WAEC SSCE - Geography - 2000 (Essay)

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First set the data out clearly. Reading the table by year-column, the quantities (in kg) are:

State	1995	1996	1997	1998
A	300,000	400,000	500,000	600,000
B	500,000	500,000	600,000	700,000
C	600,000	700,000	800,000	800,000
D	700,000	600,000	500,000	400,000
Yearly total	2,100,000	2,200,000	2,400,000	2,500,000

(a) Total quantity of yams produced by the four states, 1995 to 1998

Add the four yearly totals: \[2{,}100{,}000 + 2{,}200{,}000 + 2{,}400{,}000 + 2{,}500{,}000 = 9{,}200{,}000\ \text{kg}.\] The total quantity produced during the period is 9,200,000 kg.

(b) Pie chart of the 1998 output

The 1998 total is \(600{,}000 + 700{,}000 + 800{,}000 + 400{,}000 = 2{,}500{,}000\) kg. Each state's angle is found from \[\theta = \frac{\text{state output}}{\text{total}} \times 360^{\circ}.\]

State	1998 output (kg)	Working	Angle
A	600,000	(600,000/2,500,000)×360	86.4°
B	700,000	(700,000/2,500,000)×360	100.8°
C	800,000	(800,000/2,500,000)×360	115.2°
D	400,000	(400,000/2,500,000)×360	57.6°
Total	2,500,000		360.0°

To draw it: construct a circle of convenient radius, mark a starting radius (12 o'clock), and use a protractor to mark off the angles in order, largest to smallest. Shade each sector differently, label it with the state and its value or percentage, and add a title and key.

(c) Two advantages of a pie chart

1. It shows clearly the proportion or share that each part contributes to the whole.
2. It gives an easy visual comparison between the sectors, so the largest and smallest producers are seen at a glance.

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(a) Combined rainfall and temperature graph for Station X

The monthly figures for the station are set out below. Temperature is plotted on the left-hand vertical axis as points joined by a smooth curve; rainfall is plotted on the right-hand vertical axis as vertical bars, one for each month.

Month	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Temp (\(^{\circ}\)C)	21	21	20	17	15	12	12	13	14	18	18	20
Rainfall (mm)	5	8	20	45	80	110	105	90	60	35	15	8

The completed climate graph is shown below.

(b) Calculations

(i) Annual temperature range = temperature of the hottest month minus temperature of the coldest month:

\[ \text{Range} = 21^{\circ}\text{C} - 12^{\circ}\text{C} = 9^{\circ}\text{C}. \]

(ii) Mean annual temperature = sum of the twelve monthly temperatures divided by 12:

\[ \bar{T} = \frac{21+21+20+17+15+12+12+13+14+18+18+20}{12} = \frac{201}{12} = 16.8^{\circ}\text{C}. \]

(c) Climatic type

The station has a small annual temperature range (9\(^{\circ}\)C) with warmth throughout the year, and its highest temperatures (Dec-Feb) fall in the driest months while the heaviest rain (Jun-Aug) comes in the cooler months. Hot, dry summers combined with mild, wet winters identify the station as a Mediterranean (warm temperate western margin) climate. Because the hot dry season occurs in December-February, the station lies in the Southern Hemisphere.

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(a)(i) Outline of the map reduced to one-third of the original scale

The extract is redrawn so that every length is reduced to one-third of its length on the original map, while the shape, orientation and relative positions of all features are kept exactly the same. The reduced outline, with the required features added for part (b), is shown below.

(a)(ii) Scale of the outline drawn

The original scale is 1:50,000, meaning 1 unit on the paper represents 50,000 units on the ground. When every distance on the paper is reduced to one-third, the same piece of ground is now shown by a paper length that is three times smaller, so each paper unit must represent three times as much ground:

\[ 50{,}000 \times 3 = 150{,}000 \]

The scale of the outline drawn is therefore 1:150,000 (that is, 1 cm on the outline represents 1.5 km on the ground).

