Australia's geography: a dry continent settled at its edges

Why so little of Australia stands high

Australia is a continent of plains. Britannica puts only 6% of the land above 600 metres, and Wikipedia's geography gives an average elevation of about 330 metres, with close to 87% of the mainland below 500 metres. Mount Kosciuszko, in the Snowy Mountains of New South Wales, reaches 2,228 metres by the survey of Geoscience Australia. Mawson Peak, 2,745 metres, on the active volcano Big Ben on Heard Island in the southern Indian Ocean, stands higher, and Geoscience Australia notes peaks of up to 3,490 metres in the Australian Antarctic Territory. The lowest is the bed of Kati Thanda, or Lake Eyre, about 15 metres below sea level.

The flatness is age. Britannica dates detrital zircon grains in Australian rock to 4.4 billion years, and most of the rocks under its landforms were formed between about 4.6 billion and 252 million years ago. Long periods of weathering wore the old shield of the west down to low relief. The continent lies near the middle of its tectonic plate, so volcanoes and large earthquakes are rare; Wikipedia's geography records the volcanic field of the south-east as dormant for about 5,000 years. Australia broke away from Antarctica as Gondwana split, and Britannica dates its existence as a separate continent to about 35 million years ago. It is still drifting north, towards the South-East Asian landmass.

Geoscience Australia measures the country at 7,688,287 square kilometres, of which 7,656,127 are the mainland and Tasmania and 32,160 are the smaller islands. Western Australia alone is 32.9% of the total and Tasmania 0.9%.

How the Great Dividing Range divides the water

A chain of highlands runs close to the east coast from Cape York in northern Queensland to the south of Tasmania. From the sea it looks like a mountain range, but Britannica describes it as the escarpment of a giant plateau that slopes almost imperceptibly west to the plains, with few peaks above 1,500 metres. Wikipedia's geography gives its length on the mainland as almost 4,000 kilometres.

The range sends short rivers east to the Pacific and long ones inland. The River Murray rises in the Kosciuszko area, and is fed by snowmelt, which gives it enough water to cross the dry plains and reach the Southern Ocean south-east of Adelaide. Britannica treats it as the exception among the inland rivers. Geoscience Australia recalculated its length in September 2008 at 2,508 kilometres. Counting the Darling and its northern headwaters, the Culgoa, Balonne and Condamine, the Murray-Darling system runs 3,672 kilometres from Queensland to the Murray mouth near Goolwa in South Australia.

West of the range lie the Central Lowlands, from the Murray-Darling basin through the Great Artesian Basin to the Gulf of Carpentaria. The artesian basin is groundwater rather than river: it spans almost 1,700,000 square kilometres, more than a fifth of the continent, and in much of the interior it is the only reliable source of water.

What stands on the western plateau

The Western Plateau takes up about a third of the country, most of it below 500 metres. What rises from it rises abruptly. In the north-west, the Kimberley and the Pilbara are plateaus of flat-lying sandstone and ironstone cut into mesas, buttes and bluffs, and Britannica describes the Barkly Tableland to their east as a high plain of remarkable flatness. In the centre, the MacDonnell Ranges are eroded folds, with sandstone and quartzite holding up the ridges and siltstone and shale worn into the valleys between them; further south, the Musgrave and Everard ranges of north-western South Australia rise as isolated ranges and hills above the plain.

Uluru is the best-known single form. UNESCO describes it as a sandstone monolith and Kata Tjuta, 32 kilometres to its west, as a group of conglomerate domes, both rising to more than 300 metres above the sandplain. After rain, runoff from Uluru falls down its fissures in waterfalls up to 100 metres high. The park was inscribed on the World Heritage List in 1987 and extended in 1994, and it is listed for both natural and cultural values; and its traditional owners are the Yankunytjatjara and Pitjantjatjara people, who call themselves Anangu.

Tasmania, south across Bass Strait, has its own relief. The Midlands in the centre-east are fairly flat and mostly farmed, the Central Highlands take up most of the centre-west, and the western mountains share with those of north-east Queensland and the south-east the higher rainfall totals that elevation brings.

Where the rain falls and where it does not

Rain falls on the edges. Wikipedia's geography, citing the Bureau of Meteorology, gives the continent an average of 419 millimetres a year and says 80% of the land gets less than 600 millimetres and half less than 300. Britannica's figures are similar but not the same: an average of about 460 millimetres, and more than a third of the mainland below 250. Both describe the same shape, in which rainfall rises towards the coast and in the mountains of north-east Queensland, the south-east and western Tasmania.

Britannica uses those three zones for the plants as well, because the vegetation follows the rain. Two ocean systems move the totals from year to year. In the east, El Niño brings drought and La Niña flooding rains; in the west and north, the Indian Ocean Dipole shifts the rainfall of the Top End and the south. Droughts of several seasons are a normal part of the record. Summer and winter differ less than on the northern continents because the Southern Ocean keeps polar air away, although temperatures run from about 40 °C in the central deserts to about 0 °C in the south-eastern highlands.

