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Masako OKAGUCHI
Article type: Article
1978 Volume 23 Issue 4 Pages
231-240
Published: December 01, 1978
Released on J-STAGE: January 15, 2018
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Fission track ages of obsidians in the Aso pyroclastic flow deposits (Aso-1, 2, 3, 4) have been measured in order to bring some light on the history of the activity of the Aso volcano. As the diameter of the fission track has been considerably shortened by annealing, a correction of the age was made in the present study, using the results of the annealing examination. The fission track ages of obsidians from the Aso pyroclastic flow deposits are as follows: Fission track ages (×10
5y.) Aso-4 0.29±0.14 Aso-3 1.03±0.42 Aso-2 1.54±0.60 Aso-1 2.60±0.76 V3.58±0.72
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Tutomu SUGIURA, Yoshihiko MIZUTANI
Article type: Article
1978 Volume 23 Issue 4 Pages
241-248
Published: December 01, 1978
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Variations in temperature, chemical and isotopic compositions of fumarolic gases discharged from the summit of Yakedake volcano, Honshu, Japan, have been observed since 1965, 2 years after the 1962-63 eruption (phreatic explosions with mud flows). The temperature of 168℃ was recorded in 1965, and has been gradually decreasing since then. The existence of appreciable amounts of H
2, HCl and S0
2 in the fumarolic gases suggests the supply of high temperature gases from magma. The hydrogen and oxygen isotopic compositions of fumarolic condensates suggest that the fumarolic gases are mixtures of magmatic gases and local meteoric water, and that the contribution of local meteoric water to the fumarolic gases has been increasing since 1965. The 1962-63 eruption was possibly caused by the supply of high temperature volcanic gases to the surface mud reservoir which had been previously formed by the fumarolic activity.
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Shozo YOKOYAMA, Toru TOKUNAGA
Article type: Article
1978 Volume 23 Issue 4 Pages
249-262
Published: December 01, 1978
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Base surges from rhyolitic magma occurred repeatedly in the 1st stage of continuous eruptions which formed Mukaiyama volcano in A.D. 886. The Mukaiyama base-surge deposits constitute a low-lying and flat-topped hill, overlain by 2nd-stage pyroclastic cone and 3rd-stage lava domes. The Mukaiyama base-surge deposits are divided into two major groups; the lower coarse-grained Mukaiyama-1, and the upper fine-grained Mukaiyama-2. Both are further subdivided into two. The Mukaiyama-1L, which constitutes the lowermost part of the Mukaiyama-1, is characterized by the pile of plane beds. In the Mukaiyama-1U, which constitutes the remaining upper part of the Mukaiyama-1, the lateral transition of sedimentary structures can be seen. This is best observed along the continuous sea cliff in the eastern coast. Here, plane beds, wavy (undulating) beds large-sized “antidune” structures up to several tens of meters in wave length, and middle-sized “antidune” structures appear one after another from south to north, namely with distance from source, presumably reflecting the gradual decline of the energy of base surges. The Mukaiyama-2 is subdivided into the lower (Mukaiyama-2L) and the upper (Mukaiyama-2U) by a pyroclastic fall layer at a lower horizon. Both are characterized, all over, by the superposition of small-sized “antidune” structures and cross beddings. However, the Mukaiyama-2L is slightly bigger in size of "antidune" structures and in grain size. The upward change of type and size of sedimentary structures within the Mukaiyama base-surge deposits may indicate the general decline of the power of base surges generated with the lapse of activity, suggesting the gradual decrease of the contact of magma with sea water with the growth of the volcano from submarine to subaerial. The size of large-sized “antidune” structures in Mukaiyama-1U far exceeds any other reported ones. One possible explanation for this may be given by the best exposure along eastern sea cliff, which is large enough to expose sedimentary structures of any size and, in addition, is nearly parallel to the direction of the spread of base surges. Exposures with other directions and/or of small size inhibit the accurate measurement of large-scale sedimentary structures if any. Another more probable explanation is attribution to the rhyolitic magma of Mukaiyama volcano. The more acidic the magma is, the more powerful the base surge (and consequently, the larger the bed form) will be. In contrast to the rhyolitic magma of Mukaiyama volcano, most of the hitherto-reported base-surge deposits are from basaltic magma.
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Kazuo SATO, Jun SATO, Shigeo ARAMAKI
Article type: Letter
1978 Volume 23 Issue 4 Pages
263-265
Published: December 01, 1978
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M. Sakuyama
Article type: Abstract
1978 Volume 23 Issue 4 Pages
267-
Published: December 01, 1978
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Article type: Abstract
1978 Volume 23 Issue 4 Pages
267-
Published: December 01, 1978
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Y. Katsui, K. Onuma, K. Niida, T. Suzuki, Y. Kondo
Article type: Abstract
1978 Volume 23 Issue 4 Pages
267-268
Published: December 01, 1978
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H. Fujimaki, H. Kurasawa, K. Aoki
Article type: Abstract
1978 Volume 23 Issue 4 Pages
268-
Published: December 01, 1978
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S. Tamanyu, S. Suto
Article type: Abstract
1978 Volume 23 Issue 4 Pages
268-
Published: December 01, 1978
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S. Suto, S. Tamanyu
Article type: Abstract
1978 Volume 23 Issue 4 Pages
269-
Published: December 01, 1978
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S. Tanaka
Article type: Abstract
1978 Volume 23 Issue 4 Pages
269-
Published: December 01, 1978
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S. Tanaka
Article type: Abstract
1978 Volume 23 Issue 4 Pages
269-270
Published: December 01, 1978
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S. Tanaka
Article type: Abstract
1978 Volume 23 Issue 4 Pages
270-
Published: December 01, 1978
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S. Suzuki, Hm. Okada, Y. Nishida
Article type: Abstract
1978 Volume 23 Issue 4 Pages
270-271
Published: December 01, 1978
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M. Kasahara, S. Suzuki, M. Okayama
Article type: Abstract
1978 Volume 23 Issue 4 Pages
271-
Published: December 01, 1978
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H. Okada, H. Watanabe, H. Yamashita, T. Maekawa, I. Yokoyama
Article type: Abstract
1978 Volume 23 Issue 4 Pages
271-
Published: December 01, 1978
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H. Okada, H. Watanabe, H. Yamashita, H. Oshima, T. Maekawa, I. Yokoyam ...
