(a) On an outline map of Africa, mark and name the: (i) Equator, (ii) Greenwich meridian (iii) Tropics of Cancer an Capricorn (iv) Cape of Good Hope (v) Cap...

(a) Map work

As shown on the map above, the following features should be correctly marked and named:

• Equator (0°): crosses central Africa, passing through countries such as Gabon, Congo, the Democratic Republic of the Congo, Uganda, Kenya and Somalia.
• Greenwich Meridian (0° longitude): runs through north-western Africa, including Algeria, Mali, Burkina Faso and Ghana.
• Tropic of Cancer (23½°N): crosses the Sahara Desert in northern Africa.
• Tropic of Capricorn (23½°S): crosses southern Africa through Namibia, Botswana, South Africa and Mozambique.
• Cape of Good Hope: situated at the south-western tip of South Africa.
• Cape Blanco: located on the Atlantic coast of Mauritania in north-west Africa.
• Qattara Depression: located in the Western Desert of north-western Egypt, west of the River Nile.
• River Zambezi: rises in north-western Zambia and flows generally eastwards through Zambia, Zimbabwe and Mozambique into the Indian Ocean.

(b) Four ways in which the relief of Africa may create problems for constructing a trans-African highway from the Cape of Good Hope to Cairo

1. High mountains, plateaux and escarpments in southern and eastern Africa would require roads to climb steep slopes. This makes construction difficult and costly and may produce dangerous sharp bends and steep gradients.
2. Deep valleys and the East African Rift Valley would have to be crossed. Road engineers may need to construct long bridges, embankments, tunnels or winding roads down and up valley sides.
3. Major rivers and gorges, especially the Zambezi and other rivers along the route, would require expensive bridges and culverts. Flooding can also wash away roads and bridge approaches.
4. Desert terrain and depressions in northern Africa, including the Qattara Depression, may obstruct a direct route. Loose sand, sand dunes and wind-blown deposits can bury or damage roads, while very low-lying depressions may be unsuitable for road construction.

(c) Measures for minimizing the problems

• Carry out detailed route surveys and select relatively level lowland or gently sloping areas where possible.
• Avoid very high mountains, deep rift valleys, steep escarpments and the Qattara Depression by using alternative routes.
• Use cuttings, embankments, retaining walls, tunnels and carefully designed bends to reduce steep gradients in hilly areas.
• Construct strong bridges, culverts and drainage channels across rivers and flood-prone valleys.
• Stabilise desert roads by planting shelter belts of trees, using vegetation where possible, and constructing barriers to reduce sand encroachment and wind erosion.