日本のような島孤にみられる地すべり運動像とチェコスロバキアのような安定大陸の地すべり運動像との間には大きな差異がある。これは一義的には岩体自体のひずみ像の量的相違によるものと考える。一方, 巨大な岩塊の滑動というマスムープメントを保持するためには, その場所の基盤を構成する岩石の物理的・化学的性質が地すべり運動像に深い関係がある点をここに新しく指摘した。換言すれば地すべり面の粘土が滑剤となり, その上にのっている岩塊をすべりやすくするか否かが運動像の形態に大きく影響する。すなわち, このタイプのマスムーブメントが成り立つたあには, 地山から離脱する岩塊内部の地質分離面の分布と基盤をつくる泥岩の物性と化学的性質との相互作用によるものであることを新潟県下の代表的例をあげその発生機構を説明した。

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Geological zonation of landslides in very small scales was proposed based on major engineering geological division of Japanese Islands. In this paper, the term “landslides” involves all kinds of ground movements appeared in Japan. In the course of zoning works, the following problems are piscussed, namely; geomorphological development related to landforms which are controlled by lithological characteristics and types of landslides, recent crustal movements affecting the cause of landsliding phenomena, distribution density of landslides in narrower sense, etc.
As results, fifteen map units are defined with explanatory table of topographic, lithological, tectonic geological features, principal types of movements, possibilities of prediction and foreknowledge, planning of controll works. Also, typical geological cross sections are illustrated for each map units.
Map units represented in the zonation map are as follows:
1) Acidic intrusive rocks and gneisses
2) Ultramafic and mafic intrusive rocks
3) Paleozoic-Early Mesozoic eugeosynclinal deposits, crystalline schist facies
4) Paleozoic-Early Mesozoic eugeosynclinal deposits, non-metamorphosed facies
5) Cretaceous marine deposits of turbidite facies
6) Late Mesozoic-Paleogene eugeosynclinal and flysh-type deposits
7) Late Mesozoic-Paleogene terrestrial volcanic rocks
8) Tertiary non-marine to neritic deposits
9) Miocene submarine volcanic rocks
10) Middle Miocene-Pliocene marine clastic sediments
11) Pliocene-Pleistocene terrestrial volcanic rocks
12) Quaternary terrestrial and neritic clastic sediments
13) Quaternary pyroclastic rocks and sediments
14) Quaternary volcanic rocks
15) Late pleistocene-Holocene clastic sediments

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Green-tuff Region is defined as existence of abundant submarine volcanic rocks of Early Miocene and overlying oil-bearing pelitic clastic sediments of Late Miocene-Pliocene age. The region is also characterized by predominant distribution of landslide phenomena in the outcropping area of pelitic sediments. The region has been folded and faulted since Late Plocene age, moreover hilly and mountainous area is considered to be uplifting recently.
From paleotemperature analysis by authigenetic minerals and studies of the relation between porosity and burial depth, amounts of uplifting movements are estimated, and it is clarified that overlying Pliocene sediments has been eroded out throughout the Quaternary age, and severe fracturing occurred in the Neogene sediments. This caused the action of groundwater that accerelate landslide phenomena in the Green-tuff Region.

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Over 6, 000 spots of landslide were made clear by the Hokkaido Branch of the Japan Laadslide Society. The writer draws their digital map on 150''×225'' mesh.
Geomorphology is in low relief or was periglacial in an ice age. Heavy stormy rain is rare unlike any region else in Japan. Mass 'movement is inactive, but a great number of ancient marks remain uneroded because of low relief and light precipitation.
Mass movement groups may be divided into 19 zones according to geological classification.
Quaternary pyroclastic sediment, 13…1
Miocene-Pliocene marine sediment (Green tuff area), 10a…4
Miocene-pliocene marine sediment (non-Green tuff area), 10b…6
Miocene submarine volcanic rock, 9…2
Non-marine or neritic tertiary sediment, 8…2
Late mesozoic-paleogene tertiary orthogeosyncline sediment and flysh alternation, 6…1
Paleozoic-early mesozoic orthogeosyncline sediment (non-metamorphic), 4…1
Paleozoic-early mesozoic orthogeosyncline sediment (metamorphic) & pre-tertiary mafic rock, 3&2…2
For naturnl mass movement during the past 22 years, it is only 78 conservation areas in which stimulative deeds are prohibited and preventive and/or control works are administratively constructed.

