Zealandia

• 1. Introduction

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  Zealandia lies roughly 94 percent underwater, hidden beneath the Pacific Ocean in Oceania. Satellite imagery shows that this mass of continental crust is almost as large as Australia. Most people have never heard of it, because the parts that do rise above the waves are known by other names. So why did a landmass of this scale go unrecognised for so long? Is it a continent, a fragment, or something in between? And what has been found on it and beneath it, from ancient trees to fuel and minerals? The answers begin with the name, and with the geologist who proposed it.

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• 2. Three Names

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  In 1995, the geologist Bruce Luyendyk proposed both the name and the concept of Zealandia. The word is a latinate form of New Zealand. It was coined in the mid-1990s and became established simply through common use.

  In the Māori language, GNS Science recognises another name for the landmass, Te Riu-a-Māui. It means the hills, valleys, and plains of Māui.

  A third name, Tasmantis, comes from the Tasman Sea. Having several labels hints at how loosely scientists had treated the place, and it raised the question of whether any category truly fit a landmass this large.

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• 3. Continent Or Fragment

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  Zealandia covers approximately 4,900,000 square kilometres, which is far beyond anything normally called a microcontinent or a continental fragment. If it were classed as a microcontinent, it would be the largest in the world. Madagascar, the next largest, is only one sixth of its area. Zealandia also covers more than half of the exposed land area of the Australian continent.

  Other giants look small beside it. Greenland, the world's largest island, covers 2,166,086 square kilometres. The Ontong Java Plateau, the largest intraoceanic large igneous province, covers about 1,900,000. Zealandia is more than twice the size of each. It also exceeds the Arabian Peninsula at 3,237,500 square kilometres and the Indian subcontinent at 4,300,000.

  Mapping of Zealandia concluded in 2023. Some geologists from New Zealand, New Caledonia, and Australia argue that its crustal thickness, density, and other features meet every requirement for a continent. Geologist Nick Mortimer remarked that only the ocean level had stopped people from recognising it as one long ago.

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• 4. Deep Time

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  Between 83 and 79 million years ago, Zealandia broke away from the supercontinent Gondwana and began to subside. By about 23 million years ago, the landmass may have been completely submerged.

  Its age is also in question. A 2021 study suggests that Zealandia is more than one billion years old, which is about twice as old as geologists had previously believed. Some of the evidence for its earlier chapters can be seen on a shoreline today, exposed by the sea.

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• 5. Fossil Forests And Mammals

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  At Curio Bay, the sea has exposed the logs of a fossilised forest that grew on Zealandia about 180 million years ago, during the Jurassic period. The trees are closely related to modern kauri and Norfolk pine. They grew before the landmass split from Gondwana. Volcanic mud flows buried them, and silica gradually replaced the wood to form the fossils.

  New Caledonia sits at the northern end of the ancient continent, while New Zealand rises at the plate boundary that bisects it. Together they are two outposts of the Antarctic flora, with araucarias and podocarps among their trees.

  In 2006, a fossil mammal jaw from the Miocene turned up in the Otago region. It overturned the earlier belief that Zealandia had no native land mammals. More of Zealandia becomes dry land whenever sea levels fall during glacial periods. The same seafloor that preserves this history also holds fuel and minerals.

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• 6. Resources Below The Waves

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  The largest known gas field in Zealandia is the New Zealand Maui gas field, near Taranaki. The submerged continent also supports substantial inshore fisheries.

  In 2007, permits for oil exploration were issued in the Great South Basin. Offshore, the mineral resources include ironsands, volcanic massive sulfides, and ferromanganese nodule deposits.

  The land that rises above this resource-rich seafloor is divided among several governments, and the split is strikingly lopsided.

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• 7. Land And People

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  Zealandia's total land area, counting inland water, is 286,660.25 square kilometres. New Zealand holds 267,988 of those, or 93.49 percent, making it the largest part above sea level. That share covers the North Island and South Island, the nearby islands, and outlying groups such as the Chatham Islands, the Solander Islands, and the Three Kings Islands. The Kermadec Islands and Macquarie Island are counted as parts of the rift instead.

  New Caledonia and its surrounding islands come second, with 18,576 square kilometres, or 6.48 percent. Australian territories make up the rest. The Lord Howe Island Group has 56 square kilometres and Norfolk Island has 35. The Cato, Elizabeth, and Middleton reefs of the Coral Sea Islands Territory total 5.25.

  As of 2024, about 5.4 million people live on Zealandia. New Zealand accounts for 5,112,300 of them, and New Caledonia for 268,767. Auckland, with about 1.7 million residents, holds roughly one-third of the whole population. The Lord Howe Island Group has 382 people, while Cato Reef, Elizabeth Reef, and Middleton Reef have none at all.

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