The fertile land of the Sahara with its many lakes and mountains seems reminiscent of Plato’s Island of Atlas:
As odd at this hill with ringed lakes around it is, there was a hill with concentric circular lakes around it in the homeland of the Imazighen at the time Plato described. This strange formation is called the Richat Structure, or the Eye of the Sahara today. This structure was originally suspected of being an asteroid impact crater due to its high degree of circularity, it is now argued to be a highly symmetrical and deeply eroded geologic dome.(2)R. Dietz (1969) “Richat and Semsiyat Domes (Mauritania): Not Astroblemes,” Geological Society of America, Volume 80, Number 7, Pages 1367-1372 This structure is a deeply eroded, generally circular, 40 km (25 miles) in diameter dome. Its center consists of a siliceous breccia covering an area that is at least 3 km (2 miles) in diameter.(3)G. Matton, et al. (2005) “Resolving the Richat enigma: Doming and hydrothermal karstification above an alkaline complex,” Geology, Volume 33, Number 8, Pages 665-668 According to field mapping and aeromagnetic data, the gabbroic rocks form two concentric ring dikes. The inner ring dike is about 20 m (65 feet) in width and lies about 3 km (2 miles) from the center of Richat Structure. The outer ring dike is about 50 m (165 feet) in width and lies about 7 to 8 km (4 to 5 miles) from the center of this structure. Thirty-two carbonatite dikes and sills have been mapped within the Richat Structure. The dikes are generally about 300 m (1,000 feet) long and typically 1 to 4 m (3 to 12 feet) wide. The Richat Structure lays in a depression running from the Taoudeni basin to the Atlantic Ocean, which during the Sahara’s wet periods would have been a wide channel carrying overflow from Haijad Paleolake down the Atlantic. This would explain the legendary sudden sinking of the islands, as a flood from Haijad Paleolake could have submerged the islands in mud in hours.
Similar eroded domes and craters in the Sahara often form into oasis in they receive enough rain, although most have been drying throughout history. Greek mytho-history include many references to the drying of lakes in the Sahara, the most famous of which was Lake Tritonis. Both Herodotus(4)Herodotus (circa 440 BC) Histories, Book 4, 179 around 2,450 years ago and Diodorus around 1,900 years ago described the lake; Herodotus giving it an area of 2,300 km². Herodotus assumed that there would have to be a large river flowing into it, which he called the Triton.(5)Edward Herbert Bunbury (1883) A History of Ancient Geography among the Greeks and Romans, Volume 1, Note S, Page 315 According to Herodotus Lake Tritonis contained two islands: the Island of Phla, which had been colonized by Greeks from Laconia, and the Island of Mene. The location of Lake Tritonis in both Herodotus and Diodorus writing is consistent with the Chott el Djerid, as was the description in Apollonius of Rhodes’ work circa 2,250 years ago, who wrote that the Argonauts had to portage their ship for 12 days to reach Lake Tritonis, and when they did they found the water salty and undrinkable.(6)Apollonius of Rhodes, (circa 250 BC) Argonautica, 4.1552. The Argonauts were later shown a shallow channel out to the sea by a local so they wouldn’t have portage back to the Mediterranean.
References [ + ]
|1.||⇑||Plato (circa 360 BC) Timaeus, 113c-113e|
|2.||⇑||R. Dietz (1969) “Richat and Semsiyat Domes (Mauritania): Not Astroblemes,” Geological Society of America, Volume 80, Number 7, Pages 1367-1372|
|3.||⇑||G. Matton, et al. (2005) “Resolving the Richat enigma: Doming and hydrothermal karstification above an alkaline complex,” Geology, Volume 33, Number 8, Pages 665-668|
|4.||⇑||Herodotus (circa 440 BC) Histories, Book 4, 179|
|5.||⇑||Edward Herbert Bunbury (1883) A History of Ancient Geography among the Greeks and Romans, Volume 1, Note S, Page 315|
|6.||⇑||Apollonius of Rhodes, (circa 250 BC) Argonautica, 4.1552.|