WAEC SSCE - Geography - 1992 (Essay)

Detalhes da Resposta

Topic chosen: Water pollution.

Water pollution is the addition of harmful substances to bodies of water (rivers, lakes, seas, ground water) so that the water becomes unsafe or unfit for human use and for aquatic life.

(a) Causes of water pollution:

• Industrial waste: factories discharge chemicals, dyes, heavy metals and hot water into rivers and streams.
• Sewage and domestic waste: untreated human waste, refuse and detergents are emptied into water bodies.
• Agricultural chemicals: fertilizers, pesticides and herbicides are washed by rain from farmland into rivers.
• Oil spillage: leaks from pipelines, tankers and oil-drilling pollute rivers and coastal waters, as in the Niger Delta.
• Mining waste and refuse dumping: silt, chemicals and rubbish enter water courses.

(b) Effects of water pollution:

• Spread of water-borne diseases such as cholera, typhoid, dysentery and guinea worm.
• Death of aquatic life: fish and other organisms are killed by toxic chemicals and oil, reducing fish catches.
• Shortage of clean water: the water becomes unfit for drinking, cooking and domestic use, and costly to treat.
• Damage to farmland and eutrophication: polluted water damages crops when used for irrigation, and nutrient enrichment causes excessive weed growth that chokes the water.

(c) Control measures:

• Treatment of waste: industrial effluent and sewage should be treated before being discharged.
• Enforcement of laws: government should make and enforce anti-pollution laws and penalise offenders.
• Proper waste disposal: provide proper dumps and sewage systems so that refuse and waste are not thrown into water.
• Control of oil spills and farm chemicals: maintain pipelines, clean up spills promptly, and use fertilizers and pesticides carefully; public enlightenment on keeping water bodies clean.

Detalhes da Resposta

(a) Reasons for the relatively low level of industrial development in tropical Africa

• Shortage of capital: Most tropical African countries are poor with low per capita incomes and weak savings, so there is insufficient investment capital to establish and expand heavy industries.
• Inadequate power and energy supply: Electricity generation is irregular and insufficient, and many rural areas are not connected to the national grid, which discourages the siting of factories.
• Low level of technology and few skilled workers: There is a shortage of engineers, technicians and trained managers, and the region depends heavily on imported machinery and expertise.
• Small and low-income domestic market: Widespread poverty means low purchasing power, so demand for manufactured goods is small and cannot support large-scale industry.
• Poor transport and infrastructure: Bad roads, limited railways and inadequate port facilities raise the cost of moving raw materials and finished goods.
• Political instability and unfavourable policies: Frequent changes of government, insecurity and inconsistent economic policies scare away both local and foreign investors.
• Concentration on primary production: Colonial and post-colonial economies were geared toward exporting unprocessed raw materials rather than manufacturing them locally.
• Competition from imported goods: Cheaper and better-quality manufactured goods from industrialised countries out-compete local products.

(b) Five ways the industrial sector has contributed to economic development of the region

• Employment: Industries provide jobs to many people, thereby reducing unemployment and raising incomes.
• Revenue and foreign exchange: Taxes on industries and the export of manufactured goods earn government revenue and foreign currency.
• Provision of goods and reduced imports: Local manufacture of consumer goods reduces dependence on imports and saves foreign exchange.
• Development of infrastructure: The establishment of industries stimulates the building of roads, power supply, water and communication facilities.
• Growth of towns and other sectors: Industries encourage urbanisation and support agriculture (through processing) and mining (through demand for raw materials).

Detalhes da Resposta

(a) On an outline map of Africa, locate, name and label the following mining areas, towns and ports of export.

Use different symbols or colours for copper, gold and iron ore on the map. Mark the mining areas, dot and name the towns, and mark the ports on the coast. Add a suitable key.

(b) Four ways in which copper is important to Zambia are:

(i) Copper provides foreign exchange

Detalhes da Resposta

(a) Four functions of towns, with a specific example of each:

• Administrative (capital) function: the town is a seat of government, for example Abuja.
• Commercial/trading function: the town is a centre of trade and business, for example Onitsha (or Lagos).
• Industrial (manufacturing) function: the town is a centre of manufacturing, for example Kano (textiles) or Warri (petroleum).
• Educational function: the town is a centre of learning, for example Ibadan or Nsukka (university towns). (Others: mining town - Enugu; religious town - Mecca; port town - Port Harcourt.)

