Ito Hisatoshi
Central Research Institute of Electric Power Industry, Chiba, 270-1194, Japan.
Sci Rep. 2025 Jan 23;15(1):2968. doi: 10.1038/s41598-025-87264-5.
Reconstructing the volcanic history of the Kikai caldera, a large active volcano that produced a ~ 160 km eruption at 7.3 ka off the southern coast of Kyushu Island (southwest Japan), is crucial to assess potential future volcanic hazards at both regional and global scales. However, revealing its volcanic history before the 7.3 ka eruption has been challenging due to the caldera being mostly submerged. In this study, we present evidence that the Kikai caldera erupted a geochemically distinct silicic lava at ~ 250 ka by using zircon triple (U-Pb, Th-Pb, U-Th) dating and its chemistry. The presence of 1.5-1.0 Ma zircons in the 7.3 ka eruption deposits suggests that zircon crystallization in the Kikai caldera began during this period. We further infer large eruptions occurred around 0.7-0.6 Ma, suggesting that the Kikai caldera may have experienced at least 5 major eruptions during its 1.0-1.5-million-year magmatic evolution.
重建雾岛火山口的火山历史至关重要，雾岛火山口是一座大型活火山，在距今7300年前于日本九州岛（日本西南部）南岸外喷发了一次规模约达160公里的火山活动，这对于评估区域和全球尺度上未来潜在的火山危害意义重大。然而，由于该火山口大部分被淹没，揭示其在7300年前那次火山喷发之前的火山历史颇具挑战。在本研究中，我们通过锆石三重（铀-铅、钍-铅、铀-钍）年代测定及其化学分析，提供了证据表明雾岛火山口在约25万年前喷发了一种地球化学性质独特的酸性熔岩。在7300年前那次火山喷发的沉积物中存在150 - 100万年前的锆石，这表明雾岛火山口中的锆石结晶始于这一时期。我们进一步推断在约70 - 60万年前发生了大规模火山喷发，这表明雾岛火山口在其100 - 150万年的岩浆演化过程中可能经历了至少5次大型火山喷发。