(b) Features shown on the outline

The following are marked and named on the reduced outline above, each in its correct relative position taken from the extract:

• (i) The settlements of Okeigbo and Omifunfun, each shown by a small settlement circle and named. Okeigbo is drawn as a nodal point where several roads converge.
• (ii) The ridge east of Okeigbo, shown by its elongated pattern of closed contour lines running roughly north-south, with the crest marked.
• (iii) River Oni, drawn as a single line with an arrow indicating its direction of flow (from the higher ground in the north-east towards the lower ground in the south-west).
• (iv) The minor road from Idare to Omifunfun, drawn as a double broken line and labelled.

(c) Two reasons why Okeigbo could be considered more important than Mafoworade

1. Superior services and administrative functions: Okeigbo possesses a hospital, a district council office, a police station, schools and a piped water supply, whereas Mafoworade has none of these facilities. This concentration of social and administrative services makes Okeigbo a higher-order central place.
2. Greater accessibility as a nodal town: Okeigbo is a route centre where several roads meet, giving it far better accessibility for trade and movement of people and goods, while Mafoworade lies off the main route junctions and is far less accessible.

(d) Land-use types found in the area

• (i) Farming (agriculture): shown by the widespread areas of scattered cultivation across the mapped area.
• (ii) Transportation: shown by the presence of all categories of roads (main roads, minor roads and tracks) linking the settlements.
• (iii) Settlement: shown by the several settlements such as Okeigbo, Omifunfun and others, each performing different functions.

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(a) Four differences between local craft and heavy manufacturing industries

Local craft industry	Heavy manufacturing industry
Uses simple, locally made tools and manual skill	Uses heavy, expensive machinery and modern technology
Requires little capital to set up	Requires very large capital investment
Employs few workers, often family labour	Employs many skilled and semi-skilled workers
Small output for the local market, using local raw materials	Large-scale output for national and export markets, using bulky raw materials

Other valid contrasts: craft industries need low or no power supply while heavy industries need large power supply; craft goods are hand-made while heavy-industry goods are mass produced.

(b) Three factors that have influenced the location of an iron and steel industry in Tropical Africa (for example Ajaokuta in Nigeria)

1. Availability of iron ore and other raw materials such as limestone and coal or nearby sources, reducing the cost of assembling bulky inputs.
2. Supply of power/energy from hydroelectricity, coal or natural gas needed to smelt the ore.
3. Good transport links (rail, road and water) to bring in raw materials and move out the heavy finished products.

Also acceptable: availability of water for cooling, capital and government policy, and a market for the steel.

(c) Three ways industrialization has contributed to the economy of Tropical African countries

• Employment creation: factories provide jobs, raising incomes and reducing unemployment.
• Earning of foreign exchange through the export of manufactured goods and saving of foreign exchange through import substitution.
• Development of infrastructure and growth of towns as roads, power and water supplies expand around industrial centres, and the government earns more revenue from taxes.

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(a) Four atmospheric resources

• Air (oxygen, carbon dioxide, nitrogen and other gases).
• Sunlight (solar energy).
• Wind.
• Rainfall (water/precipitation).

(b) Three uses each of any two of the resources

Sunlight (solar energy):

• Used by green plants for photosynthesis to manufacture food.
• Provides heat and light and helps to dry crops, clothes and fish.
• Generation of solar electricity through solar panels.

Wind:

• Generation of electricity using windmills/wind turbines.
• Sailing and winnowing of grains, and pollination and seed dispersal.
• Cooling and drying, and driving of water pumps.

(Air can also be cited: oxygen for respiration, carbon dioxide for photosynthesis, air for combustion and for inflating tyres.)

(c) Three other environmental resources important to man

• Water (rivers, lakes, seas and underground water).
• Soil / land.
• Minerals (and forests/vegetation and wildlife).

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(a) Examples of rocks

• Sedimentary rocks: limestone, sandstone, shale, coal (any two).
• Metamorphic rocks: marble, slate, gneiss, quartzite, schist (any two).

