DOUGLAS JEROLMACK received his PhD in Geophysics from MIT in 2006. He is currently Assistant Professor of Earth and Environmental Science at Penn. His research focuses on the formation of landscapes on Earth and other planets, due to the movement of sediment by water and wind. His work ranges from the study of sand ripples over time scales of minutes, to the formation of river deltas, to reconstructing the evolution of continental shelves over millions of years - work he has also extended to Mars. He combines experiments, mathematical modeling and field work to understand how nature builds patterns on planetary surfaces.