SHRINK-SWELL CLAYS IN SOILS: A SIMPLE WAY TO GET MIDDLE SCHOOL STUDENTS INTERESTED IN GEOSCIENCES

Shrink-swell clays can be a nuisance as millions of homeowners with cracked basements, foundations, and driveways can attest. Unfortunately, what the clay fraction of soils does as it cycles between dry and wet is not as interesting to the general public as to geoscientists. But what if you could see it from space? That was the question we were left with after we looked at satellite data regarding surface displacement as part of an investigation into earthquakes impacting the Wichita area. What we found was data indicating an uplift of the surface of a few centimeters in the spring/early summer, with a subsequent down drop in late summer/fall over the last four years. As we worked out what to do next, we realized that we had an opportunity to involve one of our favorite groups to work with – middle schoolers.

In Fall 2021 we contacted the Public Works/Parks Departments of the cities of Wichita, Andover, Derby, and Goddard requesting permission to collect soil cores at city parks. Next, we reached out to middle school teachers in the school districts in each of those cities to set up an educational research collaboration. As part of this collaboration, we visited students in each of the participating schools to tell them about clays, why they shrink and swell, why it’s important, and why we were asking them to do this work. Each classroom was given multiple soil cores, still in the plastic liners, with a simple set of instructions: add water and see if the soils swell, then dry them out and see if they shrink. We ran duplicate experiments in the lab with the goal of comparing results to each of the schools in the winter.

We tried to be sensitive to the educational demands placed on middle school teachers, so we provided a simple methodology for adding water to the soils. The soils collected had differing clay contents and displayed varying amount of shrink-swelling capability and most classrooms reported seeing swelling and shrinking as they wetted and dried the soils. Slight variations in methodology, particularly what counted as saturated, caused some discrepancies between samples. However, teachers reported students enjoyed themselves throughout the duration of the experiments. More importantly it proved to be a simple yet effective way to engage middle school students and have them participate in an experiment in the geosciences.