WAEC SSCE - Geography - 2015 (Practical and Physical Geography)

Detalles de la respuesta

(a) Three landforms found in the upper course of a river valley

1. V-shaped valley.
2. Waterfalls and rapids.
3. Interlocking spurs (also gorges and potholes).

(b) The ox-bow lake

Characteristics: An ox-bow lake is a curved, crescent- or horseshoe-shaped body of stagnant water found on the flood plain of a river in its lower course. It lies beside, but is cut off from, the main river channel and it gradually dries up or becomes a swamp because it no longer receives flowing water.

Mode of formation:

1. In the lower course the river flows slowly across a flat flood plain and develops large bends called meanders.
2. On the outer bank of each meander the current is fastest, so it undercuts and erodes the bank laterally; on the inner bank the current is slow, so it deposits material.
3. Continued erosion on the two outer bends brings the necks of the loop closer and closer together, narrowing the neck of land between them.
4. During a flood the river cuts through the narrow neck, taking a new straight and shorter course.
5. Deposition then seals off the ends of the abandoned loop, leaving a curved stretch of water separated from the main channel. This is the ox-bow lake (also called a cut-off or mortlake).

A labelled diagram should show the meander loop, the narrowing neck, the point of cut-off, the new straightened channel, and the detached crescent-shaped ox-bow lake with deposition (plugs) sealing its ends.

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(a) Three types of mountains

1. Fold mountains (e.g. the Alps, Himalayas).
2. Block (fault) mountains (e.g. the Ruwenzori).
3. Volcanic mountains (e.g. Mount Cameroon, Kilimanjaro). (Residual mountains are a fourth type.)

(b) Four ways in which mountains are important to man

1. Source of rivers: High mountains cause relief rainfall and act as water catchment areas, feeding rivers used for water supply, irrigation and hydro-electric power.
2. Tourism and recreation: Scenic mountains attract tourists for sightseeing, mountaineering, skiing and holidays, earning foreign exchange.
3. Natural boundaries and defence: Mountains serve as political boundaries between countries and as natural barriers of defence against invasion.
4. Mineral resources: Many mountains are rich in minerals and building stones, and their forested slopes supply timber; some slopes are used for grazing and terraced farming.

(c) Two problems caused by mountains

1. They hinder transport and communication, making the construction of roads and railways difficult and costly.
2. They create leeward (rain-shadow) areas of low rainfall and, being cold and rugged, discourage settlement and farming.

Detalles de la respuesta

(a) Explanation of terms

(i) Rotation of the earth: This is the spinning or turning of the earth on its own axis from west to east. The earth completes one rotation in approximately 24 hours (one day). It is responsible for day and night and for the apparent rising of the sun in the east and setting in the west.

(ii) Revolution of the earth: This is the movement of the earth in its orbit around the sun from west to east. The earth completes one revolution in about \(365\tfrac{1}{4}\) days (one year). The axis is tilted at \(66\tfrac{1}{2}^\circ\) to the plane of the orbit (or \(23\tfrac{1}{2}^\circ\) from the vertical).

(iii) Equinox: This is the time (about 21 March and 23 September) when the sun is overhead at the equator, so that day and night are of equal length (12 hours each) all over the world. "Equinox" means "equal night".

(b) Three effects of the revolution of the earth

1. It causes the sequence and changing of the four seasons: spring, summer, autumn and winter.
2. It causes variation in the length of day and night at different times of the year (except at the equator).
3. It causes the apparent northward and southward migration of the overhead (vertical) sun between the Tropic of Cancer and the Tropic of Capricorn, and it determines the calendar year, leading to the introduction of the leap year.

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(a) Definition of climate

Climate is the average weather conditions of a place recorded over a long period of time, usually not less than 35 years. It is the aggregate of the day-to-day weather elements (temperature, rainfall, pressure, humidity, wind, etc.) for a large area over many years.

(b) The three climatic belts of the Greek system of classification

The ancient Greeks divided the world into three broad temperature zones on the basis of latitude and the amount of heat received from the sun:

1. The Torrid Zone: Lies between the Tropic of Cancer (\(23\tfrac{1}{2}^\circ\)N) and the Tropic of Capricorn (\(23\tfrac{1}{2}^\circ\)S), astride the equator. It is hot throughout the year because the sun is overhead at some time.
2. The Temperate Zones: Two belts lying between the tropics and the polar circles, that is between \(23\tfrac{1}{2}^\circ\) and \(66\tfrac{1}{2}^\circ\) in each hemisphere. They have moderate temperatures with warm summers and cool winters.
3. The Frigid Zones: Two belts lying between the polar circles (\(66\tfrac{1}{2}^\circ\)) and the poles (\(90^\circ\)) in each hemisphere. They are very cold throughout the year.

(c) Three reasons why Koppen's system is the most widely accepted

1. It is based on measurable elements of climate, namely temperature and rainfall, together with their seasonal distribution, so it is objective and can be applied anywhere.
2. It uses actual vegetation as an indicator of climate, so the climatic boundaries closely match the natural vegetation belts on the ground.
3. It provides a clear system of letters and symbols that gives each climatic type a precise code, making it simple, systematic and easy to map and compare worldwide.

Detalles de la respuesta

(a) Features of coastal erosion

1. Cliffs.
2. Wave-cut platforms (abrasion platforms).
3. Caves, arches and stacks.
4. Headlands and bays.
5. Geos and blow-holes.

(b) The beach

Characteristics: A beach is a gently sloping accumulation of sand, pebbles and shingle deposited by waves along the shore between the low-water and high-water marks. It is a depositional (constructive) feature, usually curved and widest in sheltered bays, with the finer sand near the water and coarser shingle towards the back.

Mode of formation:

1. Waves carry large amounts of eroded material (sand, shingle and pebbles) obtained from cliffs and from the sea bed.
2. When constructive waves reach a gently sloping shore, their swash (up-rush) is strong and their backwash (return flow) is weak.
3. The strong swash pushes the load up the shore, but the weak backwash cannot drag all of it back, so material is left behind.
4. Repeated deposition of this material over time builds up the ridge of sand and shingle that forms the beach, especially in sheltered bays where wave energy is low.

A labelled diagram should show the sloping shore, the swash and backwash arrows, the deposited sand and shingle, and the high- and low-water marks.