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Shigeru Suto
Article type: Article
1976 Volume 21 Issue 2 Pages
65-72
Published: October 15, 1976
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0manago volcano (2375m), situated about 120 km north of Tokyo is a member of the Nikko volcano group. The volcanic activity of this mountain can be divided into main and later stages. Between these two stages, there was a period of quiescence. In the main stage, a lava rich in cognate inclusions erupted. This lava was viscous and formed a steep-sided dome which constitutes now almost bulk of the mountain. The activity of later stage began with minor eruptions of scoriaceous materials from a newly opened top crater. This activity was followed by a eruption of lava flows from the same crater, which covered western and eastern slopes of the dome. The lava was so fluid that it formed thin lava flows about 1-2m thick even on the gentle slope at the foot of the mountain. At least two lava streams flowed down on each of west and east slopes. The rocks of two stages differ in petrographic feature and chemical composition. The lava of the main stage is olivine-bearing augite-hypersthene dacite of the calc-alkali rock series and that of the later stage is olivine-augite-hypersthene and esite of the tholeiitic one. The order of emption of calc-alkali and tholeiitic rock types in Omanago volcano is reverse to those of two stratovolcanoes; Nyoho-Akanagi and Nantai of the Nikko volcano group in which the lavas of main stage are tholeiitic and those of later stage are calc-alkaline.
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Mitsuru Sekioka, Kozo Yuhara
Article type: Article
1976 Volume 21 Issue 2 Pages
73-80
Published: October 15, 1976
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Since April 1973 a volcanic activity which brought forth a new volcanic island has been observed near 27°14.5´N and 140°53´E on the east of the Island of Nishinoshima, the Ogasawara Islands, about 930 km south of Tokyo. 0n 13 January 1974 which falled on between December 1973 when the newly-formed island was named formally the Island of Nishinoshima-Shinto and June 1974 when the new island began to connect with the Island of Nishinoshima, surface temperatures of both islands and their peripherical sea were measured at the flight levels from 300 to 900 m with the airborne infrared line scanner Model DEI-1200 (Kubotera, Tanaka and Ossaka, 1974). The distribution of surface temperatures and other information concerning with the eastern pit of the Island of Nishinoshima-Shinto observed with the eye from the aircraft were utilized to estimate heat discharge from the Island of Nishinoshima-Shinto, based on a method developed by Yuhara and Sekioka (1975) to assess heat discharge from the summit crater of Miharayama volcano. Estimation shows that total radiant flux from the eastern pit and heat discharge from the Island of Nishimshima-Shinto excluding the eastern pit were 7.4×10
6 cal/sec and 2.0×10
7 cal/sec, respectively. Furthermore, radiant flux from flying volcanic bombs spouting from the eastern pit was computed 5.3×10
2 cal/sec which is negligible amount. Total heat discharge was then of 2.7×10
7 cal/sec. Comparing this value with the other estimated one of 3.3×10
6 cal/sec at July 1975, about one and half years later, by Ehara and Yuhara (1975), cooling of the Island of Nishinoshima-Shinto seems to be suggested.
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Minoru Kasahara, Akira Kubotera, Yasuhiro Tanaka
Article type: Article
1976 Volume 21 Issue 2 Pages
81-93
Published: October 15, 1976
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Series of small eruptions frequently took place on the Miharayama Volcano from Febmary to June 1974. 0n June 12, eruption phenomena were simultaneously observed by means of an infrared radiation thermometer and a vertical type seismometer. As mentioned in our previous paper, four phases, named P
1-, P
2-, Q
- and X-phases were distinctly recognized in an isolated type eruption tremor. In this paper, some characteristics and the source mechanism of the four phases were examined and discussed. In the case of the P
1-, P
2- and Q-phases, similar broad spectra having a peak frequency of 4.6 Hz have been taken, while in the case of the X-phase, a simple spectrum having a peak frequency of 3.2 Hz which is characterized by a damping oscillation with a small damping coefficient (h=0.2~O.3) has been taken. From the consideration of the initial motion of the Q-phase and the time difference between the emission time of magma and the arrival time of the Q-phase, an asymmetrical push cone type model representing a rapid upward force is acting at the origin of eruption beneath the pit crater, is preferable for the mechanism of the Q-phase.
