WAEC SSCE - Geography - 2002

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The difference in the readings on the wet and dry-bulb thermometers is used to determine relative humidity. Relative humidity is a measure of the amount of moisture in the air compared to the maximum amount of moisture that the air could hold at a given temperature. It is expressed as a percentage, with 100% relative humidity being the point at which the air is fully saturated and cannot hold any more moisture. The wet and dry-bulb thermometers are used in a device called a hygrometer to measure relative humidity. The dry-bulb thermometer measures the actual air temperature, while the wet-bulb thermometer has a wick that is moistened with distilled water. As air passes over the wet bulb, the water evaporates, causing the temperature to drop. The amount of cooling that occurs depends on the relative humidity of the air, with more humidity resulting in less cooling. By comparing the readings on the dry-bulb and wet-bulb thermometers, it is possible to calculate the relative humidity of the air using a psychrometric chart or formula. This information is useful for predicting weather patterns, determining appropriate clothing for outdoor activities, and assessing the potential for moisture-related problems like mold growth or corrosion.

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Industries located in rural areas are often raw material-oriented. This means that they are based on natural resources that are found in the surrounding environment, such as agriculture, forestry, mining, or fishing. These industries typically rely on local resources and labor, and may produce goods that are sold locally or shipped to other markets. While some rural industries may be market-oriented or require high energy inputs, raw material-oriented industries are typically the most common in rural areas due to the availability of natural resources. Additionally, transport-oriented industries may be located in rural areas due to their proximity to major transportation routes or hubs, but this is less common than raw material-oriented industries.

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The most important cash crop grown in the Nile Basin is cotton. Cotton is a type of plant that produces fibers used to make textiles and clothing. It is a valuable cash crop because it can be sold for a high price on the market. The Nile Basin, which includes countries like Egypt, Sudan, and Ethiopia, has a climate that is well-suited for growing cotton. The warm temperatures and access to water from the Nile River provide ideal growing conditions for this crop. Cotton has been grown in this region for thousands of years and continues to be an important source of income for farmers in the Nile Basin.

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Limestone is the rock most likely to be weathered by the process of solution. Limestone is a sedimentary rock that is made up of calcium carbonate, which is soluble in water that is slightly acidic. When water containing carbon dioxide from the air or soil dissolves in limestone, it causes a chemical reaction that breaks down the rock into smaller particles. This process is known as solution and is responsible for the formation of many caves and sinkholes in areas where limestone is found. In contrast, slate, graphite, and granite are not soluble in water and are not easily weathered by the process of solution.

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The service industry refers to businesses that provide services to consumers or other businesses. Banking is an example of a service industry, as it provides financial services such as loans, deposits, and investment advice.

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Temperate statistics, which represent numerical data related to a range of temperatures or weather conditions, can best be represented with line graphs. Line graphs are effective in showing changes or trends over time, and are useful for displaying how temperature varies throughout the day, week, month, or year. They can also be used to compare temperature trends between different regions or time periods. Line graphs use a continuous line to connect the data points, allowing for easy interpretation and identification of patterns or trends.

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Détails de la réponse

The population of India is mainly characterized by a high growth rate. This means that the number of individuals living in India is increasing rapidly. India has a large population, with estimates suggesting it is the second most populous country in the world after China. The high growth rate is mainly due to the high birth rate in the country. Despite some efforts to reduce birth rates through family planning programs, the population continues to grow at a fast rate. The population of India is also characterized by a youthful age structure, with a significant proportion of the population under the age of 30. This can have implications for issues such as education, employment, and social services.

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Détails de la réponse

Environmental controls are actions or measures taken to protect, manage or enhance the environment. Afforestation, preservation, and conservation are examples of environmental controls that are used to protect and enhance the environment. Afforestation involves planting trees in an area that previously had no trees, while preservation involves protecting an area from any form of degradation. Conservation involves the careful management of natural resources to prevent their depletion. On the other hand, degradation refers to the reduction in the quality of the environment, often caused by human activities. Therefore, degradation is not an environmental control but a negative outcome of the lack of environmental controls.

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The main difference between towns and villages is that towns are urban areas with a higher population density, while villages are rural areas with a lower population density. Towns tend to have more modern infrastructure, higher levels of economic activity, and a greater range of services, such as healthcare, education, and entertainment. In contrast, villages tend to be more traditional, with a greater emphasis on agriculture and subsistence activities, and fewer modern amenities. While there may be variations in the demographic characteristics of towns and villages, such as the gender ratio or occupational profile, these are not the defining features of these settlements.

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The correct sequence in the process of denudation is: weathering, erosion, transportation, and deposition. Weathering is the initial process that breaks down rocks into smaller pieces, followed by erosion which involves the removal of these weathered materials by agents like water, wind, and ice. After erosion, the weathered materials are transported to a new location where they are deposited. Transportation can occur through various means like rivers, wind, glaciers, and gravity. Finally, the deposited materials accumulate over time to form new landforms.

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The earth rotates on its own axis from west to east, completing one rotation every 24 hours. This movement is known as rotation. Rotation causes the alternation of day and night and gives rise to various atmospheric phenomena such as wind patterns and ocean currents. The other options, revolution, friction, and gravitation, are not related to the earth's movement on its own axis. Revolution refers to the earth's movement around the sun, while friction and gravitation are physical phenomena related to the interaction of objects in motion.

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Détails de la réponse

The leading producer of diamonds in Africa is "Zaire (Democratic Republic of Congo)." Zaire is one of the richest countries in Africa in terms of natural resources. It is home to some of the largest diamond mines in the world, including the famous Mbuji-Mayi mine. The country has a long history of diamond production and has been a major producer of the precious stone since the early 20th century. Diamonds are a major source of revenue for the country and play an important role in its economy. However, the diamond trade in Zaire has been associated with conflict and human rights abuses, with some rebel groups using the profits from diamond sales to fund their activities. Despite these challenges, the diamond industry remains an important source of income and employment for many people in Zaire.

