The Bulusan volcano is one of the active volcanoes in the Philippines, and is located in southern Luzon. In 2006 and 2007, 19 and 7 distinct phreatic eruptions of the volcano occurred, respectively. Each discrete event produced tephra that was dispersed by prevailing winds mainly to the west or southwest of the summit vent, blanketing portions of the western Sorsogon Peninsula. Some events were recorded as explosion-type earthquakes. Whenever possible, fallout tephra deposits were mapped and sampled to determine the volume and composition of material produced from each eruptive event. Based on the dispersal maps, the average volume was estimated to be 10 5 m 3. No juvenile magma were detected in ash and lithic samples by petrographic and X-ray fluorescence analysis. Therefore, all analyzed samples were considered products of phreatic eruptions.
The Irosin caldera and Bulusan volcano in the Bulusan Volcanic Complex (BVC) are located at the southeastern end of Luzon Island, the Philippines. This is an overview of all of the papers in the special issue "Geology and Recent Eruptions of Irosin Caldera and Bulusan Volcano, Southern Luzon, Philippines: Parts I and II" and related studies. Moriya (2014) tentatively outlines the evolution of 84 volcanoes on the Philippine Islands. Kobayashi et al. (2014a, b) establish the sequence of calderaforming eruptions. Kobayashi (2014) compares this sequence with that of the Aira caldera in Japan.
The Irosin caldera located at the southeastern tip of Luzon Island in the Philippines was formed by the eruption of 41 cal kBP Irosin ignimbrite. Bulusan, a post-caldera volcano, has repeated phreatic eruptions during historical times. The special issue on "Geology and Recent Eruptions of Irosin Caldera and Bulusan Volcano, Southern Luzon, Philippines (Part I) " provides various data and discussion mainly on the formation of Irosin caldera. First based on interpretations of volcanic landforms, the evolution of 84 volcanoes in the Philippines is outlined (Moriya, 2014). Fifty-six stratovolcanoes, three caldera volcanoes accompanying four post-caldera volcanoes, three lava domes, four scoria cones including two maars, four lava fields, and ten shield volcanoes are identified. The sequence of caldera-forming eruption at Irosin consists of a precursory fine ash eruption (Malobago lava dome) , plinian pumice fallout, and intra-plinian 1) 福岡大学理学部・産学官連携研究機関国際火山噴火史情報研究所 2) フィリピン火山地震研究所 3) 南洋理工大学シンガポール地球観測研究所 4)
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