African Dust Takes Bermuda Vacation
Five-hundred thousand years worth of hurricanes and sea breezes weren't enough to brush the dust off Bermuda's shoulders. Over the ages, a thin red layer of soil built up over the island's gray limestone and lava rock base. Modern tourists enjoy the pink beaches the red soil created, but the origin of Bermuda's crimson cap of clay was lost to history.
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Geologists had suggested the volcanic bedrock of the island may have weathered into an iron-rich red clay or that the fine-grained soil of the Mississippi Valley may have sailed in on gusts off the prairie.
Bermuda's blood red clay actually seems to have made the trip across the Atlantic long before the Vikings. In 1996, the clay was shown to bear the physical and chemical signatures of African dust. Now, another study had confirmed that the red soil made the voyage from the Sahara, across the Atlantic on the trade winds and then settled on Bermuda. Both studies were published in the Journal of Geophysical Research.
Rocks and soils from different regions have tell-tale chemical compositions that reveal their geologic genealogy and tells scientists about the ancient conditions that put dust in the wind. The presence of African soil in Bermuda draws an ancient map of wind currents during the past half million years. During the Ice Ages the trade winds that blew from east to west across the Atlantic may have been stronger and gone further north. That enabled the winds to both fertilize the ocean with iron and give the Bahamas a scarlet cap.
Satellite image of Bermuda (NASA’s Landsat 7 satellite, Land Processes Distributed Active Archive Center)