WAEC SSCE - Geography - 1990

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The following combination can be regarded as sub-systems within the ecosystem: - Food chain, hydrological cycle, mineral nutrient cycle A food chain is a series of organisms that depend on each other for food in an ecosystem. The hydrological cycle refers to the continuous movement of water on, above, and below the surface of the Earth. The mineral nutrient cycle is the movement of essential elements from the abiotic environment into living organisms and back again. All these processes are interconnected and interdependent, forming a sub-system within the larger ecosystem.

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The angular distance of a point on the Earth's surface measured in degrees from the center of the Earth is known as latitude. Latitude is the horizontal measurement of a point's position on the Earth's surface, ranging from 0 degrees at the Equator to 90 degrees at the North and South Poles. Latitude is used in navigation, mapping, and other geographic applications to locate a point's position on the Earth's surface relative to other points.

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The earth rotates 360 degrees in 24 hours, which means that it rotates 15 degrees per hour. The time difference between Greenwich meantime and Place X is 6 hours. Therefore, the difference in longitude between Greenwich and Place X is 6 x 15 = 90 degrees. Since the time at Place X is 12 pm (noon), we know that it is halfway between sunrise and sunset, which means that it is roughly at the meridian line of that location. Therefore, we can calculate the longitude of Place X by adding or subtracting half of the 360-degree circumference of the earth from the longitude of the Greenwich meridian (which is 0 degrees). Since the time difference between Greenwich and Place X is westward (Greenwich time is ahead of Place X time), we need to subtract 90 degrees from the Greenwich meridian to get the longitude of Place X, which is 90 degrees west, or 90°W. Therefore, the correct answer is option (E) 90°W.

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When the root of a coastal cave collapses, it forms a geo. A geo is a narrow steep-sided inlet formed in coastal cliffs by the erosion of the sea. It is often created when a section of a sea cave roof collapses, leaving an opening to the sea. Over time, the waves will continue to erode the geo, deepening it and widening it to create a larger inlet. Geos are common features along the coasts of many countries and can be home to a variety of marine life.

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The soil in a natural rainforest remains fertile and suitable for agriculture because of the continuous replenishment of nutrients. The dense undergrowth and fallen leaves decay and return nutrients to the soil. Additionally, the abundant supply of sunshine and rainfall contributes to leaching the soil and removing any buildup of harmful substances. The vegetation in the rainforest is also very lush and dense, providing a continuous source of organic matter for the soil. Finally, the soil is well-drained, which prevents water from pooling and causing waterlogging or erosion. All these factors work together to maintain the fertility of the soil in a natural rainforest.

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The instrument used to record the direction of the prevailing wind of a place over a period of one month is called a wind vane. A wind vane, also known as a weather vane, is a simple device that consists of a flat or curved surface that pivots around a vertical axis. The surface is usually shaped like an arrow or a rooster, with one end larger than the other. The smaller end is pointed into the wind, while the larger end indicates the direction from which the wind is blowing. Wind vanes are commonly used by meteorologists to determine the direction of the wind at a particular location. By recording the direction of the wind over a period of time, meteorologists can create a wind rose, which is a graphical representation of the frequency and direction of the wind at a particular location.

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To find the time in Calcutta, India, we need to calculate the time difference between Munich, Germany, and Calcutta, India, and then adjust the time accordingly. The time difference between Munich and Calcutta is the difference in their longitudes, divided by 15 (since each time zone spans 15 degrees of longitude). So, the time difference is: Time difference = (96°E - 11°E)/15 = 6.33 hours This means that Calcutta is ahead of Munich by 6 hours and 20 minutes (since 0.33 of an hour is 20 minutes). If it is 9:00am in Munich, we need to add 6 hours and 20 minutes to get the time in Calcutta: 9:00am + 6 hours and 20 minutes = 3:20pm Therefore, when it is 9:00am in Munich, the time in Calcutta, India is 3:20pm. Therefore, the correct answer is option D: 2.40p.m.

