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, no.3, pp.211-212, 1995-07-31

著者

日下部 実 荒牧 重雄 金成 誠一 大隅 多加志

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.32, no.4, 1987-12-28

著者

佐藤 博明 荒牧 重雄 日下部 実 平林 順一 佐野 有司 野尻 幸宏 チュア F.

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.1991, no.1, 1991-04-02

著者

山本 裕朗

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.1, pp.11-25, 2003-03-18

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The lava effusion process from a cinder cone and its mechanism are discussed based on the field observation of Ojika-Jima Monogenetic Volcano Group (OMVG). The cinder cones of OMVG are classified into two types, C-type and D-type cones, based on the mode of lava effusion from the cone. In the C-type cone, lava overflowed from the central crater, whereas in the D-type cone, lava flowed out from the flank. These types are related to the morphology and internal structure of the cone. The ratio of cone height (H_<co>) to width (W_<co>) of the C-type is smaller than that of the D-type, and the part of the dense welding is widespread around the cone. On the other hand, the welding area of the D-type is within the limits to the central part of the cone. The D-type is further divided into two types; Dc-type is accompanied by a mountain body collapse with lava effusion and Dp-type does not have this collapse. The majority of Dc-type cones are larger than Dp-type cones, although the ratios of H_<co>/W_<co> are similar. In the OMVG, a thin dike (less than 1 m thick) is generally observed inside the cone. However, if a dike intrusion does not have enough stress to collapse a mature cone, a branched dike system could cause a much larger load to the slope of cone and push a sector of the cone outward. Therefore, a branched dike system seems to control in cone breaching. The dike system is always observed inside Dc-type cones, while it is rare inside Dp-type cones. Considering the concept of crack propagation in an elastic body, the dike branches off under the condition that the breaking strength of the deposit around the tip of a feeder dike is low. Accordingly, the collapse of a cinder cone caused by a branched dike system is incident in the larger-scaled cinder cone, especially when the welded area is restricted to the central part of the cone and altitude difference between the lava lake in the crater and the top of the dike is large. It has been assumed in previous works that the density difference between the lava and cinder cone is the main controlling factor for the mode of lava effusion from the cinder cone. In this paper, the author concluded that the degree of welding around the feeder dike and total volume of the cinder cone are the major controlling factors in the dike propagation process.

著者

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. 第2集 (ISSN:04534360)

巻号頁・発行日

vol.27, no.4, pp.277-292, 1982-12-28

被引用文献数

12

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Sakurajima Volcano consists of two main stratovolcanoes, Kitadake and Minamidake, which are composed of pyroclastic rocks and lava flows of pyroxene andesites and dacites. The basement rocks are composed of sedimentary rocks such as shale, sandstone, and acidic tuff, welded tuff, and granitic rocks. Geomorphology, large-scale historic eruptions, and the classification of surface textures of andesitic lava flows are briefly summarized. Volcanic history on the basis of the correlation between tephrochronology and the welded pyroclastic deposits is also presented. Taisho and An-ei lavas extruded at the later stage of the eruptions contain microphenocrysts of olivine. Orthopyroxenes of Bunmei pumice of later stage are rich in En content than those of early stage. These facts suggest that the volcanic products of the large eruptions were derived from zoned magma chambers.

著者

早川 由紀夫 中島 秀子

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.43, no.4, pp.213-221, 1998-08-31

被引用文献数

4

---

The 1108 eruption of Asama is the largest among numerous eruptions of the volcano during the Holocene. The magnitude is twice as large as that of the notorious 1783 eruption, which killed about 1,400 people. It is also the oldest written eruption of Asama. Chuyuki, which was written in Kyoto, 300 km SW of Asama, describes that the eruption started on September 29, 1108, by the Julian calendar, and that fields of rice and other crops were severely damaged. Many fatalities are strongly suspected by the distribution of the Oiwake ignimbrite, but no description is given for human loss in Chuyuki. A thin pumice layer intercalated between the 1108 scoria and the 1783 pumice can be correlated to a record of Pele's hair-fall in Kyoto in 1596. As many as 800 fatalities at the summit in 1598 described in Todaiki cannot be true. Tenmei Shinjo Hen'iki, which describes that a number of villages along the Jabori River were swept away by hot lahars in 1532, is not a contemporary document. It was written in the late 18th century. Fifteen fatalities at the summit in 1721 can be true. After the 1783 eruption, Asama had been relatively quiet for 100 years. During the early and middle 20th century, Asama had been very active with a peak of 398 times vulcanian explosions in 1941. About 30 Iives were lost at the summit, in the 20th century, by 12 explosions among the total about 3,000 explosions.

