WAEC SSCE - Geography - 2020 (Practical and Physical Geography)
Swali 1 Ripoti
(a) Define weathering.
(b) ldentiry three factors that affect weathering.
(c) Describe the processes of exfoliation.
(a) Definition of weathering
Weathering is the breakdown, decay or disintegration of rocks in situ (at or near the earth's surface) by physical, chemical and biological processes, without the transportation of the resulting materials. It is distinct from erosion, which involves movement of the loosened material.
(b) Three factors that affect weathering
- Climate: temperature range and moisture control the type and rate; alternate heating and cooling favours physical weathering, while heat and rainfall favour chemical weathering.
- Nature of the rock (rock type and structure): hardness, mineral composition and the presence of joints and bedding planes determine how easily a rock breaks down.
- Vegetation and living organisms: plant roots prise rocks apart and decaying organic matter produces acids that attack minerals.
(Relief/slope and time are also acceptable.)
(c) The process of exfoliation
Exfoliation is a form of physical weathering common in hot deserts and tropical regions with large diurnal temperature ranges. The process is:
- By day, intense heating causes the outer surface layer of the rock to expand more than the cooler interior.
- At night the surface cools rapidly and contracts.
- This repeated expansion and contraction sets up stresses between the outer shell and the inner rock, weakening the bond between them.
- In time the outer curved layers peel or flake off like the layers of an onion, a process aided by slight chemical action of dew.
- The result is smooth, rounded rock masses such as exfoliation domes, with the peeling shells accumulating at the base.
Maelezo ya Majibu
(a) Definition of weathering
Weathering is the breakdown, decay or disintegration of rocks in situ (at or near the earth's surface) by physical, chemical and biological processes, without the transportation of the resulting materials. It is distinct from erosion, which involves movement of the loosened material.
(b) Three factors that affect weathering
- Climate: temperature range and moisture control the type and rate; alternate heating and cooling favours physical weathering, while heat and rainfall favour chemical weathering.
- Nature of the rock (rock type and structure): hardness, mineral composition and the presence of joints and bedding planes determine how easily a rock breaks down.
- Vegetation and living organisms: plant roots prise rocks apart and decaying organic matter produces acids that attack minerals.
(Relief/slope and time are also acceptable.)
(c) The process of exfoliation
Exfoliation is a form of physical weathering common in hot deserts and tropical regions with large diurnal temperature ranges. The process is:
- By day, intense heating causes the outer surface layer of the rock to expand more than the cooler interior.
- At night the surface cools rapidly and contracts.
- This repeated expansion and contraction sets up stresses between the outer shell and the inner rock, weakening the bond between them.
- In time the outer curved layers peel or flake off like the layers of an onion, a process aided by slight chemical action of dew.
- The result is smooth, rounded rock masses such as exfoliation domes, with the peeling shells accumulating at the base.
Swali 2 Ripoti
The countries listed in Table X below contributed money as indicated for a joint project in the year 2017. Use the data in the table to answer the questions that follow.
| Country | Amount Contributed |
| A | |
| B | |
| C | |
| D | |
| E |
Represent the data in Table X on a vertical divergent bar graph. (b) State one use of divergent bar graph.
(a) Vertical divergent bar graph
Mean contribution:
\[\bar{x}=\frac{35,000+60,000+45,000+80,000+30,000}{5}=\frac{250,000}{5}=\$50,000\]
| Country | Contribution ($) | Deviation from mean ($) |
|---|---|---|
| A | 35,000 | −15,000 |
| B | 60,000 | +10,000 |
| C | 45,000 | −5,000 |
| D | 80,000 | +30,000 |
| E | 30,000 | −20,000 |
The horizontal zero line represents the mean contribution of \(\$50,000\). Bars above it show contributions above the mean, while bars below it show contributions below the mean.
Scale: vertical scale: 1 cm represents \(\$5,000\) deviation; horizontal scale: equal widths and equal spacing for the countries.
(b) A divergent bar graph is used to show and compare the deviations of values above and below a common mean.
Maelezo ya Majibu
(a) Vertical divergent bar graph
Mean contribution:
\[\bar{x}=\frac{35,000+60,000+45,000+80,000+30,000}{5}=\frac{250,000}{5}=\$50,000\]
| Country | Contribution ($) | Deviation from mean ($) |
|---|---|---|
| A | 35,000 | −15,000 |
| B | 60,000 | +10,000 |
| C | 45,000 | −5,000 |
| D | 80,000 | +30,000 |
| E | 30,000 | −20,000 |
The horizontal zero line represents the mean contribution of \(\$50,000\). Bars above it show contributions above the mean, while bars below it show contributions below the mean.
