What Is A Desert?

    Published: 06-16-2009
    Views: 12,471
    Science expert Emerald Robinson explains what a desert is and how it forms.

    Emerald Robinson: Hi, I'm Emerald Robinson, and in this What Is video we'll examine earth's most barren biome, deserts.

    Most of us recognize that a desert is an area of land that is very dry. Many deserts receive less than ten inches of rain per year. The true definition of a desert, though, is a place where more water moves from the land to the atmosphere than falls to the ground as precipitation.

    Most deserts don't have much humidity in the air to serve as insulation. As a result, deserts often undergo extreme temperature changes, sometimes experiencing daylight temperatures of over a hundred degrees Fahrenheit, then plunging to subzero temperatures at night.

    All desert plants and animals have adaptations that help them survive these harsh conditions. Many desert plants have grey or silver leaves that help to reflect sunlight. These leaves are often covered with a waxy substance that helps keep moisture in, and are dotted with prickles or spines that discourage thirsty animals from eating them. Desert animals often adapt by exhibiting special behaviors such as burrowing deep beneath the ground to stay cool, only emerging at night. But some have physical adaptations too, features like thick hides to hold water in and large ears to radiate excess body heat away.

    Though we usually think of deserts as very hot, and dry, like Africa's Sahara Desert, this connotation represents only one of the several types. Deserts can be semiarid, experiencing only slightly more rainfall than is lost by evaporation, like the sagebrush landscapes in Utah.

    Deserts can be cold, like the continent of Antarctica. Cold deserts can be covered by snow and ice, but are still considered to be deserts because the water is not available to support life.

    Some deserts are even Coastal. Chile's Atacama Desert is the earth's driest, with less than a millimeter of precipitation falling each year.