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Outline of landforms and geology of Japan
Fig.
Kitami Mountains [
]
The Kitami Mountains in northern Hokkaido are extremely gentle without dense valleys seen in Honshu. This morphology is attributed to the repetition of yielding debris and collapse of the debris slopes by frost action during ice ages. Other glaciated landforms such as a cirque are also preserved on high elevation areas of mountain ranges in Hokkaido and central Honshu.
Fig.
Hidaka Mountains []
The Hida, Kiso, Akaishi Ranges in central Honshu and the Hidaka Mountains in Hokkaido, which are in collision zones where crustal movement is very active, are markedly steep (the Hidaka Mountains is adjacent to a collision zone to be exact). Some mountains in these ranges have knife-edges and horns.
Fig. Relative height (bar) at the end of valley (dashed lines show the bottom of valley)
[Yonekura et al. 2001]
Japanese mountains can be classified into seven types based on their morphology including the altitudes of summits, cross sections of ridge and valley, and the height from the bottom to top of slope at the end of valley (Yonekura et al. 2001). This classification mainly indicates mountain steepness. The characteristics and typical mountain ranges of each type are shown in a table below.
| Type I |
Very high relief, height at the end of valley >1200
m, extremely steep, V-shaped valley Hidaka Mountains, Hida Range, Kiso Range, Akaishi Range |
| Type II | High relief, height at the end of valley >800 m Echigo Range, Asahi Mountains, Iide Mountains, Yubari Mounatains |
| Type III | Slightly high relief, height at the end of valley
>500m Kii Mountains, Shikoku Mountains, Kyushu Mountains, Kanto Mountains |
| Type IV | Medium relief, height at the end of valley between
500 m and 300 m Northern Ou Range, Kitakami Range, Tamba Highland, Chugoku Mountains |
| Type V | Slightly low relief, height at the end of valley
<300 m, mostly gentle but steep in places Teshio Mountains, mountains in southern Hokkaido and northern Kyushu |
| Type VI | Low relief, height at the end of valley between 300
m and 100 m, gentle ridges and shallow valleys,
hill-like morphology Abukuma Mountains, Iwami-Suo Highland |
| Type VII | Very low relief, extremely gentle slopes and
shallow valleys with wide valley floors Northern Kitami Mountains, Mikawa Highland, and Kibi Highland |
The distribution of each type is shown in the right figure.
Volcanoes
About 200 Quaternary volcanoes are found in Japan. Most of the volcanoes are andesitic stratovolcanoes. See the section "Volcanoes" for the details of Japanese volcanoes.
Plains
Plains in Japan are formed by deposition of clastic material derived from mountains, not by erosion for a long time. Fields for sedimentation, such as basins and plains, are mainly subsidence areas. The Kanto Plain is the largest subsidence area in Japan, sinking by more than 1000 m during the past two million years. River and coastal terraces are often developed owing to active uplift and subsidence.
