The volcanic eruptions at Unzen (Japan) during 1990-1995 took a heavy toll on life and property through devastating pyroclastic flow events. In order to understand the structure and growth history of the volcano and to clarify the eruption mechanisms of SiO₂-rich viscous magmas, the Unzen Scientific Drilling Project (USDP) was started in April 1999. The magma conduit, especially its upper part, is believed to be the site of effective degassing that is the major factor controlling eruption styles. Drilling into this region allowed for the first in situ observations and sampling of the still-hot conduit and wall rocks of a recent, well-observed eruption.

Keywords: Asia, Japan, Kyushu, Shimabara, Active Volcano, Conduit, Directional Drilling, Explosion, Hazards, Thermal Regimes, USDP, Volcanic Systems