As recognized by authorities on the subject, the Tisima (Kurile) arc meets the Honsyû arc (Sakhalin, Hokkaidô, Honsyû, and Kyûsyû) in middle Hokkaidô in a linking (“Flankenkettung”) manner, the latter meeting again the Ryûkyû are (Korea, Kyûsyû, and Ryûkyû) in the same manner at Kyûsyû. But there is so far no fixed opinion on the relation between the Honsyû are and the so-called Sititô-Mariana arc. The present author proposes here the term “crossing of two arcs” as a working hypothesis for the reason that he lays stress on the position of the giant “Yamato (or NOTOID) bank” recently discovered in the Japan Sea (Fig. 2), which he regards as the prolongation or an effect of the Sitito-Mariana arc.
He next discusses the correlation between the form of the arcs and the expressions of the Earth's endogenous actions. At the positions of the “shadow of Linking”, viz. Korea and Sakhalin, there have been very few epicenters of earthquakes, and no active volcanoes, and similarly these activities greatly diminish in the western half of Honsyû. Volcanism is most active where two arcs meet in a linking or crossing manner, and in sea-bottoms lying in the outer corner of linkings or crossings we have the largest number of earthquake epi-centers and gravity anomalies.
Arcuate mountains are classified into:
(I) Arcuate mountains as the direct result of an orogenic movement in the orogenic belt of the present.
a) The alpine type, in which the same movement has causes both the folding of strata and crustal upheaval.
b) The Japanese type, in which the folding of strata took place during either the Palaeozoic or Mesozoic era, the arcuate form of to-day being the result of a much younger orogeny.
(II) Arcuate mountains indirectly related to orogenic movements, the Appalachian highlands, for example.
Finally the author calls attention to the fact that Korea and Sakhalin belong to the “shadow” of an orogeny and their characters do not differ at all from those of the Great Kingan, Sikhota Alin, Tin Shan, and such mountain systems.
