WAEC SSCE - Geography - 2001

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When plateaux are enclosed by fold mountains, they are known as intermont plateaux. Intermont plateaux are formed by the upliftment of a large flat area of land, surrounded by fold mountains, through tectonic forces such as folding and faulting. The formation of intermont plateaux typically involves the uplift of sedimentary rocks, which are then eroded by rivers and other water bodies, leading to the formation of deep canyons and valleys. The plateau itself is usually high above sea level, and often has a relatively flat surface that may be used for agriculture or other economic activities. Intermont plateaux are typically found in areas with high tectonic activity, such as the Himalayas, the Rocky Mountains, and the Andes. They are important geographic features, as they can act as natural barriers to human movement and settlement, and are often home to unique ecosystems and wildlife.

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The dark clouds extending to a height of about 15,000 metres which bring a lot of rain to tropical lands are known as cumulonimbus clouds. Cumulonimbus clouds are large and towering, with a dark base and a fluffy top that can sometimes resemble an anvil. They are formed by a combination of rising warm air and moisture, which leads to the formation of thunderstorms and heavy rainfall. These clouds are commonly found in tropical regions where the weather is warm and humid. They can also be associated with strong winds, lightning, and hailstones. The heavy rainfall from cumulonimbus clouds is important for agriculture, as it can provide water for crops and replenish water sources. In summary, cumulonimbus clouds are large, dark clouds that bring heavy rainfall to tropical lands. They are formed by rising warm air and moisture and can also be associated with strong winds, lightning, and hailstones.

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The ocean current that enhances rainfall in its immediate hinterland is the Mozambique Current. This is because the Mozambique Current is a warm ocean current that flows southwards along the east coast of Africa, bringing warm and moist air from the Indian Ocean to the coastal regions of East Africa. As this warm and moist air rises over the land, it cools and condenses, leading to the formation of clouds and rainfall. This process is known as orographic rainfall and is responsible for the relatively high levels of rainfall experienced in coastal regions such as Tanzania, Kenya and Mozambique. In this way, the Mozambique Current plays a key role in supporting agriculture and other forms of economic activity in these regions.

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The climate of Nigeria is characterized by two seasons: the dry season and the rainy season. The dry season usually occurs from November to March, while the rainy season takes place from April to October. During the dry season, there is very little or no rainfall, and the weather is hot and dusty. On the other hand, the rainy season is characterized by heavy rainfall, high humidity, and cooler temperatures. The amount of rainfall varies across different parts of the country, with the coastal regions receiving more rainfall than the northern regions.

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Good transport network does not promote national disintegration. In fact, it can help to promote national unity by connecting different regions and making it easier for people and goods to move between them. A good transport network promotes international trade by making it easier to move goods across borders. It also promotes the movement of people and goods within a country, making it easier for people to access goods and services and for businesses to transport their products. Furthermore, a good transport network can also promote the spread of ideas and technology, as people and information can move more easily across regions and borders. This can lead to the diffusion of knowledge and innovation, which can benefit societies as a whole. In summary, good transport networks can promote international trade, movement of people and goods, and the spread of ideas and technology, but do not promote national disintegration.

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The vegetation type which is found only in the Northern Hemisphere is the "Tundra vegetation". Tundra vegetation is a type of vegetation that is found in the arctic and subarctic regions of the Northern Hemisphere, where the climate is too cold for trees to grow. Instead, the vegetation is dominated by low-growing shrubs, mosses, and lichens. Tundra vegetation is characterized by its ability to survive in extremely cold and harsh environments, and it is an important habitat for a variety of animals, including caribou, reindeer, and polar bears.

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A net population growth is the surplus of birth over death plus net migration. In other words, it is the difference between the number of births and the number of deaths in a population, plus the number of people who move into the population (immigration) minus the number of people who move out of the population (emigration). This represents the overall increase in the size of the population over a given time period.

