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High-resolution Reconstruction of the 10,000-year history of Asama-Maekake volcano, central Japan

Maya Yasui , Masaki Takahashi and Tatsuo Kanamaru

Abstract

Asama-Maekake Volcano, one of Japan's most active volcanoes, has been the focus of an ongoing, national research project "Integrated Program for Next Generation Volcano Research and Human Resources Development". This study addressed challenges in stratigraphic reconstruction caused by varying deposit distributions, burial of older layers, and lack of unique lithological features for correlation of deposits of different localities. Excavating 33 trenches of 5 meters deep near the volcanic edifice, describing deposits, creating isopach maps, and conducting over 100 radiocarbon datings were made. Combination of extensive trench excavation surveys and many datings was shown to be effective in reconstructing eruption history with high resolution (Yasui et al., 2021).   Buried older deposits were excavated and soil beneath them were dated. Eruptions predating 3,000 years ago were frequent but smaller in scale. The average eruption rate was 0.00006 km3/year from 9,000 to 6,000 years ago, and 0.0001 km3/year from 6,000 to 3,000 years ago. Since 2,000 years ago, the average eruption rate has been high at 0.0011 km3/year. Since 2,000 years ago, infrequent but large-scale sub-Plinian eruptions have occurred, with large amounts of pyroclastic material deposited near the crater (e.g. Yasui and Koyaguchi, 2004), and the volcanic edifice is thought to have grown rapidly. In addition, the shape of the step diagram has been volume predictable since 2,000 years ago. If an eruption similar to that in the 18th century were to occur in 2025, the eruption volume is predicted to be approximately 0.21 km3 (Takahashi et al., 2022).