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Geochemical monitoring of volcanic activities

Jörg Erzinger1, Martin Zimmer2
GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany.
Tel.: +49-331-288-1421, Fax: +49-331-288-1474,
E-mail: 1erz@gfz-potsdam.de,
2weihei@gfz-potsdam.de

Abstract:
While geophysical methods have became widely accepted as major tools for volcanological forecasting, geochemical surveillance of volcanic activity is still less frequently applied. This might be due to insufficient information on the relationship between volcanic gas composition and volcanic activities. Complete and accurate data sets collected during long periods of time at fumaroles are only partially available. In addition the variations of furmarolic gas composition are sensitive to variable physicochemical conditions and reactions at depth and in the surficial portion of a volcano edifice. It seems that there are still no general indicators that can be used to the forecast of volcanic activity.

We investigated the Merapi volcano, Indonesia with a continuous gas monitoring device to study the relationship between gas composition (H2O, CO2, SO2, H2S, 222Rn, 220Rn, Temp) and activity patterns. The system works on-line and is partially controlled via radio link. The continuous gas data set allows for correlation with short-term seismic and other geophysical observations.

First scientific data will be presented.

The technique is sophisticated, the equipment is quite expensive, maintenance needs trained personnel, and corrosion is a severe problem. This effort seems to be necessary to get to know of Merapiís geochemical behaviour. However, in the near future more simple and less expensive devices based on sensor techniques will be optimised and installed on the Merapi crater in order to allow the local authorities for long-term monitoring of volcanic gas emanation.