521
It may seem that the sand dunes and rocky plateaus of the Sahara are as old as the world, but this is far from the truth. As a recent study has shown, this vast North African strip changes from arid desert to green forests at intervals of about 21 millennia.
The last time there were lush forests there was between 15,000 and 5,000 years ago.
According to Dr. Edward Armstrong, the cyclical transformation of the Sahara into savannahs and forests is one of the most remarkable phenomena in the planet’s environment. It is caused by changes in the Earth’s orbit around the Sun and the Earth’s wobble on its axis.
The cycle can also be influenced by distant ice sheets in the high latitudes of the Northern Hemisphere.
