WAEC SSCE - Geography - 1995 (Essay)

Maelezo ya Majibu

How each factor affects the climate of Africa.

(a) Latitude

Latitude determines the angle at which the sun's rays strike the earth and hence the amount of heat received. Areas near the equator (low latitudes) receive the sun's rays almost vertically and are therefore hot throughout the year with heavy convectional rainfall. As one moves towards the tropics and higher latitudes, the rays become more slanting, temperatures fall and rainfall becomes seasonal and lower, giving savanna, desert and, in the far north and south, warm temperate (Mediterranean) climates. Latitude thus explains the broadly symmetrical arrangement of climatic belts north and south of the equator.

(b) Ocean currents

Ocean currents affect the temperature and rainfall of coastal areas. Warm currents, such as the warm Mozambique/Agulhas current off south-east Africa and the warm Guinea current, raise coastal temperatures and, by warming the onshore winds, encourage rainfall. Cold currents, such as the Benguela current off the south-west coast and the Canaries current off the north-west coast, lower coastal temperatures and chill the onshore air so that it holds little moisture; this produces aridity and coastal deserts (e.g. the Namib and part of the Sahara) and coastal fogs.

(c) Distance from the sea (continentality)

The sea moderates temperature, so places near the coast have a small annual range of temperature (cool summers, mild winters) and receive more rainfall from moisture-laden sea breezes. Places far inland in the interior of Africa are cut off from the moderating and moistening influence of the sea; they therefore have a large range of temperature (very hot days and cool nights, hot summers and cool winters) and low, unreliable rainfall, giving continental and desert conditions.

Maelezo ya Majibu

(a)(i) Well labelled diagram of the internal structure of the earth

The earth is made up of a series of concentric layers. Working from the outside inwards these are the crust, the mantle, the outer core and the inner core, separated by the Mohorovičić discontinuity (Moho) between crust and mantle and the Gutenberg discontinuity between mantle and core.

(a)(ii) Distinguishing characteristics of one layer (the crust)

Taking the crust (the outermost layer shown in the diagram) as the chosen layer, its distinguishing characteristics are:

• It is the thinnest and outermost layer, about 6–10 km thick beneath the oceans and up to about 35–70 km thick beneath the continents.
• Its upper (continental) part forms the continents. It is built mainly of granite and is rich in silica and aluminium, so it is called SIAL. It is the lighter part, with a density of about 2.7 g/cm³.
• Its lower part forms the ocean floor. It is built mainly of basalt and is rich in silica, iron and magnesium, so it is called SIMA. It is denser, with a density of about 3.0 g/cm³.
• It is solid rock and is the layer on which we live, containing the soil, rocks and mineral resources.
• It has the lowest temperature and density of all the layers, and it rests on the mantle at the Moho discontinuity.

(b) Importance of the hydrosphere to man

The hydrosphere is the total mass of water on, under and above the surface of the earth (oceans, seas, rivers, lakes, groundwater and water vapour). Its importance to man includes:

• It provides fresh water for drinking, domestic use, irrigation of farmland and for industrial processes.
• Oceans, seas, rivers and lakes serve as cheap routes for water transportation of people and goods.
• It is a source of food such as fish and other sea foods, and of minerals like salt and petroleum.
• Fast-flowing and dammed water is used to generate hydro-electric power (H.E.P.).
• It regulates climate and drives the water cycle that brings rainfall to the land.
• Water bodies are used for recreation, tourism and fishing, which provide employment and income.

Maelezo ya Majibu

(a) Locations on the outline map of Nigeria

(i) Highlands:

• North-Central (Jos) Highlands around Jos in the centre-north.
• Western Highlands (Yoruba/Western uplands) in the south-west.
• Adamawa Highlands in the east/north-east on the Cameroon border (Gongola/Adamawa area).
• Udi Hills (Udi Plateau) in the south-east near Enugu.

(ii) Rivers: Sokoto (north-west), Gongola (north-east, draining into the Benue), Oshun (south-west) and Anambra (south-east, draining into the Niger).

(b) Four ways the North-Central (Jos) Highlands are of economic importance

1. Mining: the plateau is Nigeria's chief source of tin and columbite, providing minerals for export and revenue.
2. Agriculture: the cool climate favours temperate crops and market gardening (Irish potatoes, vegetables, fruits) and cattle rearing on the grasslands.
3. Hydro-electric power and water supply: the high land and rivers provide sites for dams and are a source of many rivers.
4. Tourism and health resort: the cool, pleasant climate and scenery (e.g. Jos and the Assop Falls) attract tourists and make it a health resort; it also supports forestry.

