Keywords:Krakatau, caldera-forming eruption, large volume eruption, precursor events, Indonesia
Caldera-forming eruptions, erupted volume more than 10km3, occurred once or twice during 100 years. Indonesia was suffered twice for the last 200 years, and three times within 1,000 years from caldera-forming eruption. I compiled the precursor process to the caldera-forming eruptions of Krakatau 1883 after a dormant period or a long-time low activity stage (Nishimura, 1980, Yokoyama, 1981, Simkin and Fiske, 1983;Carey et al., 1996; Mandeville et al., 1996). During the last a few months, we may have caught geologically the short-term process as the progressive activity to the climax eruption in cases of Krakatau 1883 eruption (Takada, 2010; Takada et al., 2012). For Krakatau eruption, earthquakes increased; wide-range hydrothermal activity occurred; small-scale eruptions increased. However, the problem is to evaluate or predict when the volcano reaches a climax condition, and how much the volcano erupts. The evacuation plan depends on them.