著者

野上 健治 吉田 稔 小坂 丈予

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.38, no.3, pp.71-77, 1993-08-15

参考文献数

10

被引用文献数

6

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薩摩硫黄島東温泉沿岸では温泉水と海水とが様々な比率で混合した結果,極微細なSiO_2-Al_2O_3-Fe_2O_3-H_2O系の低結晶質沈殿物が生成しており,海面が様々な色調を呈している.これらの変色海水について,母液及び沈殿物のSi-Fe-Al_3成分の化学組成及び生成条件,特にpHとの関係について検討を行った.その結果,沈殿物の化学組成は温泉水と海水との混合溶液のpHに強く依存し,pHが2前後では沈殿物中のFeの割合は低いが,pHが3〜5の範囲ではFeの割合が相対的に高くなる.更にpHが上昇するとAlの割合が相対的に高くなる.また変色海水の色調はpHが2前後の時は透明から乳白色であるが,pHが3〜5の時には黄褐色である.更にpHが上昇すると色調は再び白色系になり,沈殿物中のFeの割合によって色調が変化する.これらに対して,各採取地点における沈殿物と母液との混合物の化学組成は東温泉から湧出している温泉水のそれと殆ど同じであり,見かけ上沈殿の生成過程においてSi,Fe,Alの3成分は分別していない.

著者

井口 正人

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.39, no.2, pp.49-67, 1994-05-20

参考文献数

27

被引用文献数

10

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代表的な安山岩質火山である桜島の高周波B型地震,低周波B型地震および爆発地震を,波動の特性,震源位置およびモーメント加速度・テンソルについてA型地震と比較検討することにより,火山性地震の発生機構を論じ,それを火山特有の構造である火道と関連させて考察した.高周波B型地震,低周波B型地震および爆発地震は,火口直下の半径約200mの円筒状の領域に分布し,上下方向のダイポール成分が卓越する体積膨張型の力源をもつことから,マグマに満たされた火道内において発生していると推定され,その原因として,火道に沿ったガス相の膨張が考えられる.A型地震は,これら3種類の地震の震源域の周囲に分布し,ダブル・カップル成分が大きいことから,火道周辺の岩石のせん断破壊によって発生すると推定される.高周波B型地震,低周波B型地震および爆発地震のスペクトルの相違は,震源過程の違いによるものと考えられる.これらの地震発生に伴う地盤変動,表面現象および地震発生の時系列から考えると,震源過程の相違は火道上部の閉塞状態やマグマの物性の違いに起因していると推定される.

著者

鈴木 由希 古川 晃子 中田 節也 藤井 敏嗣 渡邉 篤志 小山 悦郎

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.2008, 2008-10-10

著者

小山 真人 早川 由紀夫 新井 房夫

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.191-209, 1995-07-31

被引用文献数

4

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We reveal the eruptive history of the Higashi Izu monogenetic volcano field by tephrochronology and loess-chronometry and describe mainly volcanoes older than 32,000 years ago. The eruption of the volcano field started at about 150,000 years ago. Twelve tephra from volcanoes outside the Izu Peninsula were used as key beds. We found four eruptive fissures ; Takatsukayama-Sukumoyama, Kadono-Umenokidaira, Koike-Oike, and Numanokawa fissures, along each of which two to five monogenetic volcanoes erupted simultaneously. Interbedding of a distal wide spread tephra between eruptive deposits proper to the volcano field (the KIP-4 pumice between the Takatsukayama-Sukumoyama tephra, and the Hakone Da-4 pumice between the Kadono-Umenokidaira tephra) means that an eruption of a volcano outside the Izu Peninsula occurred simultaneously with the eruption of the volcano field. Vent locations of the volcano field were limited to the northern half of the present distribution during 80,000-150,000 years ago and were expanded in the later stage. Average frequency of eruption in the volcano field is calculated to be one/7,900 years for the period of 40,000-150,000 years ago, and one/2,500 years for the past 40,000 years. Average discharge rate of magma is calculated to be 0.64 kg/s before 40,000 years ago, and 2.5 kg/s for the past 40,000 years. Thus, both the average frequency of eruption and the magma discharge rate are higher for the past 40,000 years than those in the earlier stage. Many of the eruptions of andesite magma occurred later than 14,500 years ago, and the ones of dacite-rhyolite magma occurred only for the past 3,200 years. The cumulative pattern of the discharge mass of magma from the whole volcano field against time shows no clear predictability.