(b) Four differences between sedimentary and metamorphic rocks

Sedimentary rocks	Metamorphic rocks
Formed by the deposition and compaction/cementation of sediments.	Formed by the alteration of existing rocks by heat and pressure.
Usually arranged in layers (strata / bedding planes).	Often show foliation (banding) or are recrystallised, without simple bedding.
Generally soft and less compact, and may be porous.	Generally hard, compact and dense.
Often contain fossils of plants and animals.	Fossils are usually destroyed by the heat and pressure.

Additional difference: sedimentary rocks form at or near the surface at low temperature, while metamorphic rocks form deep within the crust under intense heat and pressure.

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(a) Combined rainfall and temperature graph for Station X

The two elements are drawn on the same base line of months but on two different vertical scales: rainfall is shown as columns read against the left-hand scale (in millimetres) and temperature is shown as a smooth line read against the right-hand scale (in degrees Celsius). The paired figures used are:

Month	J	F	M	A	M	J	J	A	S	O	N	D
Rainfall (mm)	18	17	20	39	48	90	112	90	56	47	30	25
Temp (ºC)	21	21	20	17	15	12	12	13	14	18	18	20

(b) Calculations

(i) Annual temperature range

The annual temperature range is the difference between the highest and the lowest mean monthly temperatures.

Highest temperature = 21ºC (January and February)
Lowest temperature = 12ºC (June and July)

\[\text{Range}=21^{\circ}\text{C}-12^{\circ}\text{C}=9^{\circ}\text{C}\]

(ii) Mean annual temperature

Add the twelve monthly temperatures and divide by 12.

\[\text{Sum}=21+21+20+17+15+12+12+13+14+18+18+20=201^{\circ}\text{C}\]\[\text{Mean}=\frac{201}{12}=16.75^{\circ}\text{C}\approx 16.8^{\circ}\text{C}\]

(c) Climatic type

The station shows the following features:

• Warm, moderate temperatures throughout the year (range only 9ºC, mean about 16.8ºC), so there is no true cold season.
• Highest temperatures occur in December, January and February (about 20–21ºC) and the lowest in June and July (12ºC). Since summer falls in December–February, the station lies in the Southern Hemisphere.
• The rain comes mainly in the low-sun (winter) season, June–August, reaching a maximum of 112 mm in July, while the high-sun (summer) months of January–February are the driest (17–18 mm). Total annual rainfall is 592 mm.

Warm dry summers combined with mild wet winters and a small temperature range identify the station as a Mediterranean climate (also called the Warm Temperate Western Margin climate), such as that experienced around Cape Town, Perth or central Chile.

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(a) Location on the outline map of Africa

• (i) Equatorial climatic zone: the Congo (Zaire) Basin and the Guinea coast lands lying roughly between 5°N and 5°S – town: Kisangani (or Douala).
• (ii) One Mediterranean zone: the extreme north-west coast (northern Morocco/Algeria) or the south-western tip around the Cape – town: Algiers (or Cape Town).
• (iii) Important town in each zone: as named above.

(b) Four characteristics of the equatorial climate

1. High temperatures all year, about 26 to 27°C, with a very small annual range because the sun is nearly overhead throughout.
2. Heavy rainfall all the year round, over 150 to 250cm, with no real dry season; rain is mainly convectional, falling as afternoon thunderstorms.
3. Very high relative humidity (about 80 per cent or more) and much cloud cover, giving a hot, sticky, oppressive feel.
4. Double rainfall maxima following the two equinoxes, and small diurnal (day-to-night) temperature range with regular "four o'clock" rains.

(c) Two ways the equatorial climate affects agriculture

1. The constant heat and moisture allow all-year cultivation of tree crops such as oil palm, cocoa, rubber and plantains, and support dense rainforest that yields timber; growth is rapid and continuous.
2. However, the heavy rain leaches nutrients and readily erodes bare soils, encourages rapid weed growth, pests and crop diseases, and the wetness makes drying and storage of harvests difficult, so shifting cultivation and careful soil management are needed.

