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.
(Nobody knows why it died. It's called Xiphactinus.
Wow, That's some catch! the little fossil is bigger than me!)
How did the fish become a fossil?
Most animals and plants do not become fossils
when they die. Some rot(rot-rotted-rotted, rotten)
Other 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 tottom of the sea.
Slowly, the soft parts of the fish rotted away.
Only its hard bones were left.
The bonees 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 vent by.
More layers of mud ocvered 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.
Some fossils, like the fish, are actual parts of plants or animals
that have turned to stone.
Sometimes a fossil is only an imprint of a plant or animal.
Millions of years ago, a leaf fell off a fernlike plant.
It dropped onto the swampy forest soil, which is called peat.
The leaf rotted away.
But it left the mark of its shape in the peat.
The peat, with the imprint of the leaf, hardened.
It became a rock called coal.
Coal is a fossil, too
(Peat is made up of mushy, rotted leaves.
We use peat in the garden to make plants grow.
Look how perfect the leaf looks.
Lots