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The most ideal location for an iron and steel industry is one that has an adequate supply of iron ore, a good transport network, and an adequate supply of coal. Therefore, the correct option is IV, which includes all three factors. Iron and steel production require large quantities of iron ore and coal, as well as a good transportation network to bring in these raw materials and move finished products to market. The location of iron and steel industries is therefore determined by the proximity of these resources, as well as access to transportation infrastructure. A large population, while important for providing a pool of labor and potential customers, is not as crucial to the location of an iron and steel industry as the availability of the necessary resources and infrastructure. Therefore, option I is not necessary for an ideal location. In conclusion, the most ideal location for an iron and steel industry is one that has an adequate supply of iron ore, a good transport network, and an adequate supply of coal. This is because these factors are essential for the production process and efficient transportation of raw materials and finished products.

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Sima is a layer of the Earth's crust that is primarily composed of silicate minerals, such as magnesium and iron silicates. To determine its average density, we can use the formula: Density = Mass / Volume We can estimate the mass of a unit volume of sima by looking at the average density of the Earth's crust, which is around 2.7 grams per cubic centimeter. Sima is denser than the average crust, so we can assume a density of around 3.0 grams per cubic centimeter. Therefore, the answer is 3.0.

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The intensity of erosion by a river is determined by the volume of water, gradient of the valley, and the load carried. Erosion by a river refers to the process of wearing away the river's bed and banks over time. The intensity of this erosion is influenced by several factors, including the volume of water flowing in the river, the gradient of the valley through which the river flows, and the load carried by the river. The volume of water flowing in the river determines the amount of energy available for erosion, with higher volumes of water carrying more energy and therefore causing more erosion. The gradient of the valley, or the slope of the land through which the river flows, also influences erosion by affecting the speed of the water flow. Steeper gradients generally lead to faster flow rates and more erosion. The load carried by the river refers to the amount of sediment and other materials that the river is carrying along with it. This load can range from small particles like silt and clay to larger rocks and boulders. The load carried by the river can significantly affect its erosive power, as heavier loads can cause more friction and turbulence in the water, leading to increased erosion. Overall, the intensity of erosion by a river is determined by a combination of these factors, including the volume of water, gradient of the valley, and load carried by the river.

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Cattle rearing is not a common occupation among the people of Southern coast-lands of Nigeria. This is because the Southern coast-lands of Nigeria are predominantly covered by dense tropical rainforests and mangrove swamps, which are not suitable for grazing. Additionally, the region is characterized by a high water table and periodic flooding, which makes it difficult to keep livestock. On the other hand, fishing, lumbering, and trading are common occupations in the Southern coast-lands of Nigeria. The region has a long coastline and numerous water bodies, which provide abundant opportunities for fishing. The dense forests in the region also provide opportunities for lumbering, while trading is a common occupation due to the region's proximity to the sea and the presence of several ports and markets.

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The type of rainfall characterized by torrential downpour in the tropics or during summers in the temperature interiors is called "convectional rainfall." This type of rainfall occurs due to the heating of the Earth's surface, which causes the air to rise, cool, and condense into clouds. As the clouds continue to rise, they become saturated and precipitation occurs in the form of heavy rain, often accompanied by thunder and lightning. Convectional rainfall is common in areas with high temperatures and humidity, such as tropical regions, and is usually of short duration but high intensity.

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The environmental lapse rate refers to the rate at which temperature changes as you move up or down in the atmosphere. In general, the temperature decreases as you go higher in the atmosphere, and this rate of decrease is called the environmental lapse rate. Out of the options provided, the correct answer is "0.60C for every 100 m ascent". This means that for every 100 meters increase in altitude, the temperature in the atmosphere decreases by 0.6 degrees Celsius. It's important to note that this is just an average rate, and the actual rate can vary depending on a number of factors such as time of day, location, and weather conditions. Understanding the environmental lapse rate is important in meteorology and climatology because it can help scientists and forecasters predict how temperature will change with altitude, and how this will affect weather patterns and climate conditions.

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Megalopolis is the largest settlement type among the options given. A megalopolis is a vast urban region that comprises several metropolitan areas that are physically and economically linked. It is also known as a "super city" or "conurbation." A megalopolis typically includes multiple cities and their surrounding suburbs and towns, which are connected by highways, railroads, and other forms of transportation. These urban regions can cover vast areas and have large populations, with millions of people living within them. Examples of megalopolises around the world include the Northeast megalopolis in the United States, the Pearl River Delta in China, and the Tokyo-Yokohama megalopolis in Japan. In summary, megalopolis is the largest settlement type among the options given, as it comprises multiple metropolitan areas and has a vast geographical area and population.

