Oceania is the collective name for the vast accumulation of
islands and atolls in the central and western parts of the Pacific
Ocean. The borders of Oceania are arbitrary. The island of New
Guinea is considered to be the western border, Easter Island is the
eastern border. As a rule, Oceania does not include Australia, as
well as the islands and archipelagos of Southeast Asia, the Far East
and North America. In the section of geography, country studies,
Oceania is studying an independent discipline - ocean studies.
Oceania is the world's largest cluster of islands located in the
southwestern and central parts of the Pacific Ocean, between the
subtropical latitudes of the Northern and temperate Southern
Hemispheres. When all land is divided into parts of the world,
Oceania is usually united with Australia into a single part of the
world, Australia and Oceania, although sometimes it stands out as an
independent part of the world.
Geographically, Oceania is
divided into several regions: Micronesia (in the north-west),
Melanesia (in the west), and Polynesia (in the east); New Zealand is
sometimes singled out.
The total area of the islands of
Oceania, the largest of which is New Guinea, is 1.26 million km²
(together with Australia 8.52 million km²), the population is about
10.7 million people. (together with Australia 32.6 million people).
Excluding Australia, Oceania in terms of total area and total
population is comparable to the African state of Chad.
The
islands of Oceania are washed by numerous Pacific seas (Coral Sea,
Tasman Sea, Fiji Sea, Koro Sea, Solomon Sea, New Guinea Sea,
Philippine Sea) and Indian Oceans (Arafura Sea).
Equator and
the international date line pass through Oceania. It is a broken
line, most of which runs along the 180 ° meridian.
Sea
currents
Across the whole of Oceania, along the equator, are the
warm Northern Passat and Southern Passat currents and the Passat
countercurrent. In the southwestern part of Oceania, a warm East
Australian Current passes. Characteristic of Oceania is the absence
of cold sea currents (with the exception of the Pacific Ocean region
southeast of New Zealand), which largely determines the climate of
this region.
Geology
In terms of geology, Oceania is not a continent: only
Australia, New Caledonia, New Zealand, New Guinea and Tasmania are
of continental origin, having formed on the site of the hypothetical
mainland of Gondwana. In the past, these islands constituted a
single land, however, as a result of sea level rise, a significant
part of the surface was under water. The relief of these islands is
mountainous and strongly dissected. For example, the highest
mountains of Oceania, including Mount Jaya (5029 m), are located on
the island of New Guinea.
Most of the islands of Oceania are
of volcanic origin: some of them are peaks of large submarine
volcanoes, some of which still exhibit high volcanic activity (for
example, the Hawaiian Islands).
Other islands are of coral
origin, being atolls that formed as a result of the formation of
coral buildings around volcanoes submerged under water (for example,
Gilbert Islands, Tuamotu). A distinctive feature of such islands are
large lagoons, which are surrounded by numerous islands, or motu,
whose average height does not exceed three meters. In Oceania, there
is an atoll with the largest lagoon in the world - Kwajalein in the
Marshall Islands archipelago. Despite the fact that its land area is
only 16.32 km² (or 6.3 sq. Miles), the lagoon area is 2174 km² (or
839.3 sq. Miles). The largest atoll in terms of land area is
Christmas Island (or Kiritimati) in the Line archipelago (or Central
Polynesian Sporades) - 322 km². However, among the atolls there is
also a special type — the elevated (or elevated) atoll, which is a
limestone plateau up to 50-60 m above sea level. This type of island
has no lagoon or there are traces of its past existence. Examples of
such atolls are Nauru, Niue, Banaba.
The relief and
geological structure of the bottom of the Pacific Ocean in the
region of Oceania has a complex structure. From the Alaska Peninsula
(which is part of North America) to New Zealand, there are a large
number of hollows of the marginal seas, deep-sea ocean trenches
(Tonga, Kermadek, Bougainville), which form a geosynclinal belt
characterized by active volcanism, seismicity, and a contrasting
relief.
There are no minerals on most islands of Oceania,
only the largest of them are under development: nickel (New
Caledonia), oil and gas (New Guinea island, New Zealand), copper
(Bougainville island in Papua New Guinea), gold (New Guinea , Fiji),
phosphates (on most islands, deposits are almost or already
developed, for example, in Nauru, on the islands of Banaba,
Makatea). In the past, active development of guano, decomposed
seabird droppings, which was used as nitrogen and phosphorus
fertilizer, was carried out on many islands of the region. On the
ocean floor of the exclusive economic zone of a number of countries,
there are large accumulations of iron-manganese nodules, as well as
cobalt, however, at the moment, no development is being carried out
due to economic inexpediency.
Climate
Oceania is located
within several climatic zones: equatorial, subequatorial, tropical,
subtropical, temperate. Most of the islands have a tropical climate.
The subequatorial climate dominates the islands near Australia and
Asia, as well as east of 180 meridian in the equatorial zone, the
equatorial climate west of 180 meridian, subtropical - north and
south of the tropics, temperate - on most of the South Island in New
Zealand.
The climate of the islands of Oceania is determined
mainly by the trade winds, therefore, most of them have heavy
rainfall. The average annual rainfall varies from 1,500 to 4,000 mm,
although on some islands (in particular, due to the topography and
the leeward side), the climate may be more arid or more humid.
Oceania has one of the wettest places on the planet: up to 11,430 mm
of precipitation falls annually on the eastern slope of Mount
Waiaaleale on the island of Kauai (the absolute maximum was reached
in 1982: then 16,916 mm fell). Near the tropics, the average
temperature is about 23 ° C, at the equator - 27 ° C, with a slight
difference between the hottest and coldest months.
The
climate of the islands of Oceania is also greatly affected by such
anomalies as the El Niño and La Niña currents. During El Niño, the
intertropical convergence zone moves north towards the equator,
while at La Niña it moves south towards the equator. In the latter
case, the islands experience severe drought; in the former, heavy
rains.
Most islands in Oceania are subject to the devastating effects of
natural disasters: volcanic eruptions (Hawaiian Islands, New
Hebrides), earthquakes, tsunamis, cyclones, accompanied by typhoons
and heavy rains, droughts. Many of them lead to significant material
and human losses. For example, the tsunami in Papua New Guinea
killed 2200 people in July 1999.
There are glaciers high in
the mountains on the South Island in New Zealand and on the island
of New Guinea, however, due to the process of global warming, their
area is gradually decreasing.