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.


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.


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