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Fig. 9 | Earth, Planets and Space

Fig. 9

From: Magma ascent and degassing processes of the 2011 and 2017–18 eruptions of Shinmoedake in Kirishima volcano group, Japan, based on petrological characteristics and volatile content of magmas

Fig. 9

Physical properties of magmas associated with the 2011 and 2018 eruptions at a pressure range of 5 to 500 MPa (M1 and M2 magmas at pressure ranges of 5–500 MPa and F1, F2, M1 + F1, M2 + F2, A1, A2, B1 and B2 magmas at pressure ranges of 5–200 MPa) calculated from bulk volatile content (Table 4) using MELTS calculation and the molar volume of the H2O and CO2 gases (Additional file 8): a Bubble volume of magmas (vol%), b Density of magmas (kg m−3), c Melt fraction of magmas (vol%), and d Melt viscosity of magmas (log Pa s). Further data is given in Additional files 9 and 10. Dark gray areas in a to d indicate depth of crustal deformation estimated by geophysical observation during 2009–2018 (6–10 km; GIAJ 2012; Ueda et al. 2013; Nakao et al. 2013; JMA 2019a). Light gray areas in a to d indicate depth of the silicic andesite magma chamber estimated by petrological study of the 2011 products (105–135 MPa; Suzuki et al. 2013b). Black broken lines in a indicate maximum and minimum porosities of the subplinian eruption products from 2011 (42–45 vol% for 2011-2SGP and 2011-3SGP; Additional file 2). The same bubble volumes are reproduced in the M1 + F1 to M2 + F2 magmas at pressure ranges of 50–75 MPa. Red broken lines in a indicate maximum and minimum porosities of the vulcanian eruption products in 2018 (19–49 vol% for 2018-1VGP, 2018-1VS, 2018-2VGP, and 2018-2VS; Additional file 2). The same bubble volumes were reproduced in B1 and B2 magmas at pressure ranges of 25–100 MPa. Broken lines in b indicate expected density structure of the crust based on a study by JMA (2013) that reports densities of 2000–2500 kg m−3 at depths of less than 0 km bsl (equivalent to depths of less than 1 km beneath the Sinmoedake summit) and approximately 2500 kg m−3 at depths of 0–1 km bsl (equivalent to depths of 1–2 km beneath the Sinmoedake summit) based on analyses of borehole samples around the Kirishima volcanoes. We assumed a density structure of 2000–2500 kg m−3 at a depth of 0–1 km and 2500 kg m−3 at depths of more than 1 km beneath Shinmoedake by considering the height of the Shinmoedake summit crater above sea level prior to the 2011 eruptions (1.2 km). Black broken lines in c indicate maximum and minimum groundmass content of the subplinian eruption products in 2011 (72–74 vol% for 2011-2SGP and 2011-3SGP). The same melt contents are reproduced in the M1 + F1 and M2 + F2 magmas at pressure ranges of 50–100 MPa. Red broken lines in c indicate maximum and minimum groundmass content in the vulcanian eruption products from 2018 (70–73 vol% for 2018-1VGP, 2018-1VS, 2018-2VGP, and 2018-2VS; Additional file 2). The same melt content was reproduced in the B1 magma at pressure ranges of 125–300 MPa; however, this melt content was not obtained for the B2 magma at pressure ranges of 5–500 MPa (Additional file 9), which suggests that the B1 magma with an H2O content of 3.0 wt% might be more realistic for 2018 than the B2 magma. Blue curves with arrows (i) show expected physical property changes in the 2011 mafic magma during its ascent. Gray curves with arrows (ii) and red curves with arrows (iii) show expected physical property changes in the 2011 and 2018 magmas during their ascent, respectively

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