著者

澤田 可洋 涌井 仙一郎 小宮 学

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.195-202, 1982

被引用文献数

4

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Atmospheric pressure waves generated by the big eruption of Mount St. Helens at 15 32 GMT on May 18, 1980 are recorded with microbarographs at eight stations of Japan Meteorological Agency in Japan of about 7, 000-9, 000 km in great circle distance from the volcano. The wave train is also detected with World Wide Standard Seismograph (long period and vertical component) settled at Matsushiro, Nagano Prefecture. It is the third time since the 1883 Krakatau Eruption and the 1956 Bezymianny Eruption that atmospheric pressure waves caused by volcanic eruptions at long distance are recorded with barograph or micrographs in Japan. The barograms of atmospheric pressure waves begin with increase of atmospheric pressure and distinct waves which give the maximum amplitude of 3-5 minutes of period. The mean of the maximum amplitude of records is 0.10 mb and the mean propagation velocity 308 m/sec. The antipodean wave train (A₂) and the third one (A₃) are not detected. The estimated energy of the eruption by applying the results by HUNT et al. (1960) and WESTON (1961) is at least 10²³ ergs. This estimated energy almost coincides to the energy of the 1956 Bezymianny Eruption estimated by MURAYAMA (1969). It would not be appropriate to directly compare with the kinetic energy of the eruption estimated through the amount of ejecta, but the above-mentioned estimated energy is almost same order of the mechanical energy of the blast according to DECKER R. and DECKER B. (1981). Comparing with records of atmospheric pressure waves detected in the United States, West Germany and the Netherlands, the maximum amplitude of barograms obtained in Japan is less about 10%. This may be caused by prevailing westward winds in the upper atmosphere on the propagation path from Mt. St. Helens to Japan, but the remarkable difference of propagation velocity is not seen.

著者

宮縁 育夫

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.55, no.5, pp.219-225, 2010-10-31 (Released:2017-03-20)

参考文献数

17

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Komezuka Volcano, located in the northwestern part of the post-caldera central cones of Aso Volcano, SW Japan, is a basaltic monogenetic volcano comprising a scoria cone (370-380m in basal diameter; 80m in height) and lava flows (10.5km2; 5×107m3). We obtained 14C ages of 3,070±40 years BP from a buried soil below silty ash underlying Komezuka lava, which corresponds to 3,370-3,210cal years BP, and 2,760±40 years BP (2,950-2,770cal years BP) from a soil above silty ash overlying Komezuka lava. The age of soil below the lava suggests that the eruption age of Komezuka Volcano is about 3,300cal years BP. The eruption age is consistent with the age of Ojodake Volcano (3,600cal years BP) whose lava underlies Komezuka lava. In the northwestern part of the post-caldera central cones, Late Holocene monogenetic volcanic activity commenced with sub-plinian eruptions and lava extrusion from Kishimadake Volcano at approximately 4,000cal years BP, followed by sub-plinian eruptions and lava extrusion from Ojodake Volcano at 3,600cal years BP, and ceased with strombolian eruptions and lava extrusion from Komezuka Volcano at 3,300cal years BP.

著者

水田 敏夫 小畑 正明 江上 桂子

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:24330590)

巻号頁・発行日

vol.35, no.2, pp.249-262, 1990-07-02 (Released:2018-01-15)

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Morphology, abundance and vertical distribution of vesicles were studied in a thick (40-60 m) andesitic lava flow, that lies in the underground of Kumamoto City. The vesicles are frozen bubbles that were fomed in the molten lavas at the time of its eruption. The lava can be divided into three zones: (1) an upper vesicular zone (2) a middle non-vesicular and compact zone and (3) a lower, thinner vesicular zone. The vesicles in the upper zone are elongated vertically, probably due to bouyancy-driven ascent of the bubbles, and those in the lower zone are flattened and elongated horizontally, that may be ascribed to a viscous shear flow at the bottom of the lava flow. Size distribution of the vesicles typically display nearly the log-normal distribution. Abundance, the mean size and the number density of the vesicles are greater in the upper zone than in the lower zone. Such vesicle distribution pattern is consistent to the hypothesis that the lava originally contained abundant bubbles when it was poured on the ground and then the bubbles started to ascent in the lava. Vesicles in the lower zone were the bubbles trapped by the advancing cooling front from the bottom surface of the lava. Bubbles that have escaped from the cold trap below have been accumulated in the upper zone and have been frozen in the lava upon cooling from the top surface. Mass balance calculation, however, indicates that much of the bubbles that were originally present in the lava, have been escaped through the lava surface. A dynamic cooling model was, therefore, proposed, that is to say, in the presence of surface flow in the lave during its cooling, impermeable lava crusts may not be maimtained so that gas bubbles may leak out of the lava into the air.

