The Commonwealth of Australia, a country in the South Pacific Ocean, occupies the smallest continent and covers an area of 2,966,200 mi² (7,682,000 km²). Along the northeast coast of Australia, for a distance of 1,200 mi (2,000 km) in length and offshore as much as 100 mi (160 km) into the Pacific Ocean, lies the Great Barrier Reef, the greatest assemblage of coral reefs in the world. The island of Tasmania, which is a part of Australia, lies off the southeast coast of the mainland. Australia consists mainly of plains and plateaus, most of which average 2,000 ft (600 m) above sea level. There are several low mountain ranges in the country.

Only about 16 million people live in Australia, of whom about 150,000 are native people, the Aborigines.

More than a third of Australia receives under 10 in (25 cm) of annual rainfall, while less than a third receives over 20 in (51 cm). Many areas experience prolonged drought and frequent...