Let's talk about deserts! Almost one third of all of the land surface on the planet is arid or semi-arid, in other words, a desert!
How are deserts formed?
Desert
A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation. About one-third of the land surface of the world is arid or semi-arid. This includes much of the polar regions where little precipitation occurs and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by
Aridisol
Aridisols (or desert soils) are a soil order in USDA soil taxonomy. Aridisols (from the Latin "aridus", for "dry", and "solum") form in an arid or semi-arid climate. Aridisols dominate the deserts and xeric shrublands, which occupy about one third of the Earth's land surface. Aridisols have a very low concentration of organic matter, reflecting the paucity of vegetative production on these dry soils. 
Water deficiency is the major defining characteristic of Aridisols. Also required