The Jos Plateau tin

Three ages of rock stack up under this plateau. Only the middle one holds tin.

The Jos Plateau, formerly the Bauchi Plateau, sits near the centre of Nigeria and gave its name to Plateau State, which took its own from the state capital at Jos. It covers 8,600 square kilometres, is ringed for much of its boundary by escarpments of 300 to 600 metres, and averages 1,280 metres in altitude, making it the largest area above 1,000 metres in Nigeria. The high point is 1,776 metres in the Shere Hills. Several rivers rise here: the Kaduna runs southwest to the Niger, the Gongola east to the Benue, and the Hadejia and Yobe northeast into Lake Chad.

Three kinds of rock make the plateau. The older granites date to the late Cambrian and Ordovician. The younger granites were emplaced in the Jurassic and belong to a series that includes the Air Massif in the central Sahara. It is the younger granites that contain the tin, and it has been mined since the beginning of the 20th century, through the colonial period and after it. The British established Jos as a tin-mining metropolis at the start of that century, and the industry pulled workers and traders from both southern and northern Nigeria into a city that is diverse in culture and language because of it.

The third rock type is the youngest. Volcanoes and sheets of basalt have been extruded here since the Pliocene, and the Smithsonian's Global Volcanism Program catalogues the Jos Plateau as a volcanic field of domes, single vents and clusters of three or four cones aligned mainly northwest to southeast, in named groups at Gu, Kassa, Miango and Sura. Preliminary potassium-argon dating reported in 2013 gives an age range of 2.5 to 1.34 million years. No Holocene eruption is known here.

Height changes everything up here. The climate is tropical but cooler than the lowlands, running from 15.5 degrees Celsius in the coolest months to about 30 in the hottest, and Jos itself averages 1,411 mm of rain, nearly all of it between June and September. The montane grasslands, savannas and forests hold plants and animals distinct from anything in the surrounding lowlands, though most of the tree cover is gone and woodland now survives mainly on steep and inaccessible ground.