(b) Four ways the initial function of a town can contribute to its growth:

• Attraction of population: the original function (say administration or industry) draws workers and their families, so the population increases.
• Provision of employment and services: the function creates jobs, which in turn attract shops, schools, hospitals and other services, enlarging the town.
• Development of infrastructure: to serve the function, roads, electricity, water and communication are provided, encouraging further settlement and investment.
• Attraction of other functions: the initial function attracts related activities (a capital attracts commerce, banks and industry), so the town grows and diversifies (multiplier effect).

(c) Three ways rural settlements depend on urban settlements:

• Market for produce: villages sell their farm produce and raw materials in the town's markets.
• Source of manufactured goods and services: villagers obtain manufactured goods, and specialised services such as hospitals, banks, secondary schools and administration from the town.
• Employment and income: villagers travel to the town to work and earn wages, some of which they bring back to develop the rural area (also higher-order services like courts and universities).

Detalhes da Resposta

Two vegetation types chosen: (a) Equatorial and (b) Tropical continental (savanna).

(a) Equatorial (tropical rain-forest) vegetation

(i) Vegetation characteristics:

• Tall, dense, evergreen forest arranged in three storeys (emergents, canopy, under-storey), with trees reaching 40 metres or more.
• Broad-leaved hardwoods (mahogany, iroko, ebony) with buttress roots; leaves have drip-tips.
• Great variety of species mixed together, with abundant lianas (climbers), epiphytes and a dark, bare forest floor.

(ii) How climate has influenced it: the constant high temperatures (about \(27^\circ C\)) and heavy, year-round rainfall (over \(2000\ mm\)) with no dry season allow continuous, rapid plant growth, so the forest stays green all year. Competition for light makes the trees grow tall in layers, the heavy rain produces drip-tips and buttress roots, and the warm damp conditions support a huge variety of species.

(b) Tropical continental (savanna) vegetation

(i) Vegetation characteristics:

• Tall, coarse grasses (often 1 to 3 metres) with scattered, short deciduous trees, giving a parkland appearance.
• Trees are drought- and fire-resistant, with thick bark, umbrella-shaped crowns, small leaves and deep roots (acacia, baobab, shea).
• Grass turns green in the wet season and dries brown in the dry season; trees become fewer and shorter towards the desert margin.

(ii) How climate has influenced it: the savanna has a marked wet and dry season. During the long dry season plants must survive drought, so trees shed their leaves, develop thick fire-resistant bark and long roots, and store water (baobab), while the grasses dry up and survive as roots and seeds. The seasonal, moderate rainfall (about \(750\ mm\) to \(1000\ mm\)) is enough for grass and scattered trees but not for continuous forest.

Detalhes da Resposta

(a)(i) Two local craft industries and one important town for each

• Leather working - Kano.
• Cloth weaving / dyeing (adire, aso-oke) - Iseyin/Abeokuta (also Akwete weaving at Akwete).

(Others: pottery - Ilorin; wood carving - Awka; brass/bronze - Benin; mat making - Ikot Ekpene.)

(a)(ii) Two manufacturing industries and one important town for each

• Cement manufacturing - Ewekoro (also Sokoto, Obajana).
• Textile manufacturing - Kaduna (also Lagos, Aba).

(Others: vehicle assembly - Lagos/Kaduna; petroleum refining - Port Harcourt/Warri; brewing - Lagos.)

(b) Four problems facing local craft industries (with examples)

• Competition from cheaper factory-made goods: Imported and factory textiles undersell hand-woven aso-oke and adire, reducing demand for the local product.
• Shortage of capital and credit: Craftsmen such as Ilorin potters and Awka carvers lack funds to buy better tools and expand.
• Use of crude, outdated tools: Kano leather workers and local dyers rely on simple hand tools, so output is slow and quality varies.
• Poor marketing and finance/scarcity of raw materials: Weak organisation, poor roads and rising cost of raw materials (hides, cotton, clay) limit sales and profit; young people also prefer white-collar jobs, so skills are being lost.

