Neolithic Subpluvial

The Neolithic Subpluvial, or the Holocene Wet Phase, was an extended period (from about 7500–7000 BCE to about 3500–3000 BCE) of wet and rainy conditions in the climate history of northern Africa. It was both preceded and followed by much drier periods.

The Neolithic Subpluvial was the most recent of a number of periods of "Wet Sahara" or "Green Sahara", during which the Sahara region was much more moist and supported a richer biota and human population than the present-day desert.

The Neolithic Subpluvial began during the 7th millennium BCE and was strong for about 2,000 years; it waned over time and ended after the 5.9 kiloyear event (3900 BCE). Then the drier conditions that prevailed prior to the Neolithic Subpluvial returned; desertification advanced, and the Sahara Desert formed (or re-formed). Arid conditions have continued through to the present day.

During the Neolithic Subpluvial, large areas of North, Central, and East Africa had hydrographic profiles significantly different from later norms. Existing lakes had surfaces tens of meters higher than today, sometimes with alternative drainages: Lake Turkana, in present-day Kenya, drained into the Nile River basin. Lake Chad reached a maximum extent of some 400,000 square kilometers in surface area, larger than the modern Caspian Sea, with a surface level about 30 meters (100 feet) higher than its twentieth-century average. Some shallower lakes and river systems existed in the subpluvial era that later disappeared entirely, and are detectable today only via radar and satellite imagery.

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