Summary

Natural science is the main characteristic feature of the present civilization. Science and technology have modified our homes, places of work and enjoyment, means of communications. Science expands man’s intellectual horizons. The range of human knowledge doubles every twelve years. The second half of the twentieth century brought a number of technical innovations – transistor, ICs. satellites, etc. Recent developments of nuclear weapons make wars of annihilation possible and pose the question of the survival of the human race.

2. WHAT HAPPENS TO A RIVER AS IT APPROACHES ITS MOUTH?

The flat area of land over which a river meanders is called a flood plain. During times of flood, a river will overflow its banks and cover any surrounding flat land. As the speed at which the water flows across the flood plain is less than in the main channel, then the fine material transported in suspension by the river will be deposited. Each time a river floods a thin layer of silt, or alluvium, is spread over the flood plain. The Egyptians used to rely upon the annual flooding by the River Nile to water their crops and to add silt to their fields until the opening of the Aswan Dam in 1970.

When a river floods, it is the coarsest material which will be deposited first. This coarse material can form small embankments alongside a river which the Americans call levees. Large rivers, like the Mississippi, carry tremendous quantities of material in suspension, especially in times of flood.

However, during times when the river level falls and its speed is reduced, large amounts of silt will fall out of suspension onto the bed of the river. In time the bed of the river will build up so that, when water levels are high again, the river is more likely to overflow its banks. To try to prevent this happening, large artificial levees are built. The Mississippi now flows at a much higher level than the surrounding flood plain, and cities like New Orleans and St Louis are protected by levees that are up to 16 metres high. The problem is, what happens should these levees break?

Large rivers transport great amounts of fine material down to their mouths. If a river flows into a relatively calm sea, or lake, then its speed will reduce and the fine material will be deposited. The deposited material will slowly build upwards and outwards to form a delta. River deltas provide some of the best soils in the world for farming (e.g. River Nile) but they are also prone to serious flooding as the land is so flat (e.g. Bangladesh). The Mississippi delta is extending rapidly into the Gulf of Mexico. As in all deltas, deposition blocks the main channel of the river so the Mississippi has to divide into a series of smaller channels called distributaries. These channels need constant dredging if they are to be used by ships.

Summary

By the time a large river approaches a lake or the sea it will be carrying large amounts of material. Some of this material may be spread over the flood plain during times of flood, or it may form a delta at the river mouth.

David Waugh. Key Geography for GCSE. Cheltenham: Stanley Thornes (Publishers), 1995.

3. WHERE DO MOST PEOPLE IN BRITAIN LIVE?

Map A shows the population distribution of Britain; it shows where most people in Britain live. It is obvious that people are not distributed evenly across the country. Some places are very crowded while others have very few inhabitants. The map uses population density to show how crowded different places are. Population density is the number of people living in a given area and is usually given as the number of people per square kilometre. Population density is found by dividing the total population of an area by the size of the area where they live. For example:

Population of the UK 57 237 000

Area of the UK (sq km) 244 880 = 234 per square kilometre

Places that are crowded are described as densely populated and have a high population density. Places that have few people living there are described as sparsely populated and have a low population density.

When looking at population maps which show either distributions or densities, a geographer has to try to observe any notable patterns. Map A shows two patterns:

1. Areas with the highest densities appear to be in the south and east while those places with the lowest densities are more to the north and west.

2. The highest densities are in large urban areas and the lowest densities in rural areas.

Population density maps are simplified to show general patterns. As a result they cannot show local variations.

● In urban areas, population density tends to be higher in older inner city areas, rather than towards the edge of cities.

● In rural areas population density tends to be higher in larger market towns rather than places with dispersed farms.

City	Population (‘OOOs)	City	Population (‘OOOs)
Glasgow	730	London	6378
Edinburgh	404	Bristol	367
Newcastle upon Tyne	617	Cardiff	273
Leeds	432	Southampton	192
Manchester	1669	Belfast	281
Liverpool	1060	Dublin	921
Birmingham	1400	Sheffield	445