The Eye of the Sahara, also called the Richat Structure, is a vast circular geological feature located deep in the desert of Mauritania, not far from the Canary Islands. It spans more than 50 kilometers in diameter and is believed to have formed through erosion and uplift, creating a dome that was subsequently worn down by natural forces.
At first glance it can resemble an impact crater created by a meteor strike, but it is better described as a large eroded structure. The formation results from folds in the rock layers exposed by geological processes and erosion, known as a symmetrical anticline.
It stands as one of the most striking geological formations on Earth. A Google Earth view helps illustrate its dimensions and layout in three dimensions.
It is an incredibly scenic site to observe, both from ground level and from aerial perspectives. Geologists have studied it extensively to understand the processes that produced this phenomenon.
The Eye of the Sahara lies in a remote, secluded area of the desert where fieldwork is challenging. As a result, the feature has not drawn widespread attention until recently. Some astronauts observing from space noted its striking silhouette, helping it become one of the planet’s most famous natural curiosities.
How was the Eye of the Sahara formed?
The structure likely originated through folding, creating a symmetrical anticline. Folding occurs when tectonic forces from opposite sides compress sedimentary rock. Rock that is cold and brittle may crack, while rock that is warm and malleable can bend. Upward folds are called anticlines, and downward folds are called synclines.
In a 2014 article in the African Journal of Earth Sciences, researchers proposed a alternative explanation for the Eye of the Sahara. The authors suggest the presence of volcanic rock as evidence that molten material was thrust toward the surface before erosion sculpted the rings, forming a dome. The article also notes that the breakup of the supercontinent Pangea may have influenced these volcanic and tectonic processes.
The site comprises a mix of sedimentary and igneous rocks. Erosion along the structure exposes hydrothermally altered fine rhyolite and coarser gabbro. The varied resistance of the rocks creates the distinct color patterns seen on the surface, with large megabreccias adding to the swirling, irregular look of the rings.
It has been recognized as one of the IUGS top 100 geological heritage sites, highlighting its global significance in earth science.
Reference work: Rettling the Richat enigma. Domining and colleagues provide a detailed discussion in Geology Journal.
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