Abstract
Historical documents that describe caldera-forming eruptions in Indonesia are reviewed to identify precursory events that occurred immediately before caldera-forming eruptions, and to determine the characteristics of the eruptive history before caldera-forming eruptions. The review revealed that small- to intermediate-scale eruptions occurred several months before climactic eruptions. The distribution of eruption sites or fumarole sites expanded by several kilometers during the precursor period. The long-term eruption rate remained high for around 100 ky, although the following changes have occurred in the past 5,000-10,000 years: (1) a decrease in the long-term eruption rate, (2) an increase in explosive eruption events, and (3) the migration or restriction of the distribution of eruption sites on volcano flanks. Larger pre-caldera volcano edifices tend to result in larger calderas. Finally, the range of caldera morphologies is discussed.
