Ōu Mountains

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Ōu Mountains
A section of the Ōu Mountains near Kōriyama, 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	奥羽山脈 (Japanese) Ōu-sanmyaku (Japanese)
Geography
Country	Japan
States	Aomori Prefecture Akita Prefecture Fukushima Prefecture Iwate Prefecture Miyagi Prefecture Yamagata Prefecture
Region	Tōhoku
Range coordinates	39°51.15′N 141°0.05′E / 39.85250°N 141.00083°E / 39.85250; 141.00083
Geology
Orogeny	Island arc
Rock type	Volcanic

The Ōu Mountains (奥羽山脈, Ōu-sanmyaku) are a mountain range in the Tōhoku region of Honshū, Japan. The range is the longest range in Japan and stretches 500 km (311 mi) south from the Natsudomari Peninsula of Aomori Prefecture to the Nasu volcanoes at the northern boundary of the Kantō region. Though long, the range is only about 35 kilometres (22 mi) wide. The highest point in the range is Mount 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, and Mount Adatara.

These mountains previously formed the boundary between historical provinces of Mutsu (陸奥国) and Dewa (出羽国). The kanji for the name of the mountain range was created from one kanji of the two provinces, 奥 and 羽, respectively.

The Ōu Mountains began to form in the Pliocene. They sit over the middle of the inner arc of the Northeastern Japan Arc. This is the result of the Pacific Plate subducting under the Okhotsk Plate. A chain of Quaternary volcanoes along the range forms the volcanic front.^[1]