TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 65 (No. 6), pp. 475-488, 2013

The outline of the 2011 eruption at Shinmoe-dake (Kirishima), Japan

Setsuya Nakada1, Masashi Nagai2, Takayuki Kaneko1, Yuki Suzuki1, and Fukashi Maeno1

1Earthquake Research Institute, the University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
2National Research Institute for Earth Science and Disaster Prevention, Ten'nodai 3-1, Tsukuba, Ibaraki 305-0006, Japan

(Received October 30, 2012; Revised March 11, 2013; Accepted March 31, 2013; Online published July 8, 2013)

Abstract: The climactic phase of the 2011 eruption at Shinmoe-dake was a mixture of subplinian and vulcanian eruptive events, successive lava accumulation (lava dome) within the crater, and repetition of vulcanian events after the dome growth. It was preceded by inflation and elevated seismicity for about one year and by phreatomagmatic explosions of one week before. Small pyroclastic flows and ash-cloud surges formed during the subplinian events, when the eruption column reached the highest level and the vent was widened. A lava dome, which was extruded close to the vent of subplinian events, grew by swelling upward and filling the crater. After the vent was covered by the lava, an intense vulcanian event occurred from the base of the dome and the swelled dome became deflated. After that, vulcanian events were repeated for three months. Simultaneous eruption styles in the crater (vulcanian events, continuous ash emission and dome growth) and some phreatomagmatic events in the vulcanian stage probably are due to a complex upper-conduit system developed in water-saturated country rock.
Key words: Subplinian event, vulcanian event, lava dome, phreatomagmatic event, phreatic event.

Corresponding author E-mail: nakada@eri.u-tokyo.ac.jp

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