Les études des phénomènes géologiques rencontrent de plus en plus de questions que l'on ne peut résoudre par simple combinaisons de résultats d'observations de roches naturelles et les théories fondamentaux existantes. Les recherches expérimentales de la pétrologie et de la géochimie restent empiriques malgré les progrès remarquables que l'on a accomplie. La manque des données sur les propriétés physico-chimiques des matériaux d'interêts géologiques empêche de prédire les réactions qui se produiront dans l'écorce et la partie plus profonde de notre globe. L'auteur évoque la nécéssité de créer, surtout au Japon où l'enseignement de la géologie est encore trop naturaliste, une branche qui approfondit les aspects chimiques et physiques des phénomènes géologiques. Elle consacrera également à l'acquisition des données physico-chimiques des diverses phases qui participe à ces phénomènes. L'obtention des données thermodynamiques précises des minéraux et des magmas, des. rensignements sur l'état des solutions aqueuses à hautes températures et sous hautes pressions de divers sels et celle des données sur les propriétés mecaniques des silicates sont quelques exemples à traiter dans cette branche. Les résultats de tels travaux pourront aboutir à de nouvelles conceptions qui pourront fournir aux géologues de terrain des nouveaux points d'observations. L'auteur insiste, de ce fait, que les chercheurs de cette spécialité doivent posséder à la fois des connaissances de bases et les attitudes fondamentaux d'observations de la géologie et de la physico-chimie.
Detailed and intensive investigations have been carried out on the abrupt failure of submarine slope of a small island, Shin-jima, in Kagoshima Bay, Kyushu on April 1, 1975 by the joint research group of Geographical Survey Institute of Japan, Japan Maritime Safety Agency and Geological Survey of Japan under the sponsorship of Japan Science and Technology Agency. The Shin-jima island emerged from water at the great eruption of adjacent Sakurajima Volcano in 1779 to 1780 (An-ei Eruption) as one of central corns of Aira Caldera (MATSUMOTO, 1933). The island gradually reduced its exposed area by continuous wave erosion to form truncated configuration, being surrounded by broad, shallow, flat tidal bench. Geologically the island is composed of the latest Pleistocene to the earliest Holocene thick loose pumice deposits with intercalations of silt and clay showing inner bay facies. These formations are strongly faulted by eastwest faults. The surface of the island is covered with thin shell bed dominantly composed of Ostrea and andesitic lava. The flat bench around the Shin-jima consists of recent, loose pumiceous drift sand deposits derived from the island by wave erosion. The failure of the slope now in concern occurred at the spit of the southern tip of the island, where thickness of drift sand deposits attains at most about 35 meters according to sonic prospecting and borings at the spit. It was caused by submarine landslide in the thick, loose drift sand deposits. Volume of the slide mass amounts approximately 265, 000 cubic meters. The spit had formed steep submarine slope near critical angle by abundant supply of very loose drift sand from northern part of the island before the failure occurred. Neither sensible earthquakes nor volcanic activities of the Sakurajima which might have given significant effects to submarine landslide are observed and recorded in seismometer around the crucial moment of the failure. Therefore, the cause of the landslide is considered that the increase of load resulted from the deposition of drift sand attaining about 8, 400 tons in volume atop of the slope brought about decrease of safety factor of the slope to make it slide. Wave pressure seems to have triggered the slide because safety factor decreases about 20 % when fluctuation of pressure at the bottom caused by wave agitation is taken into account.
In this paper the authors have tried (1) to clarify the regional characteristics of rural farmhouse forms, especially the distribution of farmhouse types, in the southern part of the Yokote Basin, Tohoku, northeastern Japan, and (2) to examine, through a study of recent changes, the structure of the process by which farmhouse forms change in relation to the physical and socioeconomic conditions of rural settlements. The study is divided into three parts : (1) A region-wide questionnaire survey. Approximately 3, 000 questionnaire sheets (one sheet per farmhouse) were distributed to farmhouses on the floor of the southern Yokote Basin and in the surrounding mountain region, of wihch 1, 991 were returned and analysed. (2) A field reconnaissance of house types and roof materials along a transect, from the basin floor to the surrounding mountains, consisting of fourteen villages located along the Naruse River and its tributary, the Saruhannai River. (3) An intensive survey of some sample villages selected from the abovementioned fourteen villages. 