(c) Four problems limiting the economic development of the region

1. Rugged and steep terrain which hinders the construction of roads, railways and buildings.
2. Derelict land and erosion caused by past tin mining, leaving pits and infertile spoil heaps.
3. Thin, poor soils in parts, and shortage of good farmland.
4. Isolation and inadequate infrastructure, together with communal conflicts, which discourage investment.

Maelezo ya Majibu

(a) Locations on the outline map of Nigeria

• Eastern Highlands (Obudu-Oban-Mambilla uplands) in the south-east/east on the Cameroon border - river: Cross River; town: Ogoja / Obudu.
• Eastern Scarplands (Enugu-Nsukka-Udi escarpment) in the south-east - river: Anambra (or Imo); town: Enugu.
• Chad Basin in the north-east - river: Yobe (Komadugu); town: Maiduguri.

(b) The Eastern Highlands

(i) Population and settlement

The Eastern Highlands are generally sparsely populated because of the rugged, mountainous relief and difficult access. Settlements are small and scattered, sited in the valleys and on gentler slopes and lower footslopes; density is low compared with the surrounding lowlands, though the cooler climate has encouraged some settlement and a tourist/ranch centre at Obudu.

(ii) Natural resources

The region has dense forests providing timber, fertile volcanic and upland soils, abundant rainfall and rivers offering water and hydro-power potential, cool upland grassland suitable for grazing, and scenic mountain landscapes that are a resource for tourism.

(iii) Economic activities

The main activities are farming (food crops, plantation tree crops and market gardening in the cool uplands), cattle rearing and ranching (e.g. Obudu Cattle Ranch), lumbering in the forests, and a growing tourism industry attracted by the cool climate and scenery; trade and small-scale processing also take place.

Maelezo ya Majibu

As shown on the sketch map above, the following mineral-producing areas and towns should be correctly located and labelled:

(b) Problems facing mining in Africa

• Inadequate capital: Mining requires large sums of money for exploration, purchase of machinery, construction of mines and provision of transport facilities. Many African countries depend on foreign investors for finance.
• High cost of production: Deep mining, expensive equipment, fuel costs, poor roads and the need to provide electricity and water increase the cost of extracting minerals.
• Inadequate skilled labour: There is often a shortage of trained geologists, engineers, technicians and mine managers. This may lead to dependence on expatriate workers.
• Fluctuation in world mineral prices: The prices of minerals such as crude oil, gold, copper and diamonds may fall on the world market, reducing mining profits and government revenue.

Maelezo ya Majibu

(a) Four ways water transportation is important in international trade

1. Carriage of bulky and heavy goods: ships can carry large quantities of heavy or bulky cargo (crude oil, timber, grains, machinery) that other means cannot handle economically.
2. Cheapest means over long distances: water transport has the lowest cost per tonne-kilometre, making distant trade profitable.
3. Connects countries and continents: oceans provide natural highways linking producing and consuming nations across the world.
4. Large carrying capacity: a single vessel can move enormous volumes at once, so world trade in large tonnages is possible.

(b) Four limitations of water transportation

1. It is slow compared with air and even road transport, so it is unsuitable for perishable and urgent goods.
2. It is restricted to coastlines and navigable waterways; it cannot reach inland or landlocked areas directly.
3. It is affected by weather and natural hazards such as storms, fog, ice and shallow or silted channels.
4. It requires costly port facilities and large capital for harbours, ships and dredging.

(c) How the limitations can be overcome

1. Link with other transport modes: connect ports to inland areas by good roads, railways and pipelines so goods reach the interior.
2. Dredging and canal construction: deepen and widen channels, build canals and locks, and construct artificial harbours to improve navigation.
3. Use of modern technology: equip ships and ports with radar, weather forecasting and navigational aids to reduce hazards; provide modern cargo-handling to speed up loading.
4. Provide adequate finance and maintenance of ports and vessels, and use faster and specialised ships (container and refrigerated vessels).

