著者

小野 晃司 渡辺 一徳 星住 英夫 高田 英樹 池辺 伸一郎

出版者

特定非営利活動法人 日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.40, no.3, pp.133-151, 1995

参考文献数

41

被引用文献数

21

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We describe in this paper the character of ash eruption of Nakadake volcano presently going on and maintain that the products of the volcano during the recent geologic past are the main constituents of ashy soils distributed around, especially to the east of, the volcano. Nakadake volcano, the only active central cone of Aso caldera, mainly discharges black, sandy essential ash of basaltic andesite during its active period. The ash is the most voluminous constituent of the products of Nakadake through its activity of recent more than 20,000 years. We call ash eruption for the activity which discharges dominantly ash. The ash is divided into three groups : block-type ash, splash-type ash, and free crystals. The block-type ash, most common, is polyhedral surrounded by a few flat planes. It is formed by brittle fracturing of semi-solid top part of the magma column. While, the splash-type ash, discharged only during the very active phase in active periods, is derived from liquid magma which underlies the semi-solid top of the column. The ash is transported by gas stream from the magma in a quasi-steady state or intermittently, and is distributed around Nakadake volcano in a near-circular pattern by a low eruption column usually less than 1,000 m in height. Long-term thickness contours of the ashy soil from Nakadake volcano in three time intervals, separated by the present earth surface and three ash or pumice layers, of recent more than 20,000 years also show near-circular pattern but a little elongated to the east. 'Loam beds', mainly composed of decomposed and argillized volcanic ash, are said to be formed by accumulation of aeolian dusts during periods of no eruption in volcanic districts. But, loam beds (Akaboku) and black humic soils (Kuroboku) distributed around Aso volcano are composed mainly of primary fall-out deposits of ash or pumice along with aeolian dusts. Ash eruption of Nakadake mostly produces sandy ash rather continuously without long time break but in small rate of discharge. A correlation of detailed columnar sections eastwards of Nakadake crater shows most single strata of ashy soils, light brown- to black-colored, thin according to the increase of distance from the source crater. The ash, especially very fine ash distributed in the distal area, easily decompose and lose primary stratification to form a massive layer which is hardly discernible from aeolian loam beds by their close resemblance. Not only fine ash layers but Plinian pumice fall layers form 'loam' beds which are not distinguishable with adjacent aeolian beds by further decomposition. The thickness contours of the Kanto loam elongate and thin eastward from Fuji volcano over the Kanto plain. The thickness of loam beds changes regionally, thicker in volcanic areas and thinner in non-volcanic areas. These facts suggest contributions of primary pyroclastic falls for thickening of 'loam beds'

著者

高田英樹編訳

出版者

名古屋大学出版会

巻号頁・発行日

2019

著者

高田 英樹 タカタ ヒデキ Hideki Takata

雑誌

国際研究論叢 : 大阪国際大学紀要 = OIU journal of international studies

巻号頁・発行日

vol.23, no.3, pp.131-151, 2010-03-31

著者

高田 英樹 タカタ ヒデキ Hideki Takata

雑誌

国際研究論叢 : 大阪国際大学紀要 = OIU journal of international studies

巻号頁・発行日

vol.24, no.1, pp.91-112, 2010-10-31

著者

高田 英樹 タカタ ヒデキ Hideki Takata

雑誌

国際研究論叢 : 大阪国際大学紀要 = OIU journal of international studies

巻号頁・発行日

vol.24, no.3, pp.107-130, 2011-03-31

著者

高田 英樹 タカタ ヒデキ Hideki Takata

雑誌

国際研究論叢 : 大阪国際大学紀要 = OIU journal of international studies

巻号頁・発行日

vol.24, no.2, pp.225-250, 2011-01-31

著者

高田 英樹

出版者

大阪国際大学

雑誌

国際研究論叢 : 大阪国際大学紀要 (ISSN:09153586)

