How do we make a scan of Earth's oceanic crust?

Like computed tomography (CT) scans used in medicine to look inside human bodies, marine seismologists conduct controlled-source experiments to understand the characteristics of the oceanic lithosphere (rigid outer Earth's layer) that covers > 70 % of the surface of our planet. While at sea aboard a research vessel, using the air compressed in an array of stainless-steel cylinders, we produce small earthquakes in the form of air bubbles that propagate through the water, Earth's crust, and mantle and return to be recorded by the instruments we place in the water column or on the seafloor. Although the technique was developed in the 1950s and has been extensively used by academia and industry for decades, it has remained obscured, primarily because it is conducted offshore, out of sight. To expose the less-known technique and to showcase associated career paths, we designed a hands-on model that encourages interaction. Together with the model, we present fundamental Earth processes and the methods we use to explore them, followed by video materials we recorded at sea while collecting the data. Furthermore, to quantitatively evaluate our effort, we constructed age-adapted control quizzes completed by the participants before and after the workshop. These quizzes were designed to assess the student's understanding of the concepts, providing a clear measure of the workshop's effectiveness. We have conducted the workshop package at several outreach events. Without any exception, the results of the quizzes show that students of ages 9–18 years improved their overall knowledge covered by the experiment. This result is a signal that supports the effectiveness of “learning by doing” science in a playful, interactive way.