Sakurajima volcano in Kagoshima Prefecture has had three large explosive eruptions since the 15th century alone (3, 1471, and 1779). Currently, it has been observed that the magma chamber deep beneath the Aira caldera is accumulating the same amount of magma as that released in the Taisho eruption of 1914, and it is believed that there is a high possibility of a large-scale eruption in the near future. It is known that prior to each of the three past large-scale eruptions, magma rose from the main magma chamber beneath the Aira caldera into a shallow vent, but the detailed process leading up to the eruption and the triggering factors for the eruptions were unknown.

　The research group investigated the fine chemical composition of the minerals contained in the erupted pumice (particularly the degree of homogenization of the chemical composition over time) for these large-scale eruptions. As a result, it was found that the magma that rose from the magma chamber about 10 km deep under the Aira caldera to the shallow part of the volcanic conduit (about 1 to 3 km deep) stagnated for about 50 days or more, and then began to rise again, reaching the surface in a very short time (within a few days after it started moving).

　This detailed clarification of the magma ascent process common to past large-scale eruptions has led to a better understanding of the causes of precursor phenomena, and is expected to contribute to improving technology for predicting future eruptions. In addition, it has been pointed out that if a similar large-scale eruption were to occur in the future, it would be necessary to develop disaster prevention plans that take into account the possibility that magma may move in such a complex manner.

Paper information:[Journal of Geophysical Research: Solid Earth] Time-Resolved Trigger Processes Leading to the Plinian Eruptions at Sakurajima Volcano, Japan