(a) Draw an outline map of Nigeria. On the map show and name: (i) the railway line from Lagos to Minna; (ii) one area each of limestone; coal; columbite; go...

(a) Outline map of Nigeria showing the railway line and mineral areas

The sketch map below shows the outline of Nigeria with (i) the western railway line running from Lagos northward through Abeokuta, Ibadan, Ilorin and Jebba to Minna, and (ii) one producing area each of limestone, coal, columbite and gold.

Key to the map:

• Railway (Lagos-Minna): the western trunk line, Lagos → Abeokuta → Ibadan → Ilorin → Jebba → Minna.
• Limestone: Ewekoro (near Abeokuta, in the south-west).
• Coal: Enugu (south-east).
• Columbite: the Jos Plateau (central Nigeria).
• Gold: Ilesha (south-west).

(b) Method of mining columbite in Nigeria

Columbite occurs on the Jos Plateau as loose grains mixed with tin ore in the alluvial gravels ("wash") of the stream valleys, and is worked mainly by the open-cast (surface) method. The main steps are:

1. Removal of the overburden: the soil and rock covering the mineral-bearing gravel are stripped off, at times loosened with dynamite and other explosives.
2. Digging the ore: the exposed gravel is dug out using mechanical shovels, draglines and pick-axes, and a dragline gathers the ore-bearing gravel into heaps.
3. Washing and concentration: powerful water jets from a monitor (hydraulic gun) are directed at the heaps to break them into a slurry, which is passed over sluice boxes and jigs; the heavy columbite and tin settle out while the lighter sand and mud are washed away.
4. Drying and transport: the concentrate is dried and loaded onto trucks that convey it to the factory for smelting, and it is then conveyed by rail to the port for export.

(c) Three adverse effects of mining on the Jos Plateau (columbite/tin area)

1. Loss of farmland and grazing land: stripping the overburden removes the topsoil and vegetation, leaving the land bare and infertile; farming and grazing land is destroyed and the agricultural labour force is reduced.
2. Derelict land, mining ponds and health hazards: abandoned open pits fill with stagnant water, breeding mosquitoes and drowning livestock and children; dust and poor conditions cause health problems such as asthma and lung and heart disorders.
3. Environmental degradation and pollution: loose spoil heaps are easily eroded, and silt and chemicals pollute streams and rivers, harming aquatic life and water supplies; whole settlements are displaced, sometimes leaving ghost towns behind.