1. Deserts occupy approximately 9.5% of the Earth's total surface and one third of the land area (33%).
2. They occur in areas where very little moisture or precipitation (less than 254 milimeters/10 inches) is brought by the prevailing winds. In desert areas, the total amount of transpiration and evaporation exceeds that received from rainfall.
3. A - Polar deserts found in the Antarctic and Arctic
B - Subtropical/hot-and-dry deserts - the "typical" and most known type of desert. They are the hottest type with sandy or coarse and rocky soil.
C - Semiarid/Cold winter deserts - Somewhat cooler than B with long and dry summers as well as cold winters. Both rainfall and snowfall amount is low.
D - Coastal deserts - located on the west coasts of the continents, they are moderately warm to cool. Thus, they have cool winters and long warm summers. However, they receive more rain than type B.