A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than 400 millimeters. A common definition distinguishes between true deserts, which receive less than 250 millimeters of average annual precipitation, and semi deserts or steppes, which receive between 250 millimeters and 400 to 500 millimeters.Deserts are sometimes classified as hot and cold deserts.Cold deserts can be covered in snow or ice; frozen water unavailable to plant life. These are more commonly referred to as tundra if a short season of above-freezing temperatures is experienced, or as an ice cap if the temperature remains below freezing year-round, rendering the land almost completely lifeless.Deserts take up about one third of the Earth's land surface. Hot deserts usually have a large diurnal and seasonal temperature range, with high daytime temperatures, and low nighttime temperatures (due to extremely low humidity). In hot deserts 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 at nighttime in the winter. Water vapor in the atmosphere acts to trap long wave infrared radiation from the ground, and dry desert air is incapable of blocking sunlight during the day (due to absence of clouds) 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. Urban areas in deserts lack large daily temperature variations, partially due to the urban heat island effect. The exact location of the Sahara desert is 19 degrees north and 18 degrees east. The Tibesti mountains is a range of inactive volcanoes. It is 18 degrees north and 19 degrees east. Camels store water in the bumps on the back so when they go on long trips they have some water. Fig trees start to grow on other plants and then they grow long roots that steals the sunlight and kills the other plant. Then they start to grow into the dirt. The coyote can easily adapt to surroundings and they eat a wide verity of foods so nothing over grows in the desert.