1) Regionality in farmhouse forms as determined from questionnaires and field reconnaissance. The following typology of house types was used in order to illustrate regionality in farmhouse types (ref. Fig. 2); A : Chumonzukuri, a traditional and peculiar house type with an L-shaped house plan. B : Sugoya, which literally means “straight house”. This type is subdivided into two ; Bo : the old type with a wide “domaniwa”, the dirt floored hall within the house, and Bn : the new type lacking this feature. B' : Sugoya with a protruding vestibule. This type is also subdivided into Bo' and B'n. C : Miscellaneous. Both the questionnaires and the counts made by the authors in the fourteen villages indicate considerable regional variations in the percentage of each house type (Figs. 2 and 5). Type A is scarcely seen now on the basin floor, but it is common in the mountainous areas. In contrast, Type B, especially Type Bn, is seen more frequently on the plain than in the mountains. In the period until about 1960 Type A was found more frequently everywhere in this area than at present ; even on the plain a considerable proportion of farmhouses (20-30 %) were of this type, and in the mountains the proportion exceeded 50 % (Fig. 3).The distribution of Type A farmhouses in the former period is closely related to the distribution of snowfall ; hence we may consider that house forms of this type are well adapted to snowy conditions. Attached buildings are commonly few in number ; one or two per farmhouse on average. It is noteworthy that the sagyosha (workshop or barn), the most important farm out-building, is associated with new-type houses (Bn+B'n+C) more frequently than with old-type houses (A+Bo+B'o). 2) Processes of change in farmhouse forms as determined from an intensive survey in sample villages. An intensive survey was undertaken in three sample villages ; Udekoshi, located on the basin floor, and Kawaguchi and Kamihata in the mountainous area. In this survey, recent changes in farmhouse forms were ascertained, mainly through interviews, for 82 families (20 each in Udekoshi and Kawaguchi and 42 in Kamihata). The results are summarized as follows ;In Udekoshi Village, (1) Type A has been absent for a long time (perhaps since early in the Sh6wa Period), and Type B'o was dominant in the early 1950's, (2) the dominant change in recent times has been from old-type farmhouses to new-type ones, and especially to Type B'n, (3) working and storage space is being relocated from the main house to attached buildings, and especially to newly-constructed workshops, as the number of new-type houses increases, and (4) 80 % of all dwellings today are new-type houses.
Amami-Oshima is located at the central part of the Ryukyu Arc which extends from Kyushu to Taiwan. In Kikai-Jima at about 20 kilo-meters south-east off Kasari Peninsula of Amami-Oshima, rapid uplifting (1.5-2 mm/y) during the past 130, 000 years was revealed by the altitudes of its marine terraces and their absolute ages derived from the calcareous terrace deposits (KONISHI et al., 1970). As the Ryukyu Arc has similar geological and geophysical settings to the outer arc of Southwest Japan, the rapid uplifting in Kikai-Jima was interpreted as earthquake related deformation (YONEKURA, 1975) which has been critically studied in the outermost belt of Southwest Japan. The purpose of this paper is to clarify the mode of the vertical deformation in the late Quaternary period in Amami-Oshima with relation to that in Kikai-Jima, and to present some data for comparison with above mentioned seismic crustal movements. The geomorphic surfaces of Amami-Oshima are roughly classified as follows : low, middle and high coastal terraces and the uppermost low-relief erosion surface. The low terrace (L) consist of Holocene marine terrace, wave-cut bench and alluvial plain, altitude of which does not exceed several meters high. The middle terraces (Ml and M2) are mostly developed in Kasari Peninsula at the height of 10 to 60 meters above sea level and scarcely observable in the other part of Amami-Oshima, except a minor wave-cut bench of 8 meters high above sea level with subrounded gravel and red soil observed at Honohoshi Beach, east of Koniya. The profiles of the middle terraces are, in general, continuous without any cliff or knick point in them and gently inclined seaward. However, in the east coast of Kasari Peninsula they can be divided into two levels : the higher (M1) and the lower (M2). The terrace deposits of M1 terrace are generally thin marine gravels covered with red soil, but valley fill deposits more than 40 meters thick exist inside some small isthmus such as at Taira, Kawauchi and Ogachi. The upper parts of these deposits consist of marine sands and gravels, and the basal parts of them consist of clayey deposits with a lot of breccia and fragments of plants into which a white tuff layer is inserted. M2 terrace is abrasion platform cutting M1 terrace with thin terrace gravels covered with red soil. The high terraces (H) are mainly developed in the northeastern part of Amami-Oshima (mostly included in the area of Fig. 2), which are highly dissected by V-shaped valleys but still preserve very flat original terrace surfaces. They are now at the height of 180 to 340 meters above sea level and probably can be divided into two or three levels. Terrace deposits are not observed on them. The low-relief erosion surface is widely developed in the western half of Amami-Oshima and its dependant islets at the height of 250 to 400 meters above sea level. From the evidences for a large transgression more than 40 meters deep and from the sequence of the middle and low terraces, M1 terrace is inferred to have been formed by the transgression in the last interglacial period, which is called “Shimosueyoshi transgression” in South Kanto, Japan, and dated 120, 000-130, 000 years B. P. (MACHIDA and SUZUKI, 1971). The mode of the vertical deformation during the last 120, 000 or 130, 000 years inferred from the distribution of altitudes of former shoreline of Ml terrace is as follows : (1) Kasari peninsula has been uplifting and tilting north-westward (Fig. 2). Hyakunodai terrace in Kikai-Jima 20 kilo-meters south-east off Kasari Peninsula, which is contemporaneous with Ml terrace in Amami-Oshima, is at the height of 220 meters above sea level. Therefore the tilted area is seemed to extend from Kasari Peninsula to this island.