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Man has indeed interfered with the ecosystem through farming, modification of weather and climate, and overgrazing. Farming involves clearing natural vegetation for cultivation, which leads to deforestation and soil erosion. The use of fertilizers, herbicides, and pesticides also affects the soil, water, and air quality in the ecosystem. Moreover, the introduction of genetically modified organisms (GMOs) has the potential to disrupt the ecosystem balance. Modification of weather and climate through human activities such as burning of fossil fuels, industrial processes, and transportation emissions has contributed significantly to global warming and climate change. The consequences of these activities include rising sea levels, increased frequency of extreme weather events, and changes in precipitation patterns. Overgrazing involves excessive grazing of domestic animals on natural vegetation, leading to depletion of plant species and soil erosion. This, in turn, affects the food chain and the habitat of other animal species in the ecosystem. Therefore, man's interference with the ecosystem through farming, modification of weather and climate, and overgrazing has had significant negative impacts on the environment and the balance of the ecosystem. Thus, the correct option is (d) I, II, and III.

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Transhumance is the movement of cattle up and down mountains in search of pasture. It involves the seasonal migration of livestock from one region to another, usually from highlands to lowlands, or vice versa, depending on the availability of grazing lands. This practice has been used for centuries by pastoralist communities as a way of sustaining their livestock and adapting to changing environmental conditions.

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The major hazard to both human and aquatic life in some coastal areas of Nigeria is oil spillage. Oil spills occur when oil leaks into the environment, typically from a ship or oil rig, and can have devastating effects on the surrounding ecosystem. Oil spills can harm or kill marine animals and plants, and also contaminate water sources that humans rely on for drinking, cooking, and washing. The oil can also cause air pollution, which can harm people's health, especially those with respiratory issues. Oil spills can be difficult to clean up, and can have long-lasting effects on the environment and the people who live nearby.

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Fog is not an element of climate. Climate refers to the long-term patterns of weather in a particular region, while fog is a short-term weather event that can occur in any climate. Fog is caused by the cooling of moist air, which causes water droplets to form and become suspended in the air. While fog can be influenced by climate factors such as temperature and humidity, it is not considered an element of climate itself. Rather, it is a specific type of weather event that can occur in a range of climates.

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The biggest member of the solar system is the Sun. The Sun is a star located at the center of the solar system and is by far the largest object in the solar system. It contains more than 99.8% of the total mass of the solar system and is approximately 109 times bigger than the Earth. The Sun's diameter is about 1.39 million kilometers, which is more than 100 times bigger than the diameter of the Earth. Its huge mass and size make it the dominant force in the solar system, holding all the planets in orbit around it through the force of its gravity. The Sun is also the source of most of the energy that drives the Earth's climate and weather patterns. Its heat and light provide energy for life on Earth and are essential for photosynthesis in plants. Without the Sun, life on Earth would not be possible.

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The initial problems of rain and road development in Africa were primarily due to the difficult physical environment. Africa has a diverse range of physical landscapes, including deserts, savannas, and tropical rainforests, which make it challenging to build infrastructure such as roads. Additionally, heavy rainfall in some regions can cause flooding and erosion, further complicating road development. These factors have historically made it difficult to transport goods and people, leading to economic and social challenges for the continent.

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The largest producer of gold in West Africa is Ghana. Ghana is known to have large deposits of gold and has been a major producer of the precious metal for many years. It is estimated that Ghana produces about 4.2 million ounces of gold annually, making it the 9th largest gold producer in the world. Gold mining in Ghana is a major contributor to the country's economy, and the industry employs thousands of people directly and indirectly. Ghana's gold mines are mainly located in the southwestern and western parts of the country, and the metal is a major export commodity for the country.

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The question is asking to identify which option is NOT a benefit to be derived by ECOWAS member countries. Therefore, the answer is the option that does not provide a benefit. In this case, the answer is "territorial expansion" because ECOWAS is not about territorial expansion but rather a regional economic union aimed at promoting economic integration among its member countries. The other options, such as free movement of people, free flow of capital, and the creation of a large market, are all benefits of ECOWAS as they enhance economic cooperation, integration, and development among member countries.

