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Australia is the fifth and smallest continent. It covers approximately 7.700.000 square kilometres, the mainland is almost 4.000 kilometres from west to east and over 3.000 kilometres from north to south. Most of the land is very flat. The very old Western Plateau is generally only 300 metres above sea-level and is mostly desert or semi-desert. In general Austrlia's climate has a mild drought or dry period every five years and a bad one evrey ten. One example is Central Australia which went without rain for seven years in 1970s. therefore, although the soil may be fertile in the inland , little or no water makes it almost impossible for people to live there and use the land. Much of the water that has managed to reach these dry areas over hundreds of years and run into the lake system has brought salt to the surface . the heat evaporates the water. As the lakes dry out the water just below the surface rises because of the heat and also evaporates on the surface bringing up salts from the soils. The Western Plateau contains many salt lakes . Lake Eyre, the largest , covers an area over 9.000 square kilometres and as the lowest is 16 metres below sealevel. It is the drainage basin of the inland river system that confused the early settlers who thought the area would be well supplied with fresh water. Due to these conditions there are only the two large settlements of Darwin in the north and alice springs in the centre.
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