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Volume 49 (1963)
- Issue 6 Pages 213-
- Issue 5 Pages 171-
- Issue 4 Pages 123-
- Issue 3 Pages 85-
- Issue 2 Pages 43-
- Issue 1 Pages 1-
Volume 49, Issue 6
Displaying 1-4 of 4 articles from this issue
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Yoshio Katsui, Toshimasa Takahashi, Yoshio Ôba, Yoshiro Hirai, M ...1963 Volume 49 Issue 6 Pages 213-226
Published: June 05, 1963
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSTokachi-dake, an active volcano situated in the central highland of Hokkaido, Japan, was in eruptive state three times in the last 100 years: 1857, 1887-1889, and 1926-1928. The last activity was famous for its disastrous mud flow that killed 144 people, caused by a hot volcanic avalanche. After a quiescence of 34 years from 1926-1928 activity, on June 29, 1962, Tokachi-dake was again in activity. Some abnormal phenomena were noted during the last several years prior to this activity, viz. increasing of temperature and HF, HCl, H2S and SO2 contents of fumarolic gas, activity of volcanic tremor and earthquakes, and opening of minor fissures near the central cone. The first explosion started from about 22hl5m and reached a climax at 22h45m-55m, ejecting volcanic blocks and ash derived from the surface. Five sulfur-mine workers, sleeping near the crater, deceased under the falling volcanic blocks. After a pause for about three hours, the second eruption occurred. This activity was manifested by forcible Strombolian eruption, ejecting volcanic bombs, scoriae, lapilli and ash, most of which were originated from new molten magma. The volcanic ash was blown up 12, 000m high, and fell over wide areas from eastern Hokkaido to Kurile Islands (Figs. 2-6, and Tables l&5). Several new craters and fissures opened on the southern side of the central cone. They are arranged parallel to the southwestern wall of Ground-kakô which is a somma of the central cone (Figs. 1 and 3). Total volume of ejecta is estimated as 7.1×107m3, most of which is essential volcanic ash. In both 1926 and 1962 activities, essential ejecta are olivine-bearing hypersthene augite andesitic, and they have quite similar mineral and chemical compositions (Tables 2-4).View full abstractDownload PDF (1639K) -
Tsuneo Soma, Masaru Yoshida1963 Volume 49 Issue 6 Pages 227-234
Published: June 05, 1963
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSThe gabbroic mass described in the present paper, is situated along the Sano Valley, southern Kanto, and its geologic age is probablly Miocene. The petrographic features of this mass are described here, with special reference to the anorthite contents (An%) of plagioclase in some rocks of the mass. The study of plagioclase is summarized in the An composition frequency diagram proposed by C. Kim (1962). In this diagram, it seems likely that the maximum peaks of the frequency curve show stable environments in the lithological evolution of a rock series. The conclusions derived from the above studies are as follows.
1. The mass consists of three groups; i) gabbroic rocks (norite, pyroxene gabbro, pyroxene porphyrite, uralite porphyrite, hornblende gabbro), ii) dioritic rocks (diorite, quartz diorite) and iii) albite porphyrite.
2. Various parts of gabbroic rocks and of dioritic rocks grade gradually to each other, while albite porphyrite forms another by sheared zones.
3. From the frequency curves of An% of plagioclases, it is noted that frequency curves of plaigoclase of norites and of quartz diorites are the most stable, while those of hornblende gabbros are the most unstable. The gabbros and diorites were subjected to different tectonic movements and the formation of hornblendes in pyroxene gabbro occurred at the stage between the above two tectonic movements. Coarse-medium grained plagioclases in norite, and fine grained plagioclase in quartz diorite show the most stable frequency curves.
4. The evolutional succession of the mass is as follows: i) intrusion of pyroxene porphyrite, ii) emplacement of norite, iii) transformation of the two rocks facies into uralite porphyrite and hornblende gabbro, iv) shearing movement, followed by formation of diorites, and v) formation of albite porphyrite along the sheared zones around the diorites.View full abstractDownload PDF (1391K) -
KEN-ICHIRO AOKI1963 Volume 49 Issue 6 Pages 235-236
Published: June 05, 1963
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSDownload PDF (71K) -
Tadahiro Nemoto, Kenzo Yagi1963 Volume 49 Issue 6 Pages 237-247
Published: June 05, 1963
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSSince 1957 which marked the peak in industrial hiring geology major students of the American universities have been experiencing much difficulties in finding professional employment and many trained geologists have registered themselves as unempolyed. To remedy this situation and to find solutions, efforts have been made by the geologists, both on the academic and industrial sides. Industrial-Academic Relations Committee (AAPG), Curriculum and Standard Committee (NAGT), GEO-Study (AGI), etc. are the products of such efforts and they have provided us the real pictures of these problems and the prospects of solutions. In this paper the writers are going to introduce these problems of the American geologists, based mainly on the data provided by these committees, and also on Shenon's presidental address “Economic Geology Today and Tomorrow” delivered at the 1962 Annual Meeting of SEG. They also refer to the present situation of the geology education and employment of geology major students in the Japanese universities as compared to the problems in the United States.View full abstractDownload PDF (1144K)
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