How landscapes are made, and what the model shows when you run them forward.
Why river valleys are V-shaped and glacial valleys are U-shaped, the physics behind each, and how to watch both at work in Yosemite and Milford Sound.
Where Erode Lab's rock map comes from, what "erodibility" means, and why the walls of the Grand Canyon climb in steps of cliff and slope.
How cirque glaciers bite into a mountain from several sides and leave arêtes and a pyramid peak, and what Erode Lab shows when you run the Alps forward.