Deserts Described
A desert is a landscape or region that receives very little precipitation. Deserts can be defined as areas that
receive an average annual precipitation of less than 250 mm (10 in), or as areas in which more water is lost
than falls as precipitation.
Deserts take up about one third of the Earth's land surface. They usually have a large diurnal and seasonal
temperature range, with high daytime temperatures, and low nighttime temperatures (due to extremely low humidity).
The temperature in the daytime can reach 45 C/113 F or higher in the summer, and dip to 0 C/32 F or lower in the
winter. Water acts to trap infrared radiation from both the sun and the ground, and dry desert air is incapable of
blocking sunlight during the day or trapping heat during the night. Thus, during daylight most of the sun's heat
reaches the ground, and as soon as the sun sets the desert cools quickly by radiating its heat into space.
The largest hot desert is the Sahara and the largest cold desert is Antarctica.
Deserts sometimes contain valuable mineral deposits that were formed in the arid environment or that were exposed
by erosion. Due to extreme and consistent dryness, some deserts are ideal places for natural preservation of
artifacts and fossils.
Atacama (pictured above) is the driest place on Earth and is virtually sterile because it is blocked from moisture on both sides by
the Andes mountains and by the Chilean Coast Range. The cold Humboldt Current and the anticyclone of the Pacific are
essential to keep the dry climate of the Atacama. The average rainfall in the Chilean region of Antofagasta is
just 1 mm per year. Some weather stations in the Atacama have never received rain.
Below is an example of some of the types of animals you could find in a desert. Try and spot all of them.
Below is a typical food chain for the types of animals you could find in a desert. From the predators on top all the way down to the producers on the bottom.
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