(c) Three ways the problems are being solved

• Provision of loans and grants: Government and banks give soft loans and support through agencies (e.g. SMEDAN, Bank of Industry) to fund craftsmen.
• Training and cooperative organisation: Craft centres and cooperatives train workers, improve tools and skills, and market the goods jointly.
• Promotion and protection of local crafts: Trade fairs, exhibitions and encouragement of patronage (including some restriction on cheap imports) expand the market for local products.

Detalhes da Resposta

(a)(i) The Equinoxes:

An equinox occurs twice a year, on about 21 March (spring/vernal equinox) and 23 September (autumn equinox). At these times the sun is directly overhead at the Equator (the sun's vertical rays fall on \(0^\circ\) latitude). Because the circle of illumination passes through both poles, day and night are equal in length (12 hours each) all over the world. The word equinox means "equal night". Neither the North nor the South Pole is tilted towards the sun.

(a)(ii) Great circles:

A great circle is any circle drawn on the globe whose plane passes through the centre of the Earth, dividing the globe into two equal halves (hemispheres). It is the largest circle that can be drawn on the Earth's surface. The Equator is a great circle, and every pair of opposite meridians of longitude together forms a great circle. The parallels of latitude other than the Equator are small circles, because their planes do not pass through the centre of the Earth. The shortest distance between any two points on the globe lies along the arc of a great circle, which is why aircraft and ships follow great-circle routes.

(b) Why twilight lasts longer at the Arctic Circle than at the Equator:

Twilight is the period of half-light before sunrise and after sunset, caused by the atmosphere scattering the sun's rays while the sun is still below the horizon. Its length depends on the angle at which the sun sinks below the horizon. At the Equator the sun's daily path is almost vertical (perpendicular) to the horizon, so the sun drops quickly and steeply below the horizon, passing through the twilight zone in a short time; twilight is therefore brief. Near the Arctic Circle the sun moves in a path that is greatly slanted (oblique) to the horizon; it sinks very gradually and travels a long, shallow path just below the horizon, so its rays continue to light the sky for a much longer period. Hence twilight lasts far longer in high latitudes than at the Equator.

Detalhes da Resposta

(a) Map work

As shown on the map above, the following features should be correctly marked and named:

• Equator (0°): crosses central Africa, passing through countries such as Gabon, Congo, the Democratic Republic of the Congo, Uganda, Kenya and Somalia.
• Greenwich Meridian (0° longitude): runs through north-western Africa, including Algeria, Mali, Burkina Faso and Ghana.
• Tropic of Cancer (23½°N): crosses the Sahara Desert in northern Africa.
• Tropic of Capricorn (23½°S): crosses southern Africa through Namibia, Botswana, South Africa and Mozambique.
• Cape of Good Hope: situated at the south-western tip of South Africa.
• Cape Blanco: located on the Atlantic coast of Mauritania in north-west Africa.
• Qattara Depression: located in the Western Desert of north-western Egypt, west of the River Nile.
• River Zambezi: rises in north-western Zambia and flows generally eastwards through Zambia, Zimbabwe and Mozambique into the Indian Ocean.

(b) Four ways in which the relief of Africa may create problems for constructing a trans-African highway from the Cape of Good Hope to Cairo

1. High mountains, plateaux and escarpments in southern and eastern Africa would require roads to climb steep slopes. This makes construction difficult and costly and may produce dangerous sharp bends and steep gradients.
2. Deep valleys and the East African Rift Valley would have to be crossed. Road engineers may need to construct long bridges, embankments, tunnels or winding roads down and up valley sides.
3. Major rivers and gorges, especially the Zambezi and other rivers along the route, would require expensive bridges and culverts. Flooding can also wash away roads and bridge approaches.
4. Desert terrain and depressions in northern Africa, including the Qattara Depression, may obstruct a direct route. Loose sand, sand dunes and wind-blown deposits can bury or damage roads, while very low-lying depressions may be unsuitable for road construction.

