Coastal plain - Kaiganheiya

A plain that spreads along the coast. In the narrow sense, it refers to a plain formed by the uplift of part of the seabed. In the broad sense, it is used as a general term for all low-lying landforms distributed along the coast, such as coastal sandbars and sand dunes, lagoons and back marshes inland from those, and even deltas and alluvial fans. Japan's coastal plains were widely covered by the sea due to the transgression of the Jomon period, and then became land due to the subsequent regression of the sea. For this reason, marine deposits consisting of sand and mud containing fossils such as shells can often be seen underground in the coastal plains. Such coastal plains that have been uplifted and then eroded somewhat by rivers are called dissected coastal plains. Of these, a strip-shaped landform that has become like a cuesta is called a strip-shaped coastal plain.

[Yoshinori Toyoshima]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

海岸に広がる平野。狭義には、海底の一部が隆起して形成された平野をいう。広義には、海岸砂州や砂丘、その内陸側の潟湖(せきこ)や後背湿地、さらにデルタや扇状地など、海岸地帯に分布する低平な地形全体の総称として用いる。日本の海岸平野は、縄文時代の海進作用によって広く海に覆われたのちに、その後の海退作用によって陸地化した。そのため、海岸平野の地下には、貝殻などの化石を含む砂や泥からなる海成層がみられることが多い。このような海岸平野が隆起したのちに、河川によって多少侵食されたものを開析海岸平野とよぶ。そのうち、ケスタ状になった帯状地形を帯状海岸平野という。

［豊島吉則］

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