著者

松本 哲一 水垣 桂子 玉生 志郎 小野 晃司 北原 哲郎 品田 正一 笹田 政克

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.1, pp.1-13, 1993-04-01 (Released:2017-03-20)

参考文献数

21

被引用文献数

1

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Taga Volcano, in northern part of the Izu Peninsula, central Japan, is a large Quaternary strato volcano made of andesite and basalt. The Hata Basalts underlying the Taga volcanic rocks is a pile of pyroclastics with some lava flows mainly of basalts which include the most mafic basalt in the late Tertiary to Quaternary volcanic rocks of north Izu and Hakone region. This Basalts has been treated as the late Tertiary product by previous workers. In order to clarify the volcano-stratigraphic relationship between the Hata Basalts and the Taga volcanic rocks, geologic investigations were carried out in and around the Tanna Basin, and the core and cuttings samples from three 500-600 m drill holes in the Tanna Basin were examined. The Hata Basalts is lithologically characterized by dominant pyroclastics, especially high-temperature oxidized, reddish-brown agglutinate, whereas the products of Taga Volcano are characterized by dominant lava flows. The Hata Basalts is overlain by the Taga volcanic rocks (TV4 and TV5) unconformably at the eastward of the Tanna Basin, and overlain by the Shimo-Tanna Shales and the Taga volcanic rocks unconformably at the westward. Petrography and major elements chemistry suggest that both the Hata Basalts and the Taga volcanic rocks are petrologically very similar to each other. K-Ar dating of two rock samples of the Hata Basalts and one sample of Taga Volcano revealed that they were products of almost the same age, around 600-700 ka. All the samples dated can be correlated to the Brunhes normal polarity epoch. We conclude that the Hata Basalts is the early stage products of Taga Volcano.

著者

長谷川 健 中川 光弘

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.59, no.4, pp.269-274, 2014-12-31 (Released:2017-03-20)

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This paper introduces a practical use of outcrop data in determining the correlation, stratigraphy and distribution of large-scale pyroclastic flow deposits (PFL). The studied area is the Akan and Kutcharo volcanic zone in Eastern Hokkaido, Japan, which have had a long and complex history of more than 20 caldera-forming eruptions during the Quaternary. A database of the stratigraphy and glass chemistry for the more than 20 PFL can be established by studying a sufficient number of representative outcrops. We found representative outcrops where stratigraphic relationships between several PFL can be observed at the same time. We analyzed glass chemistry of juvenile pumices (>10 clasts) of the PFL. The database enables to identify all exposed PFL in this area, thus allowing us to draw detailed maps of the distribution for each PFL. The database can be also used for correlation and chrono-stratigraphic determination of reworked volcanic deposits, such as terrigenous marine deposits in Kushiro region, located on the plains at the foot of Akan and Kutcharo volcanoes.

著者

鹿野 和彦 大場 司 石山 大三

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 2017 (ISSN:24335320)

巻号頁・発行日

pp.95, 2017 (Released:2018-02-01)

著者

藤縄 明彦 藤田 浩司 高橋 美保子 梅田 浩司 林 信太郎

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.46, no.5, pp.269-284, 2001-11-20 (Released:2017-03-20)