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The most important method of mining tin in Nigeria is the open cast mining. Open cast mining is a surface mining technique where large pits are dug to remove the mineral. This method is preferred for mining tin in Nigeria because it allows for the easy extraction of large quantities of ore, which can be mined quickly and efficiently. Additionally, open cast mining does not require as much manpower as other methods, making it a more cost-effective option.

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The planet Earth has a single satellite, which is called the Moon. A satellite is a natural or artificial object that orbits around a larger body, such as a planet. Jupiter has 79 known moons, Saturn has 82, and Uranus has 27. In contrast, the Earth has one large natural satellite, the Moon. The Moon is the fifth largest moon in the solar system and is thought to have formed about 4.5 billion years ago when a Mars-sized body collided with the Earth. It orbits around the Earth in a nearly circular path at an average distance of about 238,855 miles (384,400 kilometers). The Moon plays a significant role in the Earth's tides, and its gravitational pull affects the Earth's rotation and axis. It also has been explored by human spacecraft and is an important object of study for astronomers and planetary scientists.

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Temperatures are high throughout the year in the equatorial areas mainly because insolation is constantly high. The equatorial areas are located near the equator, which receives direct sunlight throughout the year. This region experiences very little variation in the amount of sunlight it receives. As a result, temperatures in this region remain high throughout the year. This is because the high amount of insolation leads to a high rate of evaporation, which in turn results in high atmospheric moisture content. Although other factors such as permanent cloud cover and ocean currents may influence the climate in equatorial areas, they are not the main reason for the high temperatures. For instance, although cloud cover can lead to reduced insolation, the high amount of insolation in the equatorial areas overwhelms any cooling effect that the clouds may have. Similarly, although ocean currents may influence the climate in coastal regions, the high temperatures in equatorial areas extend far beyond the coastal regions and are not solely influenced by ocean currents.

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The instrument used for measuring atmospheric pressure is called a barometer. Atmospheric pressure is the force exerted by the weight of the air on the Earth's surface. A barometer measures this pressure and is typically composed of a long glass tube that is closed at one end and open at the other end. The closed end of the tube is then placed in a container of mercury, which is a heavy liquid metal that is sensitive to changes in air pressure. As the air pressure increases, the weight of the air pushes down on the surface of the mercury, causing it to rise up the tube. Conversely, as the air pressure decreases, the weight of the air on the surface of the mercury decreases, causing the level of mercury in the tube to drop. The height of the mercury column in the tube is then used to measure the atmospheric pressure, with higher columns indicating higher pressures and lower columns indicating lower pressures. Therefore, a barometer is the instrument used for measuring atmospheric pressure.

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The correct order in which copper is produced is: blasting - crushing - grinding - floating - smelting. The process starts with blasting, which involves drilling and explosives to break up the rock. The resulting pieces are then crushed into smaller pieces using crushers. After crushing, the ore is ground into a fine powder in a grinding mill. The next step is called flotation, where chemicals are added to the ground ore to make the copper particles attach to bubbles, which are then separated from the non-copper particles. Finally, the copper concentrate is sent to a smelter where it is heated at high temperatures to melt and separate the copper from other minerals in the ore. Therefore, the correct answer is: blasting-crushing-grinding-floating-smelting.

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The shortest flying route between any two points on the earth's surface lies along a Great Circle. A Great Circle is the largest circle that can be drawn around the surface of a sphere, such as the Earth. It is formed by the intersection of a plane that passes through the center of the sphere and divides it into two equal halves. When we want to fly between two points on the Earth's surface, the shortest distance between them is along a Great Circle route. This is because a Great Circle route follows the shortest possible path on the curved surface of the Earth, rather than following a straight line on a flat map. For example, when you see a direct flight path from New York to Tokyo on a flat map, it might appear to be a straight line, but when you look at the same route on a globe, you'll notice that the route follows a curved line. This is because the shortest path between these two cities is along a Great Circle route. Therefore, the correct answer is: Great Circle.

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To answer this question, we need to determine the time difference between Accra (located on longitude 0°) and town X (located on longitude 1650E). There are 24 time zones on Earth, and each time zone is roughly 15 degrees of longitude wide. This means that for every 15 degrees of longitude that we travel eastward, we need to add 1 hour to the local time. To determine the time difference between Accra and town X, we need to calculate how many degrees of longitude separate them. Accra is located on longitude 0°, while town X is located on longitude 1650E. To convert this to degrees west of the Prime Meridian (which has a longitude of 0°), we can subtract 1650 from 360, which gives us 210 degrees. Since we are traveling eastward from Accra to town X, we need to add 1 hour for every 15 degrees of longitude. So, the time difference between Accra and town X can be calculated as: 210 degrees / 15 degrees per hour = 14 hours This means that town X is 14 hours ahead of Accra. If it is 3pm GMT on Sunday in Accra, then the local time in town X would be: 3pm GMT + 14 hours = 5am on Monday Therefore, the correct answer is: 2.00am on Monday.

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The movement and direction of ocean currents are affected by the rotation of the earth. This is because of a phenomenon known as the Coriolis effect. As the earth rotates, it causes the currents to move in a curved path. The Coriolis effect also causes the currents to move clockwise in the southern hemisphere and counterclockwise in the northern hemisphere. The rate of evaporation of sea water, volume of ocean water, and relief of the ocean bed can also have an impact on ocean currents, but the rotation of the earth is the primary factor.