Maelezo ya Majibu

(a) Five causes of flooding

1. Heavy and prolonged rainfall that exceeds the rate of infiltration and river discharge, so the excess water spreads over the land.
2. Overflow of rivers when the volume of water exceeds the capacity of the channel, especially on the flood plain of the lower course.
3. Poor or blocked drainage systems in towns, where drains choked with refuse and silt cannot carry away run-off.
4. Deforestation which removes the vegetation that intercepts rain and promotes infiltration, thereby increasing surface run-off.
5. Coastal storm surges and high tides that drive sea water inland over low-lying coastal land; dam failure or excessive release from dams may be added.

(b) Four ways flooding can be controlled

1. Construction of dams and reservoirs upstream to store excess water and release it gradually.
2. Building of embankments, dykes and levees along river banks to confine the water to the channel.
3. Provision and regular clearing of wide drainage channels to carry away surface water quickly, and control of building on flood plains.
4. Afforestation and reforestation of catchment areas to increase interception and infiltration and reduce run-off; river channels may also be dredged and straightened to speed discharge.

Maelezo ya Majibu

(a) Interdependence in trade between Nigeria and Britain

The trade between the two countries is based on the exchange of goods that each needs from the other, so that neither is self-sufficient.

1. Nigeria exports primary products (crude oil, cocoa, groundnut, rubber, timber, hides and skins) which Britain needs as raw materials for her industries and as food.
2. Britain exports manufactured goods (machinery, motor vehicles, chemicals, textiles, electrical goods) which Nigeria needs but does not produce in sufficient quantity.
3. Britain provides technical services, capital and expertise for Nigerian industries and projects, while Nigeria provides a large market for British goods.
4. Long historical, colonial and Commonwealth ties, a common language and existing business links bind the two economies together.

(b) Four factors that may limit this trade

1. Long distance between the two countries raises transport and freight costs.
2. Competition from other trading partners such as China, the USA and the European Union.
3. Trade restrictions such as tariffs, quotas and foreign-exchange controls imposed by either country.
4. Similarity/limited range of exports and fluctuation in world prices of Nigeria's primary products, which reduces her earnings and buying power; political and policy changes may be added.

(c) Three ways the trade can be improved

1. Reduction or removal of trade barriers (lower tariffs and easier exchange controls) through trade agreements.
2. Improvement of transport and port facilities to lower the cost and time of moving goods.
3. Diversification and improvement of the quality of Nigeria's exports so that they meet British standards and demand; strengthening of trade missions and credit facilities may be added.

Maelezo ya Majibu

(a) Five functions which urban centres perform for rural areas

1. Market function: towns provide markets where rural producers sell their farm produce and buy manufactured goods.
2. Provision of manufactured goods and services: urban industries supply farm inputs (fertiliser, tools, machinery) and consumer goods needed in the villages.
3. Administrative and political function: towns house government offices, courts and local administration that serve the surrounding rural districts.
4. Educational and health services: secondary schools, colleges, and hospitals in towns serve the rural population.
5. Financial and commercial services: banks, insurance and credit facilities in towns provide loans and savings for rural farmers and traders.
6. Employment and processing: urban factories process rural raw materials and offer jobs to rural migrants (also transport and communication hub).

(b) Four problems that may limit the performance of these functions

1. Poor transport links: bad roads and inadequate transport make it difficult to move goods and people between town and country.
2. Inadequate infrastructure and finance: shortage of funds, electricity and water limits the services the town can offer.
3. Rapid urban growth and overcrowding: pressure of a swelling population strains urban facilities so they cannot adequately serve rural areas.
4. Poverty and low purchasing power of rural people: low rural incomes limit demand for urban goods and services; political instability and poor planning may be added.

Maelezo ya Majibu

(a) Outline map of Nigeria showing the savanna belts and one important town in each

Nigeria's savanna belts run in broadly east–west bands that succeed one another from south to north as rainfall declines. The map below shows the three belts and one representative town in each:

• Guinea Savanna (the southernmost, widest belt) — town: Ilorin (also Kaduna, Makurdi).
• Sudan Savanna (the middle belt) — town: Kano (also Sokoto).
• Sahel Savanna (the far north-eastern belt) — town: Maiduguri (also Nguru).

(b) Three vegetation characteristics of the Guinea Savanna belt

1. Presence of tall grasses. The ground is dominated by tall, coarse grasses that may reach about 3 metres in height by the end of the wet season.
2. Presence of tall, scattered trees. Fairly tall deciduous trees such as the locust bean and shea-butter tree stand scattered among the grasses, giving an open woodland (parkland) appearance. It is the wettest and most wooded of the savanna belts.
3. Trees shed their leaves in the dry season. The trees are drought- and fire-resistant, with thick bark, and shed their leaves during the long dry season to reduce water loss.

