| Popis: |
We analyzed the major element composition of volcanic glass shards in drift pumice clasts sampled from the Japanese coast before the 2021 eruption of Fukutoku-Oka-no-Ba (FOB). Consequently, it has been explained that the source volcanoes of some drift pumice clasts are Shikotsu, Toya, Towada, Hakone, Aso, Aira, Ata, Baegdusan volcanoes, and submarine volcanoes FOB and NNE of Iriomotejima (SVI). In particular, drift pumice clasts estimated from the Aira volcano were found in broad areas from the Amami-Oshima to the Shimokita Peninsula, the southern and northern limits of our sampling sites, respectively. Furthermore, the Aira-Tn tephra, erupted from Aira volcano, forming a wide pyroclastic flow plateau in the southern part of Kyushu Island. Therefore, we interpreted that the reworking process of pyroclastic flow deposits is one of the major mechanisms of the continuous supply of pumice clasts into the sea, regardless of whether volcanic activity continues. In addition, the presence of drift pumice clasts from the FOB and SVI suggests that pumice clasts from a single submarine volcanic eruption can remain on the coast for at least several tens to a hundred years. |
