Valley
Valleys that are high in the mountains are usually made deeper by a stream or small river running fast down the mountainside, from a place where there is lots of rainwater or melting snow, or by a glacier.  The mountain stream winds around the biggest rocks and washes the soil away as it flows.  It cuts a passage for itself through the softest soil and smallest stones.  A small stream can cut a very deep valley.  Valleys that are high in the mountains are usually V-shaped.  There are many valleys like this in hills and mountains all over the world.