Unzen Volcano situated in the Shimabara Peninsula, Kyushu, Southwest Japan, initiated its activity about 500 Ka. The volcano developed in the Unzen volcanic graben characterized by EW-trending normal faults. This volcano consists of thick lava flows/domes of mainly dacite in composition, and the collapsed materials (Merapi-type pyroclastic-flow and dry avalanche deposits). The activity during recent 20 Ka has concentrated in the eastern part of the volcano, around Mt. Fugen (or Fugen-dake, 1,359 m above the sea level). Two historical eruptions produced an andesite lava flow of 2x10^6 m^3 and a dacite lava flow of 3x107 m^3 in 1663 and 1792, respectively. Earthquakes occurred before and during the 1792 eruption, and a large earthquake after the eruption triggered a large-scale collapse of an old lava dome (Mayuyama; about 4 ka); dry avalanche and the resultant tsunami took 15,000 people's lives. The present active center, Mt. Fugen, is only 6 km away from the center of the Shimabara City with 45,000 residents, the biggest city around the volcano. (written by Setsuya Nakada)

Where is Unzen Volcano?

(17 K)

What geological setting?

(26 K)

What tectonic setting?

(17 K)

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