火山災害の評価と戦略に関する考古学的アプローチ　　指宿橋牟礼川遺跡の事例から

In the early history of Japan, tephra was used archaeologically for the division of relics. Tephras were used and distributed in a wide range of areas, allowing for the comparison of chronological dating of relics and traces, and the relation or extinction between upper and lower archaeological materials.<br>During the 1990s, the discoveries of villages which were directly covered with the tephras increased. Through excavation of the Kuroimine site, the Nakasuji site, the Hashimuregawa site, and the Old Kanbara village, we could obtain concrete information for reconstructing the disasters and the structures of villages, which were buried by volcanic eruptions during earlier ages.<br>These discoveries have opened new discussions, including discussion of the continuity or extinction of the archaeological materials which were in the upper and lower layers, along with specific consideration of the process of the disaster. In short, the discussion was able to solve the following problems: (1) What kinds of cultural items were damaged in the process of the accumulation of the tephra?; (2) What kind of assessment was done by victims of the rapid change of environment?; (3) What kind of strategy was chosen to deal with it. When we proceed from an a priori idea such as ‘A disaster must influence a culture’, it seems that we have to seek more concrete information of the traces for reconstruction of the ancient victims' actions.<br>Through comparison of two volcanic eruptions of Mt. Kaimondake in the Hashimuregawa archaeological site, we recognized that there is a difference in strategies for adapting to the disasters between the two cases. The evidence of shell mound formation begins in the 6th century, and ends in 874 A. D. When we consider the continuity of the village, we can guess that the same community continued, because the second shell-mound was formed in the same place as the first. In addition, the type changes of the potteries and of the shapes of the dwelling-pits occurred without regard to the disaster. This point of change corresponds to the period of the Ritsuryo-system extension over this area. The evidence of the last quarter of the 7th century indicates that the change of life-style was not due to the disaster, but to the expansion of the Ritsuryo-system.<br>In addition, as indicated by the analysis of the traces of activities of ancient people, the evidence from the last quarter of the 7th century indicates that victims chose to continue their lives, while the evidence from 874 AD suggests that the victims abandoned their village. Thus, looking at the two volcanic disasters, I think that the victims' evaluation was different. In general, the disaster influenced culture, but that alone is not enough to explain the change of culture along with natural disasters.