地学雑誌
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
81 巻 , 2 号
選択された号の論文の6件中1~6を表示しています
  • 下村 彦一
    1972 年 81 巻 2 号 p. 65-80
    発行日: 1972/04/25
    公開日: 2009/11/12
    ジャーナル フリー
    Sakurajima Volcano is located in northern part of Kagoshima Bay which is the southern extremity of Kyushu Island. So far as the origin is concerned Kagoshima Bay is considered as a submerged caldera, known by the name of Aira Caldera, and Sakurajima Volcano is the central cone of this caldera. Among many Japanese volcanoes Sakurajima Volcano is presently one of the most violent. Owing to the great eruption in January 1914 its name resounded all over the world. There are several papers written in european languages which reported this eruption.*
    This volcano was built up in Pleistocene. It is a stratovolcano, consisting of basaltic andesite, and rises about 1, 100 meters above the sea and its coast line has a length of about 40 kilometers. Three craters on the summit line up from south to north.
    Sakurajima is not single volcano but consists of two volcanic bodies, the northern and the southern. The former, called Kitadake Volcano, is the main and has a crater on the summit, measured about 600 meters in diameter and about 100 meters in depth. The latter, called Minamidake Volcano, overlaps the southern part of the former and has an active crater on the summit, being about 650 meters in diameter and about 230 meters in depth. Between these two craters there is a middle pit, called Nakadake, where a small crater on the summit exists.
    Kitadake has been considered as a single volcano, the author, however, finds out that it should be divided into two volcanic bodies, the eastern and the western. The former is older and its summit still remains as crater wall. The latter, on the contrary, has a semicircle crater wall on it summit and at present is a dormant volcano. Between these crater walls a part of atrio of the older volcano is found. The contact zone of these two volcanoes appears as a reputured zone which extends on the northeastern mountainside of Kitadake Volcano. Great eruption as well as outflow of much lava happened along this line on the occasion of the eruption in An-ei Era, in the later half of the 18th century which may be the greatest eruption of this volcano throughout historical age. On the basis of the above-mentioned the author comes to conclusion that Kitadake is not a single but a composite volcano, consisting of the older and the younger volcanic bodies.
    Nakadake's crater is somewhat elliptical, being about 300 meters in major diameter, about 800 meters in circumference and about 35 meters in depth. Presently it is also a dormant. Nakadake has been considered as a single volcano, the author, however, has the opinion that it may be divided into two bodies, the northern and the southern. The former is a small conic-shaped volcano whose summit as well as mountainside is everywhere covered thick by pumice and is a parasitic volcano of Kitadake. The latter, on the contrary, is characterized by its shallow pan-shape, measured only about ten or a few more meters in depth. The crater wall is preserved well where andesite layers can be observed. This is a parasitic volcano which erupted in close to the summit of Minamidake Volcano.
    The above-mentioned is the author's observation on the landforms of Sakurajima Volcano, especially of its craters on the summit and neighborhood. Resulting from his field surveys the author concludes that Sakurajima Volcano is more complicated in structure than has ever been considered. Regarding the inner structure of this volcano the author expects of future researches.
  • 二谷 穎男
    1972 年 81 巻 2 号 p. 81-94
    発行日: 1972/04/25
    公開日: 2009/11/12
    ジャーナル フリー
    The review on the variation of the Kuroshio extending from several hours to ten years is described here. We have had no clear understandings on the mechanisms of occurrence of large and comparatively stable meander off Kisyu-Ensyu Nada. It is known, at present, that the selected several small meanders in spring off the east coast of Kyusyu progress towards east along the south coasts of Shikoku and Kii Peninsular and stop its advance off Ensyu Nada and become large. This large meander is always accompanied, inside of it, with the ascending cold intermediate water in the Pacific. We cannot fully understand the mechanisms of occurrence and continuation of this large meander without knowledges of the deep and bottom current based on the direct measurement and the long-term variation in the atmosphere over the Pacific especially subtropical western Pacific.
    There exist middle and small scale meanders which progress easterly almost every time except the period of large stable meander off Kisyu-Ensyu Nada. The Kuroshio which flows along the south coast of Japan might exist in the duration only about 1/4-1/6 of total period after the World War II. Therefore the paths of large scale meander off Kisyu-Ensyu Nada and Middle and small scale meanders traveling easterly must not be considered abnormal. The very short-period fluctuations, one or half a day, of the velocity and direction of the Kuroshio were observed only by several systematic programmes with several vessels in Japan. From these simultaneous observations, comparatively large variations of velocity of the Kuroshio which may mask the amplitude of long-period variation of the Kuroshio were found. The observations of detailed pattern and direction of propagation of disturbed wave will be necessary to get the causes of these variations.
  • 山口 貞雄
    1972 年 81 巻 2 号 p. 95-103
    発行日: 1972/04/25
    公開日: 2009/11/12
    ジャーナル フリー
    It was in 1901 that the Yawata Iron and Steel Works began to operate their blast furnaces. Having had many advantageous factors since that time, the N. Kyushu Area has grown into the “Mecca” of the iron and steel industry in Japan. But the advantageous factors of this area began to decrease since 1930's and it lost its monopolistic status after the World War II. Seen from the geographical view-point, the major advantageous factors of the prosperity and the disadvantageous factors of its decline are as follows :
    I) The major advantageous factors of the prosperity (1901-30)
    A) The convenience of this area for getting raw materials.
    a) This area was well situated for getting inner raw materials as the coal of Chikuho Coal-field.
    b) This area was well located at the nearest entrance of getting foreign raw materials as the iron are from Korea and China and coking coal from China.
