In earth science, after our initial tour of the earth’s formation and composition and its violent tectonic forces, Alex has started studying minerals. Today we did a great activity to understand how mineral deposits are laid down in the earth’s crust.
We started with a general overview of what minerals are made of and where they come from – we’ll study the rock cycle in more detail in the next chapter. Then we did an activity to understand how layers of rocks and minerals can shift away from the orderly strata we sometimes see at a roadside.
We piled up multiple rock layers. From oldest to youngest, we had wheat bread, peanut butter studded with Rice Krispies, raisin bread, jelly, and an English muffin half. Alex carefully drew a picture of the flat and orderly layers.
Then we started applying transformations. She bent the stacked sandwich up into an arch, which is known as an anticline, and we imagined that formation either poking up as a mountain or having the edges around it filled in by other materials. What would a geologist see, digging down? We bent it down into a trough, or syncline. Finally, we cut a fault and experimented with the different things that could happen there. The two sides could shift sideways, or one could go up while the other went down. One could slide over the edge of the other to give us an area with doubled layers. Finally, we imagined one tilting up so that the cut edge was at the surface and the previously horizontal bands of rock were now nearly vertical.
Alex did a very careful and thoughtful job of drawing the various transformations and trying to understand what they would be like. I took notes from her dictation. This was a really useful lesson; I have to admit, however, that neither one of us wanted to eat the sandwich after it had been through all of those geological processes.