Fig. 18

Changes of water and gas chemistries, steam emission and temperature of steam from newly formed fumaroles at Owakudani before and after the eruption. a Cl− content (ppm) and b Cl−/SO42− ratio of Owakuzawa River (Loc. 1) and natural spring #2 (Loc. 2). c CO2 content (ppm) and d CO2/H2S ratio of volcanic gas seeping to the surface (Loc. 3). e Average brightness of digital images of eruption area. Since steam is white, average brightness of image of eruption area is expected to increase as a function of steam emission. Red dots imply value for images taken by time-lapse cameras installed by HSRI and blue dots for webcam installed by IRI. f Temperature of 15-2 fumarole. Sampling locations are shown in Fig. 2