HR: 0830h
AN: V11C-0505    [PDF]
TI: Volcanic Gas Emissions Through History and Geography
AU: * Halmer, M M
EM: martina.halmer@univie.ac.at
AF: Inst. f. Mineralogie u. Kristallographie, Universitaet Wien-Geozentrum-, Althanstrasse 14, Vienna, 1090 Austria
AB: The total gaseous output of a volcano is in most cases closely related to its actual phase of activity. A volcano undergoes different stages of activity during its "life-time". For estimating the gas input into the atmosphere from ancient volcanoes these activity stages have to be considered very intensely. We considered the global distribution of 360 subaerial active volcanoes that erupted at least once during the past 100 years. A significant feature is the high concentration of active volcanoes along the subduction zone of the Circumpacific Ring of Fire. Volcanoes related to subduction zones are the major gas-emitters because of the large number of very active and highly explosive volcanoes. More than 300 of the 360 active subaerial volcanoes are related to subduction zones, 24 to rift zones and 22 to ocean islands. There is no tendency for volcanoes of a certain tectonic setting to be located at a specific latitude. We summarized altitudes of 360 volcanoes and determined their altitudinal range for each tectonic setting. Volcanoes of the three main tectonic settings show average heights between 1-3km: a) subduction zones: 2-3km, b) rift zones: 1-3km, and c) ocean islands: 1.5-2.5km. Active volcanoes cluster in the equatorial latitudes (0$\deg$ to 30$\deg$) on both hemispheres with volcanoes in the southern hemisphere reaching heights of over 6000m a.s.l. Thus, most eruptions (30 eruptions/a) occurred at equatorial latitudes (0$\deg$ - 30$\deg$). In general, the number of volcanoes located in the northern exceeds those in the southern hemisphere by 3:1. We assume a higher SO2 input into the northern hemisphere. But we found also a relatively high volcanic SO2 output in the southern hemisphere, which may be caused by higher magma supply rates. The increased frequency of eruptions in the southern hemisphere in the equatorial latitudes could be partly caused by shorter intervals between eruptions (Takada, 1999). Volcanoes between 50$\deg$-60$\deg$ N showed also a relatively high annual number of eruptions (7 eruptions/a). Volcanoes at polar latitudes 60$\deg$-90$\deg$ are contributing 3 eruptions/a, because only 16 out of the 360 active subaerial volcanoes are located at high latitudes. Forteen volcanoes are located at 60$\deg$-90$\deg$N and two between 60$\deg$-90$\deg$S. In summary, 54 eruptions/a are injecting gas into the atmosphere. Ref.: Takada A (1999) Variations in magma supply and magma partitioning: the role of tectonic settings. J Volcanol Geotherm Res 93: 93-110
UR: http://www.univie.ac.at/Mineralogie/martina
DE: 0370 Volcanic effects (8409)
DE: 8409 Atmospheric effects (0370)
DE: 8419 Eruption monitoring (7280)
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting