The circum-Pacific convergent margin is known as “the Ring of Fire”, with abundant volcano eruptions1. Gigantic eruptions are rare but very disastrous. It remains obscure how are large disastrous volcanos formed2,3 and where are the danger zones4-6 in the near future. Here we show that the three largest eruptions since 1900, the Hunga Tonga-Hunga Ha’apai, the Mount Pinatubo and the Novarupta volcanos, are all associated with subductions of volatile rich sediments and slab windows in the subducting plate underneath. Among them, the newly erupted Hunga Tonga-Hunga Ha’apai volcano is closely concomitant with the subduction of the Louisville Seamount Trail, whereas the Mount Pinatubo volcano is right next to the subducting fossil ridge of the South China Sea. Both seamount chains have water depths much shallower than the carbonate compensation depths in the Pacific Ocean. The water depths of the Pacific plate subducting underneath the Novarupta volcano are also shallower than the carbonate compensation depths. Therefore, these subducting slabs contain abundant carbonates. Slab windows expose the mantle wedge directly to the hot asthenosphere, which increases the temperature and dramatically promotes the partial melting of the carbonate-fluxed mantle wedge, forming volatile-rich magmas that powered explosive eruptions. Slab window and subduction of carbonate are the two most important favorable conditions for catastrophic eruptions. Considering that the Mount Fuji meets both criteria, it may be classified into a danger zone for catastrophic volcano eruptions.