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Zealandia (continent)
Encyclopedia
Continental fragment
Continental crustal fragments, partially synonymous with microcontinents, are fragments of continents thought to have been broken off from the main continental mass forming distinct islands, possibly several hundred kilometers from their place of origin...
that sank after breaking away from Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
60–85 million years ago, having separated from Antarctica between 85 and 130 million years ago. It may have been completely submerged about 23 million years ago, and most of it (93%) remains submerged beneath the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
.
Zealandia is 3500000 square kilometres (1,351,357.6 sq mi) in area, larger than Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
or India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, and almost half the size of Australia. It is unusually slender, stretching from New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
in the north to beyond New Zealand's sub-Antarctic islands
New Zealand sub-antarctic islands
The five southernmost groups of the New Zealand Outlying Islands form the New Zealand Sub-Antarctic islands. These islands are collectively designated as an UNESCO World Heritage Site....
in the south (from latitude 19° south
19th parallel south
The 19th parallel south is a circle of latitude that is 19 degrees south of the Earth's equatorial plane. It crosses the Atlantic Ocean, Africa, the Indian Ocean, Australasia, the Pacific Ocean and South America....
to 56° south
56th parallel south
The 56th parallel south is a circle of latitude that is 56 degrees south of the Earth's equatorial plane. No land lies on the parallel—it crosses nothing but ocean.Starting at the Prime Meridian and heading eastwards, the parallel 56° south passes through:...
, analogous to ranging from Haiti
Haiti
Haiti , officially the Republic of Haiti , is a Caribbean country. It occupies the western, smaller portion of the island of Hispaniola, in the Greater Antillean archipelago, which it shares with the Dominican Republic. Ayiti was the indigenous Taíno or Amerindian name for the island...
to Hudson Bay
Hudson Bay
Hudson Bay , sometimes called Hudson's Bay, is a large body of saltwater in northeastern Canada. It drains a very large area, about , that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota,...
or from Sudan
Sudan
Sudan , officially the Republic of the Sudan , is a country in North Africa, sometimes considered part of the Middle East politically. It is bordered by Egypt to the north, the Red Sea to the northeast, Eritrea and Ethiopia to the east, South Sudan to the south, the Central African Republic to the...
to Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
in the northern hemisphere). New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
is the largest part of Zealandia above sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
, followed by New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
.
The major submerged parts of Zealandia are the Lord Howe Rise
Lord Howe Rise
The Lord Howe Rise is an underwater plateau that extends from southwest of New Caledonia to the Challenger Plateau, west of New Zealand. To its west is the Tasman Basin and to the east is the New Caledonia Basin. Lord Howe Rise has a total area of about 1,500,000 square km, and generally lies about...
, Challenger Plateau
Challenger Plateau
The Challenger Plateau is a large submarine plateau west of New Zealand and south of the Lord Howe Rise. It has an approximate diameter of . The plateau originated in the Gondwanan breakup and is one of the five major submerged parts of Zealandia, a largely submerged continent....
, Campbell Plateau
Campbell Plateau
The Campbell Plateau is a large submarine plateau to the south of New Zealand and the Chatham Rise. It originated in the Gondwanan breakup and is part of Zealandia, a largely submerged continent. The Bounty Islands, Antipodes Islands, Auckland Islands and Campbell Island are on the...
, Norfolk Ridge
Norfolk Ridge
The Norfolk Ridge is a long submarine ridge running between New Caledonia and New Zealand, about 1300 km off the east-coast of Australia. Little is known about the Norfolk Ridge; however, it generally lies about 2000 m below sea level and consists of Late Cretaceous continental crust. It is...
, and the Chatham Rise
Chatham Rise
The Chatham Rise is an area of ocean floor to the east of New Zealand, forming part of the Zealandia continent. It stretches for some from near the South Island in the west, to the Chatham Islands in the east...
. Smaller provinces include the Louisiade Plateau, Mellish Rise, Kenn Plateau
Kenn Plateau
The Kenn Plateau is a large piece of submerged continental crust off northeastern Australia that rifted from northeastern Australia about 63-52 mya, along with other nearby parts of the Zealandia continent.-References:**...
, Chesterfield Plateau, and Dampier Ridge. The seemingly separate Gilbert Seamount (northwest of Fiordland
Fiordland
Fiordland is a geographic region of New Zealand that is situated on the south-western corner of the South Island, comprising the western-most third of Southland. Most of Fiordland is dominated by the steep sides of the snow-capped Southern Alps, deep lakes and its ocean-flooded, steep western valleys...
) is also part of the New Zealand continental fragment, while how strongly Bollons Seamount
Bollons Seamount
Bollons Seamount is a seamount just east of the international date line, a few hundred miles off the coast of New Zealand....
(south of the Chatham Islands
Chatham Islands
The Chatham Islands are an archipelago and New Zealand territory in the Pacific Ocean consisting of about ten islands within a radius, the largest of which are Chatham Island and Pitt Island. Their name in the indigenous language, Moriori, means Misty Sun...
