Mousterian Pluvial

The Mousterian Pluvial was an extended wet and rainy period in the climate history of North Africa. It occurred during the Upper Paleolithic era, beginning around 50,000 years before the present (B.P), lasting 20,000 years, and ending around 30,000 B.P.

During the Mousterian Pluvial, the now-desiccated regions of northern Africa were well-watered, bearing lakes, swamps, and river systems that no longer exist. What is now the Sahara desert supported typical African wildlife of grassland and woodland environments: herbivores from gazelle to giraffe to ostrich, predators from lion to jackal, even hippopotamus and crocodile, as well as extinct forms like the Pleistocene camel. In these respects the Mousterian Pluvial resembled the earlier Abbassia Pluvial; the later Neolithic Subpluvial was a weaker re-iteration of the same pattern.

The Mousterian Pluvial was caused by large-scale climatic changes during the last ice age. By 50 kybp (thousand years before present), the Wisconsin glaciation ("Würm glaciation" in Europe) was well-advanced; growing ice sheets in North America and Europe displaced the standard climatic zones of the northern hemisphere southward. The temperate zones of Europe and North America acquired an Arctic or tundra climate, and the rain bands typical of the temperate zones dropped to the latitudes of northern Africa.

Curiously, the same influences that created the Mousterian Pluvial also appear to have brought it to a close. In the period of its fullest development, c. 30 to 18 kybp, the Laurentide ice sheet not only covered an enormous geographic area, but increased its altitude to 1750 meters (more than 1 mile). It generated its own long term weather patterns, which affected the jet stream passing over the North American continent. The jet stream effectively split in two, creating a new dominant weather pattern over the northern hemisphere that brought harsher conditions to several regions (including parts of Central Asia and the Middle East) — changes that included an end to the Mousterian Pluvial and a return to a more arid climate in northern Africa.

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