In the midst of the vast, vacant Sahara desert, just outside of Ouadane, Mauritania, lies a 30-mile wide geological oddity known the Richat Structure, or the “Eye of Africa.” From space, this natural curiosity forms a distinct and unmistakable bull’s-eye that once served as a geographical landmark for early astronauts as they passed over the Sahara.

Once thought to be a crater due to its circularity, the unusual formation is now widely believed to have been caused by the erosion of what was once a volcanic dome. Over time, desert weather has caused the volcano to gradually shed layers, resulting in the structure’s remarkable flatness.

More of the Richat Structure on Atlas Obscura

Ouadane or Wadan (وادان‎) is a small town in the desert of central Mauritania on the southern edge of the Adrar Plateau, about 100 km northeast of Chinguetti. The town was a staging post in the Trans-Saharan trade and for caravans transporting salt from the mines at Idjil. A Portuguese trading post was established in 1487, but was soon abandoned. The town declined from the 16th century and most of it now lies in ruins. The old town, a World Heritage Site, is still substantially intact, while a small modern settlement lies outside its gate. Ouadane is the closest town to the Richat Structure, a massive circular landmark visible from space. 

The Path of 40 Scholars, Oudane, Mauritania

Ouadane means “two valleys”. It is an ancient city on a caravan route through N. Africa about 800 years ago and was an Islamic educational center for the region. The two valleys are the “Valley of dates & valley of knowledge”.


Introducing the Richat Structure, more commonly known as the Eye of the Sahara.

This 40km-wide dome-like structure is situated in the western Sahara Desert, near the town of Ouadane, Mauritania. 

You would be forgiven for mistaking the Eye for an impact crater - the huge domed shape certainly fooled some early geologists studying it - but there is no evidence of shock metamorphism or extraterrestrial material that we associate with such events. So what’s going on?

The Eye of the Sahara is in fact a heavily eroded dome that happens to have some very cool geology in the form of clearly-defined and varied beds.

Around 100 million years ago, an anticlinal fold formed at the site (caused by a combination of tectonic forces and a large igneous intrusion rising from deep below the crust) forcing beds of igneous, metamorphic and sedimentary rock upwards into a very neat dome. 

Since then, the structure has been heavily eroded - but the different rock types eroded at different rates. Sedimentary sandstone and limestone beds are very easily eroded, but igneous and metamorphic bodies are generally more resistant. Layers of erosion-resistant metaquartzite and rhyolite have led to the formation of escarpments and small cliffs at various points in the Structure, as layers of metamorphic and volcanic rock meet sedimentary beds. The Eye of the Sahara is, then, just a particularly impressive looking eroded dome.

Bizarrely, the Eye’s ‘pupil’ is now home to a small hotel - you can spend the night sleeping in a hut at the centre of a very cool geological formation.


Click here for a panoramic view from the centre of the Eye:http://www.youtube.com/watch?v=rNfSXYnaYDM


To see our previous post on this, please go here: https://www.facebook.com/photo.php?fbid=375240989203618&set=pb.352857924775258.-2207520000.1350167490&type=1&theater

Image: http://farm1.staticflickr.com/23/29862421_ee94e16418_z.jpg?zz=1(Credit: Flickr user 'Viva NOLA’)