著者

中村 一明

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:04534360)

巻号頁・発行日

vol.17, no.1, 1972-06-01

著者

安井 真也 高橋 正樹 島田 純 味喜 大介 石原 和弘

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.58, no.1, pp.59-76, 2013-03-29

被引用文献数

1

---

桜島火山の歴史時代の大規模噴火である安永噴火(1779-1782年)と大正噴火(1914-1915年)の噴出物の岩相や層序,地形,噴火当時の記録を比較した.両噴火では山頂をはさんだ両測山腹で割れ目火口列が活動した.割れ目の推定の長さは大正噴火で約2.3km,安永噴火では5kmに及ぶ.噴火開始後数10時間の大正噴火と安永噴火の噴火様式は共通しており,プリニー式噴煙柱から火口近傍への大量の火砕物降下により斜面上に火砕丘を形成しながら火砕成溶岩をもたらした.引き続く数週間には両噴火とも溶岩流出が繰返されて溶岩原が形成された.その後は,大正噴火が陸上での溶岩流出を主としたのに対し,安永噴火では北東沖で海底噴火が起きて安永諸島を形成した点で大きく異なる.両噴火とも噴火初期に割れ目火口近傍へ著しい火砕物降下があることが特徴的である.これは火山体形成の観点からは,両噴火では山頂部の地形変化はほどんどないが,山腹斜面が成長したことを意味する.また桜島の大規模噴火の減災という観点では,居住地域近くまで到達しうる割れ目火口の活動への迅速な初期対応の重要性を示している.

著者

植田 義夫 小野寺 建英 大谷 康弘 鈴木 晃 中田 節也

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.4, pp.175-185, 2001-08-30

被引用文献数

1

---

The Myojin-sho volcano is one of the active submarine volcanos in the northern part of the Izu-Ogasawara arc about 400 km south of Tokyo. This volcano is a somma edifice of the Myojin-sho caldera, 6.5 km×8 km in diameter and 1000 m deep. The topography, seismic profiler, magnetic and gravity surveys around the Myojin-sho caldera were conducted by the Hydrographic Department, Japan (JHD) in 1998 and 1999. The geophysical structures of the caldera were derived, and the possible cause of the caldera formation is discussed. The residual gravity anomalies were calculated from the observed free-air anomalies by subtracting the gravity effect of 2-layer subbottom model structure, which amounts to 10 m Gals in a localized zone from the caldera to the northern somma. Bouguer gravity anomalies with the assumed density of 2.0 and 2.4 g/cm^3 also show the positive anomaly over the same zone, which is accompanied by the acoustic and magnetic basement depression. Moreover, it seems that the sediment volume nearby Myojin-sho caldera cannot compensate the volume loss of caldera (20 to 41 km^3). These features insist that the Myojin-sho caldera is caused by the collapse of the pre-caldera edifice rather than the explosion. The origin of the high gravity caldera may be ascribed to the magma pocket causing the depression, instead of the high density erupted material filling the caldera floor. The magnetization intensity of 4.8-5.3 A/m at the Myojin-sho volcano is derived from the magnetic anomaly, which may claim that the Myojin-sho volcano consists of andesitic to basaltic rock rather than dacitic rock. On the other hand, magnetization of the central cone of Takane-sho volcano is estimated to be 1.1-1.9 A/m, which is consistent with the fact that dacite pumices were sampled.

著者

沢田 宗久 Servando De la Cruz Carlos Vardes Gonzales Esteban Ramos Jimenez

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.2001, no.2, 2001-10-01

著者

岡田 弘 トゥルス スパルト・シスヲウィジョヨ

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.1991, no.1, 1991-04-02

著者

関谷 慱

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.12, no.2, 1967-08-01

著者

小野 晃司 渡辺 一徳

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.29, no.2, 1984-07-01

著者

三村 弘二

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.47, no.4, pp.217-225, 2002-09-17 (Released:2017-03-20)

参考文献数

19

被引用文献数

2

---

Nekoma Volcano, situated between Bandai Volcano and the Aizu Basin in northeast Japan, is a composite volcano of andesite to dacite with a total eruption volume of 16 km3. A horseshoe-shaped caldera a few km in radius was formed at the top of the volcano, and the volcanic activity is divisible into the Old Nekoma Volcano established before the caldera forming event from ca. 1 Ma to 0.6 Ma and the New Nekoma Volcano established after the caldera forming event after ca. 0.5 Ma. Old Nekoma Volcano is subdivided into Oguninuma north lava, Hayama lavas, Hagidaira pyroclastic flow (block and ash flow) deposit, Main cone lavas, Oguniyama lavas and Ougigamine lavas, in ascending stratigraphic order. They formed a flat cone-shaped volcano. All but the Ougigamine lavas were produced by summit eruptions and the Ougigamine lavas formed monogenetic volcanoes from several vents on the western flank. New Nekoma Volcano, erupted after Oshizawa debris avalanche deposit, which related to the caldera forming event, is composed of Nekomagatake lavas and 1349 m lavas occurred at the horseshoe-shaped caldera margin.

