Volcanological challenges to understanding explosive large-scale eruptions

AbstractAn explosive eruption, associated with the formation of a large ignimbrite sheet and collapsed caldera, is the most severe volcanic disaster on Earth. As modern society has little experience with natural disasters triggered by such events, the integration of volcanological knowledge from geological, petrological, geochemical, and geophysical disciplines is necessary for risk assessment and hazard management planning of large-scale explosive eruptions. Here, I review current volcanological attempts at revealing the mechanisms underlying large-scale explosive eruptions to highlight future objectives. The detection of massive magma storage regions with the potential to generate large-scale explosive eruptions should be the first objective of risk evaluation and assessment for caldera-forming eruption scenarios. This detection requires the development of geophysical techniques used for structural exploration. Geochemical and petrological explorations of leaked gas and magma during precursory eruptions can be useful for investigating the state of a body of underground magma. Evaluation of the eruptibility of a magma chamber is also important for risk assessment, as is the estimation of the timescales of magma accumulation. Defining the triggers that destabilize large volume magma chambers that serve as zones of long-term storage is crucial for being able to provide short-term alerts. Petrological investigations of the magmatic products from past large-scale explosive eruptions are a key tool for such a goal. Modeling the distribution of erupted material, such as huge ignimbrite sheets and co-ignimbrite ash fall, is also crucial for risk assessment of large-scale explosive eruptions. Advancing the understanding of the mechanisms and effects of large-scale explosive eruptions requires development in various fields of volcanology along with the integration of knowledge from multiple disciplines, thus promoting progress and interaction across various areas of volcanology and science and technology.