Fig. 1

Sample locations with seafloor bathymetry and simplified subaerial geological map modified from Ishizuka et al. (2014). Bathymetry was obtained by a high-resolution multi-narrow beam echo-sounder survey. Major bathymetry contours are shown in black and 100 m apart, while gray contours are spaced 20 m. Color lines indicate submarine ridges identified by Ishizuka et al. (2014) based on bathymetry. Yellow stars show sample locations. Eruptive fissures on Izu-Oshima Island are shown by black lines with eruption stage names (Kawanabe 1998). Different colors on Izu-Oshima Island indicate the distribution of lavas at different stages. Inset shows the location of Izu-Oshima Island