(By contrast, the Sudan Savanna has shorter grasses and shorter, thornier, more scattered trees such as acacia, while the Sahel Savanna carries only sparse short grasses and stunted thorn scrub.)

(c) Relationship between vegetation and rainfall in the savanna belts

The vegetation of the savanna is closely controlled by the amount and duration of rainfall, both of which decrease steadily from south to north. The main points of the relationship are:

1. Rainfall decreases from the Guinea Savanna in the south towards the northern (Sahel) limit; correspondingly the vegetation changes from tall grasses and numerous trees to short grasses and sparse thorn scrub.
2. The rainy season lasts longer in the Guinea Savanna than in the Sahel Savanna, so plants there enjoy a longer growing period, grow taller and remain green for more of the year.
3. The low rainfall of the Sahel (only about 20 cm falling to as little as 7 cm a year in the far north) is too little to support tall growth, so it leads to the stunted, thorny growth of trees and grasses.
4. The arrival of the rains marks the start of grass growth (the greening of the savanna), and the length of the dry season determines how long the grasses dry up and the trees stand leafless.

Thus the density, height and greenness of the savanna vegetation diminish in step with the declining rainfall from the Guinea belt in the south to the Sahel belt in the north.

Maelezo ya Majibu

(a)(i) The three climatic belts of the Greek system

1. The Torrid Zone (hot/tropical belt).
2. The Temperate Zones (warm to cool belts, north and south).
3. The Frigid Zones (cold/polar belts, north and south).

(a)(ii) Basis of the classification

The Greek classification is based on latitude and the amount of heat (temperature) received from the sun. The belts are bounded by the tropics and the polar circles according to the angle of the sun's rays.

(b) One characteristic of each belt

1. Torrid Zone: lies between the Tropic of Cancer and the Tropic of Capricorn and is hot throughout the year with the sun overhead at some time.
2. Temperate Zone: lies between the tropics and the polar circles and has moderate temperatures with distinct warm and cool seasons.
3. Frigid Zone: lies between the polar circles and the poles and is very cold throughout the year with long, dark winters.

(c) Three advantages of Koppen's classification over the Greek system

1. Koppen uses both temperature and rainfall, whereas the Greek system uses temperature (latitude) alone, so Koppen gives a fuller picture of climate.
2. Koppen's boundaries are based on natural vegetation, so the climatic regions correspond to real plant and crop distributions on the ground.
3. Koppen's classification is more detailed and precise, recognising many climatic types with defined values, rather than only three broad zones fixed by latitude.

Maelezo ya Majibu

Give reasons for the following agricultural patterns in Nigeria.

(a) Market gardening is predominantly practised around major urban areas

1. Market gardening produces perishable crops (vegetables, tomatoes, fruits) which must reach the consumer quickly, so nearness to the urban market reduces spoilage.
2. The large urban population provides a ready and high-demand market for fresh produce.
3. Nearness to the city gives access to water (for irrigation), transport and manure/refuse from the town, and reduces transport cost of the bulky, fragile produce.

(b) Lumbering is practised mainly in the high forest belt

1. The high forest belt of the south has heavy rainfall and high temperatures that support dense evergreen tropical forest.
2. It contains large stands of valuable timber trees such as mahogany, iroko, obeche and opepe.
3. The area's rivers and nearness to ports (and sawmills) aid the movement and export of logs.

(c) Rice is cultivated in large quantity in the Middle Belt

1. The Middle Belt has extensive river valleys and fadama (flood plains) with alluvial soils that hold water needed by rice.
2. It has a moderate to heavy rainfall and a long enough wet season suited to rice.
3. There is abundant land and a smaller population, allowing large-scale cultivation, and government support for rice production.

(d) Cattle rearing is important in the Sudan Savanna Belt

1. The belt has extensive grassland that provides natural pasture for grazing.
2. The dry climate and low rainfall keep the area relatively free of the tsetse fly which spreads sleeping sickness (trypanosomiasis) in cattle.
3. The open, gently undulating land and the pastoral tradition of the Fulani favour large-scale herding.

