WAEC SSCE - Geography - 1997 (Essay)

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(a) Examples of industries in Tropical Africa

• Local crafts (two): hand-weaving of cloth (aso-oke, kente) and leatherwork; also pottery, wood-carving, blacksmithing and cane/basket weaving.
• Manufacturing industries (two): textile mills and cement manufacture; also food and beverage processing, brewing and vehicle assembly.

(b) Five factors that affect the location of manufacturing industries in Tropical Africa

1. Raw materials: industries that use bulky or perishable materials (cement, food processing) are sited near their source.
2. Power/energy supply: industries locate where electricity (e.g. from hydro dams) or fuel is available and reliable.
3. Transport: good roads, railways and ports attract industry by easing the movement of materials and finished goods.
4. Market: firms settle in or near large towns where there is a big population to buy the products.
5. Labour and capital: availability of cheap or skilled workers and of investment funds influences where factories are built. (Also water supply and government policy.)

(c) Three problems facing manufacturing industry in the sub-region

1. Shortage of capital and skilled labour, which limits the setting up and running of modern factories.
2. Inadequate and unreliable power and infrastructure, raising costs and interrupting production.
3. Small local market and low purchasing power, plus competition from imported goods, which restrict the growth of local manufacturing. (Also dependence on imported machinery and raw materials.)

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(a) Four factors that can influence the climate of a place

1. Latitude (distance from the Equator): places near the Equator receive the sun's rays nearly vertically and are hot all year, while temperature falls towards the poles where the rays are slanting.
2. Altitude (height above sea level): temperature falls with height (about 6.5°C per 1000 m), so highland places are cooler than lowlands on the same latitude.
3. Distance from the sea (continentality): coastal places have a small temperature range and moist air, while inland places have hot summers, cold winters and a large range.
4. Ocean currents and prevailing winds: warm currents/onshore winds bring warmth and rain to a coast, while cold currents/offshore winds bring cool, dry conditions. (Also relief and vegetation cover.)

(b) Three ways climate affects man

1. Agriculture: climate decides which crops can be grown and the type of farming; rainfall and temperature determine planting and harvesting, so it governs food supply.
2. Type of settlement, dress and housing: people build and dress to suit the climate (light clothing and open houses in the hot tropics, heavy clothing and heated homes in cold lands), and dense settlement avoids very harsh climates (deserts, ice).
3. Health and occupation/economic activity: climate influences the spread of diseases (malaria in the hot wet tropics) and the kind of work and industries (tourism, fishing, timber) that people undertake. (It also affects transport.)

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(a) Solstice and Equinox

(A sketch shows the sun's rays vertical over the Tropic of Cancer at the June solstice and over the Equator at the equinox.)

(b) Rotation and Revolution of the Earth

(A sketch shows the earth spinning about its tilted axis and, separately, circling the sun.)

(c) Parallels of latitude and Meridians of longitude

(A sketch of the globe shows horizontal parallels and vertical converging meridians.)

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(a)(i) One European trading partner of Nigeria: the United Kingdom (Britain).

(a)(ii) Two commodities exported by each partner

• Nigeria exports to the UK: crude petroleum (oil) and cocoa (also rubber, tin, hides and skins).
• The UK exports to Nigeria: machinery/vehicles and manufactured goods such as chemicals and electrical equipment.

(b) Four benefits both countries derive from the trade

1. Foreign exchange earnings: each country earns money from the goods it sells to the other.
2. Supply of needed goods: Nigeria obtains machinery and manufactured products it does not make, while Britain obtains raw materials (oil, cocoa) for its industries.
3. Employment and industrial growth: the trade creates jobs in production, shipping and ports and keeps industries supplied in both countries.
4. Promotion of good relations and development: the exchange strengthens diplomatic and economic ties and brings in technology and investment.

(c) Four problems facing the trade between the two countries

1. Unfavourable terms of trade: Nigeria sells cheap primary products but buys costly manufactured goods, so the balance often favours Britain.
2. Price fluctuation of primary commodities: the world prices of oil and cocoa rise and fall, making Nigeria's earnings unstable.
3. Trade restrictions and tariffs / quality standards imposed on Nigerian goods entering the European market.
4. Distance and high transport/insurance costs, plus foreign-exchange and currency-difference problems and competition from other suppliers.

