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Geomorphologists in Japan have attempted to explain geomorphologic history on an assumption that the Japan Islands were flattened in late Pliocene or early Pleistocene age. This idea supports a hypothesis that the outlines of landscape in Japan can be safely explained in relation to tectonic movement in Pleistocene age. Traces or relics of erosion surfaces represented by undulating low relieves of summit and accordance of ridge are distributed partly to sparsely almost all over Japan. So they have been regarded as an evidence of realization of planation covering Japan. The author objects to this hypothetic view, because we have not had satisfying information yet on duration needed for planation or reduction of mountain. Unfortunately, it is very difficult in Japan to reconstruct the past landscapes because of overlaping tectonic activities. Concerning this problem, the author could obtained suggestive informations from continental mountains in view of morphotectonics as C. D. Ollier and his group members suggests. The author introduces the geomorphologic development of the eastern high lands of Australia and continental mountains or Great Escarpments in some other area studied in morphotectonic view. Morphotectonic studies of continents suggest that mountains in humid temperate region do not reduce so fast as they have been expected in Japan. The author is again convinced of an idea that the landscape in the Japan Arc involves relics and remnants of old relief formed by tectonic movement in Miocene or Pliocene age, or probably in early Tertiary age. It can be safely assumed that almost erosion surfaces in Japan may be dated back to early Tertiary or older time. But it is unfruitful to discuss of their age or origin, because we have scare data concerning with them. Finally, it is proposed that the researches as follows are needed before we discuss of evolution of mountains of Japan. 1) Miocene volcanic rocks which have not been thought to be dissected enough to remained in outlines of original form, should be examined to reconstruct their original forms. 2) Mountains and highlands which have been thought to be uplifted uniformly in Pleistocene age, should be rexamined to make clear chronological order of uplift. 3) Development of drainage systems in Japan which have been rarely a matter of concern, should be researched in relation to multiple tectonic movements. 4) Miocene sediments which have not been studied in relation to surrounding landforms, should be attempted to reconstruct directions of streams and landforms.
地理科学学会の論文

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岡義記
鳴門教育大

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