Trench - Kaikou

Japanese: 海溝 - かいこう

A long, narrow trench-like undersea topography between an island arc or a land arc and the ocean floor, with a maximum depth of more than 6000 m. It is thought to have been created by the subduction of the ocean floor plate under the land. Therefore, trench-like topography with a depth of more than 6000 m that is caused by factors other than subduction (such as a fracture zone caused by a transform fault), and topography that is shallower than 6000 m even if it is caused by subduction (called a trough or basin) are not called trenches. Most trenches are distributed around the Pacific Ocean. The cross section is an asymmetric V-shape, and the width of the upper edge is less than 100 km. The bottom of the trench is filled with sediments from turbidity currents and is flat. The seaward slope has an average slope of less than 4°, and at the top there is a bulge of 500 to 1000 m, which is called a marginal swell or trench marginal rise. The landward slope has an average slope of more than 6° and is highly undulating. There are often shelf-like formations called deep-sea terraces or benches along the slope, and in many places the space between two benches is filled with sediments to form a deep-sea flat surface. → Plate tectonics → Related topics Ocean deeps | Seafloor topography | Ocean | Pacific Ocean | Island arcs | Troughs | Accretionary prisms

Source : Heibonsha Encyclopedia About MyPedia Information

Japanese:

島弧または陸弧と大洋底の間の細長い溝状の海底地形で，最深部の水深が6000mを越えるもの。海底プレートが陸の下へ沈み込むために生じた地形と考えられている。したがって，沈み込み以外の原因でできた水深6000m以上の溝状の地形（たとえばトランスフォーム断層でできた断裂帯），沈み込みでできても水深が6000mより浅い地形（これを舟状海盆またはトラフという）は海溝とは呼ばない。海溝の多くは太平洋の周囲に分布。断面は非対称のV字形，上縁の幅は100km以内。海溝底は乱泥流の堆積物で満たされて平坦である。海側斜面は平均４°以下の傾斜で，上りつめた所に500〜1000mのふくらみがあり，マージナルスウェルまたは海溝周縁隆起帯という。陸側斜面は平均６°を越え，起伏に富んでいる。斜面の途中に深海テラスまたはベンチという棚状地形があることが多く，二つのベンチ間が堆積物で埋まって深海平たん面を形成している所が多い。→プレートテクトニクス
→関連項目海淵｜海底地形｜海洋｜太平洋｜島弧｜トラフ｜付加体

出典　株式会社平凡社百科事典マイペディアについて　情報

<<: Opening - Kaikou

>>: Haikou