(c) Measures for minimizing the problems

• Carry out detailed route surveys and select relatively level lowland or gently sloping areas where possible.
• Avoid very high mountains, deep rift valleys, steep escarpments and the Qattara Depression by using alternative routes.
• Use cuttings, embankments, retaining walls, tunnels and carefully designed bends to reduce steep gradients in hilly areas.
• Construct strong bridges, culverts and drainage channels across rivers and flood-prone valleys.
• Stabilise desert roads by planting shelter belts of trees, using vegetation where possible, and constructing barriers to reduce sand encroachment and wind erosion.

Detalhes da Resposta

(a) Outline map of Nigeria: relief and drainage features

• (i) Jos Plateau - central Nigeria; Idanre Hills - south-west (near Akure).
• (ii) River Ogun - flows south-west into the Lagos lagoon; River Cross - south-east, into the Atlantic near Calabar; River Hadejia - north-east, draining toward the Lake Chad basin.
• (iii) Lake Chad - far north-east corner; Lake Kainji (artificial) - west-central, on the River Niger.
• (iv) Niger Delta - fan of creeks and swamps where the Niger reaches the sea in the south-south.

Show rivers as lines with arrows toward their mouths, lakes as shaded patches, and highlands by shading; add a key.

(b)(i) Four physical features of the Niger Delta

• Low, flat and swampy land lying near sea level.
• Network of distributaries and creeks as the Niger splits before entering the sea.
• Mangrove and freshwater swamp forest with muddy, waterlogged soils.
• Sand bars, beach ridges and lagoons along the seaward edge, deposited by the river and the sea.

(b)(ii) Four physical features of the North Central Plateau (Jos Plateau)

• High, upland surface rising above the surrounding plains (around 1200-1800 m).
• Cool climate because of the altitude, cooler than the lowlands around it.
• Volcanic hills, cones and older granite rocks giving a rugged surface.
• Source of many rivers (a water divide) with steep edges/escarpments and tin-bearing rocks.

Detalhes da Resposta

As shown on the sketch map above, the population-density areas and representative towns are:

(b)(i) Advantages of low population density in the Minna area

• There is less pressure on land, so land is more readily available for farming, housing and other uses.
• There is less overcrowding, resulting in more spacious and comfortable accommodation.
• Traffic congestion, noise and environmental pollution are generally lower.

(b)(ii) Advantages of high population density in the Lagos area

• A large population provides a wide market for goods and services, encouraging heavy commercial activity.
• It supplies a large labour force and attracts industries, thereby creating employment opportunities.
• It encourages the provision of social amenities and infrastructure such as schools, hospitals, roads, electricity and communication facilities.

Detalhes da Resposta

Comparison of irrigation agriculture in the Nile Basin and the Niger Basin

In summary, irrigation is more essential, more extensive and more highly developed in the Nile Basin because of its desert setting, whereas in the Niger Basin irrigation is more localised and needed chiefly in the drier northern and inland-delta sections, since the southern parts receive enough rain.

Detalhes da Resposta

Ways in which poor transportation can limit the economic development of a country (for example Nigeria):

Transport is the means by which people, raw materials and goods are moved from place to place. Where it is poor (few, badly maintained roads, limited rail, few navigable rivers, high costs), development is held back in the following ways:

• Restricted movement of goods and raw materials: factories cannot obtain raw materials cheaply or distribute their finished goods easily, so industries are discouraged and remain small.
• Discouragement of agriculture: farmers in remote areas cannot move their produce to market before it spoils, so they produce little for sale; farm produce rots and prices are unstable.
• High cost of goods and services: where transport is difficult, the cost of moving goods is high, which raises the prices of goods and lowers people's real income.
• Isolation of regions and uneven development: areas without good transport are cut off, so investment, trade and social services concentrate in the few accessible places, leaving other regions backward.
• Hindrance to trade (internal and external): poor links to ports, markets and neighbouring countries reduce the volume of trade and foreign exchange earnings.
• Discouragement of investment and industry: investors avoid areas that are hard to reach, so new industries and businesses are not established there.
• Limited exploitation of resources: minerals, forests and other resources in inaccessible areas cannot be developed because they cannot be moved out economically.
• Slow movement of labour and reduced tourism: workers cannot easily reach places of work, and tourists are put off by difficult travel, so both the labour market and the tourist industry suffer.

