著者

中田 節也 鎌田 浩毅

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.33, no.4, pp.273-289, 1988

被引用文献数

8

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Volcanism and deposition of volcaniclastic materials within a graben in the Shimabara area, western Kyushu, started in early Pliocene and have continued up to the present. The volcanic products comprise alkalic to high-alkali tholeiitic basalts in addition to calc-alkalic andesites. The basalts are of a member of magmas erupted extensively in NW Kyushu from late Miocene to Recent. Their incompatible-element patterns in spider gram, in which the abundances of Rb, Ba, K, Nb, Zr and Y are normalized to those of MORB, are uniform independently of their eruption-ages, and show positive Ba and Nb anomalies strongly indicative of the marked affinity with ocean-island basalts. These patterns are clearly different from those of island-arc basalts which have negative Nb anomaly, as represented by the Quaternary high-alumina basalts in central Kyushu, and from those of back-arc basin basalts usually showing the same anomaly. It is concluded that basaltic magmas in NW Kyushu were derived from partial melt of fertile mantle with high Nb/Zr. Most of the andesites in the Shimabara area have phenocryst assemblages showing co-existence of magmas with different compositions. This fact and the spidergram pattern without Nb anomaly of the andesites lead us to a magmatic model; the andesite magma originated from mixing of positive-Nb-anomaly basaltic melt with negative-Nb-anomaly acidic partial melt of lower-crust materials which were presumably heated by the former melt. The graben in the Shimabara area seems to have developed in southern periphery of the region under which fertile mantle materials have been rising up from the depth and the subducted oceanic slab has not reached, like the "hot region".

著者

伊藤 順一 星住 英夫 川辺 禎久 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 (ISSN:24335320)

巻号頁・発行日

vol.1997, 1997

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 (ISSN:24335320)

巻号頁・発行日

vol.2001, 2001

著者

鎌田 浩毅 小玉 一人

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.1993, 1993

著者

綿貫 陽子 鎌田 浩毅 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.48, no.6, pp.513-518, 2003

参考文献数

16

被引用文献数

1

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During the Taisho Eruption (1914-1915) of Sakurajima Volcano, the Secondary Lava Flows drained out from the front of the primary lava flows after a certain pause from their settlement. We investigate distribution, timing and conditions of the effusion of the Secondary Lava Flows which have not been clarified yet. We define the features of the Secondary Lava Flows by means of geomorphological interpretation using aerial photographs and field survey. More than 200 landscape photographs, which were taken at the time of the Taisho Eruption, indicate that the earliest Secondary Lava Flows effused on 14 February 1914; this date was several months earlier than those previously considered. The effusing of the Secondary Lava Flows did not occur as a single event but as several events in different areas. Based on volumetric estimation of the individual Secondary Lava Flows, the volume of the Secondary Lava Flows tend to have increased as time passed after the eruption. The Secondary Lava Flows effused from the underlying tip of river valleys.

著者

金子 克哉 鎌田 浩毅 小屋口 剛博

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.1999, 1999

著者

鎌田 浩毅 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.第2集 (ISSN:04534360)