    B) The protective policy against the disadvantages for parting the market areas.
    a) The cargoes was sent by the cheap inland sea transport.
    b) The “Tatene value system” - (CIF. and single standard price throughout country) -of iron and steel works in this area.
    Although, the area was located far from the market areas of Hanshin and Keihin, the iron and steel works in this area were not handicapped by their location, thanks to this cheap freight and special price system.
    II) The major disadvantageous factors leading to its decline.
    A) Conversion of the spatial arrangement of industries from the “areal differentiation” by the system of laissez-fair to the construction of “plural self-sufficing districts” for the purpose of the national defence. For that purpose, the whole country was divided into five self-sufficing districts, within each of which the productive capacity of iron and steel was to be equal more or less, many iron and steel works were established in each district. As the result, the percentage of production per total in this area decreased proportionately.
    B) Change of the locational factors in iron and steel industry.
    a) As the coke-ratio per pig iron fell down from 4.0t to 1.2t or more owing to the improvement of technique in the operation of blast furnaces, the locational power of coal in this area decreased.
    b) The new locational factors-1) the harbour having the depth of 17m or more, 2) a large space having an area of 165, 000, 000m2 or more, 3) supplying the power of industrial water of 9 × 108m3/ year, and so on-were occasioned by the necessity of lengthened transport distance of raw materials and big-sized vessels to exclude the pressure of higher transport cost.
    Accordingly, the huge and new picked iron and steel works began to locate on the new areas having new locational factors. Corresponded to this change, the hegemony in this area for iron and steel industry declined. Besides, it is true that the absence of machinery industry is thought to be one of the reasons for the decline in this area. But it is not owing to the self-sufficing nature of operation in iron and steel works, but the special price systems, that machinery industry did not develop in this area.
  • 薩摩 晃
    1972 年 81 巻 2 号 p. 104-126
    発行日: 1972/04/25
    公開日: 2009/11/12
    ジャーナル フリー
    The exploitation of the so-called garnieritic nickel ores was first commenced in New Caledonia in 1875. For nearly one hundred years since then, the ores of this type have been one of the most important nickel resources of the world.
    In the meantime, the ores of the same type, but characterized by higher iron and lower nickel contents, became objectives of intense exploration since some twenty years in the Southwestern Pacific. More than ten are deposits of this latter type are now waiting for exploitation. This type of ores is known as lateritic nickel ores.
    These nickel ores-both garnieritic and lateritic-are mainly located in the areas fulfilling the following conditions :
    1) Areas where the ultrabasic rocks are emplaced in the strongly incurved parts of the Circum-Pacific Orogenic Belts,
    2) Areas where the monsoon climate is prevailing and the dry and rainy seasons are regularly alternating.
    The Southwestern Pacific is one of the areas of the world which satisfy eventually the above mentioned conditions, besides the Caribbean Sea area in Middle America. There, the are deposits are formed as the residual of weathering of the ultramafic rocks.
    Generalized soil profile is given below in descending order : -
    1 st layer iron crust
    2 nd layer red laterite (upper main zone)
    3 rd layer yellow laterite (transitional zone)
    4 th layer decomposed rock (lower main zone)
    5 th layer fresh rock (basement).
    Since long time, the are bodies have been known to be emplaced in topographically particular sites ; in fact, they are located in the weakly drained sites such as wide plateaus, top of mountain ridge of which longitudinal inclination is low, and gently sloping mountain flanks.
    Actually the theory on the genesis of this type of nickel ores is still not fully developed. Although extensive field and laboratory studies are needed, the writer presents some basic facts important for genetical explanation in this paper. The relation between Fe and Mg contents is graphically presented (Fig. 5 and 6). The frequency distribution of Fe to Ni ratios in each are deposit, suggesting the process of Ni concentration, is also graphically given in Fig. 7-14. The Fe-Ni ratio is not evenly distributed within soil profile, but is concentrated into two peaks, separated by a valley which corresponds to the 25% Fe domain. The upper peaks in Fig. 7-14 represent the red laterite layer which is composed mostly of iron sesquihydroxide. The lower peaks represent in turn the layer of decomposed rock (called saprolite layer), composed of various kinds of clay minerals (montmorillonite, garnierite, serpentine, chlorite etc.).
    Finally actual relation among Fe-Ni ratio, layering, relative depth and pH of circulating water is demonstrated in Fig. 15, in order to discuss on the possible genetic interpretation of are emplacement.
  • 矢沢 大二
    1972 年 81 巻 2 号 p. 127-129
    発行日: 1972/04/25
    公開日: 2009/11/12
    ジャーナル フリー
  • 諏訪 彰
    1972 年 81 巻 2 号 p. Plate1-Plate2
    発行日: 1972/04/25
    公開日: 2009/11/12
    ジャーナル フリー
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