Answer:
Through erosion by wind and water
Step-by-step explanation:
A valley is a depression on earth’s surface that is usually occupied by any water body either a river or a stream.
Due to running water and sometimes even wind, there occurs gradual wearing of land mass which ultimately leads to formation of valleys. The shape and size of the valleys is very much defined by the force which is causing its erosion, the rock characteristics and the slope of the land.
Hence, there are three types of valleys – a) U-shaped valleys b) V-shaped valleys and c) flat-floored valleys.