Researchers discuss Mt. Unzen, a decade volcano

Abstract

In November 1989, a swarm of earthquakes deep beneath Tachibana Bay, Kyushu Island, Japan, heralded the inexorable rise of magma toward the summit of Unzen Volcano, some 15 km upward and 15 km eastward, on the Shimabara Peninsula. When the “magma head” emerged in Jigokuato Crater on May 20, 1991, a beautiful but tragic drama began. It started peacefully as a budding flower unfolding lava petals (Figure 1). But by the time lava stopped flowing in February 1995, it had cost the city of Shimabara and the surrounding towns over $2 billion in damage and 44 human lives. At its height, the crisis required the prolonged evacuation of 11,000 residents. Amid this tragedy, however, volcanologists were able to make unprecedented visual and geophysical observations of processes of magma ascent, dome growth, and dome‐fed pyroclastic flows.