Maelezo ya Majibu

(a) Outline map of West Africa showing three ECOWAS member countries and their capitals

The three member countries of ECOWAS shown on the map above, together with their capital cities, are:

(Any three of the fifteen ECOWAS states are acceptable, e.g. Cote d'Ivoire - Yamoussoukro; Mali - Bamako; Sierra Leone - Freetown; Togo - Lome; Benin - Porto Novo.)

(b) Three objectives of ECOWAS

1. Promotion of trade and economic cooperation - to increase and strengthen trade among member states and to promote cooperation and development in economic activity throughout the sub-region.
2. Free movement of persons, goods, services and capital - to remove barriers so that citizens, goods and services can move freely across the borders of member countries.
3. Economic integration and a higher standard of living - to work towards a common market and eventually a single currency, and to raise the standard of living of the peoples of the sub-region while maintaining peace and stability.

(c) Three factors that have limited the full attainment of these objectives

1. Language barrier and differences in colonial background - the members are split among English, French and Portuguese speaking states, which hinders communication, negotiation and full integration.
2. Strong colonial ties - many members remain closely linked economically and politically to their former colonial masters in Europe, so they trade more with those countries than with their West African neighbours, weakening intra-regional cooperation.
3. Similarity of economic activities and products - most member states produce and export the same primary agricultural and mineral products, so there is little to exchange among them and much competition rather than complementary trade.

Maelezo ya Majibu

(a) Economic importance of oceans to man

1. Source of food: oceans provide fish and other sea foods; fishing grounds such as those off the coast of West Africa support the fishing industry.
2. Transportation: oceans are cheap natural highways for international trade; ships carry bulky goods across the Atlantic between Africa, Europe and America.
3. Source of minerals: petroleum and natural gas are obtained from the continental shelf (e.g. Gulf of Guinea), and common salt is obtained by evaporating sea water.
4. Generation of power: tidal and wave energy can be harnessed to produce electricity.
5. Tourism and recreation: beaches and coastal resorts attract tourists and provide income, for example along the Mediterranean coast.
6. Source of fresh water: sea water is desalinated to provide fresh water in dry regions such as North Africa and the Middle East.
7. Influence on climate: oceans and their currents moderate temperatures and bring rain-bearing winds that support agriculture.

(b) A warm current in the North Atlantic and factors responsible for its movement

Selected current: the Gulf Stream / North Atlantic Drift, a warm current flowing from the Gulf of Mexico north-eastward across the Atlantic towards north-west Europe.

Factors responsible for its movement:

1. Prevailing winds: the trade winds drive the water westward across the tropics, and the westerlies then push the warm water north-eastward towards Europe.
2. Rotation of the earth (Coriolis force): deflects the moving water to the right in the Northern Hemisphere, guiding it into a clockwise circulation.
3. Differences in water temperature and density: warm, lighter equatorial water flows towards the colder, denser polar water, setting up movement.
4. Differences in salinity: variations in salt content cause density differences that help drive the current.
5. Shape of the coastline and ocean basin: the outline of the American and African coasts deflects and channels the flow of the current.

Maelezo ya Majibu

(a) Sketch map of Africa

The sketch map below shows the two highlands, one important river rising from each, one inland drainage basin, one artificial lake and one lagoon coast, each clearly named.

Reading the map:

• (i) The Fouta Djallon (Fouta Mallon) Highlands lie in Guinea, in the far west of Africa, and the Cameroon Highlands lie along the Nigeria–Cameroon border, at the inner corner of the Gulf of Guinea.
• (ii) The River Niger takes its source from the Fouta Djallon Highlands, and the River Benue takes its source from the Adamawa/Cameroon Highlands (the two join before entering the sea through the Niger Delta).
• (iii) The Chad Basin (drained inward to Lake Chad) is the important inland drainage basin.
• (iv) Lake Volta in Ghana is the artificial lake.
• (v) The Gulf of Guinea coast (from Côte d'Ivoire through Ghana, Togo and Benin to Nigeria) is the lagoon coast.

(b) Three ways river basins are important to the economy of Africa

1. Agriculture and irrigation: the fertile alluvial soils and reliable water of river basins (e.g. the Nile and Niger basins) support irrigation and intensive crop farming, which feeds the population and provides export earnings.
2. Settlement, water supply and fishing: river basins provide good sites for settlement and towns, supply water for domestic and industrial use, and support inland fisheries that give food and income.
3. Transport and hydro-electric power: navigable stretches serve as cheap communication and trade routes, while the rivers provide dam sites that generate hydro-electric power for homes and industry (e.g. Akosombo on the Volta and Kainji on the Niger).