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(a) Outline map of Africa showing the required features

Key: rivers are shown by blue lines; mountain/highland locations by black triangles; the East African Rift Valley by a broken red line.

(b) Effects of mountains on the climate of Africa

1. They lower temperature. Temperature decreases with altitude; consequently, highlands are cooler than the surrounding lowlands. For example, the East African Highlands have relatively cool conditions despite their low latitude near the Equator.
2. They cause heavy relief rainfall on windward slopes. Moist winds are forced to rise over mountain barriers, cool as they rise and condense to give rain. For example, the eastern, windward side of the Drakensberg receives heavy rainfall.
3. They produce rain-shadow conditions on leeward slopes. Air descending the leeward side becomes warmer and drier after losing much of its moisture on the windward slope. Thus, the leeward side receives scanty rainfall.

(c) Economic importance of the highlands of Africa

1. Agriculture: highlands often have fertile volcanic or well-developed soils and cooler conditions suitable for crops such as coffee, tea, pyrethrum and temperate vegetables. Examples include the Kenya and Ethiopian Highlands.
2. Minerals: many highland areas are sources of valuable minerals, thereby supporting mining and related employment.
3. Hydro-electric power: steep gradients and rapidly flowing rivers originating in highlands provide suitable sites for dams and HEP generation; they also supply water for irrigation and domestic use.
4. Tourism: mountain scenery, cool climate, wildlife and features such as volcanic peaks and escarpments attract tourists and earn foreign exchange.

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(a) Three causes of air pollution (with examples)

1. Burning of fossil fuels: factories, power stations and motor vehicles burning coal, petrol and diesel release smoke, carbon monoxide, sulphur dioxide and lead into the air (e.g. traffic fumes in Lagos).
2. Industrial and mining processes: refineries, cement works and smelters give off dust, fumes and toxic gases (e.g. gas flaring in the Niger Delta oilfields).
3. Bush burning and burning of refuse: clearing farmland by fire and open burning of waste release smoke and soot into the atmosphere. (Others: volcanic eruptions and use of aerosols/CFCs.)

(b) Three major effects of air pollution

1. Health problems in man: respiratory diseases, bronchitis, lung cancer and eye irritation.
2. Acid rain: sulphur and nitrogen gases dissolve in rain to form acids that damage crops, forests, buildings and aquatic life.
3. Global warming and ozone-layer depletion: greenhouse gases raise world temperatures, while CFCs thin the ozone layer; smog also reduces visibility and harms plants.

(c) Three ways of controlling air pollution

1. Fit filters/scrubbers and catalytic converters to factory chimneys and vehicle exhausts to trap or reduce harmful gases and smoke.
2. Use cleaner energy and fuels (gas, solar, hydro-electric power, unleaded/low-sulphur fuel) instead of dirty coal and heavy oil.
3. Legislation and public education: enact and enforce anti-pollution laws, ban indiscriminate bush and refuse burning, and encourage tree planting to absorb carbon dioxide. (Also site industries away from residential areas.)

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(a) Four factors that determine population distribution

1. Relief: flat and gently sloping lowlands are densely settled because they are easy to build on and farm, while rugged mountains are sparsely peopled.
2. Climate: areas with moderate temperature and reliable rainfall attract people, whereas very hot deserts, cold polar lands and very wet equatorial forests repel settlement.
3. Soil fertility: fertile soils (river valleys, deltas, volcanic soils) support farming and dense population; poor, thin soils carry few people.
4. Economic/mineral and industrial opportunities: mining areas, ports, industrial towns and good transport concentrate people, while remote areas lacking jobs are thinly settled. (Also water supply and political/historical factors.)

(b) Two types of population movement

1. Rural-urban migration: the movement of people from villages and rural areas to towns and cities in search of jobs, education and better amenities.
2. International migration: the movement of people across national boundaries from one country to another (emigration and immigration), which may be permanent or temporary. (Others: seasonal migration and rural-rural migration.)

(c) Four problems associated with rural-urban migration

1. Overcrowding and pressure on housing in the towns, producing slums and shanty settlements.
2. Unemployment and under-employment as job-seekers exceed available jobs, leading to poverty and crime.
3. Strain on urban services and facilities: water, electricity, transport, schools and hospitals become overstretched, and pollution and traffic congestion increase.
4. Depopulation of the rural areas: loss of the able-bodied young leaves a shortage of farm labour, falling food production and neglect of the villages.

