When streams run rapidly, as they do after a storm or when snow melts, much sediment is picked up and transported. When the velocity of the water subsides, as it does when it enters a lake or the ocean, the sediment is deposited. Notice how the water in this lake is cloudy with sediment.
Each pulse of rapidly running water transports another batch of sediment. With time, the sediment accumulates layer by layer.
Here we see hills and valleys made of layered rocks. How may these rocks be related to sediment deposited on the floor of a lake or the ocean?
Here's an explanation:
  1. First, sediment is deposited in the ocean. With time, the layers of sediment turn to rock.
  2. Next, the whole area is uplifted well above sea level. The ocean water drains elsewhere.
  3. As soon as the sedimentary rocks are exposed, they begin to erode, forming hills and valleys.

© 2001, David J. Leveson