The primary use of the term Oceania is to describe a continental region (like Europe or Africa) that lies between Asia and the Americas, with Australia as the major land mass. The name Oceania is used, rather than Australia, because unlike the other continental groupings, it is the ocean rather than the continent that links the nations together. Oceania is the smallest continental grouping in land area and the second smallest, after Antarctica in population.
Oceania has been traditionally divided into Micronesia, Melanesia and Polynesia (originally by the French explorer Dumont d'Urville in 1831). This subdivision is no longer recognized as correct by most geographers and scientists — who prefer to divide Oceania into Near Oceania and Remote Oceania — but it is still the most popular one.
The 7,686,850 km2 Australian landmass is on the Indo-Australian Plate and is surrounded by the Indian, Southern and Pacific oceans, and separated from Asia by the Arafura and Timor seas, with total of 25,760 km of coastline.
Climate is highly influenced by ocean currents, including the El Niño southern oscillation, which causes periodic drought and the seasonal tropical low pressure system that produces cyclones in northern Australia.
By far the largest part of Australia is desert or semi-arid – 40 per cent of the land mass is covered by sand dunes. Australia is the driest inhabited continent, the flattest and has the oldest and least fertile soils. The highest mountain in Australia is Maw son Peak on Heard Island at 2,745 m. At 2,228 m, Mount Kosciuszko on the Great Dividing Range is the highest mountain on the Australian mainland. Only the south-east and south-west corners of the continent have a temperate climate. The northern part of the country has a tropical climate: part is tropical rainforest, part grasslands, and part desert. The Great Barrier Reef, the world's largest coral reef, lies a short distance off the north-east coast and extends for over 1,200 km. Located in central Australia, Uluru (until 1986 officially known as Ayers Rock) is the second largest monolith in the world (the largest being Mount Augustus in Western Australia).
New Zealand comprises two main islands and a number of smaller islands. The South Island is the largest land mass and is divided along its length by the Southern Alps, the highest peak of which is Aoraki/Mount Cook, at 3754 metres.
There are 18 peaks of more than 3000 metres in the South Island. The North Island is less mountainous than the South, but is marked by volcanism. The tallest North Island Mountain, Mount Ruapehu (2797 metres) is an active cone volcano.
The total land area of New Zealand 268,680 km² is somewhat less than that of Japan or of the British Isles and slightly larger than Colorado in the USA. The country extends more than 1600 km along its main, north-north-east axis.
New Zealand is the most geographically isolated of all countries. Its closest neighbour, Australia is 2,000 km to the north-west of the main islands, across the Tasman Sea. The only landmass to the south is Antarctica, and to the north are New Caledonia, Fiji, and Tonga.
Partly because of its geographical isolation from neighbouring countries and partly because of the number and location of numerous uninhabited islands belonging to it New Zealand's Exclusive economic zone of marine resources was the world's fifth largest at 4.2 million square kilometres in the year 2000 (according to New Zealand's National Institute of Water and Atmospheric Research).
The usual climate throughout the country is mild, mostly cool temperate to warm temperate, with temperatures rarely falling below 0°C or rising above 30°C.
Conditions vary from wet and cold on the West Coast of the South Island to dry and continental in the Mackenzie Basin of inland Canterbury and subtropical in Northland.
In Wellington the average minimum temperature in winter is 5.9°C and the average maximum temperature in summer is 20.3°C. Of the main cities, Christchurch is the driest, receiving only some 500 millimetres of rain per year. Auckland, the wettest, receives a little less than three times that amount.
Polynesia (from Greek, poly = many and nesos = island) is a large grouping of over 1,000 islands in the central and southern Pacific Ocean. Geographically, Polynesia is a triangle with its three corners at Hawaii, New Zealand, and Easter Island. Samoa, Tonga, Marquesas, and French Polynesia are the other main island groups located within the Polynesian triangle.
Melanesia (from Greek "black islands") is a region extending from the west Pacific to the Arafura Sea, north and north-east of Australia. The term was first used by Jules Dumont d'Urville in 1832 to denote an ethnic and geographical grouping of islands distinct from Polynesia and Micronesia.
Today d'Urville's racial classification is considered inaccurate because it obscures Melanesia's cultural, linguistic and genetic diversity and today is used simply as a convenient geographical label. Additionally, the nations of Fiji, Papua New Guinea, Solomon Islands, Vanuatu and New Caledonia (which is legally a French dependency) use this term to describe themselves because it reflects their shared colonial history and common regional situation.
Micronesia (from the Greek words μικρόν = small and νησί = island) is the name of a region in the Pacific Ocean. The Philippines lie to the west, Indonesia to the south west, Papua New Guinea and Melanesia to the south, and Polynesia to the south-east and east.
The region consists of hundreds of small islands spread over a large region of the western Pacific. Politically, it is divided between seven territories: the Federated States of Micronesia (often referred to simply as "Micronesia"), the Republic of the Marshall Islands, the Republic of Palau, and the Commonwealth of the Northern Mariana Islands, the Republic of Nauru, the Republic of Kiribati, and the Territory of Guam. (The first four of these formerly constituted the Trust Territory of the Pacific Islands).