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(a) Four ways a town differs from a village

(A town also covers a larger built-up area and has higher-order services than a village.)

(b) Three functions a town performs for a village (with examples)

1. Market/commercial function: the town acts as a market centre where villagers sell their farm produce and buy manufactured goods they cannot get in the village (e.g. Onitsha or Kano markets serving surrounding villages).
2. Service function (health, education, administration): the town provides higher-order services such as hospitals, secondary schools, banks and government offices that serve the villagers (e.g. villagers travel to a nearby town for a general hospital or a bank).
3. Employment and industrial function: the town offers jobs in industries, offices and services, and processes the raw materials produced in the villages (e.g. a cotton-ginnery or cocoa-processing town buying and processing produce from nearby farming villages).

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(a) Location on the outline map of Nigeria

As shown on the map above:

• Rain-forest belt: This is located in the southern part of Nigeria, stretching across the coastal and inland states from the west through the Niger Delta to the south-east. It includes areas around Ogun, Ondo, Edo, Delta, Bayelsa, Rivers, Akwa Ibom and Cross River States.
• Montane vegetation: One area of montane vegetation is the Mambilla Plateau in Taraba State, in eastern Nigeria. The Obudu Plateau in Cross River State is also acceptable.
• Towns important for lumbering: Sapele, in Delta State, and Calabar, in Cross River State, are important lumbering towns within or close to the forest belt. Benin City is another acceptable example.

(b) Factors that have favoured timber production in Nigeria

1. Heavy and reliable rainfall: The forest belt receives high rainfall, often above \(1,500\text{ mm}\) annually. This supplies enough moisture for trees to grow rapidly throughout the year.
2. Uniformly high temperature: High temperatures and strong sunshine in southern Nigeria encourage continuous plant growth and the development of dense evergreen forest.
3. Fertile soils and favourable humidity: The warm, humid conditions and suitable soils support luxuriant natural vegetation and the growth of commercial tree species.
4. Presence of valuable hardwood species: The forests contain economic trees such as iroko, mahogany, obeche, afara, opepe and teak, which are suitable for furniture, construction, plywood and export.
5. High market demand: Timber is needed locally for building, furniture making, paper production and railway sleepers. There is also demand for Nigerian tropical hardwood in foreign markets.
6. Availability of transport routes: Rivers, creeks, roads, railways and seaports, especially around Sapele, Warri, Port Harcourt and Calabar, have assisted the movement and export of logs and processed timber.

(c) Problems facing the lumbering industry in Nigeria

1. Depletion of economic tree species: Excessive and uncontrolled felling has reduced the supply of mature hardwood trees in many forest reserves.
2. Poor transportation: Many forest roads become muddy, flooded or impassable during the rainy season, making it difficult and costly to evacuate logs from forests.
3. Mixed nature of the forest: Valuable trees do not usually occur in pure stands. They are scattered among less useful trees, so logging requires more time, labour and money.
4. Low level of technology: Some operators use outdated machinery and inefficient processing methods, causing waste and reducing the quantity and quality of sawn timber.
5. Illegal logging: Unauthorised felling makes it difficult to regulate forest use, collect revenue and conserve valuable tree species.
6. Inadequate reforestation: Trees are often cut faster than they are replaced. This leads to deforestation, soil erosion and a long-term decline in timber resources.

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(a) As shown on the map above:

• Area with annual rainfall below 100 cm: the far northern part of Nigeria, especially the Sokoto-Rima basin/Sahelian belt. Important towns include Sokoto and Katsina.
• Area with very high annual rainfall: the southern coastal Niger Delta belt, around Port Harcourt and Calabar. This is the area conventionally shown as receiving over 300 cm of rainfall annually. The wording “below 300 cm” in the question is inconsistent with the mangrove-swamp climate required in parts (b) and (c).

(b) Four other climatic features of the very wet coastal Niger Delta area are:

• Rainfall occurs in every month of the year; there is no true dry season.
• Rainfall has a double maximum, with two periods of peak rainfall, usually around June or July and September.
• There may be a short break in rainfall around August, known as the August break.
• Temperatures are high throughout the year, with a mean annual temperature of about \(27^\circ\text{C}\).
• Relative humidity is very high because of the frequent rainfall, cloud cover and nearness to the Atlantic Ocean.
• The annual range of temperature is small because the area lies close to the Equator and is strongly influenced by the sea.