Scale: vertical scale: 1 cm represents \(\$5,000\) deviation; horizontal scale: equal widths and equal spacing for the countries.
(b) A divergent bar graph is used to show and compare the deviations of values above and below a common mean.
Swali 3 Ripoti
(a)Lst five landforms found in the upper course of a river.
(b) Highlight three differences and two Similarities between an alluvial fan and a delta.
(a) Five landforms found in the upper course of a river
- V-shaped valley (deep, narrow valley cut by vertical erosion).
- Interlocking spurs (projecting ridges the river winds around).
- Waterfalls (and rapids where the river crosses hard rock bands).
- Gorges (steep-sided rocky valleys, often below a retreating waterfall).
- Potholes (circular hollows drilled into the rocky bed by swirling pebbles).
(Cascades and cataracts are also acceptable.)
(b) Alluvial fan and delta compared
Three differences
| Alluvial fan | Delta |
|---|---|
| Forms on land, where a river leaves a steep highland and reaches a plain. | Forms at the mouth of a river, where it enters a sea or lake. |
| Deposition is caused by a sudden reduction in gradient/slope. | Deposition is caused by the check of the current on meeting standing water and flocculation. |
| Built of coarser materials (gravel, sand) and is usually cone-shaped in profile. | Built of finer materials (silt, mud, clay) and is often triangular or bird-foot in plan. |
Two similarities
- Both are depositional landforms built from river load (alluvium).
- Both are formed where the river's velocity and carrying capacity fall sharply, and both have gentle, fan-like or spreading shapes crossed by distributaries.
Maelezo ya Majibu
(a) Five landforms found in the upper course of a river
- V-shaped valley (deep, narrow valley cut by vertical erosion).
- Interlocking spurs (projecting ridges the river winds around).
- Waterfalls (and rapids where the river crosses hard rock bands).
- Gorges (steep-sided rocky valleys, often below a retreating waterfall).
- Potholes (circular hollows drilled into the rocky bed by swirling pebbles).
(Cascades and cataracts are also acceptable.)
(b) Alluvial fan and delta compared
Three differences
| Alluvial fan | Delta |
|---|---|
| Forms on land, where a river leaves a steep highland and reaches a plain. | Forms at the mouth of a river, where it enters a sea or lake. |
| Deposition is caused by a sudden reduction in gradient/slope. | Deposition is caused by the check of the current on meeting standing water and flocculation. |
| Built of coarser materials (gravel, sand) and is usually cone-shaped in profile. | Built of finer materials (silt, mud, clay) and is often triangular or bird-foot in plan. |
Two similarities
- Both are depositional landforms built from river load (alluvium).
- Both are formed where the river's velocity and carrying capacity fall sharply, and both have gentle, fan-like or spreading shapes crossed by distributaries.
Swali 4 Ripoti
(a) Define atmospheric condition.
(b) List four major sources of air pollutants.
(c) Highlight four effects of atmospheric pollution.
(a) Definition of atmospheric condition
Atmospheric condition refers to the physical state of the atmosphere of a place at a given time, described by the weather elements such as temperature, rainfall, humidity, wind, pressure, cloud cover and the degree of purity or pollution of the air.
(b) Four major sources of air pollutants
- Industrial activities/factories: smoke, soot and gases (\(\text{SO}_2\), \(\text{CO}_2\)) from manufacturing and processing plants.
- Motor vehicles and other transport: exhaust fumes containing carbon monoxide, lead and hydrocarbons.
- Bush burning and burning of fossil fuels: release of smoke, ash and carbon gases.
- Gas flaring and oil operations: flares from oil fields (as in the Niger Delta) emit large volumes of gases and soot.
(Others: refuse/waste incineration, power stations, volcanic eruptions and dust.)
(c) Four effects of atmospheric pollution
- Respiratory and other diseases: polluted air causes bronchitis, asthma, lung cancer and eye irritation.
- Acid rain: sulphur and nitrogen oxides dissolve in rain, damaging crops, forests, buildings and water bodies.
- Global warming and climate change: greenhouse gases such as carbon dioxide trap heat, raising temperatures and disrupting rainfall.
- Depletion of the ozone layer: gases such as CFCs thin the ozone shield, increasing harmful ultraviolet radiation.
(Also: reduced visibility/smog, poor plant growth and lower agricultural yields.)
Maelezo ya Majibu
(a) Definition of atmospheric condition
Atmospheric condition refers to the physical state of the atmosphere of a place at a given time, described by the weather elements such as temperature, rainfall, humidity, wind, pressure, cloud cover and the degree of purity or pollution of the air.
