Air, Niger

Location: 17.67N, 8.75E
The Air Mountains make up one of the largest ring dike structures in the world. This Precambrian massif is famous for magmatic ring complexes 50 miles (80 km) in diameter. Ring-dikes, stocks and batholiths run 342 miles (550 km) from north to south. Some intrusions are over 19 miles (30 km) wide. Todra, the center of the massif, is surrounded by 100 basaltic strombolian cones and phreatomagmatic tuff rings. It is made of differentiated alkali lavas consisting of plugs and flows of hawaiite to trachyte.

The dark, roughly circular masses are Cenozoic lava flows on sandstones and schists. The crater at the lower left would appear to be of volcanic origin in view of its nearness to the lava flows. This area is capped by sandstone. The picture gives an excellent view of the general geology and structure of the uplift as a whole.

--Paul D. Lowman Jr.
PhD. NASA

Sources:
Dautria, J.M. and Girod, M., "Cenozoic volcanism associated with swells and rifts," Mantle Xenoliths, John Wiley & Sons Ltd., pp. 195-214, 1987.

Green, Jack and Short, Nicholas, "Volcanic Landforms and Surface Features," Springer-Verlag, New York, 519 pp., 1971.

Grove, A.T., "Geomorphology of the Tibesti Region with Special Reference to Western Tibesti," pp. 18-31.

"Earth Resource Surveys From Spacecraft," US Army Corps of Engineers, vol. 2, photo Gemini GB-58, p. E-50.



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