Aorounga is an eroded meteorite impact crater in Chad, Africa. The exposed remnant of the crater is in diameter and its age is estimated to be less than 345 million years (Carboniferous or younger). Description An outer and an inner ring (11 and 7 km, respectively) rise about 100 m above the mean level of the surrounding plain (see topographic map). Both aforementioned rings are separated by a relatively flat depression of uniform width. A possible central hill, maybe an uplift structure, of 1.5 km is almost centrally located in the depression. The crater is accompanied by two nearby circular features revealed by Space Shuttle SIR-C radar. These may be related impact craters, and if correct, Aorounga may be part of a crater chain. On the assumption that this hypothesis is correct, the exposed Aorounga crater is sometimes referred to as Aorounga South. The central highland, or peak, of the crater is surrounded by a small sand-filled trough; this in turn is surrounded by a larger circular trough. Linear rock ridges alternating with light orange sand deposits cross the image from upper left to lower right; these are called yardangs by geomorphologists. Yardangs form by wind erosion of exposed rock layers in a unidirectional wind field. The wind blows from the north-east at Aorounga, and sand dunes formed between the yardangs are actively migrating to the south-west. See also List of impact craters in Africa Gweni-Fada crater References Further reading Becq-Giraudon, J. -F., Rouzeau, O., Goachet, E. and Solages,S., Meteoritic impact origin of the annular depression of Aorounga, Chad (Africa). C. R. Acad. Sci. Paris, t. 315, série II, p. 83-88. 1992 Koeberl, C., African meteorite impact craters: Characteristics and geological importance. Journal of African Earth Sciences, v. 18, pp. 263–295. 1994 Koeberl, C., Reimold, W. U. , Cooper, G. , Cowan, D. and Vincent, P. M., Aorounga and Gweni Fada impact structures, Chad: Remote sensing, petrography, and geochemistry of target rocks, Meteoritics & Planetary Science, 40, No 9/10 P. 1455 - 1471. 2005 Koeberl, C., Reimold, W.U., Vincent, P. M., Brandt,D., Aorounga and Gweni Fada Impact Structures, Chad, Central Afr.: Petrology and Geochemistry of Target Rocks, LPSC XXIX, Lunar and Planetary Institute, Houston, TX, (CD-ROM). 1998 McHone J.F., Greeley, R., More impact and impact-like structures on the SIR-C radar; Europe, Africa, and Arabian Peninsula (abstract). Lunar and Planetary Science XXVIII, pp. 915–916. 1997 Miallier, D., Sanzelle, S., Falgueres, C.,