Phreatomagmatic eruptions of 2014 and 2015 in Kuchinoerabujima Volcano triggered by a shallow intrusion of magma

The 2014 and 2015 eruptions of Kuchinoerabujima Volcano followed a ~15-year precursory activation of the hydrothermal system induced by a magma intrusion event. Continuous heat transfer from the degassing magma body heated the hydrothermal system and the increase of the fluid pressure in the hydrothermal system caused fracturing of the unstable edifice, inducing a phreatic explosion. The 2014 eruption occurred from two fissures that traced the eruption fissures formed in the 1931 eruption. The explosive eruption detonated the hydrothermally-altered materials and part of the intruding magma. The rise of fumarolic activities before the past two activities in 1931-35 and 1966-1980 also suggest activation of the hydrothermal system by magmatic intrusions prior to the eruption. The long-lasting precursory activities in Kuchinoerabujima suggest complex processes of the heat transfer from the magma to the hydrothermal system.