(b) Four major sources of air pollutants
- Industrial activities/factories: smoke, soot and gases (\(\text{SO}_2\), \(\text{CO}_2\)) from manufacturing and processing plants.
- Motor vehicles and other transport: exhaust fumes containing carbon monoxide, lead and hydrocarbons.
- Bush burning and burning of fossil fuels: release of smoke, ash and carbon gases.
- Gas flaring and oil operations: flares from oil fields (as in the Niger Delta) emit large volumes of gases and soot.
(Others: refuse/waste incineration, power stations, volcanic eruptions and dust.)
(c) Four effects of atmospheric pollution
- Respiratory and other diseases: polluted air causes bronchitis, asthma, lung cancer and eye irritation.
- Acid rain: sulphur and nitrogen oxides dissolve in rain, damaging crops, forests, buildings and water bodies.
- Global warming and climate change: greenhouse gases such as carbon dioxide trap heat, raising temperatures and disrupting rainfall.
- Depletion of the ozone layer: gases such as CFCs thin the ozone shield, increasing harmful ultraviolet radiation.
(Also: reduced visibility/smog, poor plant growth and lower agricultural yields.)
Swali 5 Ripoti
(a) Define climate.
(b) Draw the globe and show the three climatic belts of the Greek System of Classification.
(c) List three areas of hot deserts
(d) Outline three characteristics of hot deserts.
(a) Definition of climate
Climate is the average condition of the atmosphere of a place, determined from observations of weather elements over a long period, usually about 30 to 40 years.
(b) Climatic belts of the Greek system of classification
The Greeks classified the world into three main climatic belts: the Frigid, Temperate and Torrid belts. The Frigid and Temperate belts each occur in both hemispheres.
(c) Three areas of hot deserts
- The Sahara Desert of North Africa.
- The Arabian Desert of the Middle East.
- The Thar Desert of India and Pakistan.
(d) Characteristics of hot deserts
- Rainfall is very low, usually below 250 mm annually, and is unreliable, infrequent and often torrential when it occurs.
- Temperatures are high, commonly above 30°C during the day, with a large daily range of temperature and cold nights.
- Evaporation is high because skies are mostly cloudless, humidity is low and insolation is intense.
- Vegetation is sparse and consists mainly of drought-resistant, xerophytic plants.
- Wind action is important, producing dust storms, sand dunes and other wind-eroded features.
Maelezo ya Majibu
(a) Definition of climate
Climate is the average condition of the atmosphere of a place, determined from observations of weather elements over a long period, usually about 30 to 40 years.
(b) Climatic belts of the Greek system of classification
The Greeks classified the world into three main climatic belts: the Frigid, Temperate and Torrid belts. The Frigid and Temperate belts each occur in both hemispheres.
(c) Three areas of hot deserts
- The Sahara Desert of North Africa.
- The Arabian Desert of the Middle East.
- The Thar Desert of India and Pakistan.
(d) Characteristics of hot deserts
- Rainfall is very low, usually below 250 mm annually, and is unreliable, infrequent and often torrential when it occurs.
- Temperatures are high, commonly above 30°C during the day, with a large daily range of temperature and cold nights.
- Evaporation is high because skies are mostly cloudless, humidity is low and insolation is intense.
- Vegetation is sparse and consists mainly of drought-resistant, xerophytic plants.
- Wind action is important, producing dust storms, sand dunes and other wind-eroded features.
Swali 6 Ripoti
(a) List five factors that affect climate.
(b) Highlight five characteristics of Equatorial climate.
(a) Five factors that affect climate
- Latitude (distance from the equator): places near the equator receive more direct, intense insolation and are hotter than places near the poles.
- Altitude (height above sea level): temperature falls with height (about \(6.5^{\circ}\text{C}\) per \(1000\text{ m}\)), so highlands are cooler than lowlands.
- Distance from the sea (continentality): coastal areas have a small temperature range while interiors have hot summers and cold winters.
- Ocean currents: warm currents raise the temperature and rainfall of adjacent coasts, while cold currents lower them.
- Prevailing winds and relief (aspect): onshore moist winds bring rain, offshore dry winds do not, and windward slopes are wetter than leeward slopes.
(Vegetation cover and cloud cover are also acceptable.)
(b) Five characteristics of the Equatorial climate
- High temperatures all year: mean monthly temperature is about \(27^{\circ}\text{C}\), with a very small annual range (about \(2^{\circ}\text{C}\)).