Thus poor transportation slows down agriculture, industry, trade, and the even spread of development, keeping the country's economy weak.

Detalhes da Resposta

(a) Outline map of West Africa: January conditions

• (i) ITCZ in January: draw the Inter-Tropical Convergence Zone lying to the south, roughly along or just off the Guinea coast (about 5°N over the ocean).
• (ii) Low pressure belt in January: mark it over the equatorial south, close to the ITCZ near the coast, where the sun is nearly overhead.
• (iii) High pressure belt in January: mark it over the Sahara in the north (the sub-tropical high over North Africa).
• (iv) Tropical Continental air mass (cT): show it as the dry, dusty Harmattan blowing from the north-east (Sahara) toward the south-west, with an arrow.
• (v) Guinea current: a warm current flowing eastward along the Guinea coast; (vi) Canary current: a cool current flowing south-westward along the north-west coast (Mauritania/Senegal).

(b) Relationship between pressure belts and rainfall distribution

• The rain-bearing belt follows the low pressure (ITCZ): Rainfall is heaviest where the ITCZ and the low pressure lie, because moist maritime Tropical (mT) south-west monsoon air converges and rises there, cooling to give rain.
• High pressure means dry weather: Under the sub-tropical high, air is subsiding (sinking) and the dry continental Tropical (cT) Harmattan blows out; this area (the north/Sahara) is dry, so rainfall decreases northward.
• The belts migrate with the overhead sun: In July the low pressure and ITCZ move far north, bringing the rainy season to most of West Africa; in January they move south, so only the coast gets some rain while the interior is dry. Hence rainfall is highest and longest near the coast and decreases toward the interior, following the seasonal shift of the pressure belts.

Detalhes da Resposta

(a) Meaning of environmental resource:

An environmental resource is any material or feature of the natural environment that is useful and of value to man in satisfying his needs. It includes both natural (physical) resources such as water, soil, minerals, forests, air, wildlife and sunlight, and it becomes a resource only when man has the knowledge and ability to make use of it. Environmental resources may be renewable (water, forests, wind) or non-renewable (minerals, crude oil).

(b) Importance of water as an environmental resource (with examples):

• Domestic use: water is needed for drinking, cooking, washing and other household activities.
• Agriculture: water is used for irrigation of crops and for watering livestock, for example irrigation in the Sokoto and Chad basins.
• Industry: factories use water for processing, cooling and cleaning, for example in breweries and textile mills.
• Generation of electricity: fast-flowing or dammed rivers produce hydro-electric power, for example the Kainji Dam on the Niger.
• Transport and fishing: rivers, lakes and seas serve as cheap waterways for boats and support fishing, for example on the River Niger and Lake Chad.
• Tourism and recreation: waterfalls, beaches and lakes attract tourists and provide recreation.

(c) Three sources of water:

• Rainfall collected directly or in reservoirs.
• Surface water from rivers, streams, lakes and ponds.
• Underground water obtained from wells, boreholes and springs.

Detalhes da Resposta

(a) Outline map of Nigeria: transport features

• (i) Two international airports: Murtala Muhammed (Lagos) in the south-west and Nnamdi Azikiwe (Abuja) in the centre. (Others: Port Harcourt, Kano.)
• (ii) Two domestic airports: Ibadan in the south-west and Ilorin in the middle belt. (Others: Maiduguri, Yola, Benin.)
• (iii) Two seaports: Lagos (Apapa/Tin Can) in the south-west and Port Harcourt in the south-south. (Others: Warri, Calabar.)
• (iv) Two river ports: Onitsha on the River Niger and Lokoja at the Niger-Benue confluence. (Others: Baro, Yola on the Benue.)

Mark each with a small symbol (aircraft for airports, anchor for ports) in its correct position and label it.

