Drought can be defined as a long period with limited or no rainfall. While flash droughts last only a few weeks, some historical droughts have lasted many years.
Long-lasting droughts have had a profound effect on history. Understanding these historical floods can help prevent their devastating effects in the future.
African Megadrought
By studying sediment from Lake Malawi, one of the deepest freshwater lakes in the world, researchers believe that they have discovered that a megadrought drove people out of Africa about 110,000 years ago.
They collected soil by drilling a hole in the lake's bottom. The researchers theorized that regions going down with less carbon and less pollen in the soil represented times of drought because there would have been less vegetation.