Submarine canyon

Japanese: 海底谷 - かいていこく（英語表記）submarine canyon

A relatively narrow, deep depression in the ocean floor with steep side slopes and a continuously deepening bottom. Most of these valleys are V-shaped like on land valleys, meandering, with exposed rocks on the valley walls and tributaries (e.g., Tokyo Canyon, Monterey Canyon, Hudson Canyon, Trincomalee Canyon). However, in a broader sense, ocean valleys can also include valleys cutting deep-sea alluvial fans (which meander but have no tributaries and no exposed rocks on the valley walls), shelf valleys (which are not deep and the water depth of the seafloor where the valleys are located is not great), valleys carved into the front of deltas (e.g., Mississippi), and deep-sea channels (deep-sea grooves with low relief and few tributaries). The main causes of the formation of submarine valleys are thought to be erosion by turbidity currents originating at the valley head, erosion caused by the gradual movement of sediments along the submarine valley, erosion by currents other than turbidity currents, and the submersion of valleys eroded on land.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

海谷とも呼ぶ。比較的狭く深い海底の凹所で，急な側斜面をもち底が連続的に深くなる場所。そのほとんどは陸上の谷に似てV字谷で，蛇行し，谷壁には岩石が露出し支谷がある (例:東京海底谷，モンテレー海底谷，ハドソン海底谷，トリンコマリー海底谷) 。しかし広義には，海にみられる谷状地形として，深海扇状地を切る谷 (蛇行もするが支谷をもたず，谷壁に岩石が露出していない) ，陸棚谷 (谷が深くなく，谷の存在する海底の水深も大きくない) ，三角州前面を刻んだ谷 (例:ミシシッピ) ，深海水道 (深海にみられる起伏の小さい，支谷をあまりもたない溝状地形) などを含むこともある。海谷の成因として主として考えられているのは，谷頭に発する混濁流による浸食，海底谷に沿う堆積物の徐々に動いて起る浸食，混濁流以外の流れによる浸食，陸上で浸食された谷の沈水などである。

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