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The existence of large lakes in the middle and lower portions of a river does not favor the formation of deltas. A delta is a landform that is formed at the mouth of a river where it flows into an ocean, sea, or lake. As the river reaches its mouth, it slows down and deposits sediment that it has carried from its upper course. Over time, these sediments accumulate and form a delta. A long upper course of a river and a lot of sediments in the lower course of a river both favor the formation of deltas because they provide a large amount of sediment that can be deposited at the river mouth. A reduction in river velocity at its lower course is also important because it allows the sediment to settle and accumulate. However, the existence of large lakes in the middle and lower portions of a river can prevent the formation of deltas because they can trap sediment before it reaches the river mouth. Sediment may be deposited in the lake instead of being carried to the river mouth, where it would be deposited to form a delta. Therefore, the presence of large lakes along the course of a river can interfere with the formation of a delta.

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The downward-growing pinnacles that hang from the roofs of caves in limestone regions are called stalactites. Stalactites are formed by the slow dripping of water that contains dissolved calcium carbonate. As the water drips, it leaves behind small amounts of calcium carbonate, which gradually build up over time to form a cone-shaped structure that hangs from the ceiling of the cave. Stalactites can take many years to form and can grow to be several meters long, adding to the natural beauty and wonder of limestone caves.

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Heavy rainfall is often associated with high temperature because warm air is capable of holding more moisture than cold air. When air temperature increases, the capacity of the air to hold water vapor also increases. This means that warm air can hold more moisture than cold air. As warm air rises, it cools down and the moisture it carries begins to condense, leading to the formation of clouds. If the temperature and humidity conditions are right, the water droplets in the clouds will grow in size and eventually fall to the ground as rain. Therefore, areas with high temperatures can experience heavy rainfall because the warm air in those areas can hold more moisture, leading to the formation of clouds and eventually, rain.

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Détails de la réponse

The option that is not a cause of desertification in West Africa is constant high temperature. Desertification is the process of fertile land turning into desert due to various factors, including human activities and climate change. Some of the main causes of desertification in West Africa include deforestation, overcultivation, and overgrazing. Deforestation reduces the amount of vegetation that holds the soil in place, making it more vulnerable to erosion and degradation. Overcultivation and overgrazing lead to soil depletion and compaction, which reduces its ability to hold water and support vegetation. While high temperatures can exacerbate the effects of these factors, it is not a direct cause of desertification.

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The statement is incorrect. Intensive farming is a type of agriculture that involves the use of high levels of inputs such as labor, fertilizers, and pesticides on a small area of land to maximize output. It is often practiced in areas where land is scarce or expensive, and the population is high. Intensive farming is commonly practiced in rural areas rather than urban centers, as urban centers usually have limited agricultural land. Therefore, the option "large population" might be associated with intensive farming, but the statement "usually practiced in urban centers" is incorrect.

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Détails de la réponse

The variation in salinity of seawater depends on several factors, such as the rate of evaporation, the amount of freshwater supplied by rivers, and the rate of water mixing by ocean currents. However, the slope of the land does not affect the salinity of seawater. The slope of the land refers to the angle or incline of the land surface. This factor does not directly impact the salinity of seawater. Therefore, the answer is that the variation in salinity of seawater depends on all the factors mentioned except the slope of the land.

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The most critical element in an ecosystem is the energy flow within the system. This is because all living organisms within the ecosystem require energy to survive, and this energy comes from the sun in the form of sunlight. Producers like plants use sunlight to create food through photosynthesis, which is then consumed by consumers like animals. Energy is transferred from one organism to another through the food chain, and when an organism dies, its energy is returned to the system through decomposition. Therefore, without energy flow, the ecosystem cannot sustain life.

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When granite is subjected to intense heat or pressure, it forms a rock called gneiss. Granite is a type of igneous rock that is formed from cooled and solidified magma or lava. It is a hard and durable rock that is commonly used for construction purposes. When granite is subjected to high levels of heat and pressure over a long period of time, such as during mountain-building processes or when buried deep within the Earth's crust, its mineral composition and texture can be altered. Under these conditions, the minerals in the granite can recrystallize and become more aligned, creating a banded texture. This process of metamorphosis transforms the original granite into gneiss, which is a metamorphic rock that is characterized by its banded appearance and typically has a coarser texture than granite. Therefore, when granite is subjected to intense heat or pressure, it forms gneiss.

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The largest concentration of human population is in South East Asia. This is due to several reasons such as favorable climate, availability of resources, fertile land, and economic opportunities. The region comprises countries such as China, India, Indonesia, Pakistan, and Bangladesh, which have some of the largest populations in the world. The region also has several large urban centers, including Tokyo, Jakarta, Mumbai, and Delhi, which attract people from rural areas seeking employment and better living standards. Additionally, the cultural and historical significance of the region has also contributed to the growth and concentration of human population in South East Asia.

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A feature of extrusive vulcanicity is a composite cone. Extrusive vulcanicity refers to volcanic activity that occurs on the Earth's surface, where magma, ash, and gas are ejected from the volcano. Composite cones, also known as stratovolcanoes, are formed from layers of lava, ash, and other volcanic materials that accumulate during eruptions. These cones are characterized by their steep sides and a symmetrical shape, making them some of the most recognizable volcanoes in the world. In contrast, lopoliths and batholiths are features of intrusive vulcanicity, which occurs when magma solidifies beneath the Earth's surface. Lopoliths are large, saucer-shaped intrusions that are concave upwards, while batholiths are massive bodies of intrusive igneous rock that extend over an area of at least 100 square kilometers. Sills are also a feature of intrusive vulcanicity and are horizontal sheets of magma that are forced between layers of existing rock. Overall, the key feature of extrusive vulcanicity is the formation of composite cones, which are created by the accumulation of volcanic materials during eruptions on the Earth's surface.

