were consistent with injection altitudes belo w the tropopause. An additional 300 kt of SO2 were estimated to have c ome from 64 smaller explosive eruptions, based on the detection limit of the TOMS instrument. For the first time, an extended period of volc anic activity was monitored by remote sensing techniques which enabled observations of both the entire SO2 clouds produced by large explosiv e eruptions (using TOMS), and the relatively lower levels of SO2 emiss ions during non-explosive outgassing (using the Correlation Spectromet er, or COSPEC). Based on COSPEC measurements from August 1982 to Janua ry 1983, and on the relationship between explosive and non-explosive d egassing, approximately 400 kt of SO2 were emitted during non-explosiv e activity. The total sulfur dioxide outgassed from Galunggung volcano from April 1982 to January 1983 is calculated to be 2500 kt (+/- 30%) from both explosive and non-explosive activity. While Galunggung adde d large quantities of sulfur dioxide to the atmosphere, its sporadic e missions occurred in relatively small events distributed over several months, and reached relatively low altitudes, and are unlikely to have significantly affected aerosol loading of the stratosphere in 1982 by volcanic activity.