About This Image
Australia is the world’s largest island, but at 7.7 million km² is also the sixth largest country. Its low average elevation (300 meters) is caused by its position near the center of a tectonic plate, where there are no volcanic or other geologic forces of the type that raise the topography of other continents. In fact Australia is the only continent without any current volcanic activity at all—the last eruption took place 1400 years ago at Mt. Gambier.
The Australian continent is also one of the oldest land masses, with some of its erosion-exposed bedrock age dated at more than 3 billion years. More than one-fifth of the land area is desert, with more than two-thirds being classified as arid or semi-arid and unsuitable for settlement. The coldest regions are in the highlands and tablelands of Tasmania and the Australian Alps at the southeastern corner of the continent, location of Australia’s highest point, Mt. Kosciusko (2228 meters).
Prominent features of Australia include the Lake Eyre basin, the darker green region visible in the center-right. At 16 meters below sea level this depression is one of the largest inland drainage systems in the world, covering more than 1.3 million km². The mountain range near the east coast is called the Great Dividing Range, forming a watershed between east and west flowing rivers. Erosion has created deep valleys, gorges and waterfalls in this range where rivers tumble over escarpments on their way to the sea.
The crescent shaped uniform green region in the south, just left of center, is the Nullarbor Plain, a low-lying limestone plateau which is so flat that the Trans-Australian Railway runs through it in a straight line for more than 483 km.
Two visualization methods were combined to produce this image (NASA, February 2000): shading and color coding of topographic height. The shade image was derived by computing topographic slope in the northwest-southeast direction. Color coding is directly related to topographic height, with green at the lower elevations, rising through yellow and tan, to white at the highest elevations.
(See information about this image at the bottom of this page)
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