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A limestone region is characterized by the dissolution of soluble rocks like limestone by rainwater and the formation of features like caverns, sinkholes, and underground drainage systems. Therefore, the correct answer is (c) adequate luxuriant vegetation cover, as the solubility of limestone tends to inhibit the growth of lush vegetation.

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The correct option is "the upper course has a steep gradient." This is because the upper course of a river is the section closest to its source, and it usually has a steep gradient. The steep gradient causes the water to flow rapidly, eroding the bed and banks of the river channel. As a result, gorges are formed as the river cuts through hard rocks in the upper course, creating narrow and deep channels with steep sides. The other options, such as the volume of the river being small, rocks in the upper course being less resistant, hanging valleys, and chemicals in the water, may also contribute to the formation of gorges, but the steep gradient is the main cause.

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The answer is D - The older fold mountains have been subjected to the forces of denudation for longer geological periods. Denudation refers to the wearing away of the Earth's surface by processes such as erosion and weathering. The older fold mountains have existed for much longer periods and have been exposed to these processes for a longer time, which has resulted in them being lower and less rugged than the newer ones. In contrast, the newer fold mountains are still being formed and have not yet had as much time to undergo denudation.

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A rain gauge is kept in an open place in the observatory because raindrops get into the funnel without any obstruction. The gauge is used to measure the amount of rainfall in a particular area over a period of time. It works by collecting rainwater through a funnel that directs the water into a container. If the gauge is not kept in an open space, it may not collect all the rain that falls, as raindrops may be deflected by surrounding objects or wind. Therefore, to get an accurate measurement of rainfall, the gauge must be kept in an open place where it can collect all the rain that falls directly into the funnel.

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The relief features of the submarine are the physical characteristics that make up the seafloor. A Roche moutonnee is not a typical submarine relief feature. Roche moutonnee is a type of erosional landform that is found on the surface of glaciers and mountain tops. Typical submarine relief features include the continental shelf, continental slope, and ocean deep. The continental shelf is the shallow submerged edge of the continent, while the continental slope is the steep slope leading to the ocean floor. The ocean deeps are the deepest parts of the ocean floor, which can reach depths of over 11,000 meters. Deep sea plain is also a typical submarine relief feature. It is a flat, featureless area of the seafloor that lies between the continental shelf and the mid-ocean ridges. Therefore, the correct answer is Roche moutonnee, which is not a typical submarine relief feature.

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Isothermal maps give information about temperature. Isothermal maps are maps that display areas with the same temperature. They are used to show temperature variations across a particular region. These maps can be used to identify areas that are experiencing hot or cold temperatures, and to observe the movement of these temperature patterns over time. Isothermal maps are commonly used in meteorology and climate science to track the movement of air masses and the formation of weather patterns. Therefore, the correct answer is "temperature".

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The description provided in the question is that of a coniferous forest. Coniferous trees, also known as evergreens, retain their needles throughout the year, giving the forest an evergreen appearance. These forests are typically found in regions with cold winters and cool summers, such as the northern hemisphere. The undergrowth in coniferous forests is generally thin because the canopy blocks most of the sunlight from reaching the forest floor. The small, thick, leathery and needle-shaped leaves of conifers reduce water loss due to transpiration, allowing them to survive in dry and cold climates.

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In railway transport, the term "gauge" refers to the distance between the two rails of a track. It is the fixed distance between the inside edges of the two rails that allows trains to run smoothly and safely. The gauge of a railway track is usually determined by the design and construction of the rolling stock (i.e., locomotives and railcars) that will be used on it. Different countries or regions may use different gauges depending on factors such as geography, history, and economic considerations.

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Choosing (a) Iron and steel in the Ruhr and (b) Ship building in Japan.