著者

吉永 秀一郎

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.153-166, 1995-07-31

被引用文献数

11

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Successive terrestrial coverbeds called "volcanic ash soils" are widely distributed in Japan. In this paper, the origin of parent material of volcanic ash soils is discussed from the stratigraphy and the mineralogy of volcanic ash soils to clarify the accumulation of volcanic ash soils. In the Hakkoda Mountains and in the southern part of Tokachi Plain, thickness of tephra interbeds recognized within peaty soils are almost the same as those within the volcanic ash soils. No more distinct tephra interbed is observed in the volcanic ash soils with the exception of the marker tephra interbeds. This fact indicates that the accumulation of the volcanic ash soils have occurring through the periods without tephra deposition. Moreover, the existence of soil developed on the latest Hokkaido-Komagatake tephra of 1929, also suggests that the accumulation of volcanic ash soils is almost independent of the tephra deposition. Mineralogical composition of the fraction coarser than 0.02 mm in the volcanic ash soils are mainly derived from the underlying tephra interbeds. On the other hand, the finer fraction contains amorphous clay minerals and non-volcanogeneous materials such as quartz and illite. The former is weathering products of tephra and the latter would be derived from eolian dust. In particular, several studies on oxygen isotope composition have revealed that the origin of fine quartz is the eolian dust. Accumulation rate of fine materials in the volcanic ash soils ranges from 10^<-1> to 10^0 mg cm^<-2> y^<-1>. It agrees well with those of paleosols intercalated into sand dunes along the coast of the Japan Sea, of pelagic sediment of the Japan Sea, and of eolian dust fall calculated from atmospheric dust density. From the evidence mentioned above, parent material of volcanic ash soils is originated from the reworked materials of tephra with the fine materials of the eolian dust.

著者

井村 隆介

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.119-131, 1995-07-31

被引用文献数

5

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Sedimentological study of the recent deposit of Sakurajima Volcano has exposed some properties of the deposit accumulated by small-scale eruptions. Fall-out deposit of long-term such eruptive activity occur in any nearly concentric circular area around the source. Change of the small-scale eruptive activity manifests as the facies, bulk density and carbon content of the deposit, because such characters of the deposit are reflections of the accumulation rate of pyroclastics. Gray laminated or massive volcanic sand layer indicates a period of highly active volcanism ; brownish loamy volcanic sand layer a less active one and brownish loam or humic soil a dormant or inactive one. The duration of those periods can be estimated from the facies, thickness and bulk density of the deposit and recent fall-out ash data.

著者

荒牧 重雄 早川 由紀夫

出版者

特定非営利活動法人日本火山学会

雑誌

火山. 第2集 (ISSN:04534360)

巻号頁・発行日

vol.27, no.3, pp.203-215, 1982-10-01

被引用文献数

9

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A small-scale explosive eruption of Asama volcano lasted from 02 h 25 m to ca. 06 h, April 26, 1982. It produced a thin but far-reaching ash fall bed and very minor pyroclastic flows on the upper slopes. The main axis of ash-fall deposit extended ESE passing Tokyo to reach the Boso Peninsula. Subordinate axis extended toward the southwest to reach Lake Suwa. The wind above 5, 000 m was mainly responsible for the main axis while the low altitude winds produced the subordinate axis as it blew south to southwestwards. The amount of ash fall ranged from more than 300 g/m^2 to 100 g/m^2 at the distance of ca. 10 km from the vent and the total mass erupted was estimated to be about 8 million tons. The ash traveled at an average speed of 12 m/s as far as 200 km from the vent along the main axis. Grain size of the ash regularly decreases clockwise at the distance of about 10 km from the crater reflecting the changing wind direction with altitude. No appreciable change in the medium diameter was found for samples taken in Tokyo (130 km away, Md_φ=3.32) and the one 10 km away (Md_φ=3.26). All samples show marked skewness toward fractions finer than 63 μm suggesting that such fine particles descended in aggregates. Field evidence that in some places ash was incorporated in mud droplets strongly supports this mechanism although it was reported that ash fell apparently in a "dry" state. Ash contained several percent of hydrothermally altered older volcanic materials as well as much water-soluble substances, gypsum, alunite, etc. No clay minerals were found by x-ray diffraction, a fact in strong contrast with the ejecta of 1977-1978 eruption of Usu and 1979 eruption of Ontake volcanoes although both materials had a very similar appearance and clayey physical properties as the present ash. No vesicular, juvenile matelials were identified and the bulk consisted of polyhedral grains of hyalopilitic pyroxene andesite very much similar to recent lavas of Maekawa-yama. No liquid magma but a high-temperature steam jet deep out of the vent may have been responsible for this explosive eruption. High temperature of the erupted material was clearly demonstrated by the glowing deposits observed on the upper slopes immediately after the first phase of eruption. These were mainly laid down by the very small scale pyroclastic flows which overflowed the crater rim and descended for a short distance over the northern and southern slopes.

