Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

S (Solid Earth Sciences) » S-VC Volcanology

[S-VC41] Active Volcanism

Mon. May 21, 2018 1:45 PM - 3:15 PM Convention Hall A (CH-A) (2F International Conference Hall, Makuhari Messe)

convener:Yuta Maeda(Nagoya University), Takahiro Miwa(National research institute for earth science and disaster prevention), Yosuke Aoki(東京大学地震研究所, 共同), Takeshi Nishimura(Department of Geophysics, Graduate School of Science, Tohoku University), Takahiro Ohkura(Aso Volcanological Laboratory, Institute for Geothermal Sciences, Graduate School of Science, Kyoto University), Satoshi Okumura(Division of Earth and Planetary Materials Science, Department of Earth Science, Graduate School of Science, Tohoku University), Tomofumi Kozono(Department of Geophysics, Graduate School of Science, Tohoku University), Chairperson:Nishimura Takeshi, Maeno Fukashi

2:45 PM - 3:00 PM

[SVC41-05] Recent eruptive activity at Sinabung Volcano, repeating explosive events

*Setsuya Nakada1, A Zaennudin2, Fukashi Maeno1, Natsumi Hokanishi1, Mitsuhiro Yoshimoto3, Masato Iguchi4 (1.Earthquake Research Institute, the University of Tokyo, 2.Center for Volcanology and Geological Hazard Mitigation, Indonesia, 3.Mount Fuji Research Institute, 4.Sakurajima Volcano Research Center, Kyoto University)

Keywords:Lava dome eruption, Explosive eruptive event, Lava plug development

Since the end of 2013, the eruptive activity has continued at Sinabung, North Sumatra, Indonesia, changing from continuous lava dome growth for the first 2 years into weak dome growth with periodical small vulcanian explosions later. Dome growth still continues and the explosion crater locates on the center of growing lava dome. Failures of lava domes were occasionally triggered by those explosions, generating pyroclastic density currents.

These explosive events are small vulcanian explosion which occurred normally 2 to 3 times a day and in maximum more than 10 times according to the data collected by the Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM). The ash column was normally about 2 km or less above the crater, and reached 8 km in maximum. The event interval was much variable with the average of about 400 seconds. The compositions of the bulk, minerals and glass of lava and volcanic ash samples collected irregularly show no significant changes within the errors of analysis since the vulcanian event started.

More explosive vulcanian events occurred at Unzen and Soufriere Hills volcanoes when the magma discharge rates increased rapidly. However, the events at Sinabung repeated at the discharge rate as low as ~0.1 m3/s. The explosions similar to Sinabung have repeated at Semeru, Indonesia, and Caliente dome of Santiaguito, Guatemala. Holland et al. (2011) proposed the model for Caliente dome, that small crack-network developed near the margin of dacite conduit would close by healing, leading ill-degassing of magma which generates explosion. However, this model cannot be applied to Sinabung and Semeru, because the time scale of healing of high temperature andesite to basaltic andesite magma is much different from those of the event intervals, and this model cannot explain the temporal development from dome growth to the explosive events. A possible model for Sinabung is that gaseous parts develop in different levels within the viscous and sluggish lava interior that behaves as a plug of the conduit, and explode when approach the surface. The reason that Sinabung does not end by forming a spine as in common lava dome eruptions, may be insufficient load of lava accumulated above the crater which could behave as the cap rock against the explosion from slow ascending magma.