) remains connected to Zealandia is unknown.
Zealandia supports substantial inshore fisheries
Fishing industry in New Zealand
As with other countries, New Zealand’s 200 nautical mile exclusive economic zone gives its fishing industry special fishing rights. It covers 4.1 million square kilometres. This is the sixth largest zone in the world, and is fourteen times the land area of New Zealand itself.The zone has a rich and...
and contains New Zealand's largest gas field
Maui gas field
The Maui natural gas field is the largest gas, natural gas condensate and oil field in New Zealand, producing nearly three-quarters of the country's hydrocarbons, as well as providing energy for electricity generation. It is located in the Tasman Sea, 35 km off the coast of Taranaki and to the...
, near Taranaki. Permits for oil exploration in the Great South Basin
Great South Basin
The Great South Basin is an area of mainly sea to the south of the South Island of New Zealand.Starting in the 1960s, the area was explored and drilled for oil deposits by various minerals companies, mostly international, but by 1984 all of these companies had left empty-handed...
were issued in 2007. Offshore mineral resources include iron sands, volcanic massive sulfides and ferromanganese nodule deposits.
Geology
Zealandia is largely made up of two nearly parallel ridges, separated by a failed riftRift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
. The ridges rise above the sea floor
Seabed
The seabed is the bottom of the ocean.- Ocean structure :Most of the oceans have a common structure, created by common physical phenomena, mainly from tectonic movement, and sediment from various sources...
to depths of 1,000–1,500 metres, with infrequent rocky island
Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
s rising above sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
. The ridges are continental rock, but are lower in elevation than normal continents because their crust is thinner than usual (only about 20 kilometres thick), and consequently they do not float as high above the Earth's mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....
.
About 25 million years ago, the southern part of Zealandia (on the Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
) began to shift relative to the northern part (on the Indo-Australian Plate
Indo-Australian Plate
The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters...
). The resulting displacement by approximately 500 kilometres (300 mi) along the Alpine Fault
Alpine Fault
The Alpine Fault is a geological fault, more specifically known as a right-lateral strike-slip fault, that runs almost the entire length of New Zealand's South Island. It forms a transform boundary between the Pacific Plate and the Indo-Australian Plate. Earthquakes along the fault, and the...
is evident in geological maps. Movement along this plate boundary has also offset the New Caledonia Basin from its previous continuation through the Bounty Trough.
Compression across the boundary has uplifted the Southern Alps
Southern Alps
The Southern Alps is a mountain range extending along much of the length of New Zealand's South Island, reaching its greatest elevations near the island's western side...
, although due to rapid erosion their height reflects only a small fraction of the uplift. Further north, subduction of the Pacific Plate has led to extensive volcanism, including the Coromandel and Taupo Volcanic Zone
Taupo Volcanic Zone
The Taupo Volcanic Zone is a highly active volcanic V shaped area in the North Island of New Zealand that is spreading east -west at the rate of about 8mm per year...
s.
Volcanism on Zealandia has also taken place repeatedly in various parts of the continental fragment before, during and after it rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
ed away from the supercontinent
Supercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
. Although Zealandia has shifted ~6,000 km to the northwest with respect to the underlying mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....
from the time when it rifted from Antarctica, recurring intracontinental volcanism exhibits magma composition similar to that of volcanoes in previously adjacent parts of Antarctica and Australia. This volcanism is widespread across Zealandia but generally of low volume apart from the huge mid to late Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
shield volcano
Shield volcano
A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...
es that developed the Banks
Banks Peninsula
Banks Peninsula is a peninsula of volcanic origin on the east coast of the South Island of New Zealand. It has an area of approximately and encompasses two large harbours and many smaller bays and coves...
and Otago Peninsula
Otago Peninsula
The Otago Peninsula is a long, hilly indented finger of land that forms the easternmost part of Dunedin, New Zealand. Volcanic in origin, it forms one wall of the eroded valley that now forms Otago Harbour. The peninsula lies south-east of Otago Harbour and runs parallel to the mainland for...
s. In addition, it took place continually in numerous limited regions all through the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
and the Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
. However, its causes are still in dispute. During the Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
, the northern section of Zealandia (Lord Howe Rise
Lord Howe Rise
The Lord Howe Rise is an underwater plateau that extends from southwest of New Caledonia to the Challenger Plateau, west of New Zealand. To its west is the Tasman Basin and to the east is the New Caledonia Basin. Lord Howe Rise has a total area of about 1,500,000 square km, and generally lies about...
) might have slid over a stationary hotspot
Hotspot (geology)
The places known as hotspots or hot spots in geology are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the mantle elsewhere. They may be on, near to, or far from tectonic plate boundaries. There are two hypotheses to explain them...
