The Sahara desert in Mauritania, Africa is one of the hottest places on Earth, with temperatures reaching up to 57.7 degrees Celsius. Despite the harsh, hot winds that sweep through the region, there is a mysterious place within the desert known as the "Eye of the Sahara."
The 'Eye Of The Sahara' – The Richat Structure
The Richat Structure, also known as the "Eye of the Sahara," is a geologic dome that contains rocks that date back to before the existence of life on Earth. Its circular shape, which resembles a blue bullseye, is located in Western Sahara. While its formation is still debated among geologists, many believe it began as the supercontinent Pangaea started to break apart.
Discovery Of The 'Eye Of The Sahara'
The Richat Structure, also known as the "Eye of the Sahara," was known for centuries only by a few local nomadic tribes. It was first captured on camera in the 1960s by Project Gemini astronauts, who used it as a marker for tracking their landing sequences. Later, the Landsat satellite provided more detailed images and information about the formation's size, height, and extent.
Initially, geologists thought that the "Eye of the Sahara" was an impact crater formed by an object from space hitting the Earth's surface. However, after studying the rocks within the structure, it has been determined that its origins are purely from within the Earth.
Structural Details Of The 'Eye Of The Sahara'
The Richat Structure, commonly known as the "Eye of the Sahara," is a highly symmetrical and slightly elliptical dome with a diameter of 25 miles. The sedimentary rocks found in the dome range in age from Late Proterozoic at the center to Ordovician sandstone on the edges. Erosion of the resistant layers of quartzite has formed high-relief circular cuestas. The structure's center is made up of a siliceous breccia that covers an area of at least 19 miles in diameter.
The Richat Structure, also known as the "Eye of the Sahara," has a variety of intrusive and extrusive igneous rocks exposed within its interior. These include rhyolitic volcanic rocks, gabbros, carbonatites and kimberlites. The rhyolitic rocks are made up of lava flows and hydrothermally altered tuffaceous rocks, which are part of two separate eruptive centers. These are believed to be the eroded remnants of two maars.
Field mapping and aeromagnetic data indicate that the gabbroic rocks within the Richat Structure, also known as the "Eye of the Sahara," form two concentric ring dikes. The inner ring dike is around 20 meters wide and is located about 3 kilometers from the center of the structure. The outer ring dike is about 50 meters wide and is situated between 7 to 8 kilometers from the center.
Within the Richat Structure, thirty-two carbonatite dikes and sills have been identified through mapping. These dikes are typically around 300 meters long and 1 to 4 meters wide, consisting of massive carbonatites that lack vesicles. These carbonatite rocks have been dated to have cooled between 94 and 104 million years ago.
Mystery Behind The Origin Of The 'Eye Of The Sahara'
The Richat Structure, also known as the "Eye of the Sahara," was first described in the 1930s and 1940s as the Richât Crater or Richât buttonhole. In 1948, Richard-Molard proposed it was caused by a laccolithic thrust. Its origins were later briefly considered as an impact structure, but closer study in the 1950s and 1960s revealed it was formed by terrestrial processes.
However, after extensive field and laboratory studies conducted in the late 1960s, no evidence of shock metamorphism or any type of deformation that would indicate a hypervelocity extraterrestrial impact has been found.
Initially, it was reported that coesite, a form of silicon dioxide that is considered an indicator of shock metamorphism, was present in rock samples collected from the Richat Structure. However, subsequent analysis of the rock samples revealed that barite had been mistaken for coesite.
Dating studies of the Richat Structure were conducted in the 1990s. More recent research by Matton et Al from 2005 to 2008 further confirmed that it is not an impact structure.
A 2011 study that used multiple analytical techniques on the Richat megabreccias found that the carbonates within the silica-rich megabreccias were formed by low-temperature hydrothermal waters. The study recommended that the structure should be protected and that further research should be conducted to determine its origin.
A Convincing Theory Of Origin Of The 'Eye Of The Sahara'
While the exact origins of the "Eye of the Sahara" (also known as the Richat Structure) are still not fully understood, two Canadian geologists have proposed a theory to explain its formation.
According to the Canadian geologists' theory, the formation of the "Eye of the Sahara" (also known as the Richat Structure) began more than 100 million years ago as the supercontinent Pangaea was breaking apart due to plate tectonics, causing Africa and South America to separate.
The Canadian geologists theorize that molten rock rose to the surface but did not fully reach it, forming a dome of rock layers, similar to a large pimple. This also caused the formation of fault lines that circle and cross the Eye. Furthermore, the molten rock dissolved limestone near the center of the Eye which eventually collapsed, forming a rock called breccia.
Approximately 100 million years ago, the Richat Structure had a violent eruption which caused the dome to partially collapse and erosion sculpted the structure into the Eye of the Sahara that we know today. The different ring patterns seen in the Eye are made of different types of rock that erode at different rates. The light-colored circle near the center of the Eye is made of volcanic rock created during that explosion.
The 'Eye Of The Sahara' – A Landmark From Space
Modern astronauts often use the Eye of the Sahara as a point of reference because it stands out in an otherwise unbroken sea of sand in the Sahara Desert. Visible from space, it serves as a distinctive landmark for them.
The 'Eye Of The Sahara' Is A Great Place To Visit
Although the Eye of the Sahara is located in Western Sahara, the region no longer has the same temperate conditions as it did during the formation of the feature. Visitors can still see the dry, sandy desert, but it is not a comfortable trip. To visit, one must obtain a Mauritanian visa and secure a local sponsor.
Visitors are advised to plan their travel in advance once they are able to gain access to the area. Some entrepreneurs offer aerial tours of the Eye, such as airplane rides or hot air balloon trips, for a unique vantage point. The Eye is situated near the town of Ouadane, which can be reached by car. Additionally, there is a hotel located within the Eye.