We’ve been having some fun with a mini-geology unit lately. We didn’t dive in deep to any particular area, but tried to briefly touch upon several different areas of geology. A little sample of everything to hopefully spark some interest when COVID calms down a bit and we can go and learn hands-on!

Quite a lot of my activity inspiration came from the book Geology Rocks! We really enjoyed the Ancient Egypt counterpart of this book, and the Geology edition delivered too. We’ll certainly be looking for this series again in the future. We did about one activity every week, over the course of about six weeks.

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To kick off our unit I read The Street Beneath My Feet to the girls. This book is wonderful. It folds out to give a sensorial feeling of moving down into the core of the Earth and back to the surface, showing all the things you might find along the way. We also looked at a tray of items from around the house. The girls had to decide if the materials to a penny, a ceramic cup, a tin can, a plastic container, metal scissors, and a glass lightbulb came from the ground or somewhere else. (The raw materials are all from the ground.)

In our next activity we used crackers and chocolate hummus to demonstrate the movement of the tectonic plates. The Geology Rocks! book suggests peanut butter…but chocolate hummus is WAY tastier! We spread a thick layer of chocolate hummus on a piece of wax paper and placed two crackers, side-by-side, on top. Pushing on each cracker, we dragged them apart to create a gap between the crackers, demonstrating the ridges in the ocean where magma rises up to create new ocean floor. We then slid one cracker over the top of the other to show how one plate can slide under another plate, creating volcanic activity. Next we placed the two crackers side by side and slid them by each other, demonstrating sliding boundaries or transform faults of the plates and how earthquakes happen. Finally…we ate them up! We also read up on types of volcano and plate tectonics in Nat Geo’s Absolute Expert Rocks and Minerals book.

Our next demonstration also involved chocolate! We delved into learning about the three different types of rock with an experiment from The Geological Society. We grated dark, light, and white chocolate and divided the crumbs into three foil cups. To make sedimentary rock we folded the foil over and stood on it to crush the chocolate together. We floated the other cups on a pan of boiling water. We let one melt partially to make metamorphic rock, but the other wouldn’t melt all the way! I moved the foil cup onto my griddle where it burnt, but hey! Igneous chocolate! The metamorphic chocolate won in the taste test contest! We read Rocks: Hard, Soft, Smooth, and Rough.

Even though it’s January, we had a week of fabulous weather so we were able to take a day trip to the beach to see what rocks we could find. I took along a fantastic flow chart from Science Mom’s free Earth Science unit (page 80 of the PDF), and a jar of vinegar, which we needed to follow the flow chart. We had a fabulous day out, finding lots of sandstone and some granite!

Back at home, the girls wanted to do MORE experiments with rocks. I pulled out my one purchase for this unit, a National Geographic Rock, Mineral, and Fossil box with 200 samples. I pulled out quite a few different rock samples, rocks we had around the house, and a piece of chalk. This was all set up on a table in the kitchen for the girls to explore as they wished. I also created a printable to help them document their finds. Grab your copy here.


As the week went on, the girls wanted to experiment on some of their minerals, so I pulled some out of our rock box, and also posted a mineral identification flow chart from MinimeGeology. The DK Smithsonian Rock and Gem book was invaluable for more research all through these experiments. We also read Rhoda’s Rock Hunt.

The following week we were baking again! We took sugar cookie dough and shaped it into the three main types of volcano: cinder, strato, and shield. We made a little well in the top of each and added jam. The jam was supposed to bubble up and out of the volcano, but ours didn’t. However, they were still delicious! We used the DK website to see examples of each type of volcano and also read A Rock is Lovely.

Next we took a look at Erosion. We started with the book, Erosion, by Marcia Zappa and then set up four experiments to demonstrate the role of water in the erosion process. To demonstrate physical erosion we filled a glass bottle with water. After putting the bottle in a plastic bag and wrapping in paper towel, we put the bottle in the freezer. We also placed some marshmallows in the bottom of a glass, added a layer of clay on top and poked some holes to let water seep in.

To demonstrate chemical erosion we put a raw egg in a jar of vinegar. We also make up a solution by mixing hot water and epsom salts (as much as we could mix). We hung a string across two glasses so that the salt water would travel along the string and drip down from the middle leaving mineral deposits to form stalactites and stalagmites.

After a week, we returned to view our results. The glass bottle didn’t break, but the lid did pop off and we could quite clearly see that water expands as it freezes. We talked about how this expansion could create cracks in rock, or even break rocks apart. The marshmallows in our glass mostly dissolved and compressed. We decided that this modeled how the pressure and heat under the earths crust can make metamorphic rocks – though I think it’s probably more likely that it models the formation of sedimentary rocks!

In our jar of vinegar, the eggshell dissolved which modeled acid rain eating away at rock formations (it popped when we were shaking it out of the jar!). Finally, our stalactites and stalagmites were on their way to forming…we’ll be leaving them along another week or two to see what happens!

So, that’s our mini-unit. I hope you can find some inspiration for your own activities. If we’d had another week to spend on this we would also have talked about fossil formation, but we will be able to circle back to that in the future.