(c) The vegetation associated with this hot and very wet coastal climate is the mangrove swamp forest.

Characteristics of mangrove swamp forest include:

• It is a dense, evergreen forest because rainfall and moisture are available throughout the year.
• The trees are mainly broad-leaved and grow closely together.
• It occurs in waterlogged, muddy and saline or brackish coastal swamps, especially around river mouths and creeks.
• Mangrove trees have supporting stilt roots and breathing roots, called pneumatophores, which help them to survive in soft, oxygen-poor swamp soils.
• The vegetation consists of several species of mangrove, together with palms, reeds and other swamp plants.

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(a) Five features of rotational bush fallowing in West Africa

1. Land is cultivated for a few years then rested (fallowed): A piece of land is farmed for about two to three years and then abandoned for several years to allow it to recover its fertility naturally.
2. Shifting of cultivation between plots, not settlements: The farmer moves from one plot to another within the same area while remaining in a permanent home settlement.
3. Use of simple tools and low technology: Farming is done mainly with hand tools such as the hoe and cutlass, with little or no machinery.
4. Clearing by cutting and burning the bush: The natural vegetation is cut and burnt, and the ash adds nutrients to the soil before planting.
5. Mixed cropping on small holdings: Several crops (for example yam, cassava, maize and vegetables) are grown together on small, scattered plots, largely for subsistence.

(Reliance on natural restoration of fertility and use of family labour are also acceptable features.)

(b) Four advantages of the system

1. Restores soil fertility naturally: The fallow period allows the soil to regain nutrients and structure without artificial fertiliser.
2. Cheap and low input: It requires little capital, no expensive machinery or chemicals, and uses available family labour.
3. Controls pests, weeds and diseases: Resting and burning the land breaks the life cycle of pests, weeds and crop diseases.
4. Reduces soil erosion and exhaustion: Regrowth of vegetation during fallow protects the soil surface and prevents rapid exhaustion of the land.

(c) Four disadvantages of the system

1. Requires a large area of land: Because much land is left fallow at any time, the system is wasteful of land and unsuitable where population is dense.
2. Low output and small farm size: Yields per farmer are low and production is mainly at subsistence level, giving little surplus for sale.
3. Not suited to mechanisation: The small, scattered plots with tree stumps make it difficult to use machinery, keeping productivity low.
4. Shorter fallows cause soil degradation: As population grows, fallow periods are shortened, so the soil cannot recover fully, leading to declining fertility and erosion.

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Desert encroachment (desertification) is the spread of desert-like conditions into once-productive land at the desert margins.

(a) Causes

1. Prolonged drought / declining rainfall at the desert margin (e.g. the Sahel).
2. Overgrazing by too many cattle, sheep and goats, which strips the grass cover.
3. Deforestation and over-cultivation, including bush burning and the cutting of trees for fuelwood, which expose the soil.
4. Population pressure forcing continuous farming without fallow, exhausting and loosening the soil so that wind and water erode it.

(b) Areas liable

• The Sahel belt of Africa south of the Sahara (northern Nigeria, Niger, Chad, Mali, Sudan, Sudan-savanna zone).
• Margins of other great deserts: the fringes of the Kalahari, the Arabian, Thar, Gobi and Australian deserts.
• Generally, semi-arid savanna/steppe lands with low, unreliable rainfall next to hot deserts.

(c) Effects

1. Loss of farmland and fall in crop and animal yields, leading to famine and food shortage.
2. Death of livestock and destruction of vegetation as pasture and water dry up.
3. Migration of people (environmental refugees) away from the affected land, and drying up of wells, rivers and lakes (e.g. shrinking of Lake Chad).
4. Increased soil erosion and dust storms and general impoverishment.

(d) Methods of prevention

1. Afforestation / planting of shelter belts (tree planting) to bind the soil and check the wind (e.g. the Great Green Wall).
2. Controlled grazing by limiting herd sizes and rotating pastures to allow grass to recover.
3. Good farming methods: crop rotation, fallowing, mulching and irrigation to keep the soil covered and productive.
4. Public education and enforcement against bush burning and indiscriminate tree felling, plus provision of alternative fuel to reduce fuelwood cutting.

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(a) Sketch map of Nigeria

The required locations are shown and labelled on the sketch map below. HEP means hydro-electric power station.