(a) Six factors favouring iron and steel in the Ruhr region

1. Large local coalfields of good coking coal in the Ruhr valley, the main fuel and reducing agent for smelting.
2. Nearness to iron ore, formerly local and now imported cheaply from Sweden and France by water.
3. Excellent water transport on the Rhine and its tributaries and a dense canal/rail network for moving raw materials and finished steel.
4. Abundant water supply from the Rhine and Ruhr rivers for cooling and processing.
5. Large supply of skilled and general labour from the densely-populated region.
6. Huge home and European market for steel (machinery, vehicles, engineering) plus ample capital and long industrial tradition.

(b) Six factors favouring ship building in Japan

1. A long, deeply indented coastline with many sheltered natural harbours and deep water ideal for shipyards.
2. Cheap sea transport of imported raw materials (iron ore and coal) delivered directly to coastal yards.
3. A large, well-developed iron and steel industry nearby supplying steel plates.
4. Abundant, highly skilled and disciplined labour together with advanced technology and research.
5. Ample capital and strong government support for the industry.
6. A very large market: Japan's own huge merchant and fishing fleets plus a strong world export demand for ships.

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Below is the complete answer. The required features are marked and named on the sketch map in part (a), followed by the explanation in (b) and the limiting factors in (c).

(a) Sketch map of Nigeria with the required features marked and named

On the map above the following have been marked and named:

• (i) Highlands: the Western Uplands (south-west), the Udi Hills (south-east, near Enugu) and the North Central (Jos) Plateau (centre).
• (ii) One important river basin: the Niger-Benue River Basin, formed where the River Niger and the River Benue meet at their confluence (Lokoja).
• (iii) One natural lake and one man-made lake: Lake Chad (natural, in the far north-east) and Kainji Lake (man-made, formed by the Kainji Dam on the River Niger).

(b) Importance of river basins in the development of Nigeria (with specific examples)

1. Fertile land for agriculture: the flood plains of the basins are rich in alluvial soil, providing fertile ground for the cultivation of crops. For example, the Chad Basin supports wheat, rice and vegetable farming, while the fadama (flood-plain) land of the Niger-Benue basin is used for rice and sugar cane.
2. Sites for settlement: being low-lying and well-watered, the basins are favourable sites for human habitation, so many important towns such as Lokoja, Makurdi and Onitsha have grown up along the rivers.
3. Irrigation: water from the rivers and lakes is used to irrigate farmland during the dry season, for example the South Chad Irrigation Project and irrigation schemes along the River Niger.
4. Hydro-electric power: dams built across the basins generate electricity, for example the Kainji Dam on the River Niger, which supplies power to much of the country.
5. Fishing and inland transport: the rivers and lakes support a large fishing industry (e.g. around Lake Chad and along the Niger) and serve as natural highways for the movement of goods and people by boat.
6. Domestic and industrial water supply: the basins provide water for drinking and for industries in the towns that lie within them.

(c) Three factors limiting the use of river basins in Nigeria

1. Swampy or flooded ground: large parts of the basins are marshy and are covered by water during the wet season, which makes farming and building difficult.
2. Inaccessibility: many parts of the basins are remote and lack good roads, so they are hard to reach and develop.
3. Seasonality of the rivers: some of the rivers dry up or shrink greatly in the dry season, so a steady supply of water is not always available for irrigation, transport or power.

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(a) Location on the outline map of Nigeria

(i) One important sea port and one important river port:

• Sea port: Apapa Port, Lagos – located on the south-western coast of Nigeria.
• River port: Onitsha River Port – located on the eastern bank of River Niger in Anambra State.

(ii) Road or railway serving each port:

• Apapa Port is served by the Lagos–Ibadan–Kano railway and major roads such as the Lagos–Ibadan Expressway.
• Onitsha River Port is served by the Onitsha–Enugu–Port Harcourt trunk road.

(iii) One international airport and one domestic airport:

• International airport: Murtala Muhammed International Airport, Ikeja, Lagos.
• Domestic airport: Ilorin Airport, Ilorin, Kwara State.

