https://phys.org/news/2019-01-sahara-swung-lush-conditions-years.html https://phys.org/news/2019-01-sahara-swung-lush-conditions-y... Every 20,000 years the de

https://phys.org/news/2019-01-sahara-swung-lush-conditions-years.html https://phys.org/news/2019-01-sahara-swung-lush-conditions-y... Every 20,000 years the desert becomes the rainforest. Seen this theory a few times, there are some cool animations on how the Desert essentially moves up and down Africa.