I've been getting a bit confused about the geology of the mountains and some of the information is in very technical language, so here's what I now understand to be the case in a perfect idiot's guide. (The idiot being me, not you, dear reader.)
The underlying rock of Africa was laid down in Pre-Cambrian times ie. 4500-550 million years This is the granite/quartzite base rock. In Cambrian times the area was a sea. This is also the period when most types of animals with hard parts started to evolve and life forms became much more diverse, known as the Cambrian Explosion and accounting for the fossils.
Then in the Jurassic period ( 200-145 million years ago) there was folding of the baserock uplifting the underlying earth's crust and in the Cretaceous period (145-65 million years ago) there was further crumping of the crust. This was caused by clashing of the techtonic plates of Gondawanaland, from which Africa evolved and Euramerica. This caused the base rock to extrude into the sedimentary rock covering it and produced the mountain ranges. The Atlas which seem to be later than the Anti-atlas were at one time higher than the Himalyas are now. Then erosion gets to work stripping off the softer sedimentary roks and leaving the columns of granite in a process similar to stack formation..The antiatlas was formed in the same plate clashes as the Appalachians so geologically speaking they are sort of cousins,
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