An international research team found 50 million tons of dust blow from Africa to the Amazon region annually, a much higher figure than the previously estimated 13 million tons, the American Committee for the Weizmann Institute of Science said in a news release. The new estimate matched calculations on the quantity of dust needed to supply minerals for the continued existence of the Amazon rainforest.

The Amazon rainforest depends on minerals washed off by rain from the soil in the Sahara Desert and blown across the Atlantic Ocean as dust, the institute said.

Researchers said the Bodele valley in Chad played an important role as a rainforest dust source because of its shape and geographic features. The valley is flanked by basalt mountain ridges, which create a cone-shaped crater with a narrow opening in the northeast, resulting in a wind tunnel of sorts, researchers said. As a result, gusts of surface wind lift the dust from the ground and blow it toward the ocean.