Northeastern Japan Arc
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The Northeastern Japan Arc, also Northeastern Honshū Arc, is an island arc on the Pacific Ring of Fire. The arc runs north to south along the Tōhoku region of Honshū, Japan. It is the result of the subduction of the Pacific Plate underneath the Okhotsk Plate at the Japan Trench. The southern end of the arc converges with the Southwestern Japan Arc and the Izu-Bonin-Mariana Arc at the Fossa Magna (ja) at the east end of the Itoigawa-Shizuoka Tectonic Line (ITIL). This is the geologic border between eastern and western Honshū. Mount Fuji is at the point where these three arcs meet. To the north, the Northeastern Japan arc extends through the Oshima Peninsula of Hokkaidō. The arc converges in a collision zone with the Sakhalin Island Arc and the Kuril arc in the volcanic Ishikari Mountains of central Hokkaidō. This collision formed the Teshio and Yūbari Mountains.
The Ōu Mountains form the volcanic part of the inner arc. The volcanic front consists of Quaternary volcanoes, which extend the length of the range. It also includes the Quaternary volcanoes of southwestern Hokkaidō. The Dewa Mountains and the Iide Mountains are non-volcanic uplift ranges that run parallel to the west of the Ōu Mountains.
- glgarcs, An Introduction to the Landforms and Geology of Japan, 2006, last access 2008-09-11.