MountainsTinayguk River, Gates of the Arctic National Park and Preserve, AlaskaPhotograph by Michael Melford

HillsInishowen, IrelandPhotograph by Dave Johnston, YourShot

ButteThe “Lighthouse,” Palo Duro Canyon, TexasAn isolated hill with steep sides and a flat top, smaller than a mesa, formed by erosionPhotograph by Anthony Boyer, MyShot

Natural ArchDelicate Arch, Arches National Park, Moab, UtahFormed by erosion and weatheringPhotograph by Mlcreech

River, Canyon, PlateauOwyhee River, IdahoPhotograph by Michael Melford, National Geographic, aerial support from Lighthawk

BayouAdams Bayou, Orange, TexasA slow-moving body of water

Waterfall, Cliffs, IslandBaffin Island Waterfall, Nunavut, CanadaPhotograph by Paul Nicklen

GeyserCastle Geyser, Yellowstone National ParkA geyser is a natural hot spring that sometimes erupts with water or steam.Photograph by Brocken Inaglory

VolcanoesMount Semeru, JavaAn opening in the earth’s crust from which hot magma, volcanic ash, and gas erupt.Photograph by John Stanmeyer, National Geographic

Volcanic CraterSanta Ana Volcano, El SalvadorA circular depression caused by volcanic activity

CanyonGrand Canyon ValleyA canyon is a deep, narrow valley with steep sides,created by the movement of rivers, erosion and weathering. Photograph by Barry Tessman

Sand DunesSand dunes of Khongoryn Els, Gobi Gurvansaikhan National Park, Ömnögovi Province, MongoliaCrescent-shaped sand dunes are created by winds that blow continuously from one directionPhotograph by Doron

DesertTecopa, Mojave Desert, CaliforniaEvaporation of a flooded dry lake caused these cracks in the mud.Photograph by Lorenzo Manni, MyShot

PlainsSichuan, ChinaA plain is a broad area of flat land.Photograph by Xi Luo, MyShot