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Australia’s geography is marked by uplands in the east，a large plateau in the west，and lowlands，basins and plains in the middle.Its highest point is the 2，200⁃meter Mount Kosciusko in the southeastern part of the country.Three⁃quarters of Australia takes the form of a huge dry plateau，including huge deserts like the Great Sandy Desert of Western Australia which occupies an area of about 400，000 square kilometers，the Great Victoria Desert and the Nullarbor Plain.The presence of such expansive deserts makes a quarter of Australia unsuitable for human habitation.

The Eastern Uplands include a complex series of high ridges，high plains，plateaus and basins that run along the country’s east coast.Most of the higher land that has an elevation of more than 600 meters is in this part of the country.The western plateau is composed mainly of deserts and semi⁃deserts at an average elevation of 200 to 500 meters.The central plains and basins form the bulk of the heartland of Australia.The largest basin is the one around Lake Eyre，which has a catchment extending over millions of square kilometers in central and northern Australia.It is the lowest point of the country at up to 16 meters below sea level.Many major river systems drain into the lake，such as the Georgina，the Diamantina，the Thomson and the Barcoo.These rivers from year to year bring large quantities of sediment and salt to the interior drainage areas of the lake，making the lake water very salty and the dried lake beds encrusted with salt.

Australia’s longest river is the Murray.Originating in the Eastern Uplands，it is 3，490 kilometers long，a length unrivalled by other rivers.It has many tributaries，the most important of which being the Darling.Along these tributaries as well as the Murray itself there are extensive alluvial plains.

Australia’s most famous geological feature is the Great Barrier Reef which lies under the ocean off the northeastern coast.The Reef was built by coral，which are small sea animals，and is the largest structure in the world created by living creatures（including by human beings）.It extends for about 2，000 kilometers from north to south，with a width between 20 and 240 kilometers.The Reef is home to the world’s richest collection of corals，with more than 350 species，along with thousands of species of other marine plants and animals.