My daughter is a geologist. Degree in HydroGeology. She said that the Sahara Desert used to be ocean bottom. I think the earth is a dynamic creation, always changing. Volcanoes, hurricanes, earthquakes, continental plate shift, etc.
Yea, most of us learned that in the 3rd grade.
'Cause the desert had turned to sea
There were plants and birds and rocks and things
there was sand and hills and rings
The ocean is a desert with it's life underground
And a perfect disguise above
Under the cities lies a heart made of ground
But the humans will give no love
i've always liked this song... A Horse With No Name...