A narrated film that shows how running water has changed the surface of the earth more than any other natural element and offers as examples the Grand Canyon (and how it was formed) and Niagara Falls (and why it is moving upstream). The film continues with glaciers as another land-molding force, explaining where they were and how they work to change the landscape. A prime example is the Yosemite Valley formation including its Bridal Veil Falls, Upper and Lower Yosemite Falls, and other natural formations. The geysers, steam vents, and hot water basins at Yellowstone National Park are also featured, including a model showing how geysers function. Water also causes erosion resulting in natural bridges such as Natural Bridge in Virginia and the Kachina, Owachoma, and Sipapu Bridges, known collectively by the Paiute Indians as "ma-vah-talk-tump," or "under the horse's belly," in the Four Corners area of the U.S. The program continues with a filmed sequences of caves, explaining how the Mammouth Cave in Kentucky and Carlsbad Caverns in New Mexico were formed.