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| Ōu Mountains | |
|---|---|
 A section of the Ōu Mountains nearKōriyama, Fukushima | |
| Highest point | |
| Peak | Mount Iwate, Iwate Prefecture |
| Elevation | 2,038 m (6,686 ft) |
| Dimensions | |
| Length | 500 km (310 mi) North-South |
| Width | 35 km (22 mi) East-West |
| Naming | |
| Native name | |
| Geography | |
 | |
| Country | Japan |
| States |
|
| Region | Tōhoku |
| Range coordinates | 39°51.15′N141°0.05′E / 39.85250°N 141.00083°E /39.85250; 141.00083 |
| Geology | |
| Orogeny | Island arc |
| Rock type | Volcanic |
TheŌu Mountains (奥羽山脈,Ōu-sanmyaku) are amountain range in theTōhoku region ofHonshū, Japan. It is the longest range in Japan and stretches 500 km (311 mi) south from theNatsudomari Peninsula ofAomori Prefecture to theNasu volcanoes at the northern boundary of theKantō region. Though long, the range is only about 35 kilometres (22 mi) wide. The highest point in the range isMount Iwate, 2,038 metres (6,686 ft).[1]
The range includes several widely known mountains:Hakkōda Mountains, Mount Iwate,Mount Zaō,Mount Azuma,Mount Yakeishi, andMount Adatara.
These mountains previously formed the boundary between historical provinces ofMutsu (陸奥国) andDewa (出羽国). Thekanji for the name of the mountain range was created from onekanji of the two provinces, 奥 and 羽, respectively.
The Ōu Mountains began to form in thePliocene. They sit over the middle of the inner arc of theNortheastern Japan Arc. This is the result of thePacific plate subducting under theOkhotsk plate. A chain ofQuaternary volcanoes along the range forms the volcanic front.[1]