Eric Grosfils between globes

Professor of Geology Eric Grosfils begins his GEOL129 Geophysics course each fall by having his students recall what they know about the interior of the Earth. What does the Earth’s structure look like? How do factors like velocity and density change with depth? Rather than answer these questions via lecture, Grosfils asks them to discover the answers from first principles, using data such as (a) how long it takes seismic energy to arrive at a point on Earth after a major earthquake and (b) the Earth’s own total mass and moment of inertia. To facilitate this inquiry, he used to have them experiment with online seismic wave and density modeling applets, but the applets are no longer functional. 

In order to preserve this valuable investigative experience for his students, Grosfils rebuilt the density exploration capability in Excel, then began working with ITS’ Academic Applications Manager Todd Shimoda on a way to reproduce the seismic wave applet in 2017. With the help of Pomona student Yijung Wang (’19), who had already created a MATLAB-based seismic modeling application that served as an excellent starting place, Shimoda built a fully functional seismic modeling application in the more stable MATLAB environment.

The application developed by Shimoda and Wang has now been successfully used in Grosfil’s GEOL 129 course for the past two fall semesters, providing a stable application for students to determine the structure of the Earth’s interior. By playing with variables such as the number of layers, their thicknesses, and their physical properties, students work interactively to match the knowledge they have about the travel of seismic energy with a model for the Earth’s interior. Once they have a realistic model, the process of inquiry doesn’t stop there. Grosfils then challenges students to break their model in order to consider if different structural models could explain their datasets equally well. According to Grosfils, “After having some fun exploring Jules Verne-like hollow Earth scenarios and other ideas, students conclude—in concert with the global geoscience community—our understanding of the Earth’s interior is quite robust, and satisfyingly it is something that they can deduce for themselves!”

Inspired by the success of the seismic wave application, Grosfils and Shimoda are currently collaborating on re-creating another Java-based applet used in Grosfils’ Physical Volcanology GEOL 131 course in MATLAB. This applet, which focuses on a real-life active volcano in Stromboli, Italy (which incidentally had a major eruption event this summer!) allows students to play with variables that affect the distance volcanic ‘bombs’ travel ballistically when erupted from the summit crater. With funding from a Hahn Teaching with Technology Grant, this project has also provided Pomona student Naomi Amuzie ’22 with the opportunity to develop MATLAB skills by assisting Shimoda in building the application this summer. The application is almost complete, and Grosfils hopes to be able to use it in his GEOL 131 course this spring.