Rice graduate student Kevin Gaastra is in the South Atlantic Ocean this week, working to process and inspect samples on the scientific drill ship JOIDES Resolution. Gaastra is part of JOIDES Expedition 391 to the Walvis Ridge, an unusual chain of underwater mountains more than 500 miles off the southwest African coast. Gaastra is looking for evidence that true polar wander — a shift in the whole Earth relative to its axis of rotation — occurred when Walvis Ridge was forming. His findings could have important implications for understanding mantle dynamics and changes in Earth's magnetic field over time.