As part of our earthquake unit, I had my Earth science classes try to build “earthquake” resistant structures out of toothpicks and masking tape. Different groups had different substrates to build in – dry sand, wet sand, or dough – to model the effects of different types of ground on building stability during earthquakes.
From my students’ perspective, I think this project was quite successful. The main idea that I wanted them to take away from it is that looser, less-stable ground magnifies the danger posed by earthquakes while buildings anchored to bedrock will be more likely to survive intact. They definitely got this point. They also got some practice overcoming practical building challenges, which I think is quite valuable.
As a teacher, I was forcefully reminded of the importance of details when setting up labs. I have two Earth science classes and they both did the activity, but with very different results. The first class got the results I expected – the structure built on loose, dry sand collapsed with moderate shaking, the structure built on more compact, wet sand was damaged with moderate shaking, but did not completely collapse, and the structure built on stiff, stable dough survived moderate shaking intact. In the second class, all of the structures survived moderate shaking and I had to resort to ridiculously violent shaking for the structures to experience damage. Why the difference? Well, it wasn’t because the second class built better structures. Nope. It was because I gave them too much substrate. It turns out that if the sand is deep enough, it holds onto the toothpicks quite tightly even when it is dry and therefore all of the students were effectively building on a stable substrate.
Setting up inquiry-based labs is an interesting exercise. On the one hand, students must always have choices and they must always be required to use their reasoning skills to figure things out. On the other hand, the set-up can’t be so loose that the point of the exercise is accidentally lost. There’s definitely an art to lab creation. Over the years, I’ve gotten much better at it (practice!) but there are never any guarantees. I think one of my strengths as a teacher is that when things go a little wonky, I’m willing to discuss it openly with students. Exploring the reasons for peculiar lab results is a good mental exercise for students and can often lead to valuable insights.