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Population density is the number of people living in a certain area, typically expressed as the number of individuals per unit of land area. To calculate population density, we need to divide the total population of a country by its land area. In this case, the population density of the country can be calculated as: Population density = Total population / Land area Substituting the given values, we get: Population density = 25,000,000 / 100,000 Population density = 250 people per square kilometer Therefore, the correct answer is: 250 persons per sq. km.

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Détails de la réponse

The tilting of the Earth's axis and the revolution of the Earth cause differences in the length of day and night. The Earth's axis is tilted at an angle of 23.5 degrees relative to its plane of orbit around the Sun. This means that as the Earth revolves around the Sun, different parts of the planet receive varying amounts of sunlight depending on their position relative to the Sun. During the summer solstice, the hemisphere tilted towards the Sun receives more direct sunlight, resulting in longer days and shorter nights. Conversely, during the winter solstice, the hemisphere tilted away from the Sun receives less direct sunlight, resulting in shorter days and longer nights. The revolution of the Earth also causes the length of day and night to vary as one moves closer to or farther away from the equator. This is because the Earth's rotation axis is perpendicular to the plane of its orbit, which means that the Sun's rays strike the equator more directly than they do at higher latitudes. Therefore, the tilting of the Earth's axis and the revolution of the Earth cause differences in the length of day and night, which have significant effects on the climate, plant growth, and animal behavior.

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The option that is not a characteristic of the rain-forest is "absence of epiphytes." Epiphytes are plants that grow on other plants, such as mosses, ferns, and orchids. Rainforests are known for their rich diversity of plant and animal species, and epiphytes are a common sight in rainforests. They can be found growing on tree trunks, branches, and leaves, and they play an important role in the rainforest ecosystem by providing food and shelter for many animals. Therefore, the absence of epiphytes would not be a characteristic of the rainforest, as they are an important component of the ecosystem and a common sight in these types of environments.

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When magma solidifies at the crest of an anticline or at the bottom of a syncline, the feature formed is called a "laccolith". A laccolith is a type of igneous intrusion that forms when magma is injected into a sedimentary layer and spreads out in a lens-shaped mass between the layers, causing the overlying layers to bulge upward. The magma cools and solidifies underground, forming a dome-shaped feature. Unlike a batholith, which is a large, irregularly-shaped body of intrusive rock that forms deep underground, a laccolith is a smaller, more localized intrusion that is typically lens-shaped. A phacolith is a similar feature, but it forms along the fold axis of a syncline or anticline, rather than at the crest or bottom. A lopolith is a saucer-shaped intrusion that forms when magma is injected into a basin-shaped depression in the rock.

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(a) Sketch map of Africa

Key locations shown on the sketch map:

1. Fold mountains: Atlas Mountains in north-west Africa and Cape Fold Mountains in the south-western Cape region.
2. Rivers north of the Equator: River Niger and River Nile.
3. Ocean currents: Guinea Current (warm) and Benguela Current (cold).
4. Lines of latitude: Tropic of Cancer, at approximately 23½°N, and Tropic of Capricorn, at approximately 23½°S.

(b) Effect of the cold Benguela Current on the climate and vegetation of the adjacent coastlands

The cold Benguela Current flows northwards along the south-west coast of Africa. It cools the air and surface water along the coast. Consequently, evaporation is reduced and the air contains little water vapour. Rainfall is therefore very low and conditions are dry or arid. Although fog may form where moist air meets the cold current, it produces little or no effective rainfall. The resulting lack of moisture supports sparse, drought-resistant desert and semi-desert vegetation, and the current is an important cause of the aridity of the Namib Desert.

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Irrigation Agriculture in the Niger Basin

Irrigation agriculture is the artificial supply of water to crops, especially during the dry season. It is important in the Niger Basin because much of the basin has a long dry season and unreliable rainfall.

(a) Areas

1. The inland delta and Office du Niger scheme in Mali, especially around Ségou, Macina and Mopti. This is a major irrigated rice-growing area.
2. The Sokoto-Rima Valley in north-western Nigeria, including the Bakolori and Goronyo irrigation schemes.
3. The Kano River valley in northern Nigeria, supplied principally from the Tiga and Challawa Gorge reservoirs.
4. The Niger flood plains and fadama lands in Nigeria, including the Jebba-Bacita area, as well as low-lying valleys along the Niger and Benue rivers.

(b) Methods

1. Basin or flood irrigation: river floodwater is admitted into enclosed basins or flood plains and retained for crop production as the water recedes.
2. Perennial irrigation: dams, reservoirs, barrages and canals store and distribute water throughout the year. Examples include Bakolori Dam and Tiga Dam.
3. Pump or lift irrigation: diesel or electric pumps lift water from rivers, reservoirs, wells or boreholes into channels or pipes leading to farms.
4. Shaduf and manual methods: water is lifted in buckets, calabashes or shadufs on small river-bank plots.
5. Sprinkler and furrow irrigation: water is sprayed through sprinklers or led along shallow furrows, particularly on organised schemes and vegetable farms.

(c) Crops

The main irrigated crops are rice, sugar cane, cotton, wheat, maize, sorghum, millet, barley, groundnuts and vegetables such as onions, tomatoes and peppers.

(d) Problems

1. Very high capital cost of constructing dams, canals, pumps and drainage works.
2. Silt deposition in reservoirs and canals reduces their water-holding capacity and water flow.
3. Rapid growth of aquatic weeds blocks canals and restricts irrigation water.
4. Excessive evaporation and poor drainage cause salinisation and waterlogging of soils.
5. Seasonal rivers, drought and low reservoir levels may produce inadequate water supply.
6. Flooding may destroy crops and erode irrigated fields.
7. Stagnant water encourages malaria, bilharzia and other water-borne diseases.
8. Dam construction may displace settlements and farmlands, while dam failure can cause serious flooding.

