Fundamental study on microparticle tephra

通常从源区到远区，麻药的晶粒大小和厚度都是递减的。在较远的区域，只有微颗粒颗粒散落在土壤、泥炭、雪和冰中。通过形态、大小和化学性质分析，研究了南极表层冰雪和冰芯中20 ~ 5 μm颗粒和日本土壤中100 ~ 20 μm颗粒的形态、大小和化学性质。在南极F圆顶附近的表面雪中发现的无色微粒，包括类似于1991年皮纳图博火山喷发的两种浮石样本的细颗粒。在南极洲昭和站附近的H15冰芯中发现了富含气溶胶信号峰的无色微粒，这些微粒被认为是Tambora 1815火山喷发的火山玻璃碎片。在2000年乌苏火山喷发中，从近端到远端对细颗粒的分布和粒度进行了研究。对小竹岛赤山火山碎屑涌积矿床中石英颗粒进行了单粒热释光测年。结果与放射性碳定年法测定的年代一致。

Usually tephras are decreasing in grain size and thickness from the source to distal area. In the more distal area, only microparticle tephras are scattered in the soil, peat, snow, and ice. In this study, microparticles in 20 to 5 μm included in Antarctic surface snow and ice core, and in 100 to 20 μm in Japanese soils were investigated through analyses of shape, size, and chemical properties.Colorless microparticles from surface snow near Dome F in Antarctica, include tephra grains similar to two types of pumice samples from the Pinatubo 1991 eruption. Colorless microparticles rich in the peak of aerozol signal of H15 ice core near Showa Station, Antarctica, are identified to be volcanic glass shards from the Tambora 1815 eruption.In the Usu volcano 2000 eruption, generation and dispersion of fine tephras were investigated based on the distribution and grain size from the proximal area to distal area.On the age determination for tephras, single grain method using Thermoluminescence dating were tried for quartz grains included in Chichibuyama pyroclastic surge deposit, Kozushima. The result is consistent with the ages by radiocarbon dating method.