(b) Four factors which have helped in the development of Apapa (Lagos) Port:

1. Apapa Port handles a large proportion of Nigeria’s imports and exports.
2. It is located on a good natural harbour with sheltered waters.
3. It is served by good roads, railway lines and sea routes linking it with the hinterland and foreign countries.
4. It has a large and highly populated hinterland with many industries and commercial activities.

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(a) Sketch map of Nigeria showing population density

The sketch map below shows the outline of Nigeria. On it, the south-western corner is marked and named as an area of high population density, with the town of Lagos shown within it. The Middle Belt, around the Benue valley, is marked and named as an area of low population density, with the town of Makurdi shown within it.

(b) Reasons for the type of population density shown

Four reasons for the HIGH population density of the Lagos area:

1. Commercial importance. Lagos is Nigeria's leading commercial town, with heavy wholesale and retail trading and the concentration of banks and business headquarters, which draws large numbers of people in search of livelihood.
2. Presence of industries. The area has a heavy concentration of manufacturing and processing industries, and the workers these factories employ, together with their families, swell the population.
3. Availability of employment. Because of the trade and industries, there are abundant job opportunities, so people migrate into the area from other parts of the country in search of work.
4. Former Federal Capital and chief port. Lagos was for a long time the Federal Capital and remains the country's principal seaport and gateway for imports and exports, which attracted administrative, port and service functions and the people that go with them.

Four reasons for the LOW population density of the Makurdi (Middle Belt) area:

1. Effects of the past slave raids. The area suffered from the disruption of the trans-Saharan and inter-tribal slave trade, which depopulated it in the past and left it thinly settled.
2. Insect pests and disease. The presence of the tsetse fly and black fly, associated with sleeping sickness and river blindness respectively, discouraged dense settlement and the keeping of livestock.
3. Absence of social amenities. The relative shortage of good roads, electricity, pipe-borne water, schools and hospitals makes the area less attractive, so people move away rather than settle.
4. Absence of mineral resources and industries. The area has few exploited minerals and little industrial development, so there are few jobs to attract or hold a large population.

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(a) Three reasons to show that the earth is spherical include:

(i) Circumnavigation of the earth: Ships and aircraft travelling continuously in one direction can return to their starting point without turning back. This shows that the earth is rounded.

(ii) Sunrise and sunset: The sun appears gradually at sunrise and disappears gradually at sunset. This is because the earth has a curved surface and rotates on its axis.

(iii) Eclipse of the moon: During a lunar eclipse, the earth casts a circular shadow on the moon. Only a spherical body can always cast a circular shadow.

(b) Three effects of the revolution of the earth include:

(i) It causes seasons: As the earth revolves round the sun with its axis inclined at 66½°, different parts of the earth receive different amounts of solar heat at different times of the year. Thus, when it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere.

(ii) It varies the length of day and night: The length of day and night changes during the year. Around 21 June, the Northern Hemisphere experiences longer days and shorter nights, while the Southern Hemisphere experiences shorter days and longer nights. Around 22 December, the condition is reversed.

(iii) It changes the altitude of the midday sun: The vertical rays of the sun appear to migrate between the Tropic of Cancer and the Tropic of Capricorn. The sun is overhead at the Equator on about 21 March and 23 September, at the Tropic of Cancer on about 21 June, and at the Tropic of Capricorn on about 22 December.

(c) Calculation of the noon altitude of the sun at the Tropic of Capricorn on 21 June:

On 21 June, the sun is vertically overhead at the Tropic of Cancer, 23½°N.

The Tropic of Capricorn is at 23½°S.

The angular distance between the Tropic of Capricorn and the overhead sun is:

23½° + 23½° = 47°

Noon altitude of the sun = 90° − angular distance.

Therefore:

90° − 47° = 43°

The noon altitude of the sun at the Tropic of Capricorn on 21 June is 43°.

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Choosing (b) Irrigation farming in the Nile Valley, (c) Pastoral nomadism in West Africa and (a) Plantation agriculture in East Africa.

