|
The Lake Eyre basin is a drainage basin that covers just under one-sixth of all Australia. The Lake Eyre Basin is the largest endorheic basin in Australia and amongst the largest in the world, covering about ,〔(Map of the Lake Eyre basin )〕 including much of inland Queensland, large portions of South Australia and the Northern Territory, and a part of western New South Wales.〔(Lake Eyre Basin ). Department of the Environment, Water, Heritage and the Arts.〕 The deserts that have formed in the basin, including Sturt Stony Desert, Tirari Desert and the Strzelecki Desert, are most probably the southern hemisphere's largest source of airborne dust. The basin is also one of the largest, least-developed arid zone basins with high degrees of variability anywhere.〔 Grazing is the major land use, occupying 82% of the total land within the basin. The grazing is mostly low density due to harsh and variable climatic conditions. The basin began as a sinking landmass mostly covered by forest and contained many more lakes than now. The climate has changed from wet to arid over the last 60 million years. Most of the rivers in the Lake Eyre basin are now slow flowing, flat and completely dry for lengthy periods. They all flow towards the lowest point in the basin, 16 metres below sea level, at Lake Eyre. Significant mineral deposits can be found in the basin. In 2004 the Lake Eyre Basin Intergovernmental Agreement was formed after concerns with the management of four separate state governments was raised as problems in the Murray-Darling basin arose. ==Geology== The basin began to form in the early Paleogene (about 60 million years ago) when south-eastern South Australia started to sink and rivers began to deposit sediment into the large, shallow basin. The basin is still gradually sinking, and still gradually accumulating sediment.〔Sprigg, R.C. (1991): Geological Summary in: ''A natural history of the Lake Eyre Region''. The South Australian National Parks and Wildlife Service's Northern Consultative Committee. State Print, Adelaide. ISBN 0 646 07 183 1〕 For many millions of years, the Lake Eyre Basin was well supplied with water and largely forested. About 20 million years ago, large shallow lakes formed, covering much of the area for about 10 million years. From that time on, as Australia drifted further north and the climate became gradually more arid, the lakes and floodplains started to dry. Only in the last 2.6 million years did the onset of the ice ages bring about the present climatic regime and the consequent fairly rapid desertification of the area. Significant minerals deposits such as oil and natural gas, including Australia's most significant onshore petroleum reserves, are found within the basin. The mining and petroleum industries account for the greatest economic activity in the Lake Eyre Basin. Opals, coal, phosphate, gypsum and uranium are also mined from the basin.〔 In 2009, the Queensland Environmental Protection Agency confirmed that heavy metals from mining operations near Mount Isa had entered the upper reaches of the Georgina River. The spill has the potential to contaminate parts of the basin as far south as Lake Eyre. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lake Eyre basin」の詳細全文を読む スポンサード リンク
|