From the air, it appears as a vast bull’s eye in the middle of the Sahara desert.
For centuries, only a few local nomadic tribes knew about the formation. It was first photographed in the 1960s by the Gemini astronauts, who used it as a landmark to track the progress of their landing sequences. Later, the Landsat satellite took additional images and provided information about the size, height, and extent of the formation.
Geologists originally believed that Eye of the Sahara was an impact crater, created when an object from space slammed into the surface. However, lengthy studies of the rocks inside the structure show that its origins are entirely Earth-based.
The symmetrical geological marvel in the Adrar Plateau, a rocky, isolated region in Mauritania, is now known as the Richat Structure. It's a remarkable uplifted geologic dome that's 40 km in diameter and exposes concentric rings of rock created by erosion with a centre dome nearly 20 km wide. The formation contains rocks that are at least 100 million years old; some date back to well before the appearance of life on Earth.
Erosion has sculpted this structure, forming distinctive circular ridges known as cuestas and creating an extraordinary circular pattern with sedimentary and igneous rocks, says Geographical.
Millions of years ago, volcanic activity from deep beneath Earth's surface lifted the entire landscape around the Eye. These regions were not deserts, as they are today. Instead, they were likely much more temperate, with abundant flowing water. Layered sandstone rocks were deposited by blowing winds and on the bottoms of lakes and rivers during the temperate. The subsurface volcanic flow eventually pushed up the overlying layers of sandstone and other rocks, says ThoughtCo. After the volcanism died down, wind and water erosion began to eat away at the domed layers of rock. The region began to settle down and collapse in on itself, creating the roughly circular "eye" feature.
It's quite possible that, in the distant future, the Eye of the Sahara will be inundated with sand and dust. Future travellers may find only a windswept desert burying one of the most striking geological features on the planet.