What major landform has kept North African civilizations tied to the North African coast?

The Sahara Desert has kept North African civilizations tied to the North African coast.

Explanation:

Northern Africa is a region that is among the driest in the world. The resources of freshwater are very few, and when it comes to large resources of freshwater there is actually only one, the Nile River, with the other ones being much smaller. On top of it, the vast majority of the region is dominated by the very and very dry Sahara Desert.

Since ancient times, the civilizations in Northern Africa have been tied to the coast, or along the Nile River. This is the case because the coastal area has better climate conditions and very good connections with the other Mediterranean civilizations, while the Nile River is the only major source of freshwater and fertile land. The interior is very harsh, covered with sand and rocks, with temperatures being among the highest in the world, and little to no resources on the surface that would enable humans to live and prosper there.

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the answer is blue river