Did you know that petrified rock is actually a fossil?
In this simple STEM lesson, we are going to learn a bit about petrified rock and make a petrified sponge!
Let's dig in...
Petrified rock is a type of fossil known as a replacement fossil. Replacement fossils are replicas of things that were once alive, such as trees, sea creatures, or the bones of an animal.
The living thing dies and is trapped in the ground. As it lays there, it is covered by mineral rich water. The process of decaying begins and as this happens, the organic matter from the living thing is replaced by a hard mineral called silica.
The minerals fill in the spaces and create a replacement, or replica, fossil of the living thing. Pure silica quartz crystals are colorless, but petrified rocks come in array of colors due to the presence of other elements, such as manganese, iron, and copper.
You will need the following for this science activity:
Here are the steps to make your petrified sponge:
The melted wax seeps into the holes in the sponge, filling up the spaces with liquid. As the wax cools it hardens and the sponge "petrifies," becoming hard as a rock.
In the same way, water rich with minerals seeps in the cracks and spaces found in dead organic matter, like trees. Over time it hardens, and the organic matter becomes a replacement fossil known as petrified rock.
Check out the following links to learn more about petrified rocks:
So now you know that petrified rocks are really replacement fossils! I trust that you and your students enjoyed making your own petrified sponge.
If you want to learn more about fossils, check out one of our earth science programs:
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