(c) Three major characteristics of the coastline of Africa

1. It is smooth and regular with few indentations, so it has relatively few deep bays or natural harbours and few good natural ports.
2. It has several estuaries and delta coasts, for example the estuary sections near Togo and the great deltas of the Nile and the Niger.
3. Long stretches, especially along the Gulf of Guinea, are lagoon coasts fringed by sand bars, spits and mangrove swamps, while parts of the East African coast are bordered by coral reefs.

Maelezo ya Majibu

(a) Significance of minerals as an environmental resource

1. Source of energy: fuel minerals such as petroleum, coal and natural gas provide power for industries, transport and domestic use.
2. Raw materials for industry: minerals like iron ore, bauxite, limestone and tin supply the metal, cement and manufacturing industries.
3. Source of foreign exchange and revenue: the export of minerals earns foreign currency and government revenue that finance national development.
4. Employment: mining and related activities provide jobs for many people, both directly and indirectly.
5. Development of infrastructure: mining areas attract roads, railways, electricity and towns.
6. Support for other sectors: minerals such as limestone and phosphate provide materials for construction and fertiliser for agriculture.

(b) Three major problems resulting from the exploitation of mineral resources

1. Land degradation and destruction of the landscape: opencast mining, quarrying and dredging leave pits, spoil heaps and derelict land that is unfit for farming or building.
2. Environmental pollution: mining pollutes air with dust and fumes, and pollutes rivers and soil with chemicals and oil spillage, harming plants, animals and human health.
3. Displacement of people and social disruption: communities are forced off their land, farmland is lost, and rapid growth of mining camps brings overcrowding and social vices; rapid depletion of a non-renewable resource is a further problem.

Maelezo ya Majibu

(a) Four ways a fall in birth rate can be beneficial to a country

1. Reduced pressure on resources: fewer births ease the demand on food, land, water and housing.
2. Lower dependency burden: fewer children to be catered for allows more savings and investment in the economy.
3. Improved standard of living: national income is shared among fewer people, so income per head rises.
4. Less pressure on social services: fewer schools, hospitals and other facilities are needed, so existing ones serve the people better.
5. Reduced unemployment: a slower growing labour force is easier to absorb into available jobs.

(b) Four problems that can arise from a fall in birth rate

1. Ageing population: the proportion of old people rises while the number of young people falls.
2. Shortage of labour: a smaller working population reduces the supply of workers for farms, industries and services.
3. High old-age dependency: the working population must support a large number of retired and aged people.
4. Reduced market and slower economic growth: a shrinking population means a smaller home market for goods and services and a fall in national output; the country may also weaken in defence and manpower.

(c) Four ways the birth rate can be increased

1. Payment of family allowances and child benefits to encourage couples to have more children.
2. Grant of maternity leave, free maternal and child health care and other incentives to mothers.
3. Discouraging or restricting the use of family-planning and birth-control methods.
4. Encouraging early marriage and larger families through public campaigns, and reducing the cost of raising children (free education, tax relief).

Maelezo ya Majibu

As shown on the map above, the required features are:

• Inland drainage basin: Chad Basin, in north-eastern Nigeria.
• Delta: Niger Delta, on the southern coast where the River Niger enters the Atlantic Ocean.
• Man-made lake: Kainji Lake, on the River Niger in north-western/central Nigeria.
• Confluence town: Lokoja, where the River Niger and River Benue meet.

(b) Physical factors which limit river transportation in Nigeria include:

1. Rapids and waterfalls: These occur where there is a steep gradient and prevent boats and larger vessels from moving freely along the river.
2. Seasonal fluctuation in water level: During the dry season, many rivers become shallow, narrow or partly dry, making navigation difficult.
3. Water weeds and floating vegetation: Weeds such as water hyacinth may block channels, slow down boats and damage engines.
4. Sandbanks, silt and shallow channels: Deposition of sand and silt reduces the depth of rivers and may prevent vessels from passing.

(c) These limitations can be overcome by:

1. Constructing dams and reservoirs to regulate the flow of water and maintain a more regular water level during the dry season.
2. Dredging river channels regularly to remove silt, sandbanks and other obstructions, thereby deepening and widening navigable routes.
3. Clearing water weeds and floating vegetation continuously, and controlling their growth through appropriate weed-control measures.
4. Constructing canals, locks and bypass channels around rapids and waterfalls to enable boats to move from one navigable section to another.

