Oceani | en, the islands of the Pacific Ocean between Australia, the Philippines and America, between the tropic and 50 ° south latitude. According to Countryaah.com, the more than 7,500 islands (including all reef islands from atolls up to 10,000) cover a total land area of almost 1.3 million km 2 (excluding New Guinea and New Zealand around 218,000 km 2) and cover a sea area of around 70 million km 2 distributed. Around 2,100 islands are inhabited. Of the (2005) 16.5 million residents, a total of around 12.2 million live in New Guinea and New Zealand. – In a broader sense, Oceania also includes Australasia (including Australia). Another definition restricts the term Oceania to the Pacific island world without the western part of New Guinea (Irian Jaya) and New Zealand, which belongs to Indonesia.
The structure and distribution of the various types of islands can be derived from the processes of plate tectonics. The underlying Pacific Plate, which drifts westward from the East Pacific Ridge (Sea Floor Spreading) and consists of igneous material, encounters the drifting Philippines or Indian-Australian Plate in the area of the Mariana Islands and from New Guinea via the Kermadec Islands to New Zealand. On the through deep-sea trenches and the andesite line (andesite) marked seams, the plates are submerged (subduction). The “continental islands” to the west of the plate boundary are made up of sediments, igneous and metamorphic rocks, show explosive volcanism with silica-rich, andesitic rocks and steep, ash-rich volcanic cones.
In addition to the volcanic islands (“high islands”), coral reefs and atolls are formed. The volcanic islands east of it on the Pacific plate are shield volcanoes made of thin, low-silica, basic lavas (like the oceanic crust). They are partly caused by transverse faults (transform faults, across the East Pacific Ridge), partly by hotspots (e.g. Hawaii). The volcanic islands are partly surrounded by fringing reefs and thus protected from erosion, and partly they are exposed to severe erosion. In the approximately 300 atolls of tropical Oceania, the volcanic base is underground (through subsidence to over 1,000 m deep); the fringing reef can form the coast through uplift (“raised coral islands”, e.g. Nauru).
The tropical-maritime climate is tempered mainly on the small islands by cooling sea breezes. In the vicinity of the equator, the trade winds coming from the northeast and southeast – increasing to the west and reinforced by convection – bring precipitation all year round. Occasionally, however, considerable droughts occur as a result of the cold upwelling water from South America (El Niño). The temperatures are 25 ° C or higher. Lower precipitation and temperature values (monthly mean below 20 ° C) and larger seasonal fluctuations occur in the tropics. There are clear differences in the amount of rain in the mountains from the windward or leeward location to the trade winds that constantly blow from the same directions. In summer and autumn v. a. tropical cyclones occur in western Oceania.
Flora and fauna
The flora is comparatively poor in species compared to the mainland, especially on the coral islands. Most of the useful plants, including the coconut palm, were first spread by humans. As a result of these changes (intensified since Europeanization), the composition of the original vegetation can hardly be determined. On the other hand, on the larger tropical islands (New Guinea, Bismarck Archipelago, Solomon Islands) there are extremely species-rich tropical rainforests; numerous endemic species are characteristic of New Zealand. The settlement of domestic animals (pigs, dogs, chickens) and the introduction of rats led to similar displacement phenomena in the animal world.
Territories in Oceania
Johnston Atoll [ d ʒ ɔ nstən-], atoll in the North Pacific Ocean, 1,150 km southwest of Hawaii, with four islands (along 2.8 km 2), about 300 temporary residents (military personnel and civilian employees of the military, scholars); partially nature reserve; at Johnston Island Air Force Base and Depots. – The Johnston Atoll, 1807 by the British captain James Johnston discovered, claimed by the Kingdom of Hawaii and the USA in 1856, has been under American administration since 1898; guano mining in the 19th century; At the end of the 1950s and beginning of the 60s, numerous nuclear weapon tests in the atmosphere, until 1975 the basis for rocket launches (research rockets), until 2000 military use (including storage and destruction of chemical weapons), since then conversion to civilian use.
Jarvis [ d ʒ ɑ ː v ɪ s], one of the Northern Line Islands in the central Pacific, 4.5km 2; 1858–79 guano mining, formerly a meteorological station, airfield, today uninhabited; Annexed by Great Britain in 1889, has belonged to the United States since 1935.
Howland Iceland [ ha ʊ lənd a ɪ lənd], Atoll in the central Pacific Ocean, north of the Phoenix Islands, 1.6 km 2, uninhabited; reports to the US Department of the Interior; Guano deposits (mining in the 19th century).
Cook Islands [ k ʊ k ], islands in the Pacific Ocean (Polynesia), with 240 km 2 and approximately 17 500 people (mostly Polynesian); The administrative headquarters are in Avarua on Rarotonga. – The Cook Islands were discovered by Spaniards in 1595 and partiallyexploredby James Cook in 1773. British since 1888, they came to New Zealand in 1901. In 1965 they were granted internal autonomy with free association with New Zealand.