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. 