My kids wanted to study volcanoes. I was totally uninspired by volcanoes, but I thought I’d run with it, perhaps expanding the study to include plate tectonics and the rock cycle so we’d have a bit more to talk about. While I was searching for inspiration, I ran across the idea of having a cake to show Earth’s layers. “Great!” thought I. “Sign me up and show me how!” (I’m a sucker for anything edible–particularly if it’s sweet!) Unfortunately, everyone doing this project seemed to have round bakeware–cake pop molds of varying sizes, round-bottomed oven-safe mixing bowls. Not I. And, since I am disinclined to shell out that kind of money for the props to make one cool snack, I thought I’d look for my own way.
My creation doesn’t have perfectly-nested spheres (in fact, the outer core seems to spike into the mantle in a couple of places!), but it definitely has the layers, and–most important of all–it got the point across and thrilled my kids. In case you want to try it, here’s what I did:
Supplies: White or yellow cake mix/recipe, chocolate frosting, white frosting, food coloring, multiple bowls for separating/mixing colors, two 8″ or 9″ round cake pans, large spoons, two cookie cutters (round is ideal–I didn’t have round), cake decorating set
1. I used a generic white cake mix (yellow would be fine, too–I use the yolks, so mine isn’t truly white). After mixing the ingredients, I separated the mix into three bowls: a small one that I colored yellow, a medium one that I colored orange, and a large one that I colored reddish. Make sure the mix is pretty colorful, since the color will be less concentrated once the cake poofs up during baking. (Too much food coloring tastes bitter, though, so don’t go overboard.)
2. First, I placed a cookie cutter in the center of each pan. The first one I filled with a dollop of yellow (inner core). I spooned pink (mantle) around the edges of that pan and filled the space between with orange (outer core). In the second pan, I filled the cookie cutter with orange (outer core–to cover the inner core from the first pan) and poured pink (mantle) all around it, reserving a small amount of the pink for the next step.
3. Then I removed the cookie cutters, covered the dollop of outer core in the second pan with a layer of mantle, and popped both pans in the oven. (The first pan–with all three layers–had less batter, but both seemed to cook fine.)
4. When the cake was out of the oven and cool, I used a small amount of runny white frosting (I warmed mine to make it thinner) to glue the layers together. The three-colored layer went on the bottom, capped by the layer that’s mostly mantle. Make sure the little bit of outer core is on the bottom of the top layer–you wouldn’t want to have your mantle and outer core reversed! Next, I used a very thin layer of chocolate frosting to represent the lithosphere.
5. This gray represented the solid rock of the crust. I wanted to make it clear that even the oceans have crust beneath them. Yes, I know the crust is included in the lithosphere, but the Red Cross/PBS material (more on that later) we’re using talks of them separately, so I just followed their lead. I used really runny frosting so I could make a very thin layer. (After all, this is already the second frosting layer, and I still had more to go!) The generic brand frosting I use wins for runniness! My gray, FYI, is made from a red/green mixture. If I remember right, it was two red drops and three green.
6. Time to add the thicker continental crust parts and fill the oceans! This time I thickened the frosting slightly with about a cup of confectioner’s sugar to the tub. I wanted it just stiff enough to hold some texture, but still soft enough to spread in a thin layer. Since we’re also studying the Middle Ages right now, I decided to do a rough map of Europe. (Very rough.) I rarely use the frosting tips as intended; I used the star tip loosely for a textured water look, but for the land I just did a rough outline with a tip and then spread the green around with my knife.)
The finished product! Of course, you can’t really tell how many layers of frosting went into this (except when eating it!), but if the kids watch or help, they’ll get every detail of the process. And the finished result was enough to spark their glee, so I’d consider this one a win!