著者

吉村 俊平

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.61, no.4, pp.605-613, 2016-12-31 (Released:2017-01-13)

参考文献数

37

著者

山﨑 誠子 星住 英夫 松本 哲一

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.61, no.3, pp.519-531, 2016-09-30 (Released:2016-11-08)

参考文献数

33

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Unspiked K-Ar dating procedure enables the correction for mass fractionated initial 40Ar/36Ar ratios, and has been successfully applied to young volcanic samples, especially younger than 0.5 Ma. We reconstructed the growth history of western to central part of Kuju Volcanic Group based on the unspiked K-Ar age data. The unspiked K-Ar ages for the small andesitic-dacitic volcanoes of Stage 1 (Kutsukakesan Volcano, Iozan Lava, Kuroiwasan Volcano, Narukoyama Volcano) provided with two age group of ca. 160-150 and ca. 90-80 ka, suggesting that Stage 1 may be divided into at least two sub-stages. During Stage 3 after the largest eruption associated with Handa pyroclastic flow deposit, some lava domes and stratovolcanoes in the central part (Ogigahana Volcano, Nakadake Volcano and Mimatayama Volcano) were built up from ca. 54 to 34 ka, which is older than the previous interpretation.Based on these K-Ar ages and estimated volume for each volcanic unit, we calculated the magma discharge rate during each volcanic stage and the whole period of the volcano history. The calculated magma discharge rate for Stage 1, 3 and 4 are 0.09, 0.12, 0.18 km3/ky, respectively, showing that the activity has slightly increased. The rate of 0.12 km3/ky for the whole period is similar to that for Aso and Unzen volcanoes lie to the west of this volcano.

著者

松本 亜希子 中川 光弘 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.61, no.3, pp.545-558, 2016-09-30 (Released:2016-11-08)

参考文献数

38

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On the 24th July, 2012, a large scale explosion occurred at Minamidake Summit crater of Sakurajima volcano, for the first time in last 1.5 years. This eruption is characterized by a clear, large preceding inflation ca.22 hours before the eruption. The juvenile glass particles in the volcanic ash of this eruption have less amount of microlite than those of Showa crater. The crystal size of microlite is also smaller. In contrast, their microlite number densities (MND) of plagioclase and pyroxenes are similar to those of Showa crater. According to the results of the decompression experiments by previous studies, the variations of crystallinity of microlite with the constant MND can be explained by the difference in the length of the duration for decompression, and/or the duration until the quench after the decompression. Considering these results, the juveniles of the summit eruption are derived from the eruption induced by relatively rapid decompression with rapid quench, and the juveniles from Showa crater are the products of the eruptions accompanied with the relatively slower decompression and/or the longer annealing after decompression. Therefore, it is interpreted that the 24th July, 2012 eruption was caused by rapid magma ascent with much shorter stagnation in the conduit. In contrast, the eruptions at Showa crater might have been induced by slower magma ascent and/or longer stagnation at a shallower depth of the conduit. This interpretation agrees with the data of geophysical observations. On matrix glass chemistry, juveniles of this summit eruption show the distinct trend from those of Showa crater. This feature can be produced by the difference in mode of microlite, which are crystallized during magma ascent. Accordingly, it is possible to evaluate the difference in magma ascent process, using the matrix glass chemistry.

著者

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.1, no.1, pp.47-57, 1957-01-15

被引用文献数

3

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The pyroclastic flow is defined as the flow of high-temperature, essential, fragmental materials. This is a synonym of the nuee ardente in the broad sense. Three modes of emplacement of high-temperature, essential, solid (or liquid) materials after the ejection from the crater may be recongized: 1) Projection of the fragments from the crater by the explosive expansion of gas which occurs within the crater. 2) Descent of the fragments or liquid magma from the crater which is caused only by the action of gravity. 3) Swift downflow of the mixture of gas and fragments. This is intermediate between 1) and 2) and to this corresponds the pyroclastic flow. A new classification of the pyroclastic flows is proposed. The principle is based upon the viscosity of the materials, which is inferred from the nature of the deposit. The volume of the deposit increases as the viscosity decreases. 1) Nuee ardente in the strict sense. Represented by the nuees ardentes of Mt. Pelee, Merapi, etc. The fragments are less porous, which indicates the high viscosity. The volume of the deposit is small, generally less than 0.01km^3. 2) Pyroclastic flow of the intermediate type. Represented by certain pyroclastic flows of Asama. Hakone. Myoko Volcanoes. The viscosity and volume (0.1〜1km^3) are both intermediate between 1) and 3). 3) Pumice flow. Represented by pumice and tuff flows of all sizes, such as those of Crater Lake, Hakone, Katmai. Aso Volcanoes. Low viscosity leads to the full vesiculation into pumice. Many of them are larger in volume (>10km^3) than 1) and 2), and the caldera of Krakatau type is often formed after the eruption of larger pumice flows.

著者

杉崎 隆一 杉浦 孜 水谷 義彦 日下部 実

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.25, no.2, pp.107-108, 1980-07-01

著者

高橋 正樹

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.2014, 2014-11-02