Key locations: Rivers Imo and Kaduna; HEP stations at Kainji and Jebba; thermal stations at Egbin and Afam; oil refineries at Port Harcourt and Warri.

(b) Contributions of the oil industry to the economic development of Nigeria

1. It provides a major source of foreign exchange through the export of crude oil and petroleum products.
2. It provides fuel and gas for domestic consumption, transportation and industrial use.
3. It creates employment opportunities directly in oil exploration, production and refining, and indirectly in transport, construction and other services.

(c) Problems arising from the exploitation of crude oil in Nigeria

1. Oil spills and gas flaring cause serious pollution of land, rivers and the atmosphere.
2. Oil operations can lead to rural depopulation and displacement of farming and fishing communities.
3. The industry depends greatly on foreign capital, technology and skilled manpower.
4. Oil spills, pipelines and drilling activities waste or damage farmlands and fishing waters, reducing agricultural and fish production.

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Distinguishing characteristics of the Eastern Highlands of Nigeria (the Adamawa, Mambilla and Obudu uplands along the eastern border).

(a) Relief and drainage

• It is a region of high plateaux and mountains, the highest land in Nigeria, rising above 1,500 m, with Chappal Waddi (about 2,400 m) as the highest point.
• The surface is made of ancient crystalline (basement) rocks and volcanic rocks, with steep escarpments and deep valleys.
• It forms an important watershed: several rivers rise here, and it is drained by the Benue and its tributaries (Gongola, Donga, Katsina-Ala), giving a radial pattern; there are rapids and waterfalls suitable for power.
• Because of the height the climate is cool and moist with heavy relief rainfall.

(b) Agriculture

• The cool, wet climate and rich volcanic soils favour temperate/highland crops: tea and coffee (Mambilla), Irish potatoes and vegetables.
• The extensive high grasslands support cattle rearing (grazing/ranching), e.g. the Mambilla cattle ranch, largely free of the tsetse fly.
• Food crops such as maize, yams, guinea corn and fruits are also grown on the slopes and valleys.

(c) Problems of development

• Rugged, steep relief makes farming, building and the construction of roads and railways difficult and costly.
• Poor accessibility/isolation: the area is remote from the main centres, so transport, markets and social services are limited.
• Soil erosion on the steep slopes, thin population and shortage of capital and skilled labour slow development.
• Sparse population and inadequate infrastructure discourage investment.

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(a) Four irrigation schemes within the Nile Basin:

• In Egypt: (i) the Aswan High Dam scheme (Lake Nasser); (ii) the Delta Barrage / Nile Delta irrigation scheme.
• In Sudan: (iii) the Gezira scheme (between the Blue and White Nile); (iv) the Managil (Gezira extension) scheme, and the Khashm el-Girba scheme on the Atbara.

(b) Factors that favoured the development of the Gezira scheme:

• Suitable relief: the Gezira is a flat, gently sloping clay plain between the Blue and White Nile, so water can be led by gravity through canals without pumping.
• Availability of water: the Sennar Dam on the Blue Nile stores water and provides a reliable, controlled supply for irrigation.
• Fertile soils: the heavy dark clay ("black cotton") soils are fertile and hold water well, ideal for cotton growing.
• Favourable climate and labour: the hot, sunny climate suits cotton, and a large local population supplies the labour needed.
• Government support and capital: planned investment provided the dam, canals and organisation to manage the scheme.

(c) Contributions of the Gezira scheme to economic development:

• It made Sudan a leading producer and exporter of high-quality long-staple cotton, earning foreign exchange.
• It provides employment for thousands of tenant farmers and workers.
• It supports food production (wheat, groundnuts, sorghum) grown in rotation, improving food supply.
• It has stimulated industry and infrastructure (ginneries, roads, railways, towns) and raised farmers' incomes.

(d) Three problems associated with irrigation schemes in the Nile Valley:

• Silting: canals and reservoirs become choked with silt, reducing storage and requiring costly dredging.
• Salinity and waterlogging: over-watering and poor drainage raise the water table and leave salt on the surface, damaging the soil.
• Spread of water-borne diseases: stagnant canal water encourages bilharzia (schistosomiasis) and malaria among the farming population.

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Rail transportation in African countries (examples: the Lagos-Kano line in Nigeria, the Kenya-Uganda railway, TAZARA between Tanzania and Zambia).

