Zealandia (continent)
Zealandia is a submerged continent located in the South Pacific, covering approximately 1.89 million square miles (4.9 million square kilometers), of which only about 6% is above sea level. This landmass primarily consists of the islands of New Zealand, Lord Howe Island, and New Caledonia, along with Ball's Pyramid, which is the only non-submerged part. In 2017, a significant geological study classified Zealandia as the newest continent, highlighting its unique features and distinction from the continent of Australia. Zealandia is situated across the Pacific and Australian tectonic plates, resulting in frequent seismic activity and numerous volcanic zones, particularly in Northern Zealandia.
The geological history of Zealandia traces back to