Fossils tell of long ago

Fossils tell of long ago

Once upon a time a huge fish was swimming around when along came a smaller fish. The big fish was so hungry it swallowed the other fish whole. The big fish died and sank to the bottom of the sea.

This happened ninety million years ago. How do we know? We know because the fish turned to stone. The fish became a fossil. A plant or animal that has turned to stone is called a fossil. Scientists can tell how old stones are. They could tell how old the fish fossil was.

How did the fish become a fossil? Most animals and plants do not become fossils when they die. Some rot. Others dry up, crumble, and blow away. No trace of them is left. This could have happened to the big fish. We would never know it had lived. Instead, the fish became a fossil. This is how it happened.

When the big fish died, it sank into the mud at the bottom of the sea. Slowly, the soft parts of the fish rotted away. Only its hard bones were left. The bones of the fish it had eaten were left, too. The skeleton of the fish lay buried and protected deep in the mud. Thousands of years went by. More layers of mud covered the fish. Tons and tons of mud piled up. After a long time, the surface of the earth changed. The sea where the fish was buried dried out.

The weight of the layers of mud pressed down. Slowly, the mud turned to rock. As that happened, ground water seeped through the changing layers of mud. Minerals were dissolved in the water. The water seeped into all the tiny holes in the fish bones. The minerals in the water were left behind in the fish bones. After a very long time the bones turned to stone. The fish was a fossil.