Japanese arcuate mountains are classified into a number of types, according to their outline of elevation:
(1) Normal ares possessing a smooth continuous outline: the Honsyû are from Kyûsyû to south-western Hokkaidô, for example.
(2) Arcs composed of chainlets elevated
en Echelon: Tisima are (Fig. 1 & 3), terminations of the Sititô-Mariana arc.
Also according to their inner geologic structure (Fig. 2):
(1) Arcs concordant with its inner structure and running parallel with it. Formosa, Ryûkyû, Tisima, the Sakhalin-middle Hokkaidô system.
(2) Discordant arcs with an oblique or perpendicular structure. Korea is the best example.
From the process of their development they are classified into:
(1) Arcs of one cycle, the arcuate form of which was caused by the same movement that contributed to its present inner geologic structure. Tisima, Ryûkyû and probably the Sititô-Mariana arc.
(2) Arcs that underwent many cycles, the inner structure of which is the result of older orogenic movement, while another younger cau-sed its present arcuate form: Korea, for example.
When one are meets another and their limbs are intimately joined, the author calls it “intimate” joining, while those that do not so (Fig. 5) he calls it “detached”.
In Hokkaidô, the Tisima are and the Sakhalin-middle Hokkaidô system are
intimate, while the are that, continues from south-western Hokkaidô to Honsyû is
detached. But joining the Honsyû are and the Tisima are in that part, the geologie structure is under the control of the former. Also in Kyûsyû, the Ryûkyû archipelago and Honsyû
are
intimate, while Korea is so completely detached that it has hitherto frequently been excluded from the “Peri-Tung-hai (East-China Sea) orogenic movement.” In this connection, the Honsyû are is “dominant” and the Ryûkyû are “recessive” in the structural point of view, al-though the Ryûkyû volcanic zone clearly penetrates Kyûsyû.
In middle Honsyû, while the geologic structure is highly complicated, and discordant with the Honsyû are, it seems to be concordant with Sititô-Mariana are. Therefore the most probable conclusion is that the latter was formed across the former. In concluson, the author briefly discusses the possibility of the “crossing” of ares.
抄録全体を表示