(b) Four problems facing river transportation in Nigeria

• Seasonal variation in water level: Rivers are shallow in the dry season, so large boats cannot navigate for part of the year.
• Silting and sand bars: Deposition of silt and sand blocks channels and reduces depth, making navigation difficult.
• Rapids, waterfalls and rocky obstacles: Sudden falls and rocks interrupt the courses of many rivers, so goods must be off-loaded and moved by land.
• Floating vegetation and few modern facilities: Water hyacinth and weeds clog channels, while poor port facilities, dredging and jetties limit efficiency.

(c) How the problems are being solved

• Dredging: Rivers such as the Lower Niger are dredged to deepen channels and remove silt and sand bars for year-round use.
• Construction of dams: Dams (e.g. Kainji) regulate the flow so that a steady depth of water is maintained downstream.
• Clearing of vegetation and obstacles: Water hyacinth and rocks are removed and channels are marked to guide craft.
• Provision of modern port facilities: Building and equipping river ports (Onitsha, Lokoja, Baro) with jetties and cargo-handling equipment improves the service.

Detalhes da Resposta

(a)(i) Three of Koppen's major climatic groups:

• Group A - Tropical rainy climates (hot, no cool season, every month above \(18^\circ C\)).
• Group B - Dry climates (evaporation exceeds precipitation; deserts and steppes).
• Group C - Warm temperate (mild) rainy climates (mild winters).
• (Others: Group D - Cold temperate/continental climates; Group E - Polar/ice climates.)

(a)(ii) Basis of the classification:

Koppen based his classification mainly on temperature and rainfall (precipitation) values and their seasonal distribution, using the limits of temperature and rainfall that correspond to particular types of natural vegetation. In other words, climate is defined by measurable temperature and rainfall figures which match recognisable vegetation zones.

(b) Two types of climate within Koppen's first group (Group A - Tropical) and their unique features:

• Af - Tropical rain-forest (equatorial) climate: it is hot all year (every month above \(18^\circ C\)) with heavy rainfall in every month (the driest month still has more than about \(60\ mm\)); there is no dry season, giving continuous dense evergreen rain-forest.
• Aw - Tropical savanna (wet-and-dry) climate: it is also hot all year but has a distinct dry season in the low-sun (winter) period and a wet season in the high-sun period; the marked dry season gives grassland with scattered trees (savanna).
• (A third, Am - Tropical monsoon, has a short dry season followed by very heavy monsoon rains.)

Detalhes da Resposta

(a) Relationship between rainfall and agricultural practices

(i) Tropical continental region of Nigeria (Guinea and Sudan savanna, the north)

• Rainfall is moderate to low (about 500 to 1000 mm) and highly seasonal, with a long dry season, so farming is limited mainly to the short wet season.
• The single, short rainy season permits only one cropping season per year, and drought-tolerant crops such as guinea corn (sorghum), millet, groundnut and cotton are grown.
• Where the dry season is severe, farmers depend on irrigation (for example rice and vegetables) to supplement rainfall.
• The grassland cover supports extensive livestock rearing (cattle, sheep and goats).

(ii) Sub-equatorial region of Nigeria (the south)

• Rainfall is heavy (over 2000 mm) and well distributed over most of the year, giving a long growing season.
• The abundant, double-maxima rainfall allows two cropping seasons and the cultivation of moisture-loving crops such as oil palm, cocoa, rubber, yam, cassava and plantain.
• Rainfall reliability makes rain-fed farming the norm, with little need for irrigation.
• The very heavy rainfall can cause leaching and soil erosion, so tree/perennial crops that protect the soil are favoured.

(b) Five ways agriculture contributes to the economy of Nigeria

• Provision of food: It supplies food for the rapidly growing population.
• Employment: It employs a large proportion of the working population, especially in rural areas.
• Raw materials for industry: It supplies materials such as cotton, oil palm and rubber to agro-based industries.
• Foreign exchange: Export crops such as cocoa and rubber earn foreign currency.
• Government revenue: Taxes and duties on agricultural produce provide revenue to government.
• Source of income: It provides income and improved living standards for farmers.

Detalhes da Resposta

(a) Identification of dams and rivers

As shown on the map above, the dams should be marked and named as follows:

• Kossou Dam: located in central Côte d’Ivoire, on the Bandama River.
• Kainji Dam: located in western Nigeria, on the River Niger.
• Akosombo Dam: located in south-eastern Ghana, on the Volta River.

