Viewed from above, the Eye of the Sahara looks like a massive impact crater located in the middle of the Sahara desert in Mauritania. This 50-kilometer (30-mile) diameter anomaly, consisting of a series of uniform waves, is actually entirely terrestrial.

This impressive ancient geological formation was used as a landmark by Gemini astronauts in the 1960s. Geologists initially thought that the Eye of the Sahara, or Risha Structure, was a massive impact crater. However, further studies of the sedimentary rocks forming the central dome revealed that the formation dates to the late Proterozoic, between 1 billion and 542 million years ago.

It is worth noting that some still believe that the structure is actually the ruins of the lost city of Atlantis, since its circular shape resembles the terrain described by Plato, but we will not cover this here.

It is believed that this structure was actually formed by a process called “folding”, forming what is known as a symmetrical anticline. Folding occurs when tectonic forces acting from both sides compress sedimentary rock; If the rock is cold and brittle it may split, but if it is hot enough it will fold. The upward folds are called anticlines, and the downward folds are called synclines.

However, in an article published in the Journal of African Earth Sciences in 2014, researchers put forward a completely different explanation for the formation of the Eye. The presence of volcanic rock is said to indicate that molten rock was pushed to the surface, causing a dome-like shape before forming into the rings we see today. The paper suggested that the break-up of the supercontinent Pangea may have played a role in these volcanic formations and tectonic shifts.

The structure consists of a mixture of sedimentary and igneous rocks. Erosion on the surface of the structure reveals fine-grained rhyolite and coarse-grained gabbro rocks that have undergone hydrothermal change. The rock types in the rings erode at different rates, creating colorful patterns on the surface. Large, sharp-edged pieces of sedimentary rock called megabreccia contribute to the swirling, colorful mounds that make up the formation.

At the center of the dome is a limestone-dolomite shelf consisting of kilometers of breccia, ring dykes, and alkaline volcanic rocks. The Oka’s complex geological structure has puzzled and intrigued geologists since its discovery, and it is still considered one of the most impressive geological features on Earth. Thus, it became one of the top 100 geological heritage sites recognized by the International Union of Geological Sciences (IUGS) in 2022.

Due to its enormous size, the Eye of the Sahara is best viewed from a great height (preferably from space), so we will have to rely on satellite images for now to enjoy all its beauty.