10:15 AM - 10:30 AM
[SVC28-24] Current state evaluation and long-term prediction of volcanic activity based on historical tracking of volcanic ash deposits at Suwanosejima volcano
Keywords:volcanic ash, magma plumbing system, Suwanosejima, mid- to long-term prediction
In this study, we report the characteristics of the volcanic ash that erupted during an activation from the end of 2020 up to date, and compare with that of the ejecta over the past 20 years based on systematic petrological analysis of time-series samples. Then, we interpret this time sequence of eruptive products based on the comparison with ash layers leading up to the latest sub-Plinian eruption of the 1813 eruption. The matrix glass composition of the recent 20 years has been relatively similar, including the 2020-21 products, but minor changes are observed with crystallization at shallow depth, probably reflecting magma ascent rate leading to small temporal changes in eruption styles. On the contrary, the pattern of glass composition from the pre-1813 ash up to the climactic sub-plinian phase changes systematically with SiO2 decrease and MgO increase. In addition, MgO increases as a stepwise manner which is followed by K2O increase due to microlite crystallization at shallow depth. We interpret such temporal change in glass composition to reflect evolution of magmatic system as well as magma ascent. Current state of the volcanic activity of Suwanosejima is less active than that for urgent sub-Plinian activity, because there is no clear evidence of large or frequent input of mafic magma as a precursory sign.