ABSTRACT

Kelut volcano has a notorious history of hazardous eruptions, five this century, the last in 1990. The hazards, generally lahar-related, are generated from the crater lake at its summit. Geophysical and geochemical monitoring of the volcano and lake on a continuous basis is ensured by the VSI. The results of monitoring of geochemical parameters including temperature, pH and the concentrations of sulphate, boron, magnesium, chloride and Mg/Cl ratio of the crater lake showed a significant increase about 4 months prior to the 1990 eruption, reflecting an increase in activity of the volcano.