Sahara’s dark granite towers make a green island of rock
Northern Niger’s Aïr Mountains rise more than 1,800 metres across some 84,000 square kilometres of Sahara. Unusual dark peralkaline granites punch through the sand, late-summer rains turn the massif greener than the deserts around it, more than 430 vascular plant species grow there, and rock art spans roughly seven thousand years.
The triangular massif sits inside the West Saharan montane xeric woodlands ecoregion, a rocky island amid the Ténéré dunes to the east. Geologically it spans Precambrian to Cenozoic rock: a plateau of ancient metamorphic surface studded with nine nearly circular granite massifs and flat-topped peaks that look almost black in the field—rare for granite.
Volcanic leftovers crowd the skyline: the extinct Arakao caldera, Cenozoic hawaiite-to-trachyte lava flows, cones, tuff rings, and one of Earth’s largest ring-dike systems. Marble scenery includes the Blue Mountains at Izouzaoenehe and white marble framing the lower Zagado Valley.
Although the lower plateau receives only 50 to 160 millimetres of rain a year, the massif, averaging 500 to 900 metres in altitude, stays greener than the desert around it, especially after the August–September rains, and its climate is classed as Sahel. Dry valleys known as koris funnel water into stone pools. More than 430 vascular plant species have been recorded, and because the Aïr is a southern extension of the Hoggar it bridges Saharan and Sahelian flora; tiny, isolated stands of a wild olive relative mark that plant's southern limit. Niger's highest point, Mont Idoukal-n-Taghès, reaches 2,022 metres.
Rock art made between roughly 6000 BCE and 1000 CE shows cattle and large mammals from a wetter era, then horses and chariots after desertification set in during the third millennium BC; the five-metre Dabous Giraffes carvings, found in 1999, are world-famous. Agadez is the region's capital, and Tuareg Kels have held the area since at least the twelfth century. Oases such as Timia trade their produce for salt hauled by camel caravans from Bilma and Fachi, and uranium in sandstones just west of the massif comes from its granites.
Source: Aïr Mountains
