Wildestanimal/Alamy Fin whale songs, one of the loudest animal calls in the ocean, can be used to learn about the structure of Earth’s crust. Václav Kuna at the Institute of Geophysics of the Czech Academy of Sciences in Prague and his colleague John Nábĕlek at Oregon State University thought of the idea while they were recording seismic activity from earthquakes off the coast of Oregon. Advertisement “I was processing the data and found that there were some signals recorded which I didn’t recognise,” says Kuna. The mystery was solved when he realised the stations were recording songs produced by fin whales (