We are going to see how layers are formed on the bottoms of bodies of water.

Obtain a large test tube that can be corked, or a jar with a good lid. Mix at least three sizes of gravel, some sand, and mud together. Place the mixture in the container, and fill it with water. Put on the lid and invert the tube.

You will see that as the materials fall through the water, the larger materials settle quickly at the bottom, medium sizes in the middle, and fine silt slowly at the top.

Rivers, streams, and oceans carry sediments and deposit them on the basis of weight and size.

Wait a minute! We have seen many rivers and streams with rock bottoms. What happened there?

In waterways where the flow is fast, the fine silt goes along with the water. If the water is slow-moving along the sides of the waterway, some silt would build up along the walls; however, most of it does not settle to the bottom until the waterway widens and the flow is slowed. Sometimes, the silt builds a delta where the waterway empties into a larger body of water.