著者

猿渡 英之 清水 洋 河田 陽介 増田 彰正

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.1988, no.2, 1988-11-29

著者

大木 章一 村上 亮 渡辺 信之 浦部 ぼくろう 宮脇 正典

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.50, no.5, pp.401-410, 2005-10-31

被引用文献数

11

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The Asama volcano (elevation 2568m), central Japan, erupted on September 1, 2004. Since then thick volcanic fumes prevented monitoring of the topography on the summit crater floor by standard optical methods. To detect geomorphic changes of the volcano, Airborne Synthetic Aperture Radar (AirSAR) measurements including interferometry were repeatedly carried out on September 16, October 22, December 15, 2004 and March 10, 2005. The comparison of AirSAR result in September with a digital elevation model (DEM) by laser profiling measurements in October 2003 revealed that a pancake shape lava mound (volume=0.9×10^6m^3) was formed on the floor. The subsequent AirSAR measurement on October 22 indicated that the pancake shape mound had disappeared and a small pit hole was formed. The volume of ejecta amounted to 2.1×10^6m^3. The AirSAR results in December 2004 and March 2005 suggested that the shape of the crater floor stayed generally unchanged during that time window. From these, we infer that lava extrusion during the 2004 Asama eruption occurred within a short period around September and October.

著者

松島 喜雄 大島 弘光

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.1989, no.2, 1989-10-08

著者

鎌田 桂子 鎌田 浩毅

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.1988, no.2, 1988-11-29

著者

早川 由紀夫

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.1987, no.1, 1987-04-06

著者

豊田 純一 柿沢 栄一 木村 政昭

出版者

特定非営利活動法人日本火山学会

雑誌

火山. 第2集 (ISSN:04534360)

巻号頁・発行日

vol.28, no.2, 1983-07-01

著者

山科 健一郎

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.1988, no.1, 1988-07-16

著者

関根 利守 桂 敬 荒牧 重雄

出版者

特定非営利活動法人日本火山学会

雑誌

火山. 第2集 (ISSN:04534360)

巻号頁・発行日

vol.23, no.2, pp.175-176, 1978-07-01

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

竹原 直希 高橋 栄一

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.2007, 2007-11-18

著者

早川 由紀夫

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, pp.S1-S15, 1995-12-25

被引用文献数

2

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Age of a tephra can be determined by simple stratigraphy, if adequate number of time-markers are provided. Eleven master tephras are chosen as the time-markers for the last one million years. They are Kikai-Akahoya (7.330 ka), Aira-Tanzawa (26.00 ka), Daisen-Kurayoshi (50.00 ka), Aso-4 (87.00 ka), Ata-Torihama (250.0 ka), Kakuto (340.0 ka), Suiendani-TE5 (420.0 ka), Kobayashi-Sakura (540.0 ka), Kaisyo-Toriitoge (650.0 ka), Shishimuta-Azuki (870.0 ka), and Shishimuta-Pink (1000 ka). The present earth surface and Bruhnes/Matuyama boundary (780.0 ka) play a same role as master tephras. Ages of some master tephras are assigned rather arbitrarily, however, it is productive to affix them once to a specific value. A tephra sandwiched between two master tephras is afforded its age by interpolating the thicknesses of loess between them. This technique, loess-chronometry, has the advantage of ability to measure an interval of tens to thousands years in the geologic past, over radiometric dating. More than 900 tephras are presently recorded and linked each other in a computer database including name, source volcano, age, magnitude, stratigraphy, and remarks. An updated version is listed in WWW at "http://www.la.gunma-u.ac.jp/〜hayakawa/English.html".

著者

菅野 智之 前川 徳光 森 済 鈴木 敦生 岡田 弘

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.1992, no.2, 1992-11-09

著者

岩淵 洋 浅田 昭 玉木 操

出版者

特定非営利活動法人日本火山学会

雑誌

火山. 第2集 (ISSN:04534360)

巻号頁・発行日

vol.34, no.4, pp.295-299, 1989-12