(b) Irrigation farming in the Nile Valley

• Practised in a hot desert with almost no rain, so all water comes from the River Nile led onto the land through basins, canals and lifting devices (shaduf, sakia, pumps).
• Intensive and sedentary, on narrow but very fertile alluvial flood-plain land, using much hand labour.
• Grows cash and food crops such as cotton, rice, sugar cane, wheat and vegetables, often two or more crops a year.

(c) Pastoral nomadism in West Africa

• Practised in the dry savanna and Sahel (for example by the Fulani) where rainfall is low and unreliable and crop farming is difficult.
• The herders move about (are migratory) with their cattle, sheep and goats in search of pasture and water, following the rains north and south.
• It is extensive and subsistence in nature; animals supply milk, meat and hides, and wealth is measured in the size of the herd rather than in crops.

(a) Plantation agriculture in East Africa

• Large estates, often foreign or company owned, growing a single cash crop (monoculture) such as tea, coffee, sisal or sugar for export.
• Uses much hired labour, heavy capital, scientific methods and on-site processing of the crop.
• Located where climate, soils and relief suit the crop (for example tea and coffee on the cooler, wetter highlands), with good transport to ports.

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Similarities and differences between road and railway transport

Similarities

• Both are land-based means of transport that move passengers and goods over fixed routes on the earth's surface.
• Both require heavy capital to build and constant maintenance of the track/route.
• Both are affected by relief; steep slopes, rivers and swamps raise construction costs (bridges, cuttings, embankments) for each.
• Both link production areas with markets and ports and so aid trade and development.

Differences

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(a) Outline map of Nigeria showing crop-producing areas and vegetation belts

The sketch map below shows the required crop areas and the two named vegetation belts.

• (i) Crop areas
  • Oil palm: the south-east / Niger Delta (Imo, Rivers, Akwa Ibom).
  • Cotton: the far north (Katsina, Zaria/Kaduna, Gombe).
  • Cocoa: the south-west (Ondo, Ogun, Oyo, Ekiti).
• (ii) Vegetation belts
  • Forest belt: the southern tropical rainforest belt along the coast.
  • Savanna belt: the Guinea/Sudan savanna belt of the middle and north.

(b) Four ways in which cocoa is important to the economy of Nigeria

1. Foreign-exchange earner: cocoa is a leading agricultural export and brings in foreign currency that strengthens the nation's reserves.
2. Raw material for industries: cocoa beans supply local factories that make beverages such as Bournvita, as well as cocoa butter and confectionery, so value is added at home.
3. Source of employment: cocoa growing, harvesting, processing, transporting and marketing provide jobs for a large number of people, especially in the south-west.
4. Source of income and government revenue: it gives farmers cash income while taxes and marketing-board proceeds provide revenue that funds roads, schools and other amenities in the producing areas.

(c) Three problems facing the cultivation of cocoa

1. Pests and diseases such as capsids and black-pod disease, which attack the trees and reduce yields.
2. Poor processing of the beans, leading to low-grade produce that fetches lower prices on the market.
3. Poor, low-yielding cocoa species and ageing trees, together with limited use of improved seedlings, fertiliser and capital, which keep output low.

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(a) Four reasons why countries exchange goods and services (with examples)

1. Uneven distribution of resources: a country sells what it has in surplus and buys what it lacks. Nigeria sells crude oil and buys machinery it does not produce.
2. Differences in climate and soils: countries import produce they cannot grow. Britain imports cocoa and coffee from the tropics; Nigeria imports temperate wheat.
3. Differences in technology and industrial development: less industrialised countries import manufactured goods from advanced ones. Nigeria imports vehicles and electronics from Japan, Germany and China.
4. Comparative cost advantage and specialisation: each country produces most cheaply what it is best suited for and trades for the rest, and services such as shipping, banking and tourism are also exchanged.

