Fig. 1

Location maps. a The location of Aso volcano in Japan; b distribution of the Yudamari crater lake and the fumarolic area at the southern wall of the summit crater of Nakadake central cone, Aso volcano. Contours are in 10-m intervals. The numbers in squares indicate the locations of plume measurement (Table 1). The location 8 is located further 1 km to the northeast from the point on the map