Article type: Abstract
1978 Volume 23 Issue 4 Pages
271-272
Published: December 01, 1978
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H. Ohshima, T. Maekawa, J. Amador, I. Yokoyama
Article type: Abstract
1978 Volume 23 Issue 4 Pages
272-
Published: December 01, 1978
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H. Yamashita, H. Watanabe, T. Harada, T. Maekawa
Article type: Abstract
1978 Volume 23 Issue 4 Pages
272-273
Published: December 01, 1978
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H. Watanabe, H. Yamashita, T. Harada, T. Maekawa
Article type: Abstract
1978 Volume 23 Issue 4 Pages
273-
Published: December 01, 1978
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T. Abiko
Article type: Abstract
1978 Volume 23 Issue 4 Pages
273-274
Published: December 01, 1978
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K. Ota, N. Matsuwo, T. Sugoshi
Article type: Abstract
1978 Volume 23 Issue 4 Pages
274-
Published: December 01, 1978
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T. Ozawa, K. Kimijima, J. Ossaka, J. Hirabayashi, T. Hayashi, S. Somey ...
Article type: Abstract
1978 Volume 23 Issue 4 Pages
274-275
Published: December 01, 1978
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Article type: Abstract
1978 Volume 23 Issue 4 Pages
275-
Published: December 01, 1978
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K. Niida, Y. Katsui, T. Suzuki, Y. Kondo
Article type: Abstract
1978 Volume 23 Issue 4 Pages
275-
Published: December 01, 1978
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Y. Kondo, T. Fujitani, Y. Katsui, K. Niida
Article type: Abstract
1978 Volume 23 Issue 4 Pages
275-276
Published: December 01, 1978
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Y. Oba, T. Uda, Y. Ikeda
Article type: Abstract
1978 Volume 23 Issue 4 Pages
276-
Published: December 01, 1978
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Article type: Abstract
1978 Volume 23 Issue 4 Pages
276-
Published: December 01, 1978
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Article type: Abstract
1978 Volume 23 Issue 4 Pages
276-
Published: December 01, 1978
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T. Noda, A. Koga
Article type: Abstract
1978 Volume 23 Issue 4 Pages
276-277
Published: December 01, 1978
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Y. Tanaka
Article type: Abstract
1978 Volume 23 Issue 4 Pages
277-
Published: December 01, 1978
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K. Hamuro, S. Aramaki
Article type: Abstract
1978 Volume 23 Issue 4 Pages
277-
Published: December 01, 1978
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N. Isshiki
Article type: Abstract
1978 Volume 23 Issue 4 Pages
277-278
Published: December 01, 1978
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S. Nihei
Article type: Abstract
1978 Volume 23 Issue 4 Pages
278-
Published: December 01, 1978
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T. Kumagai
Article type: Abstract
1978 Volume 23 Issue 4 Pages
278-279
Published: December 01, 1978
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T. Kumagai, H. Takahashi, N. Oyagi
Article type: Abstract
1978 Volume 23 Issue 4 Pages
279-
Published: December 01, 1978
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A. Kubotera, Y. Sudo, K. Ota
Article type: Abstract
1978 Volume 23 Issue 4 Pages
279-
Published: December 01, 1978
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H. Imai
Article type: Abstract
1978 Volume 23 Issue 4 Pages
280-
Published: December 01, 1978
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M. Churei
Article type: Abstract
1978 Volume 23 Issue 4 Pages
280-
Published: December 01, 1978
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M. Kawamura, M. Sekioka, M. Aoki
Article type: Abstract
1978 Volume 23 Issue 4 Pages
280-281
Published: December 01, 1978
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K. Yamashina, K. Tazawa, K. Nakamura
Article type: Abstract
1978 Volume 23 Issue 4 Pages
281-
Published: December 01, 1978
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K. Yamashina, K. Nakamura
Article type: Abstract
1978 Volume 23 Issue 4 Pages
281-282
Published: December 01, 1978
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Y. Tatsumi, K. Ishizaka
Article type: Abstract
1978 Volume 23 Issue 4 Pages
282-
Published: December 01, 1978
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S. Nakada, M. Takahashi
Article type: Abstract
1978 Volume 23 Issue 4 Pages
282-283
Published: December 01, 1978
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M. Seno
Article type: Abstract
1978 Volume 23 Issue 4 Pages
283-
Published: December 01, 1978
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N. Matsuwo
Article type: Abstract
1978 Volume 23 Issue 4 Pages
283-
Published: December 01, 1978
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Article type: Abstract
1978 Volume 23 Issue 4 Pages
283-
Published: December 01, 1978
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Y. Momikura, K. Watanabe
Article type: Abstract
1978 Volume 23 Issue 4 Pages
283-284
Published: December 01, 1978
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H. Matsumoto
Article type: Abstract
1978 Volume 23 Issue 4 Pages
284-
Published: December 01, 1978
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H. Matsumoto, I. Sanemasa
Article type: Abstract
1978 Volume 23 Issue 4 Pages
284-
Published: December 01, 1978
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