The Web of Life (18-7) The Sahara Desert

 The Sahara Desert

North Africa is pumping dust everywhere, all year long. ~ American meteorologist Joseph Prospero

The Sahara Desert covers most of north Africa. It is the largest subtropical desert, and the 3rd-largest desert in the world, after Antarctica and the Arctic.

The desertification of northern Africa began ~7 million years ago, an outcome of tectonic plate movements. The African plate moved north relative to the Eurasian plate, prompting a shift in weather patterns. At the same time, the Arabian Peninsula uplifted, replacing a broad swath of ocean off northeastern Africa, thereby weakening the African summer monsoon. When the westerly winds waned, the flow of moisture from the tropical Atlantic Ocean that had swept north Africa shifted south.

The Tethys Sea, the predecessor of today’s Mediterranean, gradually shrank. North Africa parched. Once semi-arid, north Africa collapsed into desert.

4,600 years ago, dust from the Sahara Desert fertilized the nutrient-poor wetlands of south Florida. Water lilies and other aquatic flowers dotted the grass carpets of the Everglades. An abrupt shift in winds 2,800 years ago downsized the dusting. The drop in nutrient flow ushered in the sawgrass-dominated ecosystem that characterizes the Everglades today.