(a) Reasons for construction

1. To move bulky mineral and agricultural exports cheaply from the interior to the ports (e.g. tin and groundnuts to Lagos, copper on TAZARA to Dar es Salaam).
2. To open up and develop the interior and link inland producing areas to the coast and markets.
3. To ease the movement of people and goods over long distances at low cost per tonne-kilometre.
4. Administrative and strategic reasons: colonial powers built lines to control territory and, later, to promote national integration and trade. (Also to reduce dependence on a neighbour's ports, as with TAZARA.)

(b) Problems

1. High cost of construction and maintenance across difficult relief (highlands, rivers, forests, deserts).
2. Disconnected networks and different gauges between countries, so lines do not link up and through-traffic is difficult.
3. Old, worn-out equipment and poor management, giving frequent breakdowns, derailments and slow, unreliable services.
4. Shortage of capital and competition from road transport, plus concentration of lines only on export routes leaving many areas unserved.

(c) Solutions

1. Provide more capital investment (government and foreign partners) to rehabilitate and extend the lines.
2. Standardise the gauge and link national networks so trains can run across borders (regional rail integration).
3. Modernise the system: replace old track, locomotives and coaches, and improve management, maintenance and staff training.
4. Extend lines into unserved productive areas and improve coordination with road and water transport. (Also privatisation/concession to improve efficiency.)

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(a) Four factors that determine the pattern of movement of ocean currents (North Pacific Ocean)

1. Prevailing winds: the planetary winds drag surface water along, giving currents their main direction. The North-East Trades drive the North Equatorial Current westward, while the Westerlies drive the North Pacific (West Wind) Drift eastward.
2. Rotation of the earth (Coriolis force): the earth's spin deflects moving water to the right in the Northern Hemisphere, so the North Pacific currents circulate in a clockwise gyre.
3. Shape and position of the land masses (coastal configuration): continents block and deflect the currents; Asia turns the equatorial water northward as the Kuroshio (Japan) Current, and North America turns the drift southward as the California Current.
4. Differences in water temperature, salinity and density: warm, less-dense equatorial water flows towards the poles while cold, dense polar water (the Oyashio/Kamchatka Current) moves towards the Equator, helping drive the circulation.

(b) One cold current: the California Current and its effects on the adjacent coast

The California Current is a cold current flowing southward along the western coast of North America.

• It lowers the temperature of the coastland, giving cool summers on the Californian coast.
• Being cold, it chills the air above it and reduces rainfall, so the adjoining coast is dry (helping to keep the California/Baja desert arid).
• It causes advection fog and mist where the cold current meets warmer air over the land.
• Where it drives cold, nutrient-rich water upward (upwelling) it encourages plankton and rich fishing grounds off the coast.

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(a) Sketch map of Africa

Key: E is the Congo Basin equatorial-climate area and K is Kisangani, a major town in that area. D is the Sahara Desert climatic area and T is Tamanrasset, a major town in that area.

(b) Characteristics of the equatorial climate

1. High temperatures throughout the year: Mean monthly temperatures are generally about 27°C, with a very small annual temperature range.
2. Heavy convectional rainfall: Strong surface heating causes warm, moist air to rise, cool and condense, producing frequent heavy thunderstorms, often in the afternoon.
3. Rainfall occurs throughout the year: Annual rainfall is commonly above 2,000 mm. There is no marked dry season and many places experience two rainfall maxima as the overhead sun passes twice yearly.

(c) Adaptations of tropical rainforest vegetation to the equatorial climate

1. Trees are tall and grow in layers, with a dense upper canopy, in order to obtain sunlight in the intensely competitive forest.
2. Many large trees develop broad buttress roots or aerial roots for support in the shallow, heavily leached and wet soils.
3. Leaves are broad and evergreen to trap available light; they often have waxy surfaces and drip tips that allow heavy rainwater to run off quickly.

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(a) Sketch map of Nigeria

Key: The shaded Y-shaped belt represents the Niger-Benue trough. Lokoja is the confluence town where River Benue joins River Niger. Bacita lies in the Niger valley, while Numan lies on the River Benue.

