Cast Fossils: Fossils In Your Very Own Hands!

Contributor: Kaitlyn Aston. Lesson ID: 12819

Did you ever find something you lost a long time ago? Or maybe find a bird or squirrel skeleton in the woods or a park? Fossils are remains of things "lost" many years ago! Would you like to make one?


Earth Science

learning style
personality style
Golden Retriever
Grade Level
Primary (K-2), Intermediate (3-5)
Lesson Type
Quick Query

Lesson Plan - Get It!


Have you ever seen how ceramics are made? As you can see in the above image, the liquid slip — or liquid ceramic — is poured into the mold. After a couple of days, a cast ceramic is made! Did you know that "fossils" can be made in a similar way?

  • Have you ever heard of a "fossil" before?
  • Do you know what a fossil is?

A fossil is a piece (what is left over) or trace (like a footprint) of an animal, plant, or object that has been preserved over time. As you can see from the images below, a process known as fossilization must take place to create a fossil. Check it out!

When the fish perishes, its body sinks to the river bed. Over time, the body of the fish decays and is eaten by bacteria. However, the bones are left! Over time, those bones get covered with layers of soil, rock, and minerals. Eventually, those minerals replace the bones. One day, the earth will move and the fossil will be closer to the surface, where someone can find it!

It may be hard to know what things looked like thousands of years ago. Looking at fossils provides a way to look into the past! Mold fossils can show you the footprints of animals, people, and even the impressions of leaves! Over time, they have been preserved for us to see!

  • What if you were to make a cast fossil out of a mold?
  • Do you know what a cast fossil is?
  • Why don’t you join Flo in order to learn more!

  • Did you see how the cast fossil formed?

When the plastic animal was used to form an outline in the sand, a mold fossil was formed! However, sand is a very loose material that will never harden well, so it is not a material that is used to form mold fossils in nature. When you place the plaster of Paris mixture inside the temporary mold and let it dry, you are able to make a cast fossil of your plastic animal!

  • Can you think of some items that make up most of the mold and cast fossils that you find today?

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