There are 2 basic processes: tectonics which builds the earth and surface processes which tear it back down again. Tectonics include volcanoes and earthquakes, and tectonic processes are responsible for plate motions, mountains and so forth. Surface processes include weathering, erosion, and the transportation of sediments, and are responsible for rounded hills, valleys, and places like Kansas.
A good local example in your area (Arizona) would be the Grand Canyon. …
