According to the U.S. Geological Survey (USGS), deserts are dry desolate areas that are classified according to geographic location and dominant weather patterns. A region is defined as a desert either through its inability to hold moisture, or its lack of significant precipitation. Hostile toward humans as well as many types of animal and plant life, deserts cover approximately one fifth of the Earth's surface; yet, the various desert ecosystems are often remarkably dissimilar and are found everywhere from the lower latitudes to polar regions, and inland areas to coastal zones.
How Deserts Form
Deserts are created by various meteorological phenomena. According to an article published by New Mexico State University, those situated relatively close to the equator are often the result of high atmospheric pressure, which brings cold dry air down from the upper altitudes.The lack of atmospheric moisture causes wide temperature variations. Rain-shadow deserts lie between mountain ranges, which cut off moisture and precipitation before they can reach the affected area. Polar deserts experience very little precipitation because moisture is locked up in unusable blocks of ice.
Hot And Dry Deserts
Because of the lack of humidity, hot and dry deserts receive more than twice the amount of solar radiation as do the Earth's moist regions. Therefore, daytime temperatures range from warm during the winter to extremely hot in summer with daily maximums reaching upward to 49 degrees C (120 degrees F) Night temperatures sometimes drop to lows of -18 degrees C (0.4 degrees F). What little rainfall occurs usually comes in short cloudbursts; this while the rate of evaporation far exceeds the amount of rainfall. Vegetation types include short woody shrubs, stubby trees or cacti. Animal life includes burrowing nocturnal mammals, reptiles and birds. Africa's Sahara and North America's Sonoran deserts typify this classification.
Semiarid Types
Deserts of this variety are found in parts of Utah and Montana, but also are situated in higher latitude areas such as Newfoundland, Greenland and Russia. Summers are moderately long with daytime temperatures averaging from 21 to 27 degrees C. Nights are cool. There is very little rainfall, but as with hot and dry deserts, it is usually concentrated during the summer. Plant life, generally of the spiny variety, coexists with mammals such as jack rabbits and skunks, insects and various reptiles.
Coastal Deserts
Typical of this classification is the Atacama of Chile. These ecosystems are created by cold-water currents that parallel a coastline. Coastal deserts usually exist on a continent's west coast. During winter these places are often engulfed in a thick fog that blocks solar radiation. Summer daytime temperatures range from 21 to 25 degrees C. These regions are inhabited by various mammals such as coyotes, great horned owls and eagles, various amphibians and insects.
Polar Deserts
These extremely cold regions occupy nearly 5 million square kilometers of the Earth's surface and exist in Antarctica, Greenland and other parts of the Nearctic areas. Summertime high temperatures rarely exceed 10 degrees C and precipitation averages less than 250 mm annually. In Antarctica plant life exists only on the extreme coastal edges of the continent where lichens, mosses and algae are found. Some animals, such as penguins, have adapted to the harsh environment.
Tags: daytime temperatures, daytime temperatures range, degrees degrees, deserts usually, Earth surface, from degrees, little rainfall