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An example of a crystalline rock is granite. Granite is a type of igneous rock that is formed from the slow cooling and solidification of magma deep beneath the Earth's surface. Granite is composed mainly of quartz, feldspar, and mica, which are minerals that have a crystalline structure. The minerals in granite are visible to the naked eye and give the rock its characteristic speckled appearance. Crystalline rocks like granite are formed through a process of crystallization, in which minerals solidify from a liquid or gas into a highly ordered, three-dimensional structure. This gives them a unique set of physical and chemical properties that distinguish them from other types of rocks. Crystalline rocks are found all over the world and have a variety of uses, including as building materials, decorative stones, and sources of minerals and ores. They can also provide important clues about the geological history and evolution of the Earth's crust.

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The correct answer is a sill. When molten magma intrudes into the bedding plane of sedimentary rocks, it can form a horizontal sheet-like body called a sill. The magma solidifies and becomes a new layer of rock that is parallel to the existing sedimentary layers. Sills are usually less than a few hundred meters thick and can vary in size from a few meters to several kilometers in length and width. Sills are commonly found in areas of volcanic activity and are an important feature in the study of geology.

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A planet that is adapted to living in a region where little moisture is available is called a xerophyte. Xerophytes are plants that have evolved to survive in environments with limited water availability, such as deserts, arid regions, and rocky terrain. Xerophytes have a variety of adaptations that enable them to conserve water and tolerate dry conditions. For example, they may have deep root systems that can access water deep in the soil, or they may have specialized leaves that reduce water loss through transpiration. Some xerophytes also have thick, waxy cuticles on their leaves to prevent water loss. Overall, xerophytes are well adapted to living in regions where little moisture is available, and their unique adaptations allow them to survive in some of the harshest environments on our planet.

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(a) Four major ocean routes used in world trade

1. The North Atlantic route linking Western Europe with eastern North America (busiest in the world).
2. The Mediterranean-Suez-Red Sea route connecting Europe to the Middle East, South and East Asia through the Suez Canal.
3. The Panama Canal route linking the Atlantic and Pacific oceans (Eastern USA/Europe to western America and the Pacific).
4. The Cape of Good Hope route round southern Africa linking Europe/West Africa to East Africa and Asia. (Others: the North Pacific route and the West African coastal route.)

(b) Four ways water transportation has contributed to economic development

1. It permits the cheap, bulk movement of heavy goods (crude oil, ores, grain, timber) over long distances at low cost per tonne.
2. It has opened up trade and international exchange, allowing countries to export surplus produce and import needed goods.
3. It has promoted the growth of port towns and industries (e.g. Lagos, Port Harcourt) around harbours, creating employment.
4. It earns foreign exchange through shipping services, fishing and tourism, and links inland regions to world markets via rivers and lakes.

(c) Four ways of improving transportation on inland waterways

1. Dredging the rivers to deepen and widen the channels and remove silt so that larger vessels can pass.
2. Clearing obstacles such as rocks, rapids, sand bars and floating weeds (e.g. water hyacinth) from the channels.
3. Constructing locks, dams and canals to by-pass waterfalls and rapids and to maintain a steady water level in the dry season.
4. Providing modern port facilities and navigation aids (jetties, buoys, lighthouses) and regular maintenance to keep routes safe and usable. (Also linking rivers by canals.)

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(a) Instruments used for measuring

(b) The instrument used to measure rainfall - the rain gauge

The rain gauge is used to measure the amount of rainfall that falls at a place over a given period. It consists of:

• A funnel of standard diameter fixed into the mouth of the gauge to collect the rain.
• A cylindrical copper (outer) case that is partly buried in the ground so that the rim stands about 30 cm above the surface.
• A narrow collecting bottle (jar) inside the case into which the funnel directs the rain.
• A measuring cylinder (glass jar) graduated in millimetres, used to read the collected water.

A labelled diagram should show the funnel, the outer copper case set in the ground, the inner collecting bottle and the graduated measuring cylinder.