参考文献数

24

被引用文献数

3

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Kurikoma volcano is located at the volcanic front of northeastern Japan arc. The volcano can be divided into 6 volcanic edifices on the bases of the inferred eruption centers, relative preservation of primary micro-topographic features on the eruptive materials, and stratigraphic relations. Lava flow has been dominant through the development history of each edifice, while pyroclastic deposits are conspicuous near the craters of several ones. Newly analyzed 7 K-Ar ages for the representative samples range from ca. 0.53 to around 0.11 Ma, practically reconcilable with the stratigraphy. Based on these data, an internally consistent scenario on the development history is summarized as follows: 1) Magmatic eruption started at about 0.5 Ma to make up the southern volcanic row. South and east to northeast flank of the Higashi-Kurikoma volcanic edifice was probably formed nearly the same time. Following these eruptions from the southern vents, central vents effused lava flows, resulting to build the Higashi-Kurikoma edifice and Kokuzou lavas (part of Kurikoma edifice) around 0.4 Ma. 2) After terminating eruption from the southern and east-north eastern vents, the Higashi-Kurikoma vent had been active until 0.1 Ma, and Kurikoma vent lasted several tens of thousands years ago. 3) Magusadake cone was built through repeated lava effusions from several vents in the western part of the volcano from 0.45 Ma to 0.1 Ma. 4) Viscous magma erupted to form Tsurugidake lava dome as the last event of magmatic eruption so far in the Sukawa horse-shoe shaped crater which was formed in northern portion of the Kurikoma (Okomayama) volcanic edifice.

著者

永田 武

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.1, pp.109-112, 1978

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The observation networks for monitoring volcanic activities of 66 active volcanoes in Japan are reviewed. For the purpose of improving the present observation networks to strengthen efficiency of the prediciton of possible volcanic eruptions of these volcanoes, several practieal technical proposals are made.

著者

河野 長 小林 和男 永田 武

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

巻号頁・発行日

vol.12, no.2, 1967

著者

兼岡 一郎 小嶋 稔 小嶋 美都子 鮎川 勝 国分 征 永田 武

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

巻号頁・発行日

vol.12, no.3, 1967

著者

高木 朗充 高山 博之 前田 憲二 中村 雅基 黒木 英州 ト部 卓

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 2004 (ISSN:24335320)

巻号頁・発行日

pp.76, 2004-10-19 (Released:2017-02-10)

著者

木股 文昭 山岡 耕春 藤井 直之

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 (ISSN:24335320)

巻号頁・発行日

vol.1991, 1991

著者

小坂 丈予 小沢 竹二郎 酒井 均 平林 順一

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.1, pp.59-74, 1983

被引用文献数

6 1

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Kiso-Ontake Volcano erupted suddenly on the 28th of October, 1979. The eruption started forming ten new craters on the southern flank of the volcano's summit. This paper deals with geochemical study on its volcanic activity after the eruption. The ratio of Cl to S was found to be high in the water-soluble components of the volcanic ash. The content of SO₂ was larger than that of H₂S in the volcanic gas. According to these observations and considering the sulfur isotopic ratio, the under ground temperature was estimated to be higher than 250℃, while that at the orifice was measured to be as low as 90℃. These facts and seismic observation indicate that magma was not elavated to a sarrow part, but that only high temperature-gas, which was separated from the magma, came up rapidly along the crack, and then rushed into the mud reservoir near the surface, where a large amount of water was evaporated, following the eruption caused by prompt increase of pressure. At an early stage of the eruption, the content of Cl^- was larger than that of SO²₄ in spring and pond waters, which were in contact with the fumarolic gases at the summit, but its relation was reversed later. This has been explained by the absorption of HCl, which had been contained in the volcanic gas at the early stage, into the water phase near the summit. From 1980 to 1982, the outlet temperature of fumarole increased to 108-145℃. However, the ratio of SO₂ to H₂S reduced rapidly, which indicates the decrease of temperature at depth. Therefore, the increase of the temperature of the fumarole is thought to be caused due to the decrease of cooling effect by ground water, because water was evaporated by the continuation of the eruptive activity. Recently no significant changes have been observed in temperature and chemical compositions of volcanic gas, suggesting that the activity will remain to be low for the time being.