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As shown on the map above:

• Area with annual rainfall under 100 cm: the extreme north-eastern part of Nigeria around the Lake Chad Basin. An important town in this area is Maiduguri.
• Area with annual rainfall over 300 cm: the south-eastern coastal belt, especially around Calabar and the eastern Niger Delta. An important town is Calabar.

(b) Other climatic features of the area receiving over 300 cm of rainfall

• There are usually two rainfall maxima, commonly around June or July and September, with a short break in August.
• There is no completely dry month; rain falls throughout the year.
• Temperatures are high throughout the year, with an average of about \(27^\circ\text{C}\).
• The annual temperature range is small, usually about \(2^\circ\text{C}\) to \(3^\circ\text{C}\), because of the equatorial coastal influence.
• Relative humidity is very high, often above \(90\%\) in the mornings.
• Cloud cover is heavy and sunshine duration is relatively low.

(c) Vegetation associated with this climate

The vegetation is the mangrove swamp forest, also called coastal swamp forest. It occurs in the tidal, waterlogged and saline or brackish parts of the Niger Delta and along parts of the coast.

Characteristics of mangrove swamp vegetation include:

• It is a dense, evergreen forest because rainfall and humidity are high throughout the year.
• The trees are mainly broad-leaved and occur in different species of mangrove.
• The plants are adapted to waterlogged, muddy soils and salty water.
• Many trees have aerial roots, prop roots or breathing roots which help them obtain air from the swampy soil and also support them.
• Vegetation is generally low to medium in height, often about \(10\) to \(15\) m in wetter sections, though it may be shorter in more saline areas.
• Palms, reeds and coconut trees may occur along the shore and on relatively drier coastal land.
• The forest contains valuable hardwood species in places, although access is difficult because of the swampy ground.

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(a) Three differences between rail and water transport

Rail transport	Water transport
Moves on fixed rails/tracks on land	Moves on rivers, lakes, seas and oceans
Faster over land for medium distances	Slower but suited to very long, heavy hauls
Higher cost per tonne-kilometre for bulky goods	Cheapest means for carrying bulky, heavy goods over long distances

Also acceptable: rail follows a fixed inland route and can reach interior areas, while water transport is limited to navigable waterways and coasts.

(b) Four ways transportation can influence economic development (using Nigeria as the named West African country)

1. Opening up of remote areas: roads, rail and waterways make interior farming and mining regions accessible, encouraging production.
2. Movement of raw materials and finished goods: good transport links farms, factories and markets, promoting trade and industry.
3. Encouragement of agriculture and marketing: farmers can move perishable produce quickly to urban markets, raising farm incomes.
4. Employment and growth of towns: transport construction and services create jobs, and towns grow at route junctions and ports (for example Lagos, Kano, Port Harcourt).

Also valid: it promotes tourism, national integration and even distribution of development.

(c) Three problems of rail transport development in developing countries

• Shortage of capital to build and maintain the expensive rail lines and rolling stock.
• Difficult physical relief such as rivers, swamps, mountains and hard rock that raise construction costs.
• Obsolete equipment and poor maintenance leading to frequent breakdowns, derailments and unreliable services, worsened by shortage of spare parts and skilled personnel.

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(a) Four differences between lines of longitude and lines of latitude

Lines of longitude (meridians)	Lines of latitude (parallels)
Run in a north-south direction, joining the poles.	Run in an east-west direction.
They are all equal in length (each a great semicircle).	They are unequal in length; the Equator is longest and they shorten toward the poles.
Measured in degrees east or west of the Prime (Greenwich) Meridian, up to 180.	Measured in degrees north or south of the Equator, up to 90.
They converge (meet) at the poles and are widest apart at the Equator.	They are parallel to one another and never meet.

