Valley
A valley is a type of landform.  A valley is a lower part in the land that sits between two higher parts which might be hills or mountains.  Valleys often start as a downward fold between two upward folds in the surface of the Earth, and sometimes as a rift valley.  A valley is made deeper by a stream of water or a river as it flows from the high land to the lower land, and into a lake or sea. Some valleys are made by glaciers which are slow-moving rivers of ice.  Water or ice make a valley deeper or wider by erosion.  Wind can also make valleys larger by erosion.