make fossilized dino footprints and skeletons

instructions

1. Mix all the ingredients together to make a dough that is dry, but will hold it's shape when molded or when things are pressed into it.

2. Press the feet of dinosaur toys into the dough to make tracks.

3. Press the body of the dinosaur into the dough at different angles to make tissue fossils.

4. If you don't have any dinosaur toys, look up pictures of dinosaur tracks (you can find some local ones at Dinosaur Ridge in Morrison). Use the end of a chopstick or other kitchen tool to make the imprint.

5. Bake your finished fossils at 350F until the dough is hard and dry if you wish to keep your fossils (which you should!).

The science

There are many kinds of fossils archaeologists use to learn about what life was like on Earth millions of years ago. Fossils can preserve ripple marks from water, plants, footprints, bones, and animal tissue like skin. Even though there are many kinds of fossils, all fossils are made in a similar way.

To make a fossil, the ground must be soft, like mud or sand. When an animal walks through soft ground or dies on soft ground, it leaves an impression like in your salt dough. Over time, minerals work themselves in between the particles of mud and sand and cause them to stick together and harden, like the salt dough in the oven. These minerals turn mud into shale and sand into sandstone, which are rocks that change very little over millions of years. Any impression made in the ground by a dinosaur's feet as it walked or body as it died will be frozen in this newly created rock. This is very similar to the fossil you created with salt dough!

As thousands and millions of years pass, more and more rock is formed on top of the fossil. A dead dinosaur's body will get covered by this rock and sealed in, creating a kind of rock mold around the dinosaur. After it decays, minerals will move in to the space left by the dinosaur's body or skeleton and harden, filling the mold. The fossil that is created is not the dinosaur's actual body or skeleton, but it is a very accurate cast of it. These casts, which are now made of rock, can last MUCH longer than any part of the dinosaur could. They preserve detail about the dinosaur's anatomy, and if an archaeologist is lucky, can also give clues about how the dinosaur lived and died.

Experiment idea

Use your dinosaurs and salt dough to act out different scenes. Look for specific patterns that an archaeologist could use to learn about how a dinosaur lived or died. Here are some ideas:

• dinosaur fight where one dinosaur dies

• dinosaur herd moving together

• dinosaur dying of an injury or sickness

• dinosaur foraging for food

How are the tracks and fossil marks left in the salt dough different for the different scenes?If you were an archaeologist, what would you look for in the fossil record to learn more about the lives of dinosaurs?