Lake Chad high-water stand marked by Bama Ridge

Before the great dry period of 20,000 BCE, Lake Chad had been far more extensive and its level higher, probably around 40,000 BC. This high lake is marked by the Bama Ridge, on which Maiduguri stands; the ancient lake stood at a height of some 50 m above its present level and had an extent twelve times greater; at times it overflowed and drained down the Benue.