(b) Reasons for the low volume of trade between Nigeria and the rest of Africa

1. Similar (competing) economies: most African countries export the same primary products (cocoa, oil, minerals) and want to buy manufactures from outside, so they have little to sell one another.
2. Poor transport links between African countries: roads, railways and shipping lines were built to carry goods to Europe, not across Africa, so movement of goods within the continent is slow and costly.
3. Colonial trade ties and currency differences: long-standing links bind each country to former colonial and overseas partners, and different, non-convertible currencies plus trade barriers hamper intra-African trade.
4. Low levels of industrialisation and small purchasing power, together with language differences, political instability and smuggling, keep official trade among African states low.

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(a) Three types of mountains with an example of each

1. Fold mountains – the Atlas, Alps or Himalayas.
2. Block (fault) mountains / horst – the Ruwenzori (or the Vosges).
3. Volcanic mountains – Mount Cameroon (or Kilimanjaro).

(Residual mountains, such as inselbergs on the Jos Plateau, are also acceptable.)

(b) Process of formation of fold mountains

Fold mountains are formed by compression (lateral squeezing) of the earth's crust. Over long periods, thick layers of sediment collect in a large downwarp of the crust called a geosyncline, usually beneath a sea. When two crustal plates move towards each other, the intervening sediments are squeezed from both sides. Because they cannot escape, the rocks are buckled and folded into a series of upfolds (anticlines) and downfolds (synclines). Continued pressure raises these folds high above sea level to form fold mountains; where pressure is very great the folds may become overfolded or overthrust. The Himalayas, formed by the collision of the Indian and Asian plates, are a good example.

(c) Four ways mountains are of great importance to man

1. They act as sources of rivers (water towers), feeding streams used for water supply, irrigation and hydro-electric power.
2. They influence climate and rainfall, causing relief rainfall on their windward slopes and creating cooler, healthier highland areas.
3. They are storehouses of minerals, forests and good grazing/farming land on their slopes and provide sites for tourism and mountaineering.
4. They serve as natural boundaries and defensive barriers between peoples and countries.

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A geographical account of fishing in Southern Africa

Southern Africa is one of the richest fishing regions in the world because the cold Benguela Current flows northward along its western (Atlantic) coast. This current causes upwelling of cold, nutrient-rich water from the sea bed, which supports enormous quantities of plankton and therefore vast shoals of fish. The map below shows the main fishing grounds and ports.

(a) Important fishing areas and fishing ports

Fishing is carried out in two main settings:

• Offshore (marine) fishing is by far the most important. The richest grounds lie off the cool Atlantic (Benguela Current) coast of Namibia and the western Cape of South Africa, where upwelling supports huge shoals. Fishing also extends along the southern and eastern (Indian Ocean) coasts and into the deep seas of both the Atlantic and Indian Oceans.
• Inland fishing is minor and much less important. It is carried out on rivers such as the Orange River and the Great Fish River, and on inland lakes and dams by local fishermen.

The chief fishing ports are Walvis Bay (Namibia), and Saldanha Bay, Cape Town, Port Elizabeth, East London and Durban in South Africa.

(b) Methods of fishing

• Trawling: large motorised trawlers drag bag-shaped nets along or near the sea bed to catch demersal (bottom-living) fish such as hake. This is the main large-scale method used in the deep oceans.
• Purse-seining and drift/gill netting: nets are used to surround and trap surface-swimming (pelagic) shoal fish such as pilchard and anchovy.
• Line fishing: hooks and lines are used for larger fish such as tuna and snoek.
• Traps and small nets: used by local fishermen inland on rivers, lakes and estuaries on a small scale.

(c) Major types of fish caught

The main catch consists of:

• Pelagic (surface) species - pilchard (sardine), anchovy, herring and mackerel (horse mackerel).
• Demersal (bottom) species - hake (stockfish).
• Other valuable species - tuna, snoek and rock-lobster (crayfish).

(d) Preparation and marketing of fish

Once landed, the fish are cleaned and chilled or frozen on board the vessels and in cold stores on shore. The catch is then either sold fresh, or processed by canning (for example sardines), salting, drying and smoking. Much of the pelagic catch is turned into fish meal and fish oil for animal feed and fertiliser. The products are sold fresh in local markets, distributed inland, and large quantities of frozen, canned and processed fish are exported to Europe and other overseas markets.