(c) How the rain gauge is used

• The gauge is set on open, level ground away from buildings, trees and walls that would shelter it, with the rim about 30 cm above the ground.
• Rain falling into the funnel drains into the collecting bottle inside the case.
• At a fixed time each day (usually 9.00 a.m.) the collecting bottle is removed and its water is poured into the graduated measuring cylinder.
• The depth of water is read off in millimetres; this reading is the amount of rainfall for that day. The bottle is then emptied and replaced for the next reading.

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(a) Four characteristics of urban centres

1. High population size and density: large numbers of people living closely together.
2. Non-agricultural occupations: most inhabitants work in industry, commerce, administration and services rather than farming.
3. Presence of infrastructure and social amenities: good roads, electricity, pipe-borne water, hospitals, banks and schools.
4. Complex functions and land use: distinct commercial, industrial, residential and administrative zones with high-rise buildings.

(b) Four ways urban centres depend on surrounding rural areas

1. Food supply: the rural areas produce foodstuffs and livestock that feed the urban population.
2. Raw materials: agricultural and mineral raw materials from rural areas feed urban industries.
3. Labour supply: rural migrants provide much of the cheap labour used in urban factories and services.
4. Market for goods: rural people buy manufactured goods and services produced in the town.

(Also: rural areas supply water, fuelwood and land for urban expansion, waste disposal and recreation.)

(c) Three problems facing rural areas

1. Poor social amenities: lack of good roads, electricity, hospitals and pipe-borne water.
2. Out-migration of youths: loss of the active labour force to towns, leaving the aged behind.
3. Low income and unemployment: dependence on subsistence farming with poor returns and few job opportunities.

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(a) Major method of gold mining in South Africa

Gold in South Africa (chiefly the Witwatersrand around Johannesburg) occurs in thin reefs that dip steeply to great depths, so it is worked by deep-shaft (underground) mining. The main steps are:

• Vertical shafts are sunk from the surface, some reaching over 3 km deep, to reach the gold-bearing reefs.
• Horizontal tunnels (drives and stopes) are driven from the shaft along the reef, and the ore is blasted loose with explosives.
• The broken ore is hauled up the shaft in cages/skips to the surface.
• At the surface the ore is crushed and milled to a fine powder.
• The gold is extracted by treatment with cyanide solution and recovery of the metal (cyanidation), then smelted into bars.
• Because of the great depth, the mines need refrigeration/ventilation, pumping of water and support of the workings.

(b) Four benefits of gold mining to South Africa

1. It earns large amounts of foreign exchange as a leading export.
2. It provides employment for a very large mining and support workforce.
3. It has stimulated the growth of towns and infrastructure (Johannesburg, railways, power supply).
4. It generates government revenue and has encouraged the growth of allied engineering, chemical and manufacturing industries.

(c) Three problems resulting from gold mining

1. Environmental damage: huge waste dumps (mine tailings) and dust disfigure the land and pollute air, soil and water (cyanide/acid drainage).
2. Health and safety hazards: deep mining exposes workers to heat, rock falls, accidents and lung disease (silicosis).
3. Social problems: migrant-labour system separates workers from families and crowds them into camps, and abandoned/worked-out mines leave derelict land and unemployment.

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(a) Distinction between Meridians and Parallels

(b) Time calculation

Given: New Zealand kick-off is 4.00 p.m. at longitude 150 E; Nigeria is at longitude 15 E.

Step 1 - difference in longitude (both places are east, so subtract):

\[150^{\circ}E - 15^{\circ}E = 135^{\circ}\]

Step 2 - convert to time (1 degree = 4 minutes):

\[135 \times 4 = 540 \text{ minutes} = 9 \text{ hours}\]

Step 3 - apply the difference. New Zealand (150 E) lies east of Nigeria (15 E), so its time is ahead. Nigeria is therefore 9 hours behind New Zealand:

\[4.00\text{ p.m.} - 9\text{ hours} = 7.00\text{ a.m.}\]

Answer: Nigerians should tune in their television sets at 7.00 a.m. (on the same Saturday) to watch the kick-off.

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(a) The Prismatic Compass

The prismatic compass is a small, portable hand instrument used for measuring the bearing (direction) of objects and for carrying out compass traverses in surveying.

