A tributary valley that joins a main valley where the latter has been deepened, usually by glacial erosion, resulting in a steep drop from the floor of the tributary valley to the floor of the main valley.悬谷：交集于主要山谷的附属山谷，其中主要山谷通常较深，常常由于冰河的侵蚀导致从附属山谷层至主要山谷层间有着较大的落差