If there’s one thing my kids never get tired of learning about – it’s rocks. We had so much fun studying sedimentary rocks last week! I love how much joy can come from such a simple element of nature.
Here’s a rundown of our lesson on sedimentary rocks and the books and resources we used:
How Sedimentary Rocks Form
We began the lesson with this coloring page from The Rocks and Minerals Journal, which explains how erosion and weathering cause sediment to move, settle and eventually compact and form sedimentary rock. We followed this up with a hands-on experiment, which you can read more about below.
Investigating Rock Samples
Next came the boys’ favorite part – experimenting with their rock samples. For this, we used sedimentary rocks we’ve collected from nature hikes, as well as this rock kit, which contains five different sedimentary rock samples.
(Our sediment rock flash cards were also very useful for this part of the lesson.)
First, they performed a permeability test to see if their rock samples were permeable or impermeable. Using a pipette, they squeezed a drop of water onto each sample. Interestingly, almost all of their sedimentary samples were permeable (the water soaked in).
Next came the scratch test. For this, they used their fingernails, a carpentry nail and sandpaper to test the hardness of their samples. We discussed how many sedimentary rocks are soft, and some are even crumbly. A sandpaper block was an interesting way to see the color of each rock as it was scratched.
Finally, they performed the acid test. Since I obviously don’t let my kids play with real acid, we used vinegar – which isn’t strong enough to dissolve rocks, but it can provide a very satisfying fizz. The boys really loved dropping each sample into the vinegar and seeing which ones produced bubbles.
We discovered a possible fossil in our limestone sample, as one whitish area of the sample was producing a large amount of bubbles! (The calcium carbonate in the fossils make some sedimentary rocks fizz when they come in contact with the vinegar.)
Making a Sediment Jar
Of course, it wouldn’t be a proper science lesson without an experiment!
How to make a sediment jar:
You will need:
- A large glass or plastic jar with a lid
- A large handful of sand
- Large handful of gravel
- Large handful of pebbles or small rocks
- Water
Set your jar on a flat surface. Pour the sand into the bottom of the jar, followed by the gravel, then lastly pour in the small rocks. Fill the jar almost to the top with water. Screw the lid on as tightly as you can (secure it with duct tape if your lid isn’t tight).
Shake the jar well, then place back on to the surface. Observe what happens as the layers settle. You should see the lighter, finer sediments forming on the top layer – this is called the “fining up” sequence and is a geologic process of how sedimentary rocks form over time. You may also notice silt in the water, which will eventually settle.
This also led to a discussion of where sedimentary rocks typically form – in water!
More Sedimentary Rock Experiments
We didn’t have time to do additional experiments, but here are some that look fun to try:
Rock in a Cup: https://www.education.com/science-fair/article/making-a-rock-in-a-cup/
Sedimentary Rock Books
We used two books for this unit of study:
This one isn’t specific to sedimentary rocks, but it’s a great book about the different layers of rock below the Earth’s surface.
Sedimentary rocks form the middle and top layers of Grand Canyon. This was a great book for my older kiddo to learn about how this massive canyon was formed.
For a comprehensive study into all things rocks, check out my new Rocks + Minerals Journal!
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