What landform acts as a natural barrier between north africa and the rest of africa?

My first thought: The Sahara

Reason:

 It covers a large portion of Africa. It covers 10 countries, which happen to be in the north of Africa. These ten countries are: Tunisia, Niger, Libya, Algeria, Sudan, Mali, Mauritania, Egypt, Morocco and Chad, I believe.

Hopefully this helped and good luck.

P.S. Sahara means Desert in Arabic so when you say Sahara Desert you are saying Desert Desert. :)

i am a little confused myself with what goes with the letters and what goes with the numbers but ill do my best to you

the cordillera states and grand canyon are along the southwest u.s. and northern mexican pacific.

the great plains and southwest desert are also the prairie and home to many earthquakes too .

the coastal plains have poor soil and many factories started in the south.

is this what u needed? if not i can see what i can do