- Heavy rainfall throughout the year: totals exceed \(2000\text{ mm}\), with no true dry season (double maxima near the equinoxes).
- High relative humidity: often above 80 per cent, giving a hot, damp, uncomfortable feel.
- Convectional rainfall: intense afternoon thunderstorms occur almost daily due to strong heating and rising moist air.
- Small diurnal and seasonal contrast with heavy cloud cover: days are consistently hot, humid and cloudy with little seasonal variation.
Maelezo ya Majibu
(a) Five factors that affect climate
- Latitude (distance from the equator): places near the equator receive more direct, intense insolation and are hotter than places near the poles.
- Altitude (height above sea level): temperature falls with height (about \(6.5^{\circ}\text{C}\) per \(1000\text{ m}\)), so highlands are cooler than lowlands.
- Distance from the sea (continentality): coastal areas have a small temperature range while interiors have hot summers and cold winters.
- Ocean currents: warm currents raise the temperature and rainfall of adjacent coasts, while cold currents lower them.
- Prevailing winds and relief (aspect): onshore moist winds bring rain, offshore dry winds do not, and windward slopes are wetter than leeward slopes.
(Vegetation cover and cloud cover are also acceptable.)
(b) Five characteristics of the Equatorial climate
- High temperatures all year: mean monthly temperature is about \(27^{\circ}\text{C}\), with a very small annual range (about \(2^{\circ}\text{C}\)).
- Heavy rainfall throughout the year: totals exceed \(2000\text{ mm}\), with no true dry season (double maxima near the equinoxes).
- High relative humidity: often above 80 per cent, giving a hot, damp, uncomfortable feel.
- Convectional rainfall: intense afternoon thunderstorms occur almost daily due to strong heating and rising moist air.
- Small diurnal and seasonal contrast with heavy cloud cover: days are consistently hot, humid and cloudy with little seasonal variation.
Swali 7 Ripoti
(a) State two differences between weather and climate.
(b) Name the instruments used in measuring the following weather elements: (i) sunshine (ii) rainfall (iii) cloud cover.
(c) Explain how Wind speed is measured and recorded.
(a) Two differences between weather and climate
| Weather | Climate |
|---|---|
| The state of the atmosphere of a place over a short period (a day or a few days). | The average weather conditions of a place taken over a long period, usually at least 30 to 35 years. |
| It changes frequently from hour to hour or day to day. | It is relatively stable and changes only over a long time. |
(b) Instruments used to measure the weather elements
- (i) Sunshine: the Campbell-Stokes sunshine recorder.
- (ii) Rainfall: the rain gauge.
- (iii) Cloud cover: estimated by the eye in oktas (eighths) of the sky (an instrument such as a nephoscope observes cloud movement).
(c) How wind speed is measured and recorded
- Wind speed is measured with a cup anemometer, which consists of three or four hemispherical cups mounted on horizontal arms that rotate freely on a vertical spindle.
- The wind pushes the cups round, and the rate of rotation is proportional to the wind speed.
- The rotations are transmitted to a dial or counter which is calibrated to read the speed in kilometres per hour, metres per second or knots.
- The instrument is mounted in an open, exposed place about \(10\text{ m}\) above the ground, free from obstruction.
- Readings are taken at fixed times and recorded; average and gust speeds may be logged, and on the Beaufort scale the values are expressed in numbered wind forces.
Maelezo ya Majibu
(a) Two differences between weather and climate
| Weather | Climate |
|---|---|
| The state of the atmosphere of a place over a short period (a day or a few days). | The average weather conditions of a place taken over a long period, usually at least 30 to 35 years. |
| It changes frequently from hour to hour or day to day. | It is relatively stable and changes only over a long time. |
(b) Instruments used to measure the weather elements
- (i) Sunshine: the Campbell-Stokes sunshine recorder.
- (ii) Rainfall: the rain gauge.
- (iii) Cloud cover: estimated by the eye in oktas (eighths) of the sky (an instrument such as a nephoscope observes cloud movement).
(c) How wind speed is measured and recorded
- Wind speed is measured with a cup anemometer, which consists of three or four hemispherical cups mounted on horizontal arms that rotate freely on a vertical spindle.
- The wind pushes the cups round, and the rate of rotation is proportional to the wind speed.
- The rotations are transmitted to a dial or counter which is calibrated to read the speed in kilometres per hour, metres per second or knots.
- The instrument is mounted in an open, exposed place about \(10\text{ m}\) above the ground, free from obstruction.
- Readings are taken at fixed times and recorded; average and gust speeds may be logged, and on the Beaufort scale the values are expressed in numbered wind forces.