(e) Solutions

1. Provide adequate government funding, credit and technical support for irrigation projects and their maintenance.
2. Dredge river channels and desilt reservoirs and canals regularly.
3. Clear aquatic weeds continuously and maintain canal banks and gates.
4. Construct and maintain proper drainage channels; use controlled watering to prevent waterlogging and salt accumulation.
5. Store floodwater in reservoirs and small dams, and use boreholes or pumps where appropriate.
6. Build or widen flood-control channels, embankments and spillways to protect farms from flooding.
7. Provide medical care, safe water, sanitation and mosquito control in irrigation settlements.
8. Use improved dam-construction technology and resettle people displaced by irrigation projects adequately.

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(a) Explanation of terms with examples

(i) Light industry: A light industry is one that uses light, small quantities of raw materials to produce light, small or low-weight finished goods, generally requiring less capital, space and power. Its products are usually not bulky and are often consumer goods. Examples: textile/garment making, food and beverage processing, soap making, electronics/assembly of small appliances.

(ii) Heavy industry: A heavy industry is one that uses large quantities of heavy, bulky raw materials to produce heavy, bulky finished goods, requiring large capital, much power, large space and heavy machinery. Examples: iron and steel manufacturing, shipbuilding, cement production, petroleum refining, automobile (heavy machinery) manufacturing.

(b) Four factors that limit industrial development in tropical Africa

1. Shortage of capital: There is inadequate finance to establish and run modern industries and to buy machinery.
2. Inadequate skilled labour: There is a shortage of trained technicians, engineers and managers to run industries efficiently.
3. Poor infrastructure and power supply: Unreliable electricity, poor roads, railways and water supply raise costs and discourage industry.
4. Small home market and poor technology: Low incomes give a small purchasing market, while poor level of technology and over-dependence on imported machinery and spare parts slow industrial growth (political instability also discourages investment).

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(a)(i) Three reasons for the high volume of trade between Nigeria and the U.S.A.

1. The U.S.A. is a large buyer of Nigeria's crude oil, which is Nigeria's main export, creating a high value of trade between them.
2. The two economies are complementary: the U.S.A. produces manufactured goods, machinery and technology that Nigeria needs, while Nigeria supplies raw materials, so they exchange different goods.
3. The U.S.A. has large capital, advanced technology and huge industries and a strong currency, enabling it to buy in large quantities and to invest in Nigeria.

(a)(ii) Three reasons for the low volume of trade between Nigeria and Ghana

1. The two countries produce similar goods (cocoa, timber, agricultural produce), so their economies compete rather than complement each other, giving little to exchange.
2. Both are developing countries with weak industrial bases, so neither produces much manufactured goods that the other needs.
3. Different currencies, trade barriers/tariffs and poor transport links between them make cross-border trade difficult and reduce its volume.

(b) Four ways of improving trade between Nigeria and other West African countries

1. Strengthen and enforce regional economic cooperation (ECOWAS) by removing tariffs and trade barriers and establishing a common market.
2. Improve transport and communication links (roads, railways, air and sea routes) between the countries.
3. Introduce a common currency or a workable payment/exchange system to ease cross-border transactions.
4. Diversify and industrialise their economies so that they produce different goods to exchange, and check smuggling while harmonising trade policies.

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(a) Outline map of West Africa

The map below shows the required population-density areas outside Nigeria. Dense areas are shown by close diagonal hatching and sparsely populated areas by stippling.

Key to locations shown

1. Over 500 persons per km²: Freetown Peninsula, Sierra Leone; Accra-Tema coastal belt, Ghana.
2. Less than 50 persons per km²: northern Mali (Sahara region); northern Niger (Sahara region).
3. Important town in a densely populated area: Accra, in the Accra-Tema coastal belt of Ghana.

(b) Factors favouring the high population density of the Accra-Tema coastal belt

1. Port and commercial activities: Tema Harbour and the coastal location encourage imports, exports, trade and related services.
2. Industries and employment: industries, offices and businesses provide employment and attract migrants from other parts of Ghana and West Africa.
3. Administrative and social facilities: Accra is the national capital and has many schools, hospitals, roads, electricity and other social amenities which attract settlement.

(c) Problems caused by high population concentration in the Accra-Tema coastal belt

1. Housing shortage and slum growth: demand for houses exceeds supply, leading to overcrowding and poorly planned settlements.
2. Unemployment and poverty: the number of job seekers may be greater than the available jobs, causing unemployment and underemployment.
3. Overstretching of amenities: water supply, schools, hospitals, drainage, electricity and waste-disposal services become inadequate.
4. Traffic congestion and pollution: heavy movement of people and vehicles causes delays, air and noise pollution, and difficulties in disposing of refuse.

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(a) Definition of ecosystem

An ecosystem is a natural unit made up of all the living organisms (plants, animals and micro-organisms) in a given area interacting with one another and with the non-living (physical) components of their environment such as soil, water, air, sunlight and temperature, functioning together through the flow of energy and the cycling of materials.

(b) Four ways in which man has interfered with the ecosystem

1. Deforestation: Man clears forests for farming, timber, settlement and fuelwood, destroying plant and animal habitats.
2. Bush burning and overgrazing: These destroy vegetation, kill soil organisms and expose the soil.
3. Pollution: Man discharges industrial waste, sewage, oil and chemicals (fertilizers, pesticides) into air, water and soil, poisoning organisms.
4. Overhunting and overfishing (and mining/urbanisation): Man kills wildlife and fish faster than they can reproduce and destroys land through mining and building.