(b) Straight-line distance between Tema (6 degrees N) and London (52 degrees N)

Both places lie on (or near) the same meridian, so the distance is measured along a line of longitude. The difference in latitude is:

\[ 52^{\circ} - 6^{\circ} = 46^{\circ} \]

Along a meridian, 1 degree of latitude = 111 km (approximately). Therefore:

\[ \text{Distance} = 46 \times 111 \text{ km} \] \[ = 5{,}106 \text{ km} \]

The approximate straight-line distance is 5,106 km. (Using 110 km per degree gives \(46 \times 110 = 5{,}060\) km.)

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(a) Outline map of West Africa showing three ECOWAS members and their capital cities

The sketch map below shows the outline of West Africa with three member countries of the ECOWAS shaded and named, and the capital city of each country marked with a dot and named.

The three member countries and their capital cities shown are:

Member country	Capital city
Senegal	Dakar
Ghana	Accra
Nigeria	Abuja

(b) Three objectives of the ECOWAS

1. Promotion of trade and economic integration: to increase and liberalise trade between member states by removing tariffs and other trade barriers so as to build a common market in the sub-region.
2. Free movement of persons, goods, services and capital: to allow citizens, goods and services to move freely across member borders, including the right of residence and establishment.
3. Co-operation and joint development: to promote co-operation and development in economic, social and cultural activities, including the joint development of transport, communication and other infrastructure, and eventually the establishment of a common currency.

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

1. Language barrier and strong colonial ties: members are split into English-, French- and Portuguese-speaking blocs with differing colonial links, which hinder easy communication and full co-operation. Some Francophone states also maintain rival sub-regional bodies that work against ECOWAS.
2. Similarity of economic activities and currency problems: most members produce and export the same primary products, so they compete with rather than complement one another, keeping intra-regional trade low. The use of many different national currencies further complicates trade and payments.
3. Political instability and inability to meet obligations: frequent coups, border disputes and mutual mistrust, together with the failure of some members to pay their financial dues and the poor transport and communication network, weaken the pace of integration.

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(a) Two methods of irrigation agriculture in the Nile Valley

1. Basin (flood) irrigation: low earth banks divide the flood plain into large basins. During the annual flood, river water is led into the basins and allowed to stand for several weeks so that it soaks the soil and deposits fertile silt; the surplus is then drained back and crops are sown on the moist land. This is the older, traditional method.
2. Perennial (canal) irrigation: water is stored behind dams and barrages (for example the Aswan High Dam) and released all year through a network of canals to the fields. Water may be lifted onto the land by the shaduf, sakia (water wheel) or Archimedes screw, or nowadays by mechanical pumps and modern canal/sprinkler systems, allowing two or more crops a year.

(b) Three reasons for the development of irrigation agriculture in this region

1. The region has a hot desert climate with very low, unreliable rainfall, so farming is impossible without added water.
2. The Nile provides a permanent, dependable supply of water fed from distant rainy highlands, guaranteeing water even in the rainless valley.
3. The valley has fertile alluvial silt and a large population that must be fed, so intensive irrigated cropping (cotton, rice, sugar cane, cereals) is worthwhile.

(c) Four problems associated with irrigation agriculture in the Nile Valley

1. Salinisation and waterlogging of soils where drainage is poor and evaporation leaves salts behind.
2. Loss of natural silt fertility below the Aswan Dam, forcing farmers to buy expensive artificial fertilisers.
3. Spread of water-borne diseases such as bilharzia (schistosomiasis) and malaria that breed in the standing canal water.
4. Silting of canals and reservoirs, plus high cost of maintaining dams, pumps and canals, and pressure of population on the limited irrigated land.

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Comparison of the North Central Highlands with the Cross River Plain

(a) Relief and Drainage

Heading	North Central Highlands	Cross River Plain
Relief	A highland region with an average height of about 750 m, although parts of the Jos Plateau are much higher. It has plateaux, isolated hills, ridges, volcanic cones and steep slopes.	A lowland region, mainly about 120–180 m above sea level. It is generally flat to gently undulating, with isolated hills and ridges in some places.
Drainage pattern	It has mainly a radial drainage pattern because several rivers flow outward from the high plateau areas.	It has mainly a dendritic drainage pattern, with the Cross River and its tributaries flowing southwards towards the Atlantic Ocean.
Drainage condition	It is generally well drained because of its high elevation and sloping land.	Some parts are poorly drained, with swampy clay depressions, flood plains and seasonal flooding along rivers.

