Reconnaissance study on the stratigraphy and characteristics of eruption products associated with basaltic caldera in Raung volcano, East Java, Indonesia

Abstract As one of the most active volcanoes with significant eruptive impact in Indonesia, Raung volcano shows a trace pre-historical devastating eruption as evidenced by morphology caldera at its summit. Our fieldwork revealed occurrence four pyroclastic fall deposits, two lava flows, ignimbrite, block and ash flow deposit, lahar products eruption. There is evidence Plinian phase represented layers pumice without any time gap, which uncommon for an andesitic-basaltic stratovolcano. Thin section observation on lithic fragment deposits reveals that composition volcanic mainly basalt consisting plagioclase, clinopyroxene, olivine, orthopyroxene primary crystal phases. Hornblende biotite also compose minor constituent. This implies magmatism may potentially evolve long enough to produce such massive deposits.