(c) Three consequences of man's interference with the ecosystem

1. Extinction or reduction of plant and animal species and loss of biodiversity, and disruption of the food chain and natural balance.
2. Soil erosion, loss of soil fertility and desertification following the removal of vegetation cover.
3. Pollution of air, water and land, leading to disease, climate change and general degradation of the environment.

Détails de la réponse

(a) Open traverse

An open traverse is a series of connected survey lines whose lengths and bearings are measured, beginning at one station and ending at another station. It does not return to, or close at, the starting point. It is suitable for surveying linear features such as roads, railway lines, rivers and pipelines.

(b) Compass traverse of the school compound

The given field lengths are taken as metres. At a scale of 1 cm to 50 m, the representative fraction is:

\[1:5\,000\]

Line	Ground length (m)	Bearing	Length on plan (cm)
AB	370	260°	7.4
BC	450	198°	9.0
CD	265	110°	5.3
DE	560	35°	11.2
EA	140	330°	2.8

(i) Plot of the compound

Using a protractor, set off each bearing clockwise from north at the appropriate station and draw the corresponding scaled length. The completed traverse is shown below.

(ii) Direct distance DA

From the plotted plan, the straight-line distance from D to A measures approximately \(12.7\text{ cm}\).

\[DA=12.7\times 50\text{ m}=635\text{ m}\]

Therefore, the direct distance between D and A is approximately 635 m.

Check by computation from the first three traverse lines:

Line	Easting, \(L\sin\theta\) (m)	Northing, \(L\cos\theta\) (m)
AB	\(-364.4\)	\(-64.2\)
BC	\(-139.1\)	\(-428.0\)
CD	\(+249.0\)	\(-90.6\)
D relative to A	\(-254.5\)	\(-582.8\)

\[DA=\sqrt{(254.5)^2+(582.8)^2}\approx636\text{ m}\]

This agrees with the scaled answer of 635 m, allowing for plotting and measurement.

Détails de la réponse

(a) Definition of mass wasting

Mass wasting (mass movement) is the downslope movement of weathered rock materials, soil and debris under the direct influence of gravity, without the help of a transporting agent such as running water, wind or ice. It ranges from slow, gradual creep to sudden, rapid falls and slides.

(b) Two types of mass wasting

1. Soil creep: This is the very slow, almost imperceptible downhill movement of soil and fine rock particles on gentle slopes. Individual particles move a little at a time as the soil is alternately wetted and dried, heated and cooled, or frozen and thawed. It is shown by tilted poles, bent tree trunks and small soil terraces.
2. Landslide (rock/debris slide): This is the rapid, sudden movement of a large mass of rock, soil and debris down a steep slope. It occurs when the slope becomes unstable, often after heavy rain saturates the material or after an earthquake, and the mass slides or falls quickly along a slip surface. (Other types include earthflow, mudflow and rockfall.)

(c) Three effects of mass wasting

1. It destroys farmland, buildings, roads and other property, and can bury or kill people and animals.
2. It lowers slopes and alters the shape of the landscape, exposing bare rock and forming scars and heaps of debris at the foot of slopes.
3. It can block rivers and roads and, by removing the topsoil, reduces soil fertility and encourages further erosion.

Détails de la réponse

(a) Characteristics of the equatorial rain-forest

1. It is dense, evergreen and luxuriant, with vegetation growing all year round.
2. The trees form three distinct layers or storeys of different heights (canopy structure), with tall emergent trees rising above a continuous canopy.
3. Trees are very tall (up to 45-60 m), with straight, branchless trunks supported by buttress roots, reaching up to the sunlight.
4. There is a great variety of tree species (hardwoods such as mahogany, iroko, ebony and obeche), and they are broad-leaved.
5. Climbers (lianas), epiphytes (such as orchids and ferns) and parasitic plants are common, while the dark forest floor has little undergrowth except along river banks and clearings.

(b) Four ways in which climate influences the equatorial rain-forest

1. Heavy rainfall (over 2,000 mm, well distributed throughout the year) provides abundant moisture that supports continuous, luxuriant plant growth and the evergreen nature of the forest.
2. High, uniform temperatures (about \(27^\circ\text{C}\) throughout the year) with no cold season allow plants to grow and photosynthesise all year round, so there is no leaf fall in a common season.
3. High humidity and constant warmth encourage rapid growth, luxuriant foliage and the abundance of climbers and epiphytes, and speed up the decay of dead matter.
4. Absence of a marked dry season means the trees do not need to shed their leaves to conserve water, so the forest remains evergreen and the tall, broad-leaved species can develop.

Détails de la réponse

(a) Sketch map of Nigeria

Key labels on the sketch map:

• Chad Basin: extreme north-eastern Nigeria, around Lake Chad.
• Western Highlands: south-western Nigeria.
• River: River Yobe in the Chad Basin.
• Towns: Maiduguri in the Chad Basin and Ibadan in the Western Highlands.

(b) Differences between the Chad Basin and the Western Highlands

Basis	Chad Basin	Western Highlands
Relief	It is a low-lying, gently sloping plain.	It is an elevated and more undulating or hilly upland.
Underlying rocks	It is mainly underlain by sedimentary rocks.	It is mainly underlain by ancient crystalline Basement Complex rocks.
Drainage pattern	It has inland drainage; rivers such as the Yobe flow towards Lake Chad. Parts around the lake are swampy.	It has external drainage; rivers flow southwards to the Atlantic Ocean or northwards to the River Niger system. Swamps are generally absent.

(c) Problems of development in the Chad Basin

1. Harsh, dry climate: scanty and unreliable rainfall, together with frequent drought, reduces agricultural production and water supply.
2. Desert encroachment and wind erosion: sandy soils are easily removed by wind, while desertification reduces grazing land and farmland.
3. Poor transport and sparse population: settlements are widely scattered and roads are inadequate, making the movement of people, farm produce and equipment difficult and costly.

