Eight 14C ages of the Hijiori pyroclastic flow deposit (stage 1 and 4, Kawaguchi and Murakami , 1994) are reported. Calibrated 14C ages of the stage 1 pyroclastics fall in a relatively narrow range, while those stage 4 are more fluctuated. The larger fluctuation may be attributed to nature of samples collected (lower organic carbon concentration and poor state of sample preservation relative to the stage 1). No significant difference in the 14C age is recognized between the stage 1 and stage 4. It is concluded that the eruptive activities of Hijiori volcano reached its peak shortly after the outbreak at about 12,000 y.B.P. (calendar age).

Key words:
caldera, Hijiori, hot dry rock, 14C, radiocarbon