(e) Importance to the economy

• It provides a rich and cheap source of protein food for the people.
• The export of frozen fish, canned fish, fish meal and lobster earns valuable foreign exchange for the countries.
• It provides employment for many people in fishing, canning, processing, transport and boat building.
• It has led to the establishment of fish-processing and canning industries and supplies raw material (fish meal) for animal feed and fertiliser, supporting related industries.

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Factors responsible for very high population density

(a) North-East of the USA (the Manufacturing/Boston-Washington belt)

1. Early settlement and industrialisation: this was the first area settled by Europeans and the cradle of American manufacturing, so towns and industries grew early.
2. Rich resources and power: nearby coalfields (Appalachians), iron ore from the Great Lakes and abundant capital fed heavy industry, attracting workers.
3. Excellent transport and trade: fine natural harbours (New York, Boston), navigable rivers, the Great Lakes-St Lawrence route and dense rail/road networks made it a great commercial and port region.
4. Concentration of commerce, finance and services in great cities such as New York, together with continuing in-migration, keeps densities high; the cool temperate climate is also favourable to work.

(b) The Indus and Ganges deltas/plains

1. Fertile alluvial soils deposited by the rivers, giving high crop yields that can feed a dense population.
2. Ample water for irrigation from the rivers plus the monsoon rains, allowing intensive, often double-cropped, farming of rice, wheat and jute.
3. Flat, easily-cultivated and easily-settled lowland that supports intensive wet-rice agriculture, which itself demands much labour.
4. Long history of settlement and agrarian civilisation, with many old towns and cities and a favourable warm climate, so numbers have built up over centuries.

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(a)(i) Two distinct types of soil erosion

1. Sheet erosion (thin, even removal of topsoil by surface run-off over a wide area).
2. Gully erosion (deep channels and ravines cut by concentrated running water). Rill and wind erosion are also acceptable types.

(ii) Where each type is most common

• Sheet/wind erosion – the semi-arid far north of Nigeria (Sokoto, Katsina, the Sahel margin) with sparse cover and dry, loose soils.
• Gully erosion – the south-east, especially the Agulu-Nanka and Udi areas of the Anambra/Enugu region.

(b) Three factors responsible for gully erosion

1. Heavy, intense rainfall with strong surface run-off that scours and deepens channels.
2. Steep, sloping land that increases the speed and cutting power of running water.
3. Removal of protective vegetation (through farming, bush burning, over-grazing and building) on loose, easily-eroded sandy soils, so the bare surface is quickly cut into gullies.

(c) Three measures being taken to solve soil erosion in the area

1. Afforestation and re-vegetation: planting trees, grasses and cover crops to bind the soil and break the force of rain and run-off.
2. Construction of check dams, drains and terraces / contour ploughing to slow run-off, trap sediment and lead water away safely.
3. Filling and stabilising existing gullies with sandbags, stones and gabions, controlling farming on steep slopes, and public enlightenment against bush burning and overgrazing.

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(a) Sketch map of Nigeria showing three vegetation belts

The three main vegetation belts of Nigeria run in roughly east-west zones from the humid south to the drier north: the Tropical Rainforest (south), the Guinea Savanna (middle) and the Sudan Savanna (north).

(b) Effects of climate on the vegetation of the Tropical Rainforest belt

1. Heavy rainfall throughout the year (over 1500 mm, well distributed) keeps the soil constantly moist, so the trees stay green all year and the forest is evergreen.
2. High temperatures (about 27°C, uniform through the year) speed up plant growth and encourage tall, broad-leaved forest trees arranged in distinct storeys (canopy layers).
3. Abundant sunshine and consistently high relative humidity promote very rapid, luxuriant growth, giving the belt its dense undergrowth and a great variety of plant species.
4. The absence of a long dry season means there is no period of leaf-fall or dormancy, so the plants grow continuously and the vegetation remains lush all year.

