![]() ![]() Volcanism on Zealandia has taken place repeatedly in various parts of the continental fragment before, during, and after it rifted away from the supercontinent Gondwana. ![]() Associated rifting and subsidence has produced the Hauraki Graben and more recently, the Whakatane Graben and Wanganui Basin. Farther north, subduction of the Pacific Plate has led to extensive volcanism, including the Coromandel and Taupo Volcanic Zones. Movement along this plate boundary also has offset the New Caledonia Basin from its previous continuation through the Bounty Trough.Ĭompression across the boundary has uplifted the Southern Alps, although due to rapid erosion their height reflects only a small fraction of the uplift. The resulting displacement by approximately 500 km (310 mi) along the Alpine Fault is evident in geological maps. The ridges are continental rock, but are lower in elevation than normal continents because their crust is thinner than usual, approximately 20 km (12 mi) thick, and consequently, they do not float so high above Earth's mantle as that of most landmasses.Ībout 25 million years ago, the southern part of Zealandia (on the Pacific Plate) began to shift relative to the northern part (on the Indo-Australian Plate). The ridges rise above the sea floor to heights of 1,000–1,500 m (3,300–4,900 ft), with a few rocky islands rising above sea level. Zealandia is largely made up of two nearly parallel ridges, separated by a failed rift, where the rift breakup of the continent stops and becomes a filled graben. Ball's Pyramid, near Lord Howe Island, is one place where it rises above sea level. Offshore mineral resources include ironsands, volcanic massive sulfides and ferromanganese nodule deposits. Permits for oil exploration in the Great South Basin were issued in 2007. Zealandia supports substantial inshore fisheries and contains gas fields, of which the largest known is the New Zealand Maui gas field, near Taranaki. Geologist Nick Mortimer (in German) commented that if it were not for the ocean level, it would have been recognized as such long ago. Due to these and other geological considerations, such as crustal thickness and density, some geologists from New Zealand, New Caledonia, and Australia have concluded that Zealandia fulfills all the requirements to be considered a continent rather than a microcontinent or continental fragment. Zealandia is also substantially larger than the Arabian Peninsula (3,237,500 km 2 or 1,250,000 sq mi), the world's largest peninsula, and the Indian subcontinent (4,300,000 km 2 or 1,700,000 sq mi). Zealandia is more than twice the size of the largest intraoceanic large igneous province (LIP) in the world, the Ontong Java Plateau (approximately 1,900,000 km 2 or 730,000 sq mi), and the world's largest island, Greenland (2,166,086 km 2 or 836,330 sq mi). Its area is six times the area of Madagascar, the next-largest microcontinent in the world, and more than half the area of the Australian continent. If classified as a microcontinent, Zealandia would be the world's largest microcontinent. With a total area of approximately 4,900,000 km 2 (1,900,000 sq mi), Zealandia is substantially larger than any features termed microcontinents and continental fragments. New Zealand is the largest part of Zealandia that is above sea level, followed by New Caledonia. Today, most of the landmass (94%) remains submerged beneath the Pacific Ocean. īy approximately 23 million years ago the landmass may have been completely submerged. ![]() A 2021 study suggests Zealandia is 1 billion years old, about twice as old as geologists previously thought. The name and concept for Zealandia was proposed by Bruce Luyendyk in 1995, and satellite imagery shows it to be almost the size of Australia. It has been described variously as a submerged continent, a continental fragment (or microcontinent), and a continent. Zealandia (pronounced / z iː ˈ l æ n d i ə/), also known as Te Riu-a-Māui ( Māori) or Tasmantis, is an almost entirely submerged mass of continental crust that subsided after breaking away from Gondwanaland 83–79 million years ago. The linear ridges running north-northeast ( Colville to the west and Kermadec to the east, separated by the Havre Trough and Lau Basin) and southwest (the Resolution Ridge System) away from New Zealand are not considered part of Zealandia, nor are Australia (upper left), Vanuatu, or Fiji (top centre). ![]() Topography of Zealandia, outlined in pink. ![]()
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