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Outline of landforms and geology of Japan
Fig.
17
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.
18
Hidaka Mountains []
The Hida Range, the Kiso Range, the Akaishi Range 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. 19 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 |
Fig.
20
Distribution of mountain range types []
The distribution of each type is shown in Figure 20.
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
High relief of mountains and rapid erosion in a mobile belt and humid
temperate climate zone are responsible for the production of large
volume of clastic material in mountains. Produced material by erosion is
carried by stream and deposited in depressions (relatively subsidence
areas such as basins and bays) to make plains. Japanese plains adjacent
to mountains are formed by this process. Therefore, the plains can be
regarded as accessories of mountains. Japanese plains are divided into
intermontane basins and coastal plains. The sizes of plains are
generally small. The largest plain in Japan is the Kanto Plain with 100
km width, formed in the largest subsidence area in Japan, sinking by
more than 1000 m during the past two million years.
Plains consist of alluvial lowlands, platforms (terraces), and hills.
The area proportions of these topographic parts reflect crustal movement
of each plain in the Quaternary period. Plains dominated by platforms
and hills, such as the Konsen, the Tokachi, and the Miyazaki
Plains, are in areas where subsidence movement has been inactive. Plains
with broad lowlands, such as the Ishikari, the Nobi, and the
Osaka Plains, are in subsidence areas.
Fig. 21 Kanto Plain
Red arrows: intermontane basins
Black arrows: coastal plains
