Descriptionary

Bedouin one of the groups of nomadic Arabs that roam the deserts of Syria and Arabia.

desert pavement a sand-free area of rocks and pebbles fitted together and highly polished by abra­sion, forming a colorful mosaic bed. Known as gib­ber plain in Australia, serir in Libya, and reg in the Sahara.

erg the vast area where sand accumulates in the Sahara, opposed to the sand-free areas of desert known as reg.

gypsum the white mineral making up many of the sand dunes at White Sands National Monument in New Mexico.

inselberg a vestigial mountain reduced by erosion to a rocky nubbin or isolated "island," found in the most ancient desert areas.

mesa an eroded mountain with a flattened top and sheer rock walls; a smaller version of a mesa is known as a butte.

mirage an optical illusion caused by the refraction of light, sometimes causing the illusion of water in the desert, which in reality is only a mirror image of a shimmering blue sky.

oasis an isolated fertile area in the desert, fed by groundwater or irrigation and surrounded by lush vegetation.

phantom rain rain that passes through hot, dry des­ert air and evaporates before hitting the ground.

playa a level plain that can become a temporary lake after a rain.

pyramid a pyramid-shaped dune.

rain shadow the leeward side of a mountain, where little or no rain falls.

seif a sand dune elongated in the prevailing wind direction, known to grow up to 300 feet high and 1,500 feet long. Also known as a sword or longitudi­nal dune.

star sand dune formed by winds from several dif­ferent directions, creating a stationary series of hum­mocks in the shape of a star.

steppe a semidesert plain devoid of trees.

transverse type of dunes characterized by ridges, giving the appearance of a series of ocean waves.

whaleback a giant sand dune that may stretch as far as 100 miles, sometimes seen in the Sahara.

desert vegetation

barrel cactus a succulent of the U.S. Southwest, known for its stout, branchless barrel shape.

century plant a succulent of the amaryllis family, flowering after about 25 years of growth but popu­larly thought to bloom after a century; tequila and mescal are derived from it.

cereus a night-blooming succulent that stores water in an underground container.

cholla a cactus with detachable joints that sticks to anything that brushes it, popularly known as a jump­ing cholla or teddybear cactus.

creosote bush shrub of the American Southwest whose name is derived from the acrid odor it gives off after a rain.

elephant tree tree found in Baja California, having a pulpy trunk serving as a water reservoir.

hedgehog cactus ground-hugging succulent produc­ing brilliant blooms and red fruit.

ironwood a desert tree known for its unusually hard wood.

Joshua tree a member of the yucca family that grows up to 25 feet high and may live for hundreds of years, commonly found in the Mojave.

mesquite a spiny tree yielding pods and particularly dense wood.

ocotillo barbed shrub with small leaves.

paloverde desert plant with minute leaves, whose stems and branches contain chlorophyll, allowing photosynthesis even after the leaves have dropped.

prickly pear cactus a cactus growing in clumps of spiny paddles.

sagebrush an aromatic shrub commonly found throughout the U.S. Southwest.

saguaro a giant cactus known to grow as tall as 50 feet.

earthquakes

aftershock an earthquake that follows a larger earthquake.

dendrochronology the study of forest trees' growth rings to determine the location of past earthquakes; the rings reveal when a tree has been partially toppled over—evidence of an earthquake.

earthquake lights mysterious flickering glow seen over the ground during an earthquake, thought to be a natural reaction of rocks when stressed to the breaking point.

earthquake storm a cluster of earthquakes, with each quake triggered by the movement of the previ­ous one.

epicenter the area directly above the center of an earthquake, where the largest vibrations are usually felt.

fault a fracture in rock strata or, on a larger scale, in the Earth's crust.

foreshock a small earthquake that precedes a larger one by several days or weeks.

liquefaction the shaking and churning of wet clay and sand into a dense liquid, as in severe earthquake activity.

Love waves earthquake waves causing side-to-side shaking, similar to the motion of a snake.

megathrust earthquake a massive earthquake gen­erated by shifting tectonic plates at subduction zones.