姶良Tn火山灰 (AT) 噴火が生態系に及ぼした影響

抄録

In this paper we discuss the effects of Aira-Tn Ash (AT) eruption on ecosystem, based on fossil pollen and diatom assemblages obtained from central and northern Honshu in Japan. This eruption occurred during the Last Glacial Maximum (21, 000-22, 000 or 24, 000 years ago) in the Aira Caldera in southern Kyushu. The fossil pollen accumulation rate and pollen assemblages from AT deposits show that the ash fall occurred in the spring. We conclude that the AT fall occurred during, and accelerated, the last stage of climate change to a colder phase, and of attendant vegetation change to coniferous forests, that began about 30, 000 years ago. The AT fall also caused a rise in level and a change in pH from acid to alkaline of the sedimentary environment water. Some of these phenomena changed in proportion to volume or thickness of ash. It seems that the AT eruption caused widespread dry climatic conditions that were felt, at least to some degree, over long distances.