There are many factors that contribute to the formation of deserts. Some of the most important factors include:

• Low precipitation: Deserts are defined as areas that receive less than 25 centimeters (10 inches) of rain per year. This is because the air that passes over deserts is dry, either because it has already rained elsewhere or because it has come from over land, where there is less moisture.
• High evaporation rates: Deserts also tend to have high evaporation rates, which means that the water that does fall as rain or snow quickly evaporates into the atmosphere. This is because the sun is very strong in deserts, and the air is dry.
• Rain shadow effect: The rain shadow effect is a phenomenon that occurs when mountains block the passage of moist air. This causes the air to rise and cool, and the moisture to condense and fall as rain or snow on the windward side of the mountains. The air that passes over the leeward side of the mountains is dry, and this can lead to the formation of a desert.
• Tropical high pressure systems: Tropical high pressure systems are areas of high pressure that occur near the equator. These systems are characterized by sinking air, which warms and dries. This can lead to the formation of deserts in the subtropical regions.
• Ocean currents: Ocean currents can also affect the formation of deserts. The cold Benguela current, for example, flows along the coast of Africa and brings cold water to the surface. This cold water cools the air above it, which can lead to the formation of a desert.

Deserts can be found on every continent, but they are most common in the subtropical regions between 30 and 35 degrees north and south of the equator. The largest desert in the world is the Sahara Desert, which covers much of North Africa. Other major deserts include the Arabian Desert, the Gobi Desert, and the Australian Desert.

Deserts are home to a variety of plants and animals that have adapted to the harsh conditions. Some of the most common desert plants include cacti, succulents, and grasses. Desert animals include snakes, lizards, rodents, and birds.

Deserts play an important role in the global climate system. They help to regulate the Earth’s temperature and moisture balance. They also store carbon dioxide, which helps to mitigate climate change.