Catastrophic volcanic eruptions that discharge magmas of more than 100 km3 occur repeatedly about once every 1000 years on the Earth. These catastrophic eruptions have a significant impact on the conditions and environment of the earth's surface. In this session, we will discuss mechanisms of catastrophic eruptions based on geological and petrological approaches and numerical simulations, including the following topics: how does a large amount of magma form in the crust? and how does the magma ascend and erupt to the surface? These are the input parameters for quantitative prediction of their impact on the surface conditions and environment. We will then collect case studies on the impact of catastrophic eruptions on the atmosphere, oceans, and life and comprehensively organize them. For example, analysis of pollen and phytolith shows that vegetation destroyed by pyroclastic flows had not recovered for a long period, and even explosive eruptions with an erupted magma volume of ~10 km3 (the 1991 eruption of Pinatubo volcano) can induce global temperature changes due to volcanic gas emissions. Through the discussion in this session, we hope to develop a framework for quantitatively predicting the impact of future catastrophic eruptions on the surface environment.