• Eye of the Sahara
Structure Richat or eye Sahara, as still call it, it is a geological formation with a circular relief in Moorish portion near the Sahara Desert ouadane settlement. Surrounded by thousands of square kilometers of totally lifeless and shapeless desert this part of the relief in the form of concentric circles with a diameter of 40-50 kilometers visible even from space.
For a long time it was believed that its appearance this amazing natural site is obliged fallen hundreds of years ago, a meteorite on the surface of the Earth. However, after a series of studies that theory had to admit anecdotal evidence, and to take its place came another - a full geological origin of the Sahara's eyes.
For a long time, ever since the first space missions, Rishat structure served as a landmark for astronauts in orbit, as among the vast expanse of unremarkable desert was our well-visible object.
Rishat structure is not followed by the fall of an ancient meteor as many thought and still think. These concentric circles in fact - alternating layers of sedimentary, metamorphic and igneous rocks, formed in a symmetrical anticlines exposed to erosion.
It is believed that the Eye of the Sahara was formed in the period between the Late Proterozoic (2, 5 billion years) and Ordovician (480 million years). The most ancient ring about 600 million years.
The original version of the origin as a result of a collision with a meteorite later changed version fully geological origin of these concentric circles.
In spite of the extensive field and laboratory studies that have been conducted, geoscientists failed to find evidence that would indicate that the impact of an extraterrestrial object.
Moreover, there is an annular structure Rishat depression that characterizes the place of a meteorite of this size. By meteorite impact sites of the Sahara eye is characterized also by the fact that the sedimentary rocks in it occur in normal, "unspoiled" and not the inverted form.
According to a recent study analytical breccia (rock consisting of cemented fragments of one or more rock) Richat structures rich in carbonate rocks silica was formed under the influence of the hydrothermal treatment, and the structure itself requires special protection and further studies of its origin.