The Australian continent extends from east to west some 2,400 mi (3,860 km) and from north to south nearly 2,000 mi (3,220 km). It is on the whole exceedingly flat and dry. Less than 20 in. (50.8 cm) of precipitation falls annually over 70% of the land area. From the narrow coastal plain in the west the land rises abruptly in what, from the sea, appear to be mountain ranges but are actually the escarpments of a rough plateau that occupies the western half of the continent. It is generally from 1,000 to 2,000 ft (305–610 m) high but several mountain ranges rise to nearly 5,000 ft (1,520 m); there are no permanent rivers or lakes in the region. In the southwest corner of the continent there is a small moist and fertile area, but the rest of Western Australia is arid, with large desert areas.
The northern region fronts partly on the Timor Sea, separating Australia from Indonesia; it also belongs to the plateau, with tropical temperatures and a winter dry season. Its northernmost section, Arnhem Land (much of which is an aboriginal reserve), faces the Arafura Sea in the north and the huge Gulf of Carpentaria on the east. On the eastern side of the gulf is the Cape York Peninsula, which is largely covered by woodland. Off the coast of NE Queensland is the Great Barrier Reef, the world's largest coral reef.
In E Australia are the mountains of the Eastern Highlands, which run down the entire east and southeast coasts. The rivers on the eastern and southeastern slopes run to the Coral Sea and the Tasman Sea through narrow but rich coastal plains; the rivers on the western slopes flow either N to the Gulf of Carpentaria or W and SW to the Indian Ocean. The longest of all Australian river systems, the Murray River and its tributaries, drains the southern part of the interior basin that lies between the mountains and the great plateau. The rivers of this area are used extensively for irrigation and hydroelectric power.
Australia, remote from any other continent, has many distinctive forms of plant life—notably species of giant eucalyptus—and of animal life, including the kangaroo, the koala, the flying opossum, the wallaby, the wombat, the platypus, and the spiny anteater; it also has many unusual birds. Foreign animals, when introduced, have frequently done well. Rabbits, brought over in 1788, have done entirely too well, multiplying until by the middle of the 19th cent. they became a distinct menace to sheep raising. In 1907 a fence (still maintained) 1,000 mi (1,610 km) long was built from the north coast to the south to prevent the rabbits from invading Western Australia.