• It consists of a circular metal box (case) containing a magnetic needle fixed to a graduated circular card (dial) marked from 0 to 360 degrees.
• The needle always points to the magnetic north, so bearings are read as whole-circle bearings from north in a clockwise direction.
• It has a sighting vane (with a fine vertical hair or slit) on one side and a prism with an eye-hole on the opposite side. The prism reflects and magnifies the reading on the card so that the observer can sight the object and read the bearing at the same time.
• It is fitted with a lifting/brake device to steady the swinging card and a lid that also acts as a sighting slit, and it can be mounted on a tripod or held in the hand.

(b) Four precautions when making a compass traverse

• Keep the compass away from metal objects, electric wires and magnetic materials, which deflect the needle and give wrong bearings.
• Hold the compass steady, level and horizontal, and allow the needle to come to rest before taking each reading.
• Take both fore-bearings and back-bearings at each station to check and correct errors.
• Record all readings, station names and distances carefully and immediately in a field notebook.
• Sight the object accurately through the sighting vane and read the bearing through the prism at eye level to avoid parallax error.

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(a) Sketch map of Africa (to show and name)

• Nile Basin: in north-east Africa, the White and Blue Nile draining northward through Sudan and Egypt to the Mediterranean.
• Zaire (Congo) Basin: the large equatorial basin of central Africa drained by the River Congo.
• Mediterranean region in North Africa: the coastal strip of the Maghreb (Morocco, Algeria, Tunisia) along the Mediterranean Sea.

(See the sketch map of Africa with these three regions marked.)

(b) Geographical notes (any two)

(i) Irrigation agriculture in the Nile Basin

• Egypt receives almost no rain, so farming depends entirely on water from the River Nile.
• The Aswan High Dam stores the Nile flood in Lake Nasser and releases water all year, giving perennial (all-year) irrigation in place of the old seasonal basin irrigation.
• Water is led to the fields through canals, and lifted by pumps, the shaduf, sakia and Archimedes screw.
• The rich alluvial soil of the floodplain and delta, plus abundant sunshine, allows several crops a year of cotton (chief cash crop), rice, wheat, maize, sugarcane and vegetables.
• Problems include salinisation, silting behind the dam, and loss of the natural silt that once fertilised the fields.

(ii) Lumbering in Zaire (Democratic Republic of Congo)

• The Congo Basin has vast equatorial rain forest with valuable hardwoods such as mahogany, ebony, iroko and okoume.
• Trees are felled and dragged to the numerous rivers of the Congo system, which float the logs to sawmills and river ports.
• Timber is sawn or exported as logs through ports such as Matadi.
• Difficulties include dense mixed forest (trees of one kind scattered), thick undergrowth, tropical disease, poor roads and heavy rain that hinder transport.

(iii) Fruit farming in North Africa

• The Mediterranean coastlands (Morocco, Algeria, Tunisia) have a Mediterranean climate: hot dry summers and mild wet winters, ideal for fruit.
• Chief products are citrus fruits (oranges, lemons), olives, grapes (vines) and dates (dates in the oases of the desert margin).
• Winter rain and summer irrigation, warm sunshine and terraced hillsides favour the vines and orchards.
• The fruits and wine, olive oil and dates are important exports to Europe.

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(a) Definition of flooding

Flooding is the overflow of a large body of water (usually a river, lake or the sea) onto adjoining land that is normally dry. It occurs when the volume of water in a channel or basin exceeds the capacity that the channel, drainage system or land surface can hold or discharge, so the excess spreads over the surrounding area.

(b) Four causes of flooding

1. Heavy and prolonged rainfall: when rain falls faster than the soil can absorb it or the rivers can carry it away, the excess water spills over the banks.
2. Overflow of rivers: when a river receives more water than its channel can hold, especially at its lower course, it overtops its banks and floods the flood plain.
3. Poor or blocked drainage: in urban areas, drains blocked by refuse, silting, or inadequate drainage channels cause water to accumulate on the surface.
4. Coastal storm surges and tidal action: strong onshore winds and high tides push sea water inland, flooding low-lying coastal land.

