WAEC SSCE - Geography - 2002 (Essay)

Answer Details

(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.

Answer Details

(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.

Answer Details

(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.

Answer Details

(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.

Answer Details

(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.

Answer Details

(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).

Answer Details

(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.

Answer Details

(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.

Answer Details

(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.

Answer Details

(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.

Answer Details

(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.

Answer Details

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.

Answer Details

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.

Answer Details

(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.

Answer Details

(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.

Answer Details

(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.

Answer Details

(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.