巻号頁・発行日

vol.26, no.4, pp.281-292, 1981

被引用文献数

2

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Kuju Volcano (1, 786m high) consists of dacitic lava domes and the associated non-welded pyroclastic flow deposits, Handa pyroclastic flow deposits, covering 60 km² area (Fig.2). The original vents of the pyroclastic flow deposits, whose age is estimated to be 0.04 Ma, have not been located. The volume is about 2km³. They contain pumice and accessory lithic fragments and very seldom show welding. At the upper and the basal parts of one flow unit, imbrications of pumice and lithic fragments are well developed with 10°-20°dip against the flow unit boundary (Figs. 4, 5). This dip (Table 1) is apparently not as steep as that of the other pyroclastic flow deposits. Imbrications are clearly observed at 6-12km from the center of the lava domes, while the distribution of the pyroclastic flow deposits covers 4-13km from the center (Fig. 7). The pyroclastic flows ran down 1000m in a vertical distance. The method of determining the flow direction by imbrication is very simple as shown in Fig. 6. Imbrication is most visible from the direction (a) perpendicular to the flow direction on the surface of each outcrop. The flow direction (f) is determined by the bisector (f') of the error angle 2θ formed by the two directions (b, c), between which imbrication is not observed. Data are classified into 3 ranks by the error angle θ as shown in Table 1. The flow directions at 52 outcrops (Table 2) are shown by classified arrows in Fig. 7. The estimated flow-direction patterns are largely divided into the north-flank flows and the south-flank flows (Fig. 7). The north-flank pyroclastic flow deposits flowed along the 2 km-wide major valley on ca 2°slope shown in K-L profile in Figs. 8, 10. Then it diverged to the west at the outlet of the valley, and finally collected in a small basin in the west. Such flow directions suggest that the flow was not derived from the adjacent domes D, E, F in Fig. 7. On the south flank, a fan-shaped pattern of the flow direction is generally observed. But the flows toward Aso volcano are sharply separated into two flows at the boundary between Kuju and Aso ("col" in Figs 7, 9). This is because the flow had not enough power to rush up the very gentle slope of Aso volcano. The evidence shows that the southward flow gradually bent 120°, and it rapidly went down eastward on the south flank. At Takenohata (n. in Fig. 7) this eastward flow crossed the southward flow. At this cross point, lower outcrops show eastward flow (A-B profile in Fig. 8), and higher ones show southward flow (C-D profile) as shown in Fig. 11. This means that after the eastward flow filled the old valley extending in east-west direction, the later pyroclastics flowed southward over the older deposits forming a fan-shaped deposit. Data clearly suggest that the vent for the pyroclastics is located within the circle around A, B, C lava domes, and not in the other domes. The flow directions indicated by imbrications agree with the distribution of the pyroclastic flow deposits. Pyroclastic flows follow the previous topographic relief such as valley, fan, and col. Kuju Volcano may not have emitted the flooded sheet-flows in all directions, but have emitted the tongue-shaped flows intermittently to different directions.

著者

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 (ISSN:24335320)

巻号頁・発行日

vol.1986, 1986

著者

須藤 茂 阪口 圭一 松林 修 鎌田 浩毅 加藤 完 山本 隆志

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

巻号頁・発行日

vol.29, pp.S253-S265, 1984

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Temperature measurements of the lava of 1983 in Miyake-jima in the Ako district were started fifty days after the eruption and have been continued since then. The following three kinds of temperature data have been obtained (Fig. 2). 1. Temperatures at 20 cm depth along a graveled temporary road on the clinkery surface of the lava using mercury and alcohol thermometers. 2. Temperatures at 0.5 to 2.5 m depth in iron pipes inserted into the clinker layer using thermocouples and mercury thermometers. The pipe holes were distributed along the temporary road and at scattered stations on the surface of the lava. 3. We drilled a borehole (DH-1) which penetrates through 5.5 m-thick lava into the previous ground. Temperature was measured at 10 points in the hole using thermocouples. For comparison, similar measurements in the Awabe district were made in pipes with depths up to 2.5 m (Fig. 3). These pipes were buried in the holes dug into the massive part of the lava for electric poles. The temperature data at 20 cm depth and in the pipe holes (Figs. 5-10) indicate that isothermal surfaces in the clinker layer are very complicated. This complexity is explained by rising plumes of hot vapor irregularly present in the lava field. The vapor is produced by degassing process in the massive part of the lava and comes up through newly formed cooling joints. Once a cooling joint is formed, the temperature of the massive part of the lava around the joint fell rapidly because a gas plume effectively transports the heat from the massive part to the surface. But the rate of temperature decrease varies greatly from one station to another. New plumes were formed sporadically and the temperatures of the new plumes were much higher than the decreased temperatures of the older plumes. Some older plumes died out because degassing process ended or the joints were self sealed by sublimates. It is necessary to arrange a number of observation stations and to add stations timely in order to reveal a cooling history of aa lava like the lava of 1983 in Miyake-jima. Around a plume, a convection cell was identified in the clinker layer (Figs. 16-18), which is similar to a hydrothermal convection system usually found in geothermal areas. The change of the temperature-depth profile of DH-1 with time (Figs. 11, 12) clearly shows that the lava heated the underlying previous ground. The peak shape of the profile has become broader and the depth of the maximum temperature has steadily fallen. The change of the temperature-depth profile also suggests that the upper clinker layer prevented rainfall from effective cooling of the massive part of the lava for the first 250 days. During that time, raindrops were evaporated in the clinker layer and did not reach the massive part below the clinker layer. Difference of cooling rate between Awabe lava and Ako lava may be due to the difference of the thickness of the clinker layers (Figs. 15, 19).

