A common negative effect of mining minerals from the earth’s surface is the destruction of its natural landscape, creating open space in the ground and generating heaps of rock wastes that cannot be easily disposed of. These phenomena are amply demonstrated in several parts of Nigeria, where commercial mining or quarrying had occurred in the past or is currently taking place. In the Younger Granite Province, especially the Jos Plateau, tin and columbite mining has resulted in the destruction in places of the scenic landscape which is replaced by unsightly large irregular holes and heaps of debris produced by the opencast method of mining.
The alteration of the landscape almost invariably creates a problem of erosion in the mining localities with the result that most of the opencast pits are filled with water. A similar situation exists in all the limestone and marble quarries in differing proportions at Ewekoro, Sagamu, Nkalagu, Gboko, Ashaka, Kalam-baina, Okpilla, Jakura, etc. In many localities, particularly near centres of heavy construction works (road and building), large granite and gneiss inselbergs with their delightful scenic view are now being pulled down to produce rock aggregates e.g. at Abuja, Abeokuta, Ibadan, Ilorin, Minna, Kaduna, Kano, Bauchi, etc.
More details on PROBLEMS OF EXPLORATIONS
In recent times, the search for gemstones in Oyo, Kwara, Edo and Ondo States by illegal miners have resulted in haphazard pitting and trenching of the Older Granites pegmatites that host the minerals, without regard to the mining regulations. At present, irregular holes and heaps of rock materials characterize the areas that have fallen victims of illegal miners.
Notable examples can be found at Ijero, Ekiti State; Igbojaiye, Olode, Falansa and New Target in Shaki area. Oyo State; Iwo, Osun State, and Oro in Kwara State. The natural land-scape in these areas is now replaced by a kind of bad land or hummock topography punctuated by irregular holes.
PROBLEMS OF EXPLORATIONS: GEOLOGICAL HAZARDS
Mining operations normally upset the equilibrium in the geological environment, which may trigger off certain geological hazards such as landslide, subsidence, flooding, erosion and tremors together with their secondary effects. Some cases of subsidence and instability associated with draining of oil and gas from the subsurface reservoir have been reported in the Niger Delta.
Similar subsidence has occurred in the Iva valley, Enugu area, as a result of coal mining. The subsidence led to diversion of water into the mines, which had to be pumped out at high cost. Minor earth tremors are generated due to blasting of rocks in various quarries.
Villages and settlements in the neighborhood of the quarries have experience unpleasant earth movements when the rocks are blasted. Some buildings are damaged by developing cracks due to minor tremors occasioned by the incessant blasting of the rocks.
PROBLEMS OF EXPLORATIONS: DEGRADATION OF NATURAL LANDSCAPE