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Studies on the volcanic ash soils in the environs of Mt. Daisen

1955; Taylor & Francis; Volume: 1; Issue: 1 Linguagem: Inglês

10.1080/00380768.1955.10434381

1747-0765

Mitsuru Harada,

Geology and Paleoclimatology Research

Abstract The environs of Mt. Daisen, Tottori Prefecture, are generally mountainous or hilly, and apart rom small areas of alluvial and coastal flats there is little level ground. The volcanic ash soils derived from the quartz biotite hornblende andesitic ejecta occur on the gently undulating foot-hill and on the level ground with exception of alluvial flats. Considering the fact that these soils were formed from not only volcanic ash but the coarser materials, they may be properly called volcanogenous soils. The volcanic ejecta have been deposited on the soils from diluvial series, andesite, basalt, granite, and tertiary sedimentary rocks. It was recognized that in an eruption the large ejecta, such as fine porous pumiceous lapiili descended first, then the smaller Particles such as sands, and finally the smallest, as ashes. All of these deposits have been highly weathered, but the quartz and hornblende remain in a fresh state1). The author has studied some characteristics of these volcanic ash soils.