Rejuvenation - Kaishun

When a river valley has developed to a certain stage through the process of river erosion, some cause causes the process to be interrupted, causing the river to return to the starting point of the process and erosion to become active again, developing the infant valley. This is also called revival of erosion or rejuvenation, and a river that has undergone rejuvenation is called a rejuvenated river.

An increase in the riverbed gradient or a decrease in the erosion base level due to crustal movements such as uplift, tilt, or bending of the ground can cause respring. A drop in sea level has the same effect as ground uplift. Other causes of respring include an increase in flow rate due to river competition or climate change, a decrease in the load carried by a river due to climate change or the rise and fall of volcanic activity, and the disappearance of local erosion base levels in lakes and hard rock layers. River terraces and transition points are created by respring.

[Shigemi Takayama]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

河谷が河食輪廻(りんね)の進行によってある段階にまで発達したのちに、なんらかの原因によって輪廻の進行が中断され、輪廻の出発点に戻ってふたたび下方侵食が活発化し、幼年谷を発達させること。侵食の復活、若返りともいい、回春のおこった川を回春川という。

　地盤の隆起、傾動、撓曲(とうきょく)などの地殻変動によって河床勾配(こうばい)の増大や侵食基準面の低下がおこった場合、回春の原因となる。海面低下も地盤の隆起と同じ効果をもたらす。そのほか、河川争奪や気候変化に起因する流量の増大、気候変化や火山活動の消長に伴う川の運搬荷重の減少、湖沼や硬岩層などの局部的侵食基準面の消失なども回春の原因となる。河成段丘、遷移点は回春により生ずる。

［髙山茂美］

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