The process by which the earth's surface is eroded by wind, flowing water, and other external forces. Depending on the type of force, it is called fluvial erosion, wind erosion, sea erosion, glacial erosion, snow erosion, etc. Erosion can be mechanical or chemical, and chemical erosion caused by rainwater or groundwater, which is particularly noticeable in limestone regions, is called dissolution erosion. The most significant mechanical erosion is fluvial erosion. Depending on the direction of fluvial erosion, it can be divided into three types: downward erosion (incision), which cuts down the riverbed; lateral erosion (incision), which widens the valley floor; and head erosion (retreat erosion), which extends the valley toward the water source. When the type of erosion varies depending on the rocks or geological structure, it is called selective erosion or differential erosion. Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information |
地表面が風,流水その他の外因的な営力によって削られる作用。働く営力の種類によって河食,風食,海食,氷食,雪食などと呼ばれる。浸食には機械的作用と化学的作用とがあり,特に石灰岩地域に顕著な雨水や地下水による化学的浸食作用を溶食作用という。機械的浸食作用のなかで最も著しいものは河食作用である。河食はその働く方向によって,河床を掘下げる下方浸食 (下刻) ,谷床を広げる側方浸食 (側刻) ,水源の方向に谷を延長する頭部浸食 (後退浸食) の3つに分けられる。岩石や地質構造によって浸食の働き方に差異が生じる場合には,選択浸食または差別浸食という。
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