Détails de la réponse

Formation of any two features

(a) Waterfalls

A waterfall is a sudden vertical or near-vertical fall of a river as it flows over a steep step in its bed. It is formed mainly where a band of hard, resistant rock lies across the river course above a band of softer rock. The river erodes the soft rock more quickly than the hard rock, so a step develops. Water plunging over the step erodes a deep plunge pool at the base and undercuts the soft rock beneath the hard cap. In time the overhanging hard rock breaks off and the waterfall retreats slowly upstream, leaving a steep-sided gorge below it. Waterfalls also form where a river crosses a fault scarp or plunges over the edge of a plateau (e.g. relief and knick-point falls).

(b) Deltas

A delta is a low, flat, often triangular tract of alluvium formed at the mouth of a river where it enters a sea or lake. As the river reaches its mouth, its velocity is suddenly checked by the standing water, so it loses energy and can no longer carry its load. It therefore deposits its sediment (sand, silt and mud) in layers. The river splits into several branches called distributaries as it flows over the deposited material. Continued deposition, faster than the sea can remove it, builds up the land seaward, forming the delta. Deltas form best where the river carries a large load, the sea is shallow and tides/currents are weak (e.g. the Niger Delta).

(c) Inselbergs

An inselberg is an isolated, steep-sided residual hill of resistant rock (often granite) rising abruptly from a level plain, common in the savanna and semi-arid tropics. It is formed by long-continued weathering and erosion of the surrounding land. Chemical weathering, aided by wet-and-dry conditions, attacks and rots the less-resistant rock at depth, and running water and wind remove the loosened material (the weathered mantle), lowering the general land surface. The more resistant masses of rock survive and are gradually exposed as the plain around them is worn down, remaining as isolated upstanding hills (inselbergs), for example Olumo Rock and Zuma Rock.

Détails de la réponse

(a) Outline map of Nigeria showing vegetation belts

Show the vegetation belts as broad east-west bands, correctly ordered from south to north, and label:

• (i) Mangrove swamp forest: along the coast and the Niger Delta in the far south.
• (ii) Sahel savanna: the extreme north-east around the Chad Basin.
• (iii) Guinea savanna: the wide middle-belt band across the country.
• (iv) One major town: in the mangrove belt - Port Harcourt (or Warri); in the Guinea savanna - Ilorin (or Makurdi, Minna).

(b) Three main characteristics of the Guinea savanna vegetation

• It consists of tall grasses (often 1.5 to 3 metres high) growing in the wet season and drying up in the dry season.
• Trees are scattered and of medium height, mostly deciduous and fire-resistant (e.g. locust bean, shea, isoberlinia), with broad, gnarled trunks.
• It is a transition (mixed) zone of grass and trees, denser and more wooded than the Sudan/Sahel savanna to the north but more open than the forest to the south.
• Many trees have thick bark and deep roots as adaptations to seasonal drought and bush fires.

(c) Four ways the mangrove swamp forest is of economic importance

• Fishing grounds: the creeks and estuaries are rich breeding grounds for fish, prawns and shellfish, supporting a large fishing industry.
• Timber and wood products: mangrove wood provides fuelwood, poles for building and material for making charcoal.
• Raw materials and tannin: the bark yields tannin used in tanning leather, and raffia palms supply fibre and wine.
• Petroleum and site value: much of Nigeria's crude oil and gas is exploited in the delta mangrove belt, and the sheltered creeks provide sites for ports and harbours.
• Tourism and salt-tolerant farming: the wetlands support tourism and, where reclaimed, rice and coconut cultivation.

Détails de la réponse

(a)(i) Total population

\(5.4 + 4.2 + 6.5 + 3.2 + 7.4 = 26.7\) million, i.e. 26,700,000 people.

(a)(ii) Total land area

\(120{,}000 + 85{,}000 + 135{,}000 + 98{,}000 + 140{,}000 = 578{,}000\ \text{km}^2\).

(a)(iii) Population density

\[\text{Density} = \frac{\text{total population}}{\text{total land area}} = \frac{26{,}700{,}000}{578{,}000} \approx 46.2\ \text{persons per km}^2.\] The population density of Country X is about 46 persons per km².

(b) Four factors responsible for the distribution of world population

1. Climate: areas with moderate, favourable climates attract dense settlement, while very hot deserts, very cold polar lands and wet equatorial forests repel people.
2. Relief and soils: lowland plains and river valleys with fertile soils support large populations, whereas rugged mountains and infertile land are sparsely peopled.
3. Water supply and drainage: reliable fresh water (rivers, lakes, wells) draws people, so populations cluster along rivers and coasts and avoid arid interiors.
4. Economic and industrial development: areas with mining, industry, commerce and good transport offer jobs and services, pulling in large populations (urbanisation), while remote areas remain thinly settled.

(c) Three factors that cause increase in world population

1. A high birth rate resulting from early marriage, large-family preferences and low use of family planning.
2. A falling death rate brought about by better medical care, immunisation, improved sanitation and food supply.
3. Improved standards of living and nutrition, together with in-migration into an area, which raise life expectancy and add to numbers.

Détails de la réponse

(a) Location of mining and power areas on an outline map of Nigeria

On the outline map, mark and label the following named areas:

• (i) Tin mining: Jos Plateau (around Jos, Bukuru and Barkin Ladi) in Plateau State.
• (ii) Limestone mining: Ewekoro (Ogun State), or Nkalagu (Ebonyi State), or Sokoto and Yandev.
• (iii) Thermal power station: Egbin (near Lagos), or Afam (Rivers State), or Ughelli/Delta, or Sapele.
• (iv) Oil refinery: Port Harcourt (Rivers State), or Warri (Delta State), or Kaduna (Kaduna State).
• (v) Hydro-electric power station: Kainji Dam on the River Niger (Niger State), or Jebba, or Shiroro.