著者

金川 和人 長橋 孝倫 山田 晴輝 古本 貴仁 豊原 澪 保田 牧子

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.2011, 2011

被引用文献数

1

著者

岩崎 岩次 小沢 竹二郎 平山 光衞 鎌田 政明

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:24330590)

巻号頁・発行日

vol.3, no.2, pp.165, 1959-02-20 (Released:2018-01-15)

著者

福島 大輔 小林 哲夫

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.45, no.4, pp.225-240, 2000

参考文献数

38

被引用文献数

2

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The Tarumizu pyroclastic flow deposit with intercalation of Osumi plinian fall deposit of 25 ka eruption is distributed in Tarumizu area, southeast of Aira caldera. The deposit is composed of many flow units and the source is estimated to be at the same position as the vent of plinian eruption based on grain-size variation and depositional structure. From these facts, the Tarumizu pyroclastic flow is considered to be a type of intra-plinian fiow generated by successive partial collapse of the sustained plinian eruption column. Based on the stratigraphic suecessions, the generation of this flow is estimated to be a continuous process from the early to the terminal stage of the plinian eruption. The pyroclastic flow distribution, which is in the same direction with the dispersal axis of plinian fall deposit, may suggests that the wind influenced the direction of partial column collapse. Two lithofacies were identified in the Tarumizu pyroclastic flow deposit: the massive facies and the stratified facies. The former is a 'normal' pyroclastic flow, while the latter is a pile-up of many thin layers of pyroclastic flow and pumice fall. The massive facies are mainly distributed on the lower plain near the coast and differ from the stratified facies that accumulated at a bit higher level, usually along the foot of the mountain. These facts suggest that the main pyroclastic flow accumulated on the lower level and that the corresponding marginal part of the flow eventually reached the higher level exhibiting characteristic thin stratified structure.

著者

鈴木 毅彦

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.37, no.5, pp.251-263, 1992

参考文献数

22

被引用文献数

11

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Nasu Volcano is a polygenetic volcano locating on the volcanic front of Northeast Japan Arc. The eruptive history of this volcano during the last 350,000 years is clarified by tephrochronology. On the eastern foot of this volcano, 16 pyroclastic fall deposits are identified. The stratigraphic relations of these deposits with well dated tephra layers derived from other volcanoes provided the chronological framework for the eruptive history. Moreover, the estimated ages and volumes of each deposits, determined by an empirical formula, gave eruption rate of pyroclastic fall deposits. Nasu-Shirakawa Tephra Group (Sr1 to Sr12) erupted from 350 ka to 200 ka. The frequency of explosive eruption during this period is 0.08 times per 1000 years, and eruption rate of pyroclastic fall deposits in dense rock equivalent volume is 0.016 km³ per 1000 years. On the other hand, a K-Ar dating chronology for Nasu Volcano carried out by a previous study shows that no effusions of lava flows occurred during this period. After this period, no obvious explosive eruptions occurred until 55 ka. This non explosive period is most likely corresponds to the stage characlerized by effusions of lava flows which was recognized by the K-Ar dating chronology. The eruption rate of this period is larger than that of former period from 350 ka to 200 ka. The younger stage from 55-50 ka to present is not characterized only by explosive eruptions (occurrences of Kuromori Tephra and Oshima Tephra 1 and 4; Kr, Os 1 and 4) but also by effusions of lava flows, occurrences of pyroclastic flows, formations of lava dome and pyroclastic cone. The frequency of explosive eruption and the eruption rate of pyroclastic fall deposits during this period are 0.06 times per 1000 years and <0.003 km³ per 1000 years, respectively. Both are smaller than those of the period from 350 ka to 200 ka.

著者

風早 康平 安原 正也 佐藤 努

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 1999.2 (ISSN:24335320)

巻号頁・発行日

pp.141, 1999-10-09 (Released:2017-02-10)

著者

古本 定

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

巻号頁・発行日

vol.2, no.1, pp.37-46, 1957

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An attempt was made to discover any statistical relation of earthquakes as premonitory phenomena to volcanic eruptions on the basis of reports of the Hawaiian Volcano Observatory. The results seem to be negative. However certain factors must be kept in mind. First, seismic activity was tabulated according to the method of weekly local seismicity, an unique method employed in Hawaii. Secondly, the data used were obtained from low-powered seismometers. Hence, the possibility of seismic activity serving as premonitory phenomena of eruptions is still not excluded. It is then inferred that for further investigations seismometers of higher magnifications are necessary and consonantly a better way of tabulating seismic activity must be devised. It has also been found that there is a definite statistical relation between the frequency of earthquakes and their strength.

著者

長岡 優 西田 究 青木 陽介 武尾 実 大倉 敬宏 吉川 慎

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.2017, pp.88-88, 2017