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Landslides were mapped by air-photograph interpretation in the main part of the Tohoku District in Northern Japan and characteristics of landslide distribution are discussed from geological point of view. The Tohoku District can be divided into two parts from geology and geomorphology and also from landslide distribution. The Kitakami Mountain area, the east part, underlain by hard rocks of Palaeozoic to Mesozoic Eras is rarely covered by landslides or landslide deposits. The Oh-u and Dewa Mountain areas, the west, underlain by the Lower Miocene marine volcanics called green tuff and the Upper Miocene to Pliocene clastic rocks are characterized by crowded and dense distribution of landslides in several scales. In detail, landslides medium to small in scale are more densely observed in the areas underlain by the Upper Miocene clastic rocks. Large and medium landslides are often observed in the area of “green tuff”, though the area has been believed to be barren in landslide distribution. It is considered that landsliding is one of main processes of erosion for the Neogene rocks in the Tohoku District. Gigantic or large landslides are often recognized on the slope of the Quaternary volcanoes. Those volcanoes have several extra conditions different from other geologic bodies.

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Landslides, like the most of geological phenomena, has a duality represented by its natures characteristic of both material science and historical one. Such a duality is unified and comprehensively revealed in “regionality” of landslides. Two series of landslides can be distinguished in Niigata region by examination of the landslides in relation with each geologic system, lithology and geologic structure of the bed rocks. It is a remarkable fact that the types, characteristics, phases and domains of the late Cenozoic crustal movements are conformable with the distribution pattern and the series of the landslides. This suggests that the essential properties of the landslides are based on the tectonic history, specifically on its latest one of the region. Problems on protection and prevention of landslides should be considered from such a point of view.

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Attempts have been made from previously by a number of investigators to classify geologically the occurrence conditions and the characteristics of landslides in Japan. In this report, landslides in the Kanto district and its vicinity (Kanagawa, Gunma, Chiba, Yamanashi and Nagano Prefectures) are investigated from the viewpoint of the geological zoning and the occurrence conditions of landslides. Landslides triggered by the continual creep movement of earth and avalanche-type landslides suddenly caused by the earthquake are studied simultaneously. Landslides due to the earthflow induced by a localized torrential downpour are ex-cluded from this study. This report consists of a part of the Geological Classification Committe reports in the Japan Society of Landslides.

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A geological zoning for landslides is performed in Kinki district, Southwest Japan, and 12 geological zones are obtained, as shown in Fig. 1 and Table 1 (in Japanese). The landslide areas are northern Tajima area (Zones 9 and 10), Sanda area (Zone 8), Awaji island (Zones 6 and 11), Izumi mountains (Zone 6) and Wakayama area (Zone 2 and 3). These zones are as follows:
Zone 2; ultrabasic and/or basic rocks
Zone 3; pre-retaceous geosynclinal sediments (metamorphosed facies)
Zone 6; Cretaceous marine sediments
Zone 8; Neogene non-arine or marine sediments
Zone 9; Neogene geosynclinal sediments and volcanic rocks (so-called “green tuff” area)
Zone 10; Pliocene-Quaternary terrestrial volcanics (lavas and pyroclastic rocks, associated with sediments)
Zone 11; Pliocene-Quaternary sediments (shallow sea or non-arine deposits)

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From the view points of geology and geomorphology, the writer treated the so-called fractured zone type landslides, and pointed out their characters.
The one is a large scale landslide caused by a certain character of deep-seated shear plane and tectonic movements, and has often a uphill-facing scarplets and double ridges at adjacent areas.
The other occurs in the areas with Quaternary detrital deposits which is often originated from the large Scale landslides.

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