, forming the Lord Howe seamount chain
Lord Howe seamount chain
The Lord Howe seamount chain is a Miocene seamount chain on northern Lord Howe Rise, Zealandia. The chain is defined by coral-capped guyots, extends to the north for 1000 km , most likely the result of the Indo-Australian Plate moving northward over a stationary hotspot....
.
Biogeography
Antarctic flora
The Antarctic flora is a distinct community of vascular plants which evolved millions of years ago on the supercontinent of Gondwana, and is now found on several separate areas of the Southern Hemisphere, including southern South America, southernmost Africa, New Zealand, Australia and New Caledonia...
, including Araucaria
Araucaria
Araucaria is a genus of evergreen coniferous trees in the family Araucariaceae. There are 19 extant species in the genus, with a highly disjunct distribution in New Caledonia , Norfolk Island, eastern Australia, New Guinea, Argentina, Chile, and southern Brazil.-Description:Araucaria are mainly...
s and Podocarps. At Curio Bay
Curio Bay
Located near the southern end of New Zealand's South Island, Curio Bay is a coastal embayment best known as the site of a petrified forest some 180 million years old. It also hosts a yellow-eyed penguin colony, arguably the rarest of penguin species, with approximately 1600 breeding pairs in the...
, logs of a fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
ized forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
closely related to modern Kauri and Norfolk Pine can be seen that grew on Zealandia about 180 million years ago during the Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
period, before it split from Gondwana. These were buried by volcanic mud flows and gradually replaced by silica to produce the fossils now exposed by the sea.
During glacial periods more of Zealandia becomes a terrestrial rather than a marine environment. Zealandia was originally thought to have no native land mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
fauna, but a recent discovery in 2006 of a fossil mammal jaw from the Miocene in the Otago region shows otherwise.
Political divisions
- New CaledoniaNew CaledoniaNew Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
and surrounding islands - 18576 sqkm (7%) - New ZealandNew ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
- 267988 sqkm (93%)- Includes the mainland, nearby islands, and most outlying islands including the Antipodes IslandsAntipodes IslandsThe Antipodes Islands are inhospitable volcanic islands to the south of—and territorially part of—New Zealand...
, Auckland IslandsAuckland IslandsThe Auckland Islands are an archipelago of the New Zealand Sub-Antarctic Islands and include Auckland Island, Adams Island, Enderby Island, Disappointment Island, Ewing Island, Rose Island, Dundas Island and Green Island, with a combined area of...
, Bounty IslandsBounty IslandsThe Bounty Islands at are a small group of 13 granite islets and numerous rocks, with a combined area of , in the south Pacific Ocean that are territorially part of New Zealand. They are located between 47°44'35" and 47°46'10" S, and 179°01' and 179°04'20" E, southeast of the South Island of New...
, Campbell Islands, and Chatham IslandsChatham IslandsThe Chatham Islands are an archipelago and New Zealand territory in the Pacific Ocean consisting of about ten islands within a radius, the largest of which are Chatham Island and Pitt Island. Their name in the indigenous language, Moriori, means Misty Sun...
, but not the Kermadec IslandsKermadec IslandsThe Kermadec Islands are a subtropical island arc in the South Pacific Ocean northeast of New Zealand's North Island, and a similar distance southwest of Tonga...
- Includes the mainland, nearby islands, and most outlying islands including the Antipodes Islands
- Various territories of Australia
- Norfolk Islands - 35 sqkm (0.01%)
- Lord Howe IslandLord Howe IslandLord Howe Island is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, directly east of mainland Port Macquarie, and about from Norfolk Island. The island is about 11 km long and between 2.8 km and 0.6 km wide with an area of...
Group (New South Wales) - 56 sqkm (0.02%) - ElizabethElizabeth ReefElizabeth Reef is a coral reef in the Tasman Sea. The reef is separated by a deep oceanic pass, some 45 km wide, from nearby Middleton Reef, both of which are part of the underwater plateau known as the Lord Howe Rise. Elizabeth Reef is around 160 km from Lord Howe Island and...
and Middleton ReefMiddleton ReefMiddleton Reef is a coral reef in the Tasman Sea. It is separated by a deep oceanic pass some 45 km wide from nearby Elizabeth Reef, forming part of the Lord Howe Rise underwater plateau. Middleton Reef is around 220 km from Lord Howe Island and 555 km from the coast of New South...
s (Coral Sea Islands Territory) - 0.25 sqkm (land area)
Total land area (including inland water bodies): ~ 286655 sqkm
Population
- New Caledonia - 250,000
- New Zealand - 4.4 million
- Norfolk Islands - 2,141
- Lord Howe Island - 347
Total population: 4.65 million
External links
- Zealandia the New Zealand (drowned) Continent, from Te Ara
- The coast and beyond, including map of the New Zealand continent, from GNS ScienceGNS ScienceGNS Science is a New Zealand Crown Research Institute. It focuses on geology, geophysics , and nuclear science ....