The deserts of western South America and the Namib Desert of southwest Africa are among
the driest deserts in the world. They remain so even though they are located by the
ocean and are surrounded in fog for part of each year. This fog is first formed over
the ocean when cold water currents saturate the air with moisture. Winds then carry the
fog over the desert, where it is eventually burned away under the sun. The deserts
remain so dry because a dome of high pressure always remains overhead, preventing the
formation of rain clouds.