巻号頁・発行日

vol.23, no.3, pp.131-151, 2010-03-31

著者

高田 英樹 タカタ ヒデキ Hideki Takata

雑誌

国際研究論叢 : 大阪国際大学紀要 = OIU journal of international studies

巻号頁・発行日

vol.23, no.2, pp.133-152, 2010-01-31

著者

石坂 信也 渡辺 一徳 高田 英樹

出版者

日本第四紀学会

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.31, no.2, pp.91-99, 1992-05-30 (Released:2009-08-21)

参考文献数

25

被引用文献数

3

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熊本平野とその周辺には多くの活断層が存在することが知られている. 筆者らは, 熊本平野やその周辺に掘られた多数のボーリングの中で重要なもの50本余りのコアを, 改めて詳細に観察した. ボーリングコアには, 約6,300年前に鬼界カルデラから噴出したアカホヤ火山灰, 約30万年前以降に阿蘇カルデラから噴出したAso-1~Aso-4火砕流堆積物などの重要な鍵層が認められる. それらの放射年代と深度の差異から, 熊本平野における最近の約15万年前以降の第四紀層の沈降速度を見積もることができた. 平野南部での平均沈降速度はおよそ0.2~0.5mm/年であり, そこは, 熊本平野の周辺で確認されていた活断層による木山-嘉島地溝 (渡辺ほか, 1979) およびその西方延長部にあたる. 平野西部での沈降速度はおよそ0.2~0.3mm/年である. これらの沈降は, 熊本平野地下の活断層の動きによって引き起こされていると考えられる.

著者

宮縁 育夫 星住 英夫 高田 英樹 渡辺 一徳 徐 勝

出版者

特定非営利活動法人日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.48, no.2, pp.195-214, 2003-05-20

被引用文献数

12

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Aso central cones located within Aso caldera, central Kyushu, southwestern Japan, initiated their activity soon after the formation of the caldera (ca. 90 ka). The cones have produced voluminous airfall tephra layers and lava flows. Most of the tephra layers distributed in and around Aso caldera are andesite to basaltic-andesite scoria-fall and ash-fall deposits. Their stratigraphy is very complicated because it is difficult to distinguish between scoria-fall layers in the field. However, dacite to rhyolite pumice-fall deposits from some central cones interbedded between the tephra layers are very useful to correlate stratigraphic units at separated localities. Therefore, we used the pumice-fall deposits in order to construct the tephrostratigraphy and eruptive history of Aso central cones during the past 90,000 years. Thirty-six pumice-fall deposits were identified including eleven major key beds. In ascending order they are Nojiri pumice (NjP), Ogashiwa pumice (OgP), Yamasaki pumice 5 (YmP5), Sasakura pumice 2 (SsP2) and 1 (SsP1), Aso central cone pumice 6 to 3 (ACP6-ACP3), Kusasenrigahama pumice (Kpfa) and Aso central cone pumice 1 (ACP1). Phenocrystic minerals of most pumice are plagioclase, ortho- and clino- pyroxene and magnetite, but NjP, ACP5, ACP3 and ACP1 include biotite, and NjP and SsP2 contains hornblende phenocrysts. On the basis of several ^<14>C ages of buried soils just below pumice (above Kpfa) and stratigraphic position eruption ages for the eleven major pumice are estimated as follows: NjP (85 ka), OgP (80 ka), YmP5 (69 ka), SsP2 (57 ka), SsP1 (56 ka), ACP6 (52 ka), ACP5 (45 ka), ACP4 (40 ka), ACP3 (39 ka), Kpfa (31 ka) and ACP1 (4ka). During the past 90,000 years Aso central cones produced pumice-fall deposits at an interval of about 2,500 years. Many of the sources of the pumice appear now buried under the present Aso central cones.

著者

渡辺 一徳 高田 英樹 岡部 良子 西田 晃代

出版者

熊本大学

雑誌

熊本大学教育学部紀要. 自然科学 (ISSN:04546148)

巻号頁・発行日

vol.44, pp.15-22, 1995-12-15