Why most rivers never reach the sea

Permanent rivers flow only in the east, the south-west and Tasmania. Britannica describes every other river as seasonal or intermittent, and the rivers of the arid interior as episodic, running only after rare heavy rain. Wikipedia's geography puts about half of the country's rivers as draining inland, most of them into salt lakes that hold no water for years at a time.

Kati Thanda-Lake Eyre is the best known. Full, it covers up to 9,700 square kilometres; most of the time it contains little or none, because its whole catchment lies in the arid zone. Only about 9% of the rain that falls on Australia becomes surface runoff, by the figures Wikipedia cites, and Britannica compares the combined discharge of every Australian river, the Murray-Darling included, to about half that of the Yangtze.

Where the water goes, the deserts are. Geoscience Australia lists ten named mainland deserts covering 1,371,000 square kilometres, about 18% of the mainland, of which the Great Victoria Desert across Western and South Australia is 348,750. The broader dry country is much larger: Britannica counts a third of the continent as desert and another third as steppe or semi-desert. Sand ridges run in a great swirl around the centre, and the Nullarbor Plain on the south coast is limestone so flat that the Trans-Australian Railway runs straight across it for some 500 kilometres.

What grows on old and poor soils

Most Australian soils are poor by Britannica's account, with chemical deficiencies common, so that farmland often needs generous amounts of phosphate. The plants that dominate are the ones that cope: hard-leaved species, the sclerophylls, a trait that Britannica reports has been linked to low soil nutrients. The seed-plant flora runs to about 20,000 species. Eucalyptus accounts for more than 400 of them, from mallee shrubs smaller than a person to forest trees, and Acacia for about 700, from the mulga of the arid centre to ground-level grass wattles.

The flora came from two sources. The older stock is Gondwanan and shared with South America, Africa, New Zealand and Antarctica: southern beech, which forms forests in Tasmania, and the podocarp conifers are among it. The younger arrived from the Malay Archipelago when the drifting continent came close to it in the Miocene, and it is strongest in the tropical north.

Britannica calls the changes since European settlement cataclysmic. It records that settlers cleared native vegetation from most of the potentially arable land, stocked the dry interior with sheep and cattle and introduced animals and plants that ran wild, camels among them, and that much of the inland has been overgrazed. Aboriginal burning had already shaped the older landscape; the pollen record reviewed by the botanist Helene Martin shows fire deflecting the course of arid and coastal vegetation over several thousand years.

Where Australians live on the continent

The table sets the land area of each state and territory, measured by Geoscience Australia, beside its population at 31 March 2026 as estimated by the Australian Bureau of Statistics.

Victoria is 3% of the land and held about 7.2 million people in March 2026; the Northern Territory is 17.5% and held about 269,000. Wikipedia's geography places almost 80% of Australians within 25 kilometres of the coast and the centre of population, in 2024, some 30 kilometres east of Ivanhoe in western New South Wales, a point that shows how far the weight sits in the south-east.

The cities are recent and spread out. Britannica notes that more than two-fifths of Australians lived in rural areas in 1911 and about one-seventh by the 1970s, and describes the metropolitan areas as low-density and built around the car. Canberra, the planned federal capital designed by Walter Burley Griffin and begun in 1913, sits inland between Sydney and Melbourne. The interior is organised around pastoral stations that Britannica sizes at between 80 and 15,000 square kilometres, held under leasehold, and around mining towns such as Mount Isa and Broken Hill.

What lies offshore and overseas

The Great Barrier Reef runs about 2,000 kilometres along the Queensland coast. UNESCO inscribed practically the whole system on the World Heritage List in 1981, covering 348,000 square kilometres with some 2,500 individual reefs and more than 900 islands. UNESCO dates the growth of reefs on the continental shelf to the past 15,000 years.

Australian jurisdiction reaches far beyond the continent. External territories include Norfolk Island, Christmas Island, the Cocos (Keeling) Islands, the Coral Sea Islands, Ashmore and Cartier Islands and Heard and McDonald Islands, and Australia claims the Australian Antarctic Territory, which Geoscience Australia measures at 5,896,500 square kilometres, 42% of Antarctica. That claim is recognised by only four states, by Wikipedia's account. Wikipedia's geography gives the exclusive economic zone as 8,148,250 square kilometres, larger than the land itself, and the mainland coastline as 35,821 kilometres, with 23,860 more around the islands. Australia has no land border; its maritime boundaries meet those of Indonesia, Timor-Leste, Papua New Guinea, Solomon Islands, New Caledonia and New Zealand.

How fire and heat shape the country

Bushfire belongs to the ecology. Many native plants are highly flammable and some need fire to regenerate, and the risk peaks in summer and autumn across most of the country and in spring in the far north. Cyclones form most often off the north-west coast of Western Australia, by Wikipedia's account, and also off north-east Queensland. Wikipedia's geography names heatwaves as the deadliest hazard, accounting for more deaths than bushfires, cyclones, earthquakes, floods and storms together, and records that the frequency of consecutive days of heat stress doubled between 1960 to 1970 and 2000 to 2008.

The named disasters of the record include Cyclone Mahina in 1899, the New South Wales floods of 1955, Cyclone Tracy in 1974 and the Ash Wednesday bushfires of 1983.