|The entire area is the Air and Tenere Natural Reserve in Niger. The overlay image shows some solid circles cover up several Precambrian volcano craters. The weird thing is a huge " ring gap" cuts through the Air Mountains , just like a vestige of a cup presses into sand upside down. |
Geologists say that the 63km-length diameter ring is called " ring dike",also the biggest ring dike in the world, their concentric or radial geometric distribution around a centre of volcanic activity indicates their sub-volcanic origins.