What is a fossil?

Minerals & Materials

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by Kate Simmons >> more about the author

Have you ever turned over a rock, only to find evidence of something that once lived? Maybe it’s an imprint of a shell, plant or bone. If so, you may very well have found a fossil! Fossils are the remains of living things. Some fossils are billions of years old!

When most living things die, they decompose, or break down, becoming part of the earth. However, instead of breaking down, some living things may become fossils. There are several different ways that fossils can form. For example, some fossils are created when a plant or animal makes an imprint in a soft substance, such as mud. When the mud hardens, the imprint is preserved.

Other fossils are formed when part or all of a living thing is buried, slowing down its process of decomposing. Over time, minerals seep in and replace the living bone or tissue, eventually hardening into a stony version of the once-living thing!

We can learn a lot from studying fossils, such as how living things have changed over time, and what the earth was like at the time the living thing existed. Scientists who study fossils are called paleontologists.

Now you can duplicate the process of fossil formation with craft dough and a few found items! Begin by searching for small items that can be covered with play dough or clay. You may decide to pick objects from nature, such as seashells, or to include “just for fun” items, like small toys. Make sure you pick objects that you don’t mind getting a bit dirty.

Can you now cover your finds with the play dough? Start by rolling a ball of the dough or clay, then flattening it on the table with your palms and fingers. Peel the dough off the table and wrap it around the item(s) you have chosen. You may need to repeat this process if you have more than one find. Covering the items with clay reminds us of how living or once-living things can be covered with substances like mud in nature. See if you can smooth the dough or clay over the item, covering every part without hiding the object’s shape.

Now imagine that the item inside the clay begins to break down over time, and minerals seep in and take the place of the particles that once made up the original object. This is the process of fossil formation!

When this process is complete in nature, what you have is a bit like what you’re now holding in your hand—an item that has been covered, then preserved!