(b) People and Settlement

Heading	North Central Highlands	Cross River Plain
People	It is inhabited by many ethnic groups, including the Berom (Birom), Ngas/Angas, Tarok, Mwaghavul, Afizere and other Plateau peoples. There are also in-migrants in towns such as Jos.	It is also inhabited by many ethnic groups, including the Efik, Ibibio, Ejagham (Ekoi), Bekwarra, Yala, Ukelle and related groups.
Population distribution	There are both densely populated areas, especially around Jos and fertile plains, and sparsely populated hill and plateau areas.	There are densely populated farming areas as well as sparsely populated swampy, forested and poorly accessible areas.
Settlement pattern	Settlements are commonly found on plains, valley sides and at the foot of hills. Both nucleated villages and dispersed farmsteads occur; Jos and Bukuru are important urban centres.	Settlements are commonly located on interfluves and relatively dry land above swampy valleys. Both nucleated and dispersed settlements occur, while Calabar is the major urban centre.

(c) Economic Activities

Heading	North Central Highlands	Cross River Plain
Crop farming	Crop farming is important. Food crops include maize, yam, millet, sorghum, beans and soya beans. The cool climate also favours Irish potatoes and temperate vegetables.	Crop farming is also important. Food crops include yam, cassava, rice, maize, cocoyam and vegetables.
Cash crops	Groundnut, cotton and wheat are grown in suitable parts, while market gardening supplies vegetables to nearby towns.	Oil palm, rubber and cocoa are important cash crops.
Mining and other activities	Tin and columbite mining are important, particularly around the Jos Plateau. Livestock rearing, tourism and local crafts such as leatherwork, brasswork and dyeing are also carried out.	Timber extraction, fishing, canoe transport, trading and local crafts such as raffia work, cane work and wood carving are important. Calabar also promotes trade and port-related activities.

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(a) Location on the outline map of Nigeria

• Gold: Ilesha/Maru-Anka area (Osun and Zamfara/Niger belt of the Basement Complex) – town: Ilesha (or Maru).
• Petroleum: the Niger Delta (Rivers, Bayelsa, Delta States) – town: Port Harcourt (or Warri).
• Columbite: the Jos Plateau – town: Jos (or Bukuru).

(b) Three contributions of mineral resources to the economy of Nigeria

1. Source of government revenue and foreign exchange: crude oil exports supply the greater part of federal revenue and foreign earnings used to finance development.
2. Provision of employment and income: mining, drilling, refining and servicing industries create jobs for many Nigerians, raising incomes and living standards.
3. Basis for industrialisation and infrastructure: minerals supply raw materials and energy (petroleum, natural gas, tin, columbite, limestone) for industries, and mineral revenue funds roads, ports, schools and power projects.

(c) Four factors that limit the exploitation of minerals in Nigeria

1. Shortage of capital for the heavy investment needed in exploration, drilling and machinery.
2. Inadequate skilled manpower and technology, forcing reliance on expensive foreign experts and equipment.
3. Poor transport and infrastructure to many mineral sites, raising the cost of moving ores to processing points and ports.
4. Insecurity, pipeline vandalism and environmental problems (oil spillage, community unrest), plus fluctuating world prices, which discourage steady production.

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(a) Four factors that led to the high population density in Japan

1. Extensive coastal lowlands and plains: Although Japan is largely mountainous, the limited flat land such as the Kanto, Nobi and Kinki plains concentrates settlement, industry and farming, forcing very high densities onto the small habitable portion.
2. Highly developed industry and commerce: Japan is one of the world leading industrial nations (vehicles, electronics, iron and steel, shipbuilding). The abundance of factory and service jobs in cities like Tokyo, Osaka and Yokohama attracts and holds a large population.
3. Intensive and productive agriculture: The fertile alluvial soils, favourable monsoon rainfall and intensive rice cultivation (double cropping, terracing) support a dense rural population on very little land.
4. Excellent transport and long history of settlement: A dense network of railways, expressways and ports links the crowded core regions, while long-established urban centres have grown continuously over centuries, adding to concentration.