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Daisuke Shimozuru, Tsuneomi Kagiyama
Article type: Article
1976 Volume 21 Issue 2 Pages
95-105
Published: October 15, 1976
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Infra-red radiometer, one of the remote sensing tools, are, in recent years, successfully used to measure the surface temperature of the volcanic and geothemal area. Many handy radiometers have been commercially produced for industrial purposes. Utilization of these radiometers in volcano observations has the following disadvantages; 1) wide field of view, and 2) difficulties of pointing the radiometer to the very points on the photographs. The authors purchased the commerial radiometer (Thermo Ace Model TA-60S) and mounted the optical part (camera) on the base of the baloon theodite. The base of the theodolite is rotated horizontally driven by a DC micro-motor attached to the theoaolite. A telescope was also attached to the camera so as to enable us confirm the observed point even during the scanning. The output of the radiometer can be recorded either with MT data recorder or ink writing recorder. Tis type of radiometer is also useful for continous monitoring the temperature of the vent or fumaroles. The observed temperatures depend on the wave length of the actual spatial temperature distribution, the field of view of the optical system and scanning speed. Detailed examination both on theoretical and experimental on the above points were made and described in the text. Thus, the improved IR radiometer was successfully utilized to observe the surface temperature of the crater bottom of Mihara-yama, 0-shima Volcano, on March 14, 1976. It was found that the temperature of the vent showed remarkable decrease compared with the previous values as well as the average surface temperature of the crater bottom.
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Katsutada Kaminuma
Article type: Article
1976 Volume 21 Issue 2 Pages
107-115
Published: October 15, 1976
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Mt. Erebus, the most active volcano on the Antarctic continent, was discovered by Sir James Ross on January 27, 1841. Since this time, some volcanic activities such as steam eruptions, reflection of glow, volcanic flame, lava lake in crater etc., have been observed on and off. Steam eruptions have been occurred frequently since the end of 1972. For the purpose of observing small/micro earthquakes around McMurdo Sound and Mt. Erebus, seismological observations were carried out in the austral summer seasons of 1974-75 and 1975-76, as one of the research programs of the Dry Valley Drilling Project (DVDP) which was carried out by scientists from Japan, New Zealand and the United States. Background seismicity in and around the McMurdo Sound area is estimated to be one small/micro earthquake every two days. In addition to this background seismicity, one earthquake occurs in every two days in the volcanic area around Mt. Erebus.
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Sadakatu Taneda
Article type: Letter
1976 Volume 21 Issue 2 Pages
117-119
Published: October 15, 1976
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T Kumagai, H Takahashi, N Oyagi, F Shimizu
Article type: Abstract
1976 Volume 21 Issue 2 Pages
121-
Published: October 15, 1976
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S Aramaki, T Ui
Article type: Abstract
1976 Volume 21 Issue 2 Pages
121-
Published: October 15, 1976
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I Yokoyama, S Ohkawa
Article type: Abstract
1976 Volume 21 Issue 2 Pages
121-122
Published: October 15, 1976
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K Nishi
Article type: Abstract
1976 Volume 21 Issue 2 Pages
122-
Published: October 15, 1976
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K Kamo, T Furusawa, J Akamatsu
Article type: Abstract
1976 Volume 21 Issue 2 Pages
122-
Published: October 15, 1976
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J Ossaka, J Hirabayashi, T Ozawa, S Aramaki, M Kamada, H Sakamoto, S H ...
