How Fossils Form

0:00How does a living thing, like this fish, become a fossil?

0:05When the fish dies, it sinks to the muddy sea floor.

0:09Mud and sand quickly cover the body. This has to happen fast, before it rots away or is eaten.

0:17Under the mud, the soft parts of the fish rot away.

0:21The hard parts, like bones, teeth and shells, stay behind.

0:26Over thousands and millions of years, more and more layers settle on top.

0:32Deeper layers are older, and each layer can hold the remains of living things from its own time.

0:39The weight of all those layers squeezes the lower ones until they harden into rock.

0:45Water seeping through the rock carries minerals into tiny spaces in the bones.

0:51Slowly, the minerals turn the bones to stone. Now it is a fossil.

0:57Many millions of years later, movements in the Earth push the rock up above the sea.

1:03Wind, rain and rivers slowly wear the top layers away.

1:08At last the fossil is uncovered, and someone finds it.

1:13Buried quickly, turned to stone, then uncovered. That is how a fossil forms, and why rock layers hold a record of past life.