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Understanding what fossils are and how they show us what life was like long ago.
What if you could hold a piece of a creature that lived millions of years before the first human was ever born?
A fossil is the preserved remains or traces of a living thing from long ago. It isn't just a bone; it is a clue left behind by plants or animals. Most fossils are found in sedimentary rock, which is rock made from layers of mud and sand. Fossils can be many things: a hard bone, a delicate leaf, or even a footprint left in the mud! Because it takes so long for fossils to form, they are usually at least years old.
Quick Check
Is a fossil just a regular rock you find on the playground?
Answer
No, a fossil is the preserved remains or traces of a living thing that lived a very long time ago.
Fossils don't happen by accident; they need special conditions. First, an animal or plant must be buried quickly by sediment (like mud or sand) after it dies. This protects it from being eaten or rotting away. Over millions of years, more layers pile on top. The weight of these layers creates pressure. Slowly, minerals from the water seep into the remains and turn them into stone. This process is called permineralization.
1. A fish dies and sinks to the bottom of a lake. 2. Mud covers the fish quickly. 3. Over years, the mud turns into hard rock. 4. The fish's bones are replaced by minerals, leaving a perfect stone copy of the skeleton.
Quick Check
Why does an animal need to be buried quickly to become a fossil?
Answer
To protect it from being eaten by other animals or rotting away before it can turn into stone.
Fossils are like puzzle pieces. They show us animals that are extinct, which means they no longer live on Earth today. By looking at fossils, scientists (called paleontologists) can tell if an area used to be an ocean or a forest. For example, if you find a shark tooth fossil in the middle of a dry desert, you know that desert was once underwater!
Imagine you are hiking on a tall, snowy mountain and you find a fossil of a sea snail. 1. You know snails live in the ocean. 2. This tells you that the land you are standing on was once at the bottom of the sea. 3. Over millions of years, the Earth's surface shifted and pushed that sea floor up to become a mountain.
A scientist finds a fossilized tooth that is inches long, sharp, and jagged. 1. Based on the shape, the scientist knows this animal ate meat, not plants. 2. Because no animal alive today has a tooth like that, the scientist concludes the animal is extinct. 3. By comparing it to other bones found nearby, they can reconstruct what the whole creature looked like.
What is the name for a scientist who studies fossils?
In which type of rock are most fossils found?
A footprint left by a dinosaur can be a fossil.
Review Tomorrow
In 24 hours, try to explain to a friend the three steps of how a 'fossil sandwich' is made.
Practice Activity
Draw a picture of an imaginary animal. Now, draw what its fossil might look like if it were found million years from now!