Australia is roughly crescent-shaped. It is lower and flatter than any other continent; three-fourths of the land lies 600 to 1,500 feet (180 to 460 m) above sea level.
Running along the east coast and increasing in height from north to south is the Great Dividing Range. At the range's southern end are the Australian Alps, which rise to 7,316 feet (2,230 m) at Mount Kosciusko, the highest peak in Australia. The mountains also occur in Tasmania, where most of the terrain is rugged.
Inland from the Great Dividing Range are the plains and basins of the central lowlands, a region extending north-south from Spencer Gulf to the Gulf of Carpentaria. The land is generally flat to rolling and only slightly above sea level. At Lake Eyre in the south it dips 52 feet (16 m) below sea level.
The western two-thirds of Australia consists of a low plateau. Several mountainous areas break the generally level terrain. The Macdonnell and Musgrave ranges in the heart of the continent rise to almost 5,000 feet (1,520 m); the Hamersley Range in the west to more than 4,000 feet (1,220 m). Deserts, such as the Great Sandy, Gibson, and Great Victoria, make up much of the region.
Numerous arms of the Pacific and Indian oceans border Australia's coast. Among them are the Timor Sea, the Arafura Sea, and the Gulf of Carpentaria in the north; the Coral Sea and the Tasman Sea in the east; and the Great Australian Bight in the south. In the Coral Sea, paralleling the shore for some 1,250 miles (2,000 km), is the Great Barrier Reef, the world's largest coral formation.
Australia has only one major river system, the Murray-Darling, which flows westward from the Great Dividing Range. With a combined length of 2,310 miles (3,718 km) from the source of the Darling to the mouth of the Murray, it drains a huge area in the southeast. There are also permanently flowing streams along the eastern and southwestern coasts. Major rivers of the north occasionally turn into a mere series of waterholes during extremely dry weather. In the south and throughout much of the interior there are no rivers.
Australia has no large permanent lakes, only small ones in the southern part of the Great Dividing Range. The interior has shallow salt lakes that are usually dry, but periodically fill with water. Largest of these are Lakes Eyre, Gairdner, and Torrens.
Underlying about a third of Australia are artesian basins, areas with underground water-bearing rock. The Great Artesian Basin, the largest such basin in the world, covers an area of more than 600,000 square miles (1,500,000 km2).
Because of a latitudinal span of some 34 degrees (about 10º to 44º South), the climate varies from tropical and monsoonal in the north to temperate and oceanic in the south. Temperature differences between the warmest and coldest months are everywhere relatively small, much less than those in comparable latitudes of the Northern Hemisphere. The climate in general is also marked by limited precipitation, abundant sunshine, low relative humidity, and moderate winds. Typhoons occasionally strike the north coast. Summer lasts from December to March; winter from June to September.
Except in the high mountains of the southeast and in Tasmania, summers are hot. Northwestern Australia is particularly torrid—maximum temperatures of 100º to 120º F. (38º to 49º C.) have been recorded for as many as 160 consecutive days. Winters are generally warm to mild. In tropical northern Australia, winter is hot, much like the rest of the year. Elsewhere, except in the extreme southeast, temperatures rarely, if ever, fall below freezing.
The total amount of rainfall in Australia is small, and it varies enormously from year to year. Devastating droughts occur periodically. In a broad belt extending from the west coast through the vast interior and curving down to the south coast, the annual precipitation is less than 20 inches (508 mm). Much of this region receives less than 10 inches (254 mm) a year. In areas along the northern, eastern, southeastern, and southwestern coasts, precipitation is more abundant, some 20 to 50 inches (508 to 1,270 mm) a year. Small areas along these coasts receive larger amounts—up to 160 inches (4,064 mm) of rain in northern Queensland, and 140 inches (3,556 mm) in western Tasmania. Snow falls in the high southern part of the Great Dividing Range and in Tasmania.