著者

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 (ISSN:24335320)

巻号頁・発行日

vol.1994, 1994

著者

宇井 忠英 井田 喜明 鎌田 浩毅 林信 太郎 川邊 禎久 加藤 幸弘 千葉 達朗 藤田 浩司 塩谷 みき

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.2002, 2002

著者

前嶋 美紀 早川 由紀夫 田中 千尋 村井 佳彦

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.50, no.5, pp.411-416, 2005

参考文献数

4

被引用文献数

2

著者

多田 訓子 市原 寛 中野 優 宇津木 充 小山 崇夫 馬場 聖至 高木 朗充 前野 深 武尾 実

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 2020 (ISSN:24335320)

巻号頁・発行日

pp.93, 2020 (Released:2021-02-01)

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

火山 (ISSN:04534360)

巻号頁・発行日

vol.43, no.5, pp.385-401, 1998-10-30 (Released:2017-03-20)

参考文献数

69

被引用文献数

2

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Various suggestive documents and associated sketehes are collected for understanding the pre-eruptive and the earliest stages of the 1914 great eruption of Sakurajima volcano, southwestern Japan, in Taisho era. Based on these records, the premonitory process to the eruption was reviewed especially with respect to the occurrence of many earthquakes which resulted in repeated rock falls with dust clouds, unusual upwelling of water and hot spring, and emission of volcanic smoke in the morning of January 12. Although there are many descriptions on the beginning of the remarkable eruption, they are sometimes inconsistent with each other. In the present paper, it is proposed that the valcano started to erupt around 09 : 58 on January 12 (Japanese Standard Time) at 200 m in height in the western slope of the mountain. In several minutes, a line of craterlets was formed between 200-500 m in height in the WNW-ESE direction. The development of a subsurface fissure in this direction resulted in another outbreak in the southeastern slope probably around 10 : 05. For the better understanding of this important eruptive event, discoveries of additional references are still desired.

著者

上澤 真平 中川 光弘 宮地 直道

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 2011 (ISSN:24335320)

巻号頁・発行日

pp.69, 2011-10-02 (Released:2017-02-10)

著者

秋本 俊一 西川 正名 桂 敬 中村 保夫 久城 育夫

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:24330590)

巻号頁・発行日

vol.15, no.1, pp.39, 1970-04-01 (Released:2018-01-15)

著者

長宗 留男 横山 博文 福留 篤男

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.1, pp.1-8, 1992-04-01 (Released:2017-03-20)

参考文献数

16

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Earthquake swarms which have frequently occurred off the east coast of the Izu Peninsula since 1978 are investigated, and the relationships between the swarms and the submarine volcanic eruption at Teisi Knoll in 1989 are discussed. The results are summarized as follows: 1) Shapes of epicentral areas of the earthquake swarms can be classified into the following two types, Type I and Type II. The former is an ellipse elongated NE-SW; the latler, an eilipse elongated approximately NW-SE. The swarms in the early years are of Type I, and those in the later stage (in particular, since 1984), for the most part, are of Type II.2) The largest earthquakes in the respective swarms for Type I are located along a straight line in the NE-SW direction, and those for Type II, along a curve line in the E-W to NW-SE directions. These two lines are probably indicative of active tectonic lines. 3) The epicentral areas for Type I and Type II, migrate periodically with a recurrece time of 6-7 years along the tectonic line in the NE-SW direction, and with a recurrence time of about 3.7 years along the tectonic line in the E-W to NW-SE directions, respectively. 4) Teisi Knoll where the submarine volcanic eruption took place on July 13, 1989, is situated in the northwestern part of the tectonic line trending E-W to NW-SE. The eruption was triggerd by the largest shock in the swarm which occurred around the northwestern end of the line.

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.43, no.5, pp.419-421, 1998-10-30 (Released:2017-03-20)

参考文献数

5

被引用文献数

1

著者

小園 誠史 小屋口 剛博

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.2003, 2003

著者

小屋口 剛博

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, pp.S151-S166, 2005

被引用文献数

1

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About thirty years ago Walker (1973) proposed a diagram to classify explosive volcanic eruptions producing pyroclastic falls on the basis of extensive field data. This diagram has provided us a framework to quantitatively describe explosive eruptions in terms of the characteristics of fall deposits and has also motivated us to develop theoretical models of explosive eruptions. Some of the universal relationships observed in this diagram, such as the positive correlation between the degree of tephra dispersal and the degree of magma fragmentation from sub-plinian to ultra-plinian eruptions may be useful as criteria to verify existing theoretical models. Recent progress in theoretical models of eruption columns, conduit flow, bubble nucleation and growth and magma fragmentation is reviewed from the viewpoint how these models are verified by field data of pyroclastic fall deposits.