Other accepted causes include deforestation which reduces interception and infiltration, dam failure or excessive release from dams, and rapid melting of snow.

(c) Four effects of flooding

1. Loss of lives and displacement: people and livestock are drowned or swept away, and many are rendered homeless.
2. Destruction of property and infrastructure: houses, roads, bridges, railways and electricity installations are damaged.
3. Destruction of crops and farmland: farm produce is washed away or submerged, leading to food shortage and famine.
4. Outbreak of water-borne diseases: contamination of water sources spreads cholera, typhoid and diarrhoea; stagnant water also breeds mosquitoes.

(d) Two measures to control flooding

1. Construction of dams and dykes: dams store excess water while embankments (dykes) and levees are raised along river banks to prevent overflow.
2. Provision of good drainage and afforestation: constructing and clearing wide drainage channels to carry away excess water, together with planting trees to increase interception and infiltration and reduce surface run-off.

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(a) Characteristics of the equatorial climate

• High temperatures all year round: Mean monthly temperatures are about 27 C, with a very small annual range (about 2 to 3 C) because the sun is nearly overhead throughout the year.
• Heavy rainfall: Rainfall is high, usually over 2000 mm a year, and is well distributed over all the months (no real dry season), often with two maxima following the overhead sun.
• Convectional rainfall: Rain falls mainly in the afternoon as heavy convectional thunderstorms, often preceded by a hot, sticky morning.
• High relative humidity: Humidity is very high (about 80 per cent or more), making the weather hot and uncomfortable.
• Small diurnal and annual temperature range; cloudy skies and light, variable winds (doldrums).

(b) Main features of the vegetation (tropical/equatorial rainforest)

• The vegetation is dense evergreen tropical rainforest because the hot, wet conditions allow continuous growth all year.
• Trees are tall, with straight trunks, and are arranged in layers (storeys), the tallest reaching over 45 metres and forming a closed canopy that shuts out sunlight from the forest floor.
• There is a great variety of tree species (hardwoods such as mahogany, ebony and iroko) growing mixed together rather than in pure stands.
• Trees have broad leaves, buttress roots and drip-tips; climbers (lianas) and epiphytes grow on the tall trees.
• Because sunlight cannot reach the floor, undergrowth is thin except along rivers and clearings; along the coast and river mouths there is mangrove forest.

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(a) What is a spring?

A spring is a natural flow of underground water that comes out onto the surface of the earth, usually at the base of a slope or where the water table meets the ground surface. It marks the point where water stored in permeable rock is forced to emerge.

(b) Three ways by which springs may be formed

• At the junction of permeable and impermeable rock (spring line): Rain water sinks through a permeable layer such as sandstone or limestone until it reaches an underlying impermeable layer such as clay. Unable to sink further, the water flows sideways along the top of the impermeable rock and emerges as a spring where this junction is exposed on a hillside.
• Where the water table cuts the surface: In a valley cut into a permeable rock, the land surface may drop below the level of the water table. Water then seeps out along the valley side wherever the ground level falls below the water table, forming a spring.
• From a dipping aquifer/faulted rock (including artesian): Where a permeable rock (aquifer) lies between two impermeable layers and is tilted, or where a fault brings permeable rock against impermeable rock, water under pressure is forced up along the fault or outcrop and emerges as a spring.

Well-labelled diagrams should show permeable and impermeable layers, the water table, and the point of emergence of the water at the junction of the rock layers.

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(a) Outline map of Nigeria (Niger-Benue trough)

• Niger-Benue trough: the broad lowland forming a Y-shape across central Nigeria.
• Rivers: the Niger (from the north-west), the Benue (from the north-east), the Gongola (a tributary joining the Benue) and the Donga (joining the Benue from the south-east).
• One confluence town: Lokoja, where the Niger and Benue meet.

(See the sketch map showing the Y-shaped trough, the four rivers and Lokoja.)

