It has been 150 million years since South America and Africa were joined as a single continent, but even the ocean dividing them today can’t separate them completely from each other. This photo-like satellite image from June 1, 2010, shows their modern connection: Saharan dust ferried across the Atlantic on easterly winds.
The image has been stitched together from a series of images collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite during successive orbits. Terra orbits from pole to pole. It returns to the same latitude roughly every 90 minutes, progressing westward with each orbit. Thus, the right side of this image was captured before the left side; gray areas show gaps between satellite overpasses.
The long-distance connection between these two former neighbors may seem tenuous, but in fact, it’s tremendously important. Each year, mostly in the Northern Hemisphere winter, storms like the one pictured here deliver about 40 million tons of dust from the Sahara to the Amazon River Basin. The minerals in the dust replenish nutrients in rainforest soils, which are continually depleted by drenching, tropical rains. From more than 8,000 kilometers (5,000 miles) away, the barren Sahara nourishes the lush vegetation of the Amazon.
The dust plume approaches the northeast coast of South America in this image, and then it arcs northward, hinting at the seasonal shift in the trajectory of Saharan dust transport. As the seasons change, the primary path of dust storms shifts northward, reaching the Caribbean in the spring and the Southeast United States in the summer.