Name : NAKADA,  Setsuya
            Position : Professor
            Division/Center : Volcano Research Center
            Research Area : Petrology and geology of volcanoes
 

Research:

       Our research group's interests are petrological studies on magmatic processes in the reservoir and during ascent in the conduit. The
       latter includes degassing and crystallization processes of felsic magma; degassing efficiency and the resultant change in physical
       properties of magma control manners of volcanic eruption. The products of the 1991-1995 eruption at Unzen have been mainly
       investigated these 9 years. At Unzen, originally hydrous felsic magma could not explode due to high efficiency of degassing during
       ascent in the conduit. Degrees of crystallization and dehydration of magma that are related intimately to each other seem to have
       controlled both the effusion rate and mode of eruption. On the other hand, the petrological evolution of magma in the reservoir closely
       reflects its complicated cooling history. Heterogeneous texture and disequilibrium of crystals with melts are so common in volcanic
       rocks that a simple model of mixing of magmas with different compositions has been accepted widely. When cooling history of a
       magma reservoir was taken into consideration, however, the processes including incorporation (or recycling) of crystals and melt from
       partial melting zone or chilled zone surrounding the reservoir, can explain most of heterogeneous and disequilibrium phenomena found
       in volcanic rocks. Research on the genesis of phenocrysts in volcanic rocks is another big theme of our group. Our research group
       targets mainly Unzen, Haruna, and Izu-Oshima volcanoes presently. Rock samples from scientific drillings at Izu-Oshima and Unzen
       are used to investigate the geochemical evolution in their magma reservoirs.

       In addition to these petrological researches, geological researches on newly-erupted products have been performed. The objects are
       to interpret the present condition of eruption and to predict modes and scales of the forthcoming eruption and volcanic disaster. Based
       on geological monitoring of 1991-1995 eruption at Unzen, models of lava dome growth and a flowing mechanism of dome
       collapsed-type pyroclastic flows were proposed.

Publications:

Nakada, S., H. Shimizu, and K. Ohta, Overview of 1990-1995 eruptions at Unzen Volcano, Journal of Volcanology and Geothermal Research, 89, 1/4, 1--22, 1999.

Fujii, T. and S. Nakada, The 15-September 1991 pyroclastic flows at Unzen Volcano (Japan): a flowing model, Journal of Volcanology and Geothermal Research, 89, 1/4, 159--172, 1999.

Nakada. S. and Y. Motomura, Petrology of the 1991-95 eruption at Unzen: effusion pulsation and groundmass crystallization, Journal of Volcanology and Geothermal Research, 89, 1/4, 173--196, 1999.

Sato, H., S. Nakada, T. Fujii, M. Nakamura, and K. Suzuki-Kamata, Groundmass pargasite in the 1991-1995 dacite of Unzen volcano: phase stability experiments and volcanological implications, Journal of Volcanology and Geothermal Research, 89, 1/4, 197--212, 1999.

Kusakabe, M., H. Sato, S. Nakada, and T. Kitamura, Water contents and hydrogen isotopic ratios of rocks and minerals from the 1991 eruption of Unzen volcano, Japan, Journal of Volcanology and Geothermal Research, 89, 1/4, 231--242, 1999.

Chen, C.H., S. Nakada, Y.N. Shieh, and D.J. DePaolo, The Sr, Nd and O isotopic studies of the 1991-1995 eruption at Unzen, Japan, Journal of Volcanology and Geothermal Research, 89, 1/4, 243--253, 1999. \item Nakada, S., Hazards from pyroclastic flows and surges, In Sigurdsson, H. (ed.) 'Encyclopedia of Volcanoes', Academic Press, 945--955, 2000.

Wooster, M.J., Kaneko, T., Nakada, S., Shimizu, H., Discrimination of lava dome activity styles using stallaite-derived thermal structures, Jounral of Volcanology and Geothermal Research, 102, 97--118, 2000.

Nakada, S., J.C. Eichelberger, and H. Shimizu, Preface-Unzen eruption: Magma ascent and dome growth, Journal of Volcanology and Geothermal Research, 89, 1/4, VII--VIII, 1999.

Uto, K., S. Nakada, H. Shimizu, J.C. Eichelberger, and H. Shinohara, Unzen Scientific Drilling Project (USDP). Unzen Volcano: International cooperative research with Scientific Drilling for Understanding eruption mechanisms and magmatic activity, ICDP Newsletter, 2, 22--28, 2000.