DiscoverScroll article

The Richat Structure, or Guelb er Richât (Arabic: قلب الريشات, romanized: Qalb ar-Rīšāt, Hassaniyya: ), often called the Eye of Africa is a prominent circular geological feature at the northwestern edge of the Taoudeni Basin, on the Adrar Plateau of the Sahara.

In Hassaniya Arabic, rīšāt means feathers and it is also known locally in Arabic as tagense, referring to the circular opening of the leather pouch that is used to draw water from local wells. It is an eroded geological dome, 40 kilometres (25 mi) in diameter, caused by a subsurface igneous intrusion deforming the overlying sedimentary rock layers, causing the rock to be exposed as concentric rings with the oldest layers exposed at the centre of the structure. Igneous rock is exposed inside and there are rhyolites and gabbros that have undergone hydrothermal alteration, and a central megabreccia. The structure is also the location of exceptional accumulations of Acheulean Paleolithic stone tools. It was selected as one of the 100 geological heritage sites identified by the International Union of Geological Sciences (IUGS) to be of the highest scientific value.

The Richat Structure is a deeply eroded, slightly elliptical dome with a diameter of 40 kilometres (25 mi). Its center consists of a siliceous breccia covering an area that is at least 30 kilometres (19 mi) in diameter.Exposed within the interior of the Richat Structure is a variety of intrusive and extrusive igneous rocks. The inner ring dike is about 30 metres (98 ft) in width, 3 kilometres (1.9 mi) from the center of the Richat Structure. These intrusive igneous rocks are interpreted as indicating the presence of a large alkaline igneous intrusion that currently underlies the structure and was created by uplifting the overlying rock. Spectacular hydrothermal features are a part of the Richat Structure.

A study of the formation of the structure by Matton, et al. (2005, 2008) concluded it was not an impact structure. Further analysis of deep structure underneath the surface, including with aeromagnetic and gravimetric mapping, concluded that the structure is the result of ring faults which led to gabbroic ring dikes over a large intrusive body of magma, and the uplifting and later erosion of a dome, through intense hydrothermal activity through the fractured substructure.

In respect of it being "a spectacular example of a magmatic concentric alkaline complex", the International Union of Geological Sciences (IUGS) included the Richat Structure in its assemblage of 100 geological heritage sites around the world, in October 2022.

The Richat Structure is the location of exceptional accumulations of Acheulean artifacts. However, since these sites were first discovered by Théodore Monod in 1974, mapping of artifacts within the area of the structure have found them to be generally absent in its innermost depressions. The Pleistocene to Middle Holocene sediments occur along wadis as the thin, meter- to less-than-meter-thick accumulations in the interior annular depressions to 3-to-4-metre-thick (9.8 to 13.1 ft) accumulations along the wadis in the outermost annular depression of the structure. In addition to Acheulean artifacts, the Richat Structure contains Middle Stone Age Aterian stone artifacts produced by modern humans, dating to the latest Middle Pleistocene to Late Pleistocene period, around 145,000-29,000 years ago. The protruding land dikes of the Richat Structure are lined with thousands of stone burial mounds in various styles.

The Richat Structure has been the subject of unsubstantiated fringe claims to be the site of Atlantis mentioned in the works of Plato. Rafferty, other than superficially matching Plato's Atlantis description in being circular, in its particular details, including being a geologically ancient natural structure, the Richat Structure bears little resemblance to Plato's description of Atlantis, with the Richat Structure's location far inland in a desert contradicting Plato's information regarding the location of Atlantis.

Bonnell (2002) Earth's Richat Structure, Astronomy Picture of the Day, October 28, 2002. Documentary film WHAT is the Richat Structure / The Eye of the Sahara

Quick Facts

• The structure is also the location of exceptional accumulations of Acheulean Paleolithic stone tools.
• The inner ring dike is about 30 metres (98 ft) in width, 3 kilometres (1.9 mi) from the center of the Richat Structure.
• Its center consists of a siliceous breccia covering an area that is at least 30 kilometres (19 mi) in diameter.Exposed within the interior of the Richat Structure is a variety of intrusive and extrusive igneous rocks.
• The Richat Structure is a deeply eroded, slightly elliptical dome with a diameter of 40 kilometres (25 mi).
• Spectacular hydrothermal features are a part of the Richat Structure.

Source material: Wikipedia - "Richat Structure". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.