Each point should be located in its correct relative position, with the coastline, the confluence of the Niger and Benue, and state boundaries shown for orientation. A key/legend should distinguish mining sites from power stations.

(b) Method of mining tin in Nigeria

Tin in Nigeria occurs mainly as cassiterite in alluvial (placer) deposits on the Jos Plateau, so it is worked chiefly by open-cast and hydraulic (surface) methods rather than deep shafts.

1. The overlying soil and rock (overburden) covering the tin-bearing gravel is first stripped off using bulldozers, draglines or manual labour.
2. The exposed tin-bearing gravel is then broken up and washed. In hydraulic mining, powerful jets of water are directed at the gravel to break it and wash it into channels.
3. The muddy mixture of water and gravel (slurry) is passed through sluices, jigs and washing pans, where the heavier cassiterite settles and is separated from the lighter waste sand by gravity.
4. The concentrated cassiterite is collected, dried and further purified before being smelted to obtain metallic tin.

Small-scale miners also use simple panning in streams, while larger firms use dredges in the flooded workings.

(c) Four ways minerals are of economic importance to Nigeria

• Source of government revenue and foreign exchange: the export of petroleum and solid minerals earns large amounts of foreign currency and taxes.
• Employment: mining, refining and allied services provide jobs for many people, raising incomes and living standards.
• Industrial raw materials: limestone feeds cement factories, tin and columbite supply metal industries, and crude oil feeds refineries and petrochemical plants.
• Infrastructural development: mining areas attract roads, railways, electricity and towns, opening up otherwise remote regions.
• Energy supply: petroleum, natural gas and coal provide power for industries, homes and transport.

Détails de la réponse

(a) What is environmental pollution?

Environmental pollution is the introduction of harmful substances or contaminants (pollutants) into the natural environment (air, water, land or soil) in quantities that are injurious to human health, other living things and property, and that degrade the quality of the environment.

(b) Four causes of environmental pollution

1. Industrial activities: Factories release smoke, poisonous gases, chemical wastes and effluents into the air and water.
2. Vehicular and machine exhausts: Motor vehicles and generators emit carbon monoxide, smoke and other gases that pollute the air.
3. Improper waste disposal: Dumping of refuse, sewage and untreated waste on land and into rivers pollutes the soil and water bodies.
4. Oil spillage, gas flaring, bush burning and use of agro-chemicals: These release oil, smoke, soot and chemicals (fertilizers, pesticides) that contaminate air, land and water.

(c) Three ways environmental pollution can be controlled

1. Treat industrial effluents and sewage before they are discharged, and install filters to trap smoke and gases.
2. Provide proper waste collection and disposal systems (recycling, sanitary landfills) and enforce anti-pollution laws.
3. Educate the public on sanitation, control bush burning and the use of chemicals, and encourage afforestation and cleaner sources of energy.

Détails de la réponse

(a) Reduced outline map, scale 1:150,000

The reduction factor is:

\[\frac{1:150,000}{1:50,000}=3\]

Thus, every length on the original map is reduced to one-third. The outline measures 12.2 cm by 12.2 cm.

Key features inserted:

1. the full length of River Oshin;
2. Igporin Hill, the named watershed north-east of River Oshin;
3. Marafa settlement; and
4. the ridge east of the main road.

(b) Distance along the main road from Onikoko to Alade

Distance measured along the road on the map = \(16.0\text{ cm}\).

Scale \(=1:50,000\).

\[1\text{ cm}=50,000\text{ cm}=\frac{50,000}{100,000}\text{ km}=0.5\text{ km}\]

\[\text{Ground distance}=16.0\times0.5=8.0\text{ km}\]

Distance from Onikoko to Alade = \(8\text{ km}\).

(c)(i) Likely occupation

Farming is a likely occupation because areas of scattered cultivation are shown on the map.

(c)(ii) Features likely to be seen along the main road from Woru to the south-western edge of the map

Physical features:

1. Rivers or streams.
2. Ridge or isolated hills.
3. Light forest, scrub or orchard bush.

Human features:

1. Settlements, including built-up areas and isolated compounds.
2. Roads, bridges, footpaths and areas of scattered cultivation.

Détails de la réponse

(a) Internal structure of the Earth

(b) Main features of the parts

1. Crust

• This is the thin, outermost, solid layer of the Earth.
• It varies in thickness: about 5 to 10 km beneath oceans and about 30 to 70 km beneath continents.
• It consists mainly of granitic rocks in the continental part, called sial because it is rich in silica and aluminium, and basaltic rocks in the oceanic part, called sima because it is rich in silica and magnesium.
• It forms the land and ocean floor, provides the soil, and supports life.

2. Mantle

• This is the middle layer lying immediately below the crust and surrounding the core.
• It is about 2,900 km thick and is made up of very dense silicate rocks, rich in minerals such as olivine and basaltic materials.
• It is very hot; although largely solid, parts of it behave plastically and contain molten material.
• Convection currents in the mantle help to move tectonic plates and are associated with volcanic and earthquake activity.

3. Core

• This is the innermost layer of the Earth, extending from below the mantle to the centre.
• It has a radius of about 3,476 km and consists mainly of iron and nickel, hence it is often called nife.
• It is divided into a liquid outer core and a solid inner core. The inner core remains solid because of the extremely high pressure.
• It is the hottest and densest part of the Earth, and movement in the liquid outer core produces the Earth's magnetic field.