Article type: Abstract
1976 Volume 21 Issue 2 Pages
123-
Published: October 15, 1976
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M Miyazaki, F Yamaguchi, F Masutani, H Terao
Article type: Abstract
1976 Volume 21 Issue 2 Pages
123-124
Published: October 15, 1976
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S Taneda
Article type: Abstract
1976 Volume 21 Issue 2 Pages
124-
Published: October 15, 1976
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S Nakada
Article type: Abstract
1976 Volume 21 Issue 2 Pages
124-
Published: October 15, 1976
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K Yamashina, T Mitsunami
Article type: Abstract
1976 Volume 21 Issue 2 Pages
124-125
Published: October 15, 1976
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K Ota
Article type: Abstract
1976 Volume 21 Issue 2 Pages
125-
Published: October 15, 1976
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K Watanabe
Article type: Abstract
1976 Volume 21 Issue 2 Pages
125-126
Published: October 15, 1976
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K Watanabe
Article type: Abstract
1976 Volume 21 Issue 2 Pages
126-
Published: October 15, 1976
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H Fujimaki, T Fujii, H Kurasawa
Article type: Abstract
1976 Volume 21 Issue 2 Pages
126-127
Published: October 15, 1976
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J Matsuda, I Kaneoka, S Zashu, E Takahashi
Article type: Abstract
1976 Volume 21 Issue 2 Pages
127-
Published: October 15, 1976
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T Kaneko, M Yamasaki, H Sato
Article type: Abstract
1976 Volume 21 Issue 2 Pages
127-128
Published: October 15, 1976
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M Sakuyama
Article type: Abstract
1976 Volume 21 Issue 2 Pages
128-
Published: October 15, 1976
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T Yajima, M Kajima
Article type: Abstract
1976 Volume 21 Issue 2 Pages
128-
Published: October 15, 1976
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K Kobayashi
Article type: Abstract
1976 Volume 21 Issue 2 Pages
128-129
Published: October 15, 1976
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A Kubotera
Article type: Abstract
1976 Volume 21 Issue 2 Pages
129-
Published: October 15, 1976
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M Ishikawa, R Egawa
Article type: Abstract
1976 Volume 21 Issue 2 Pages
129-130
Published: October 15, 1976
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M Tsuchide
Article type: Abstract
1976 Volume 21 Issue 2 Pages
130-
Published: October 15, 1976
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M Sekioka, K Yuhara
Article type: Abstract
1976 Volume 21 Issue 2 Pages
130-
Published: October 15, 1976
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S Ehara, K Yuhara
Article type: Abstract
1976 Volume 21 Issue 2 Pages
130-131
Published: October 15, 1976
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[in Japanese]
Article type: Abstract
1976 Volume 21 Issue 2 Pages
131-
Published: October 15, 1976
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Y Tanaka
Article type: Abstract
1976 Volume 21 Issue 2 Pages
131-132
Published: October 15, 1976
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M Fujita, Y Tanaka, M Fukasawa
Article type: Abstract
1976 Volume 21 Issue 2 Pages
132-
Published: October 15, 1976
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H Komuro, M Fujita, K Kodama
Article type: Abstract
1976 Volume 21 Issue 2 Pages
132-
Published: October 15, 1976
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J Shimada
Article type: Abstract
1976 Volume 21 Issue 2 Pages
132-133
Published: October 15, 1976
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K Hamuro
Article type: Abstract
1976 Volume 21 Issue 2 Pages
133-
Published: October 15, 1976
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T Awaya, T Hirano, Y Oki
Article type: Abstract
1976 Volume 21 Issue 2 Pages
133-
Published: October 15, 1976
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S Yokoyama, T Tokunaga
Article type: Abstract
1976 Volume 21 Issue 2 Pages
133-134
Published: October 15, 1976
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D Shimozuru, T Kagiyama
Article type: Abstract
1976 Volume 21 Issue 2 Pages
134-
Published: October 15, 1976
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T Yukutake, T Yoshino, E Kimoto, T Shimomura, S Koyama, H Watanabe, H ...
Article type: Abstract
1976 Volume 21 Issue 2 Pages
134-135
Published: October 15, 1976
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J Ossaka, J Hirabayashi, I Minato, T Ozawa, A Nomura, T Ossaka, A Taka ...
Article type: Abstract
1976 Volume 21 Issue 2 Pages
135-
Published: October 15, 1976
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H Harada
Article type: Abstract
1976 Volume 21 Issue 2 Pages
135-136
Published: October 15, 1976
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S Suto
Article type: Abstract
1976 Volume 21 Issue 2 Pages
136-
Published: October 15, 1976
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K Yamawaki, C Kitsunezaki
Article type: Abstract
1976 Volume 21 Issue 2 Pages
136-
Published: October 15, 1976
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C Kitsunezaki, T Maruyama, T Sakuma
Article type: Abstract
1976 Volume 21 Issue 2 Pages
136-137
Published: October 15, 1976
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I Yokoyama, S Ehara, H Yamashita
Article type: Abstract
1976 Volume 21 Issue 2 Pages
137-
Published: October 15, 1976
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S Ehara, H Yamashita, I Yokoyama
Article type: Abstract
1976 Volume 21 Issue 2 Pages
137-138
Published: October 15, 1976
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T Soya, Y Katsui
Article type: Abstract
1976 Volume 21 Issue 2 Pages
138-
Published: October 15, 1976
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H Yamashita
Article type: Abstract
1976 Volume 21 Issue 2 Pages
138-
Published: October 15, 1976
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H Yamagishi, I Moriya
Article type: Abstract
1976 Volume 21 Issue 2 Pages
138-139
Published: October 15, 1976
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