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Australia is the world’s smallest, flattest, and (after Antarctica) driest
continent, but at 7.7 million square kilometers (3.0 million square miles) it is
also the sixth largest country. Its low average elevation (300 meters, or less
than 1000 feet) 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, or 7310 feet.)
Prominent features of Australia include the Lake Eyre basin, the darker green
region visible in the center-right. At 16 meters (52 feet) below sea level this
depression is one of the largest inland drainage systems in the world, covering
more than 1.3 million square kilometers (500,000 square miles). 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
kilometers (300 miles) (NASA).
