At this moment I would like to share about Northeast Japan’s Landform (Northeast Honshu – Tohoku Region). Northeast Honshu is located on the convergent plate boundary at the northwestern Pacific, and is a mature double volcanic arc with a back-arc marginal sea basin. Three major mountain ranges (Dewa, Ou, and Kitakami/Abukuma Mountains) cross this area from north to south. On the northeast side, the Kitakami Mountains with a ria coast (Sanriku coast), and on the southeast side, the Abukuma Mountains occur.
The most part of the Kitakami Mountains have elevation ranging from 600 to 1300m. The west side is relatively hilly (Dewa Hills) with alluvial plains on the Japan Sea Coast. In the central part, the Ou Backbone Ranges extend 400km north to south. All parts of the Backbone Ranges above 1500m are Quaternary volcanoes where the highest summit is at Iwate Volcano (2038m). Northeast Honshu shows a zonal arrangement of geological and geophysical features from the trench to the back-arc side (Kaizuka, 1972; Yoshida and Aoki, 1984; Hasegawa et al., 2000). It consists of pre-Tertiary basement rocks, Tertiary volcano-sedimentary strata associated with large calderas, and Quaternary volcanoes. The Quaternary volcanoes (shown by dot-red symbols in figure above) are divided into four volcanic zones (Nakagawa et al., 1986). The Sekiryo (Ou Backbone Ranges) volcanic zone is an axial zone of arc volcanism where magma temperatures were higher than the other zones, and the eruptive materials are more voluminous (Yoshida et al., 2005). As we can see from figure below, the Ou Backbones Ranges is extrusive volcanic rocks area with ages more than 65Ma, meanwhile intermountains basin area are sedimentary rock from Cenozoic Era
Large area of intermountains basin situated between Dewa and Ou. These region is the most suitable area for inhabitants with elevation ranging from 0 to 500 meters above sea level, there are two main cities in this region; Yamagata and Akita. Between Ou and Kitakami there are Sendai -as the biggest city in Tohoku region- and Morioka. As we know, the soil in the volcanic area is very rich of mineral which is needed for agricultural plant. Tohoku’s rice is the most delicious rice in whole Japan (Hino, 2010)
Hasegawa, A., Yamamoto, A., Umino, N., Miura, S., Horiuchi, S., Zhao, D., Sato, H., 2000. Seismic activity and deformation process of the overriding plate in the northeastern Japan subduction zone. Tectonophysics 319, 225-239.
Hino, Masateru., 2010. Formal discussion in lecture class
Kaizuka, S., 1972. Megageomorphology of island arc system and plate tectonics. Kagaku 42, 573-581 (in Japanese).
Nakagawa, M., Shimotori, H., Yoshida, T., 1986. Aoso-Osore volcanic zone the volcanic front of the Northeast Honshu arc, Japan. Journal of Japan Association for Minerals and Petroleum Economic Geology 81, 471-478 (in Japanese with English abstract).
Yoshida, T., Aoki, K., 1984. Geochemistry of major and trace elements in the quaternary volcanic rocks. Science Reports, Tohoku University, Series 3, Mineralogy, Petrology, and Economic Geology 16, 1-34.
Yoshida, T., Nakajjima, J., Hasegawa, A., Sato, H., Nagahashi, Y., Kimura, J., Tanaka, A., Prima, O.D.A., Ohguchi, T., 2005. Evolution of late Cenozoic magmatism in the NE Honshu arc and its relation to the crust-mantle structures. The Quaternary Research 44 (4), 195-216 (in Japanese with English abstract).