Contrary to initial impressions, the world’s deserts are not on the equator where the sun is the hottest. Deserts occur on two separate latitudes known as the tropic of Cancer and the tropic of Capricorn, 23° north and south of the equator. As the sun heats the equator, the rising hot currents pull large amounts of water vapor from the oceans. As these currents move over the tropics, they lose most of their moisture in heavy monsoon rains that create the world’s rainforests, while the remaining dry currents that reach the margins of the tropics create the world’s driest regions in a natural process called aridification. Once lush grasslands, Jordan’s dry deserts were formed by aridification around 5,500 years ago when a change in the Earth’s tilt moved the tropical rain belt southwards. Regular wobble in Earth’s rotational axis shifts the tropics and swings the Middle East between wet and dry once every 20,000 years.
Jordan is located at the margins of the Arabian Desert, just north of the tropic of Cancer.