Alluvial Fan: A large, fan-shaped pile of sediment forming at the base of narrow canyons onto a flat plain at the foot of a mountain range. Alluvium: Unconsolidated gravel, sand, silt and clay deposited by streams. Anticline: An arched fold, usually in the shape of an inverted U. Arroyo: A dry desert gully. Bajada: A broad, sloping depositional deposit caused by the coalescing of alluvial fans. Biome: Defined as "the world's major communities, classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment" (Campbell). Blowout: A depression in the land surface caused by wind erosion. Butte: A narrow flat-topped hill of resistant rock with very steep sides. Probably formerly a mesa. Cactus: channels: The beds of streams or rivers, sometimes underground. Desert: Receiving less than 10 inches of precipitation annually. Desert Pavement: A thin, surface layer of closely packed pebbles. Desert Varnish: A hard, dark, shiny coating on rocks caused by chemical action. Detritus: Boulders, rocks, gravel, sand, soil that has eroded from mountains over time. Dunes: Mounds of loose sand grains shaped up by the wind. Ecosystem: Ergs(ERGZ): These are found in huge areas of shifting sand. Hammadas(hah-MAH-das): Areas of flat, raised land, also known as plateaus. Hogback: An eroded, steeply tilted ridge of resistant rocks with equal slopes on the sides. Hoodoo: A column or pillar of bizarre shape caused by differential erosion on rocks of different hardness.
Loess: A deposit of windblown sand and clay weakly cemented by calcite. Mesa: Broad, flat-topped hill rounded by cliffs and capped with a resistant rock layer. Playa: A very flat, dry lake bed of hard, mud-cracked clay. Paleozoic Era: 245 to 570 million years ago. Pangea: The super continent that broke apart 200 million years ago to form the present continents. Pediment: A gently sloping surface, usually covered with gravel, the result of erosion. Plate Tectonics: The theory that the earth's surface is divided into a few large, thick plates that are continually moving. Precambrian Era: Prior to the Paleozoic Era, 570 millions years ago. Regs(REGZ): Another type of landform. They are broad plains covered with sand and gravel. Semiarid: Receiving between 10 and 20 inches of precipitation annually. Syncline: An arched fold in the shape of a U. Triassic Period: 208 to 245 million years ago when large predatory reptiles (dinosaurs) evolved. wadis(WAH-dees): dried up riverbeds |