Erg Aoukar

Erg Aoukar lies in southeastern Mauritania between Kiffa and Néma, south of the Tagant Plateau. The depression is also known as Hodh or El Hodh. Its present surface consists of sand dunes and salt pans, enclosed on the northern and eastern sides by escarpments. The rocky arc continues through Dhar Néma, Dhar Walata, Dhar Tichitt and Dhar Tagant, linking the basin's dry floor to a broken rim of cliffs and uplands.

Before 4000 BCE, this was a country of considerable lakes. A vast endorheic lake covered the basin, left its reed beds in the sediment, and extended toward Tichit along the foot of the Tagant Plateau. After 1000 BCE the environment became increasingly dry. During the Tichitt Tradition, dated from about 2200 to 200 BCE, the basin remained an oasis region. Around 400 villages have been found below the cliffs that once faced the lake, where former shorelands preserve signs of a more favourable climate. The Aoukar's open dunes and salt flats then support very little settlement, although they remain one of the few refuges of the critically endangered addax. The contrast between the extinct lake and in that era's barren waste records the gradual southward retreat of the Sahara's humid margin.