Geographical Review of Japan

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Regarding the position of the Japanese Islands, the present author attaches importance to the fact that they correspond to the discon-tinuous line of the Earth's crust. In explaining the origin of the Sititô-Marianna Arc, two circulating currents of sima on the bottom of the Pacific Ocean are assumed, namely, the North-Pacific Current. flowing counter-clockwise along Tisima and North-East Honsyû, and the Philippine-Sea Current flowing clockwise along Formosa and the Ryûkyû Islands. As the result of these two currentsof sima drawing close together, the Sititô-Marianna Arc was built along this current line by shear or vortex motion. The triangular Caroline-Sea Neutral. part of the Sima (Fig. 2, 3) comes to be situated between the southern continental ring (New Guinea, New Britain Is.) and these two currents of sima. The sialic character of the Sititô-Marianna Arc, which is proved by the existence of granitic rocks and crystalline schists, is believed to have its explanation in the convergence owing to the discontinuous line to which the sialic relics on the ocean-bottom ten-ded to drift (Fig. 3). In the southern hemisphere, there may exist a South-Pacific Current of Sima that originated mainly under the influence of its outline. Many rows of islets south of the equater are also interpreted as corresponding to the boundary of the South and North-Pacific Currents of Sima. The geological evidences in Hon-syû lead us to conclude that the growth of the Sitito-Marianna Arc began from the middle of the Tertiary period, and the orogenic movements resulted in the Himalayas, the Alps, etc., which affected the circulation of sima on the Pacific bottom, after which the Philip pine Sea Current of Sima began to flow as it is doing now.

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