In addition, navigation aids such as buoys, beacons and properly marked channels can improve the safety and efficiency of river transport.

Maelezo ya Majibu

(a) Four factors that have favoured plantation agriculture in East Africa

1. Favourable climate: the highlands and coast provide the warm to cool temperatures and reliable rainfall suited to crops such as tea, coffee, sisal and sugar cane.
2. Fertile soils: the deep volcanic soils of the East African highlands are rich and suitable for tree and cash crops.
3. Availability of land and cheap labour: large areas of suitable land and a supply of cheap local labour make large-scale estate farming possible.
4. Capital, transport and market: foreign (colonial) capital and management, railways and roads to the ports (e.g. Mombasa), and a ready overseas market for the produce encouraged the establishment of plantations.

(b) Four ways plantation agriculture is important to the economy

1. Foreign exchange: export crops such as tea, coffee and sisal earn foreign currency.
2. Employment: plantations and processing factories provide jobs for many workers.
3. Raw materials and processing industries: they supply raw materials that support agro-based industries (tea factories, sugar mills).
4. Infrastructure and revenue: they generate government revenue and attract roads, railways, health and social services to rural areas.

(c) Four problems facing plantation agriculture in the region

1. Fluctuation of world prices of the export crops, which makes income unstable.
2. Pests and diseases that attack the crops and reduce yields.
3. Over-dependence on one or few crops (monoculture), which exhausts the soil and exposes the economy to risk.
4. Shortage of labour and capital, and competition from other producing regions; unreliable rainfall/drought and land-tenure disputes may be added.

Maelezo ya Majibu

(a) Five factors to consider in the location of a cement factory

1. Availability of raw materials: the factory must be sited close to deposits of limestone (the main raw material) together with clay/shale and gypsum, because these are bulky and weight-losing.
2. Source of power/fuel: cement manufacture uses much energy for the kilns, so nearness to coal, gas or electricity supply is important.
3. Water supply: an adequate supply of water is needed for the manufacturing process and cooling.
4. Transport facilities: good roads and railways are needed to bring in fuel and take the heavy, finished cement to markets.
5. Nearness to market: siting near large urban and building markets reduces the cost of distributing the heavy product.
6. Availability of labour and land: a large flat site and a supply of skilled and unskilled workers are required; capital is also considered.

(b) Three problems facing cement factories in Tropical Africa

1. Inadequate and unreliable power supply: frequent electricity failures disrupt the energy-intensive kiln operations and raise costs.
2. Poor transport network: bad roads and limited railways make it costly to move fuel to the factory and cement to distant markets.
3. Shortage of capital, skilled manpower and spare parts: heavy dependence on imported machinery, foreign experts and imported fuel, together with obsolete plant and low local demand in some areas, limits production.

Maelezo ya Majibu

Selected vegetation: the tropical continental (savanna) climate.

(a) Distinguishing characteristics of the tropical continental (savanna) vegetation

1. It is dominated by tall grasses (which may grow 1-3 metres high) that turn brown and dry during the dry season.
2. Trees are scattered and short, growing in isolation or small clusters rather than forming a continuous canopy (open woodland/parkland).
3. The trees are deciduous or drought-resistant, shedding their leaves in the dry season to reduce water loss; many are umbrella-shaped (e.g. acacia) with broad, flat crowns.
4. Trees have adaptations such as thick, fire-resistant bark, long tap roots, small waxy leaves and thorns to survive drought and bush fires.
5. Vegetation becomes thicker and taller towards the wetter margin and thins into semi-desert scrub towards the drier margin (a clear north-south gradation).
6. Characteristic trees include the baobab, acacia, shea and locust bean.

(b) Factors that have aided the occurrence of this vegetation

1. Rainfall regime: a marked wet season followed by a long dry season allows grasses to flourish in the rains but prevents the growth of dense forest.
2. Moderate to low total rainfall: decreasing away from the equator, favouring grassland rather than rainforest.
3. High temperatures throughout the year which increase evaporation and moisture stress during the dry season.
4. Seasonal bush fires: frequent burning in the dry season kills seedlings of trees but favours the regrowth of fire-resistant grasses.
5. Human activities: farming, grazing by cattle and clearing of land have opened up the woodland and encouraged grassland.
6. Soil and relief: porous soils that dry out quickly and gently undulating land also favour grass over forest.