Other acceptable points: good fishing grounds offshore, high standard of living and medical care giving long life expectancy, and government concentration of development in the coastal belt.

(b) Three problems of the high population density in Japan

1. Housing shortage and overcrowding in the large cities, leading to very small dwellings, high rents and pressure on land.
2. Heavy pressure on land for farming, industry and building, causing high land prices and reclamation of the sea.
3. Traffic congestion and environmental pollution (air and water) arising from dense industry and heavy commuter movement in the urban regions.

Also acceptable: strain on social services and disposal of waste.

(c) How these problems are being solved

• Building of high-rise blocks of flats and reclaiming land from the sea to create more space for housing and industry.
• Construction of efficient mass-transit systems such as the bullet train (Shinkansen) and city subways to ease congestion.
• Decentralisation of industry and population to smaller towns and new towns to reduce pressure on the core cities.
• Strict pollution-control laws and the encouragement of family planning to check further rapid growth.

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(a)(i) Two landforms produced by faulting

• Block mountain (horst).
• Rift valley (graben).

(Other examples: fault scarp, tilted block.)

(a)(ii) Characteristic features of a rift valley

A rift valley is a long, narrow trough of land that has sunk (subsided) between two roughly parallel faults. Its features are:

• It has a flat, sunken floor bordered by steep, parallel fault scarps (walls) on both sides.
• It is long and narrow, running for great distances (e.g. the East African Rift Valley).
• The floor often contains long, narrow lakes (e.g. Lakes Tanganyika, Nakuru) and sometimes volcanic activity.

(Alternatively, a block mountain/horst is an upstanding block bounded by fault scarps, with a fairly flat or dome-shaped top and steep sides, e.g. the Ruwenzori.)

(b) Importance of mountains to man

• They cause relief rainfall and are sources of rivers used for water supply, irrigation and hydro-electric power.
• They contain mineral resources and forests that provide timber.
• Their cooler, healthier climate and scenery attract settlement, farming and tourism (hill resorts).
• They serve as natural boundaries and defence barriers between regions or countries.
• Highland pastures support grazing of animals.

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(a) A typical soil profile

A soil profile is a vertical section through the soil, from the surface downwards to the underlying parent rock. It reveals a series of distinct layers, called horizons, which differ in colour, texture, humus content and mineral composition. A well-labelled diagram of a typical soil profile is shown below.

Working downwards, the horizons are:

• O horizon (litter layer): the thin surface layer of fresh and partly decayed plant and animal remains (leaf litter and humus).
• A horizon (topsoil / zone of eluviation): a dark, humus-rich mineral layer where biological activity is greatest. Most plant roots and soil organisms occur here, and soluble minerals are washed downward (leached) out of this zone.
• B horizon (subsoil / zone of illuviation): lighter in colour because it contains less humus. Clay and minerals leached from the A horizon (chiefly iron, aluminium and calcium compounds) accumulate here, making it denser and more compact.
• C horizon (regolith): partly weathered, broken fragments of the parent rock from which the true soil above has developed; it acts as a reservoir of fresh minerals.
• R horizon (bedrock): the solid, unweathered parent rock at the base of the profile.

(b) Importance of soil

1. It is the main medium of plant growth, supplying nutrients, water and anchorage for roots.
2. It forms the basis of agriculture and grazing, and therefore of food production; soil type largely determines the kind of farming practised.
3. It is a habitat for micro-organisms, earthworms, reptiles and other soil organisms that recycle nutrients.
4. It provides raw materials for industry, such as sand, clay and limestone.
5. It stores, filters and releases water, and holds the essential minerals needed by plants.
6. It serves as a firm foundation for buildings, roads and other structures.