The are a mountain range in the Tà Âhoku region of Honshà «, Japan. It 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 Kantà  region. Though long, the range is only about wide. The highest point in the range is Mount Iwate, .
The range includes several widely known mountains: Hakkà Âda Mountains, Mount Iwate, Mount Zaà Â, Mount Azuma, Mount Yakeishi, and Mount Adatara.
These mountains previously formed the boundary between historical provinces of Mutsu (é¸奥å½) and Dewa (åº羽å½). The kanji for the name of the mountain range was created from one kanji of the two provinces, 奥 and ç¾½, respectively.
The à Âu 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.