regressive erosion

• 下切,向源侵蚀

regressive erosion的用法和样例：

例句

1. It will lengthen as a result of headwater erosion and, thereby, will cut a valley through both hard and soft rock.
   由于向源侵蚀的结果，它不断延长并且穿过软硬岩石从中切出一条河谷来。