The are a mountain range in the Tōhoku region of

Honshū , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island separa ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. The range is the longest range in Japan and stretches south from the Natsudomari Peninsula of Aomori Prefecture to the Nasu volcanoes at the northern boundary of the

Kantō region The is a geographical area of Honshu, the largest island of Japan. In a common definition, the region includes the Greater Tokyo Area and encompasses seven prefectures: Gunma, Tochigi, Ibaraki, Saitama, Tokyo, Chiba and Kanagawa. Slight ...

. Though long, the range is only about wide. The highest point in the range is Mount Iwate, . The range includes several widely known mountains:

Hakkōda Mountains The are an active volcanic complex in south-central Aomori Prefecture, Japan, in Towada-Hachimantai National Park. Often called or simply , the mountains are collectively listed as one of the 100 Famous Japanese Mountains. Its highest peak, ...

, Mount Iwate, Mount Zaō, Mount Azuma,

Mount Yakeishi Mount Yakeishi ( jp: 焼石岳) is a mountain in the Ōu Mountains on Honshu, Japan. The mountain, which rises to a height of 1548 meters, is part of Kurikoma Quasi-National Park. See Also * List of mountains in Japan * List of volcanoes in Japan ...

, and Mount Adatara.

Naming

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.

Geology

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 The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Iza ...

subducting under the Okhotsk Plate. A chain of

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

volcanoes along the range forms the volcanic front.

References

{{DEFAULTSORT:Ou Mountains Mountain ranges of Akita Prefecture Mountain ranges of Aomori Prefecture Mountain ranges of Iwate Prefecture Mountain ranges of Miyagi Prefecture Mountain ranges of Yamagata Prefecture Mountain ranges of Fukushima Prefecture