Physical The extreme north-east of the African continent shows topographical and structural transition from the relatively accidented and disturbed conditions of the Levant to a simpler and more uniform condition of the interior plateaux of Africa. The great tear-faults of the Red Sea system are, however, a reminder of the disturbed geological history. North-east Africa comprises the rifted edge of the main Gondwana Kraton, with crystalline basement rocks underlying most of the area, and occasionally outcropping. Within Egypt, which forms a convenient territorial delimita tion, four major sub-regions can be distinguished:
(1) the Sinai peninsula, (2) the eastern highlands of Egypt, (3) the Nile valley, (4) the western desert of Egypt,
and of these, the Nile valley is of overwhelming importance, since it contains over 95% of the total population of the region.