(b) Geographical essay: physical characteristics of the Niger-Benue trough

The Niger-Benue trough is a broad, low-lying structural depression that runs across the middle of Nigeria in a Y-shape, formed where the two great rivers and their valleys meet at Lokoja. Its relief is generally low and flat, mostly below 300 m, bordered on either side by higher plateaux and highlands (the Jos Plateau to the north, the western uplands and the eastern highlands). The floor is a wide alluvial plain built up of sand, silt and clay deposited by the rivers, with extensive floodplains that are inundated in the wet season. The rivers Niger and Benue and their tributaries (Kaduna, Gongola, Donga) drain the trough, joining at the confluence at Lokoja before flowing south to the delta. The trough lies within the tropical continental (savanna) climate, with a marked wet and dry season and moderate rainfall, and it carries guinea savanna vegetation of tall grasses and scattered trees, with gallery (fringing) forest along the river banks. The soils are mainly fertile alluvial and hydromorphic soils on the floodplains.

(c) Four ways economic activities relate to the physical characteristics

1. The fertile alluvial floodplains (fadama) support intensive farming of sugarcane, rice and vegetables (e.g. at Bacita and Numan).
2. The rivers provide inland water transport and fishing, moving goods and supplying fish to riverside communities.
3. The rivers are dammed for hydro-electric power and irrigation (Kainji, Jebba, Shiroro on the Niger).
4. The flat land and river gaps ease the routing of roads and railways, and the water supports livestock grazing on the savanna grasses.

Detalles de la respuesta

(a) Four patterns of population movement within a country

1. Rural to urban migration: movement of people from villages to towns and cities.
2. Rural to rural migration: movement from one rural area to another, often in search of farmland.
3. Urban to rural migration: movement of people from towns back to rural areas, for example on retirement.
4. Urban to urban migration: movement from one town or city to another.

(b) Five reasons for rural to urban migration

1. Search for employment and higher wages in industries and offices located in towns.
2. Availability of better educational facilities (schools and higher institutions) in urban centres.
3. Better social and medical facilities such as hospitals, electricity, pipe-borne water and recreation.
4. Escape from the drudgery and low income of subsistence farming in rural areas.
5. Attraction of the bright lights and superior standard of living in the city.

(c) Effects of population movement

(i) On the source (rural) region:

1. Reduction in labour force, leaving mainly the aged and children, so farm output falls.
2. Reduction in population pressure on the land and resources.
3. Inflow of remittances (money) sent home by the migrants, raising income.

(ii) On the destination (urban) region:

1. Increased supply of cheap labour for industries and services.
2. Overcrowding leading to housing shortage, slums and pressure on facilities.
3. Rise in unemployment and social vices such as crime and prostitution.

Detalles de la respuesta

(a) The term vulcanicity

Vulcanicity (or vulcanism) is the process by which solid, liquid or gaseous materials (magma, lava and gases) from the interior of the earth are forced into the earth's crust or poured out onto its surface. It includes both intrusive activity, where magma cools within the crust to form features such as batholiths, dykes and sills, and extrusive activity, where lava reaches the surface to build volcanoes and lava plateaux.

(b) Characteristics and mode of formation (one chosen: the Batholith)

Batholith - characteristics:

• It is a very large intrusive (plutonic) igneous body, usually made of coarse-grained rock such as granite.
• It forms the deep core or root of large mountain ranges and covers a very wide area.
• It becomes exposed at the surface only after long-continued erosion of the overlying rocks, often forming inselbergs and domed uplands.

Mode of formation: A large mass of molten magma rises from deep within the earth and is intruded into the crust, deep below the surface. Because it lies far below ground, it cools and solidifies very slowly, giving large crystals. Over a long time, the overlying rocks are stripped away by weathering and erosion, exposing the massive granite batholith at the surface.

(If the Dyke is chosen: a dyke is a narrow, wall-like sheet of igneous rock that cuts across the bedding of the surrounding rocks; it forms when magma is forced into a near-vertical crack or joint and solidifies. If the Composite cone is chosen: it is a tall, steep-sided volcano built of alternating layers of lava and pyroclastic materials from repeated eruptions of fairly viscous lava.)

(c) Four ways volcanic rocks are important to man

• On weathering they form very fertile soils that are good for agriculture.
• They provide hard, durable building and road-making materials (for example basalt).
• They are associated with valuable minerals and, where volcanic activity persists, with hot springs and geothermal energy.
• Volcanic landscapes and features attract tourists, bringing revenue.