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Big desertsEarth is a planet covered with habitable areas, but some of those locations are a little more hostile to life than others. In deserts, which generally are defined as areas that receive less than 10 inches (254 millimeters) of rain or snow annually, the plants and animals must subsist on this meager precipitation.
The world's 10 biggest deserts are found on just about every continent, many of them forming in the shadow of immense mountain ranges that block moisture from nearby oceans or bodies of water. They're often the site of unusual rock formations and, in some cases, amazing archaeological finds.
Chihuahuan DesertSlide 2 of 21
175,000 square miles (282,000 square km)
Straddling the U.S.-Mexico border, the Chihuahuan Desert is bigger than the state of California, according to New Mexico State University. Parts of it are in the states of Texas, New Mexico and Arizona. Less than 9 inches (228 mm) of rainfall falls on average every year, according to the Chihuahuan Desert Education Coalition.
As with many other deserts worldwide, the Chihuahuan Desert formed in the rain shadow of both the Sierre Madre Occidental (on the west) and the Sierra Madre Oriental (on the east), which both stop water from the Pacific Ocean and the Gulf of Mexico from getting inland.
Underneath the desert and New Mexico's Guadalupe Mountains lies more than 300 caves. Those in at least one of those regions, Carlsbad Caverns National Park, were created after sulfuric acid penetrated the surrounding limestone.Slide 3 of 21
Great Basin DesertSlide 4 of 21
Great Basin Desert
190,000 square miles (492,000 square km)
Unlike every other desert in the United States, the Great Basin is a "cold" desert — one where most of the precipitation falls as snow. Its geographic extent includes most of Nevada, part of Utah and parts of many surrounding states. Rainfall in the region ranges between 6 and 12 inches (150 and 300 mm) annually.
The desert came to be because it was in the rain shadow of the Sierra Nevada Mountains of eastern California, according to the National Park Service. The desert, in turn, also affects surrounding areas. Strong winds known as the Santa Ana often blow into Southern California after forming in areas of high pressure in the Great Basin.
The Great Basin is also home to some unusual rocks, such as some found in central Nevada in 2009 that were described as dripping like honey. The deformation is taking place due to changes in the Earth's mantle, which alters due to intense pressure and heat within Earth's surface. Heavier material in the lithosphere, as it warms up, sinks through the lighter mantle, trailing material after it.Slide 5 of 21
Syrian DesertSlide 6 of 21
200,000 square miles (518,000 square km)
The Syrian Desert is described as an "arid wasteland" by Merriam-Webster. Covering much of Iraq, Jordan, Saudi Arabia and Syria, the region is marked by lava flows and was an "impenetrable barrier" to humans until recent decades. Now, highways and oil pipelines cross the region, which receives less than 5 inches (125 mm) of rain annually, on average.
Humans were able to reach parts of it in ancient times, though. One area, now dubbed "Syria's Stonehenge," was discovered in 2009. It includes stone circles and possibly, tombs, according to a 2012 Discovery News report.
The Es Safa volcano field near Damascus is Arabia's largest volcanic field. The vents found in that area were active about 12,000 years ago, during the Holocene Epoch. More recently, a boiling lava lake was spotted in the region around 1850.Slide 7 of 21
Great Victoria DesertSlide 8 of 21