[8] Today the eastern Sahara is among the driest locations on Earth[3] as it is far removed from oceanic moisture sources.

[14] There is also evidence of shorelines at altitudes of 570–576 metres (1,870–1,890 ft) above sea level;[15] if they reflect the lake reaching that altitude, this stand would reach a surface of 30,750 square kilometres (11,870 sq mi) and a volume of 2,530 cubic kilometres (610 cu mi) at that stage.

[19] The lake floor in its southern and western sectors reaches 549 metres (1,801 ft) elevation above sea level.

River deltas formed where wadis entered Lake Ptolemy,[24] and alluvial fans have been identified on the northwestern shores.

[6] Today the oases of Oyo, Bidi and Nukheila are located on the lake-floor that Lake Ptolemy occupied at maximum highstand.

[28] The lake was nourished by runoff from the Ennedi, Erdi Ma and part of the Kufrah Depression, as well as groundwater;[2] at least one site of the lake floor shows evidence of the release of pressurized water[21] and evidence of higher groundwater levels is widespread in the eastern Sahara.

[38] At a water level of 550 metres (1,800 ft) Lake Ptolemy would have been connected with a paleodrainage system belonging to the Abyad Plateau.

[43] Reed vegetation formed on the southern and western shores of the lake,[24] and probably extended over its entire perimeter and sometimes into open water.

[45] Ostracods found in the lake include Candonopsis, Cyprideis, Cypridopsis, Cyprilla, Darwinula, Herpetocypris and Limnocytherae.

[36] About 10-18 fish species existed in Lake Ptolemy,[5][28] such as Clarias lazera, Lates niloticus and Synodontis.

[46] The south shore of Lake Ptolemy could have been inhabited by neolithic pastoralists,[47] while the swampy conditions at the northern margin rendered it presumably inhospitable.

[46] Radiocarbon dating of chalks in a wadi that entered the lake from the north has yielded ages for a highstand of 6,680 ± 135 and 6,810 ± 70 years before present.

[54] Dates obtained from fish fossils in the northern reaches are 2,360 ± 65 and 3,285 ± 70 years before present, during times where lake levels were less stable.

[56] Wadis flowing into the lake were transporting water as late as 3,300 – 2,900 and 3,300 – 2,400 years before present on the southern and northern side, respectively.

[46] Today wind-driven erosion is the dominant process in the area; the northeasterly trade winds have formed sand deposits including barchans on the southwestern side of the former lake.