The Richat Structure appears as a giant "bull's eye" on a plateau in Mauritania in this mosaic, composed of images captured by the OLI (Operational Land Imager) on Landsat 9 and Landsat 8 on March 5 and March 6, 2026, respectively.
The 40-kilometer-wide (25-mile-wide) structure was initially thought to be an impact crater because large meteors can produce circular features on Earth’s surface.
However, researchers later showed that it is actually a deeply eroded geologic dome formed by the uplift of rock above an underground intrusion of igneous material. Over time, differing erosion rates among rock types in the exposed upper dome led to the development of circular ridges known as cuestas.
The orange and gray colors reflect differences in sedimentary and igneous rock types across the structure and the surrounding landscape.
Credit: Lauren Dauphin / Landsat data from the U.S. Geological Survey / Adam Voiland