(b) Ways climate affects dams in West Africa

• Amount and reliability of rainfall: Heavy and regular rainfall raises river discharge and fills reservoirs, improving the supply of water for hydro-electric power, irrigation and other uses. Low rainfall may cause water levels in dams to fall.
• Length of the dry season: A prolonged dry season reduces inflow into reservoirs. This can lower hydro-electricity generation, reduce water available for irrigation and limit navigation.
• High temperature and evaporation: High temperatures increase evaporation from the surface of reservoirs, causing loss of stored water, especially during dry periods.

(c) Advantages of dams to West Africa

• They generate hydro-electric power for homes, industries and commercial activities.
• They provide water for irrigation, making dry-season farming and increased food production possible.
• They promote fishing, inland water transport and recreation through the creation of large reservoirs.

Disadvantages of dams to West Africa

• Construction of dams and reservoirs may flood settlements, farmland, forests and mineral-bearing areas, leading to the displacement of people.
• During drought or prolonged low rainfall, low reservoir levels can reduce hydro-electric power output and cause power shortages.
• Dam failure or the sudden release of excess water may cause serious flooding downstream, resulting in loss of lives, destruction of property and crops.

Detalhes da Resposta

(a) Difference between deflation and abrasion:

Deflation is the lifting and blowing away of loose, dry, fine material (dust, sand and silt) from the desert surface by the wind, so that the surface is lowered. Abrasion (corrasion) is the wearing away of rock surfaces by the wind using its load of sand grains as tools, rather like a natural sand-blasting; here the wind actively cuts and grinds solid rock. In short, deflation removes already-loose material, while abrasion erodes solid rock by rubbing sand against it.

(b) One landform produced by each process, with examples:

• Landform of deflation - a deflation hollow (blowout): where the wind repeatedly scoops away the loose sand, a shallow, saucer-shaped depression is formed. If the hollow is deepened until it reaches the water table, an oasis may develop. The Qattara Depression in Egypt is a large example.
• Landform of abrasion - a rock pedestal (mushroom rock, or zeugen/yardang): because the sand load is concentrated near the ground, the base of an upstanding rock is undercut faster than its top, leaving a mushroom-shaped rock with a narrow stem and broad cap, as seen in the Sahara.

(c) Two reasons why wind erosion is more active in arid than in humid regions:

• Scanty vegetation cover: deserts have little or no plant cover to bind the soil or shield the surface, so the wind can pick up and move material freely; in humid regions dense vegetation protects and holds the soil.
• Dry, loose surface material: the ground in arid areas is dry, so the fine particles are loose and easily lifted; in humid regions moisture binds the particles together and makes them heavy, so the wind cannot move them (strong steady winds in deserts also aid erosion).

Detalhes da Resposta

(a) (i) One sea route linking Nigeria with Europe

The Cape Route (round the Cape of Good Hope) is one such route. A more direct alternative is the route through the Gulf of Guinea, across the Atlantic Ocean to the English Channel and the ports of north-western Europe. (Either the Cape Route or the trans-Atlantic Gulf of Guinea route is acceptable.)

(ii) Two European countries that trade with Nigeria using the route

• United Kingdom
• Netherlands (others acceptable: France, Germany, Spain, Italy)

(b) Four products carried along the route

• From Nigeria: crude petroleum, cocoa, and rubber.
• To Nigeria: manufactured goods such as machinery and vehicles.

(c) Five ways international trade is important to Nigeria

• Foreign exchange earnings: The export of crude oil, cocoa and other goods earns foreign currency used to finance development.
• Government revenue: Import and export duties provide substantial revenue to the government.
• Supply of goods not produced locally: Trade makes available machinery, vehicles and manufactured goods that Nigeria does not produce in sufficient quantity.
• Employment: Trade-related activities in ports, shipping, banking and haulage provide jobs for many people.
• Promotion of international relations: Trade fosters friendly and cooperative relations between Nigeria and her trading partners.
• Market for surplus: It provides an outlet for Nigeria's surplus agricultural and mineral products.