1. In the Saharan summer the sun warms the sand, which warms the air near the surface.
2. This hot air rises and brings small particles of Saharan soil with it.
3. As the hot, dusty air rises it joins in with the strong prevailing easterly winds and blows across the Atlantic to South America and the Gulf of Mexico.
Saharan soil is full of iron and phosphorus. These minerals act as a fertilizer in the Amazon, replenishing the minerals that are often leached out of soils by the frequent rains. Think of it this way: when you have a big year in your garden you have to replenish the nutrients lost in the soil. The Amazon needs the same thing.