The Nubian Swell is a geologic structural uplift in northern Africa that trends east-west and separates the lower Nile of Egypt from the Sudan basin. The Nubian Swell has been geologically active since early Mesozoic times, and portions are still active. The Nile traverses the uplift through geologic fractures and faults, and four of six cataracts of the Nile occur where the river crosses the uplift.