Mainland Australia

Mainland Australia is the main landmass of the Australian continent, excluding the Aru Islands, New Guinea, Tasmania, and other Australian offshore islands. The landmass also constitutes the mainland of the territory governed by the Commonwealth of Australia, and the term, along with continental Australia, can be used in a geographic sense to exclude surrounding continental islands and external territories. Generally, the term is applied to the states of New South Wales, Queensland, South Australia, Victoria, and Western Australia, as well as the Australian Capital Territory, Jervis Bay Territory, and Northern Territory.

The term is typically used when referring to the relationship between Tasmania and the other Australian states, in that people not from Tasmania are referred to as mainlanders. Tasmania has been omitted on a number of occasions from maps of Australia, reinforcing the divide between Tasmania and the mainland. The 1982 Commonwealth Games in Brisbane left Tasmania off the map of Australia during the opening ceremony, as did the designs of the Australian Swim Team uniform for the 2014 Commonwealth Games in Glasgow.

The land mass covers 7,591,608 km² (2,931,136 sq mi), about 98.7% of the area of the country of Australia and 1.5% of Earth's surface. It is sometimes described as an island, in which case it would be the largest island by area–more than three times the size of Greenland. Its population is about 25.9 million, 98% of Australia's total population. Mainland Australia has a variety of climatic regions, ranging from tropical rainforests and deserts to cool temperature rainforests to snow-covered mountains. It is in these mainland regions that much of Australia's native flora and fauna can be found.

Early in the Cretaceous period, 130 million years ago, Australia (and Antarctica) separated from a supercontinent known as Gondwana. Antarctica's separation from Australia began roughly 85 million years ago, at a rate of a few millimetres per year. It took over 30 million years (53 million years ago), toward the end of the Palaeocene epoch, for Australia to fully separate from Antarctica and set course for where we see the two continents today.

During the last ice-age around 35,000 years ago, sea levels (around Australia) dropped by 120 metres (390 ft), developing a continuous stretch of land between what is now Papua New Guinea, Australia and Tasmania. Over the next 6,000 years the ice gradually melted, increasing sea-levels, cutting off Papua New Guinea and Tasmania from mainland Australia.

It has been estimated that Australian Aborigines occupied mainland Australia up to 50,000 to 60,000 years ago, well before the last ice-age. Although an exact figure has not been decided on, numerous DNA studies all confirm that Aboriginal Australians are one of the oldest living populations in the world outside of Africa. Prior to the arrival of Europeans on the Australian mainland in the late 18th century, over 500 different clan groups (nations) each with unique cultures, beliefs and languages inhabited territories on the mainland. Currently, Indigenous people living on the mainland make up 2.4% of the total Australian population, encompassing over 250 language groups.

The first documented encounter of the Australian mainland was by Willem Janszoon in 1606, as he sailed around Australia's north coast arriving in present-day Cape York, Queensland. These explorations led way to the term 'Terra Australis', Latin for South Land, which was hypothesised on the notion there must be land in the Southern Hemisphere to balance the land mass in the Northern Hemisphere. This encounter led several other Dutch, Spanish, Portuguese and British journeyings to Terra Australis throughout the 17th and 18th century, progressively mapping what we now know to be as (mainland) Australia. The most famous and well documented expedition of Australia occurred 164 years after Janszoon's journey, through British navigator and explorer James Cook. He documented the first interaction of the Eastern Australian coastline, and on 23 April 1770, Cook made the first recorded observation of Indigenous Australians at nowadays Brush Island. This journey, coupled with numerous other reports, ultimately led the British to establish a penal colony in Australia, firstly at Botany Bay.

The Australian mainland's geology and climate is one of its defining features. Despite being surrounded by ocean, approximately 20% of the Australian mainland is classified as desert. This is due to the extremely variable rain patterns across the mainland. Toward the barren centre of the mainland, the rainfall pattern is concentric and sparse, whereas there is higher intensity rainfall toward the mainland's tropics and coastal areas. Australia lies on the middle of the Indo-Australian tectonic plate and as a result is not influenced by any severe tectonic activity. Over millions of years, the shifting of these tectonic plates has seen the Australian mainland undergo many physical changes. Mountain ranges and seas have come and gone, and the forces of weathering and erosion have formed much of the mainland's current topography. These physical changes developed four primary landform divisions spread throughout the mainland states and territories; the Coastal Plains, the Eastern and Southern highlands, the Central Lowlands (and Deserts) and the Western and Northern Plateaus (and Basins).