(b) Commercial production of sugarcane in the Niger-Benue Trough

(i) Method of cultivation

• Sugarcane is cultivated commercially on large estates, especially on the fertile, level alluvial floodplains of the Niger and Benue valleys.
• The land is cleared, ploughed, harrowed and made into ridges or furrows, often with tractors and other machinery.
• Short pieces of mature cane stem, called setts, each with buds, are planted in furrows. Planting is commonly carried out from about November to April.
• Water from Rivers Niger and Benue is used to irrigate the farms during the dry season.
• The crop is weeded, supplied with fertiliser where necessary, protected from pests and allowed to mature before harvesting.

(ii) Method of harvesting

• Mature cane stalks are cut a few centimetres above ground level, either manually with cutlasses or mechanically with harvesters.
• The leafy tops and dry leaves are stripped off and the stalks are tied or loaded.
• The cut cane is transported quickly by lorry or rail to the sugar factory for crushing, since delay reduces its sugar content.

(iii) Economic importance

• It supplies raw material to sugar-processing industries, including the sugar estates and factories at Bacita and Numan.
• It provides employment and income for farm workers, factory workers, transporters and farmers.
• It produces sugar for consumption and thereby helps to reduce the importation of sugar and conserve foreign exchange.
• Its by-products are useful: molasses may be used in alcohol production and animal feed, while bagasse may be used as fuel, for paper-making or as livestock feed.
• The cane itself may be chewed as food, and its residues can serve as fodder for cattle.

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As shown in the diagrams above, two desert landforms are described below.

(a) Rock pedestal

Appearance: A rock pedestal is an isolated pillar of rock with a broad upper part and a narrow, undercut base. It is sometimes called a mushroom rock because it may resemble a mushroom. Its sides are often smooth, grooved or polished by wind-blown sand. It is common in hot, dry desert areas where vegetation is sparse.

Formation:

• It develops where alternating layers of hard and soft rocks occur, or where the lower part of a rock mass is less resistant than the upper part.
• Strong winds carry sand particles close to the ground surface.
• The sand particles strike and scrape the lower part of the rock by abrasion or sand-blasting.
• Since most sand is carried within about one metre of the ground, erosion is greatest at the base of the rock.
• The softer lower layers are worn away faster than the harder upper layers.
• Continued undercutting leaves a narrow base supporting a wider, more resistant top, thereby producing a rock pedestal.

(d) Inselberg

Appearance: An inselberg is an isolated, steep-sided mass or hill of resistant bare rock rising abruptly from a flat or gently sloping plain. It may have a rounded, dome-shaped, conical or flat-topped summit. Inselbergs are usually made of hard rocks such as granite, gneiss or quartzite, and are common in arid and semi-arid regions.

Formation:

• An inselberg is formed from a former extensive upland, plateau or rock surface containing both resistant and less resistant rocks.
• Weathering attacks the weaker rocks more rapidly. In granite regions, water may enter joints and cause deep chemical weathering below the surface.
• The more resistant rock remains relatively unweathered, while surrounding rocks are broken down into loose weathered material.
• Running water, sheet wash and wind remove the weathered debris and softer materials from the surrounding area.
• As denudation continues, the resistant rock is left standing above the lowered plain as an isolated rocky hill, called an inselberg.

Thus, the rock pedestal is mainly produced by wind abrasion concentrated near ground level, whereas the inselberg results mainly from differential weathering and the removal of softer surrounding materials.

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(a) Sketch map of Africa showing the vegetation belts

Key: Dark green represents tropical rain-forest; yellow represents tropical grassland (savanna); orange represents temperate grassland (veld).

(b) Characteristics of the tropical rain-forest of Africa

1. It is a dense, luxuriant and evergreen forest because rainfall and temperatures are high throughout the year.
2. The trees are very tall, commonly about 45 to 60 metres, and form a continuous closed canopy.
3. Vegetation occurs in distinct layers or storeys: emergent trees, canopy, under-storey and shrub or ground layer.
4. There is a great variety of mixed tree species. Lianas and epiphytes are common, while many tall trees have buttress roots for support.

(c) Economic importance of the tropical rain-forest

1. It supplies valuable hardwood timber, such as mahogany, iroko and ebony, for construction, furniture-making and export.
2. It provides fuelwood and charcoal for domestic and small-scale industrial use.
3. It supplies food and other forest products, including fruits, nuts, mushrooms, honey, rubber, medicinal plants, raffia and oil-palm products.
4. It provides raw materials for local craft and processing industries, such as carving, basket-making, paper-making and furniture production, and creates employment in logging and sawmilling.