(c) Two resources found in the Tropical Rainforest belt and two uses of each

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Choosing (i) delta and (iii) caldera.

(a) Characteristics

Delta

• A roughly triangular or fan-shaped mass of alluvium built up where a river enters a sea or lake and drops its load.
• The main channel splits into many branching distributaries separated by low, flat, marshy islands and mud-flats.
• Composed of fine, fertile silt, sand and clay; very low-lying and liable to flooding (for example the Nile and Niger deltas).

Caldera

• A very large, roughly circular, basin-shaped hollow at the summit of a volcano, far wider than an ordinary crater (often several kilometres across).
• Bounded by steep inward-facing walls; the floor may hold a crater lake or later small cones (for example Ngorongoro).

(b) Mode of formation (with diagrams)

Delta: As a heavily-laden river reaches the still water of a sea or lake, its speed and carrying power suddenly fall. It deposits its sediment, coarsest first, building up beds of alluvium. Continued deposition blocks the mouth so the river divides into distributaries that push the land seaward. It forms best where the load is large, the current gentle and the tide/waves weak. A diagram shows the river dividing into distributaries across a triangular deposit.

Caldera: A caldera forms when a violent eruption empties the magma chamber beneath a volcano, or when the summit is blown off by an explosion. Losing this support, the unsupported top of the cone collapses inward (subsides) into the emptied chamber, leaving a huge circular depression far wider than the old vent. A diagram shows the cone before eruption, the emptied chamber, and the collapsed wide basin (caldera) afterwards.

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Petroleum Mining in North Africa

The sketch map below shows the major petroleum-producing areas of North Africa, the main pipelines and the coastal export terminals referred to in this answer.

(a) Major areas

The chief producing countries are Libya, Algeria, Egypt and, in smaller quantities, Tunisia.

• Libya: the main fields lie in the Sirte (Sirtica) Basin - Zelten (Nasser), Sarir, Amal and Waha.
• Algeria: the great inland Saharan fields of Hassi Messaoud (oil) and Hassi R'Mel (oil and natural gas).
• Egypt: production comes from the Gulf of Suez, the Sinai Peninsula and the Western Desert.
• Tunisia: smaller fields such as El Borma in the south.

(b) Methods of mining

Petroleum is obtained by drilling, in the following stages:

1. The oil-bearing (reservoir) rocks are first located by geological and geophysical survey, chiefly seismic prospecting, and the underground rocks are sampled and tested for traces of oil.
2. When a promising oil trap is found, a well is sunk to reach it by means of a drilling rig (derrick). Drilling may be on land in the desert or offshore on the continental shelf (as in the Gulf of Suez).
3. Where there is enough natural underground (gas) pressure, the crude oil flows up the well on its own; where the pressure is low it is brought up by pumping.
4. A system of valves fitted at the well-head, called a "Christmas tree", is used to control the flow of crude oil into storage tanks.
5. At the surface the crude oil is separated from gas and water and stored in tanks before being sent for refining or export.

(c) Transportation

Crude oil is moved from the desert fields to the coast mainly through pipelines - for example to the Libyan terminals at Marsa el Brega and Es Sider, and to the Algerian terminals at Skikda and Arzew. From these coastal terminals the oil is loaded into oil tankers (ships) and exported across the Mediterranean Sea to Europe and beyond. Natural gas is likewise piped to the coast and shipped as liquefied natural gas (LNG).

(d) Importance to the economy

1. It is the chief source of foreign-exchange earnings and government revenue.
2. When refined it yields petrol, kerosene, diesel and gas for domestic use and industry.
3. Its by-products are used in making insecticides, petroleum jelly, lubricating oil and other chemicals, so it has led to the growth of refineries and petro-chemical industries.
4. It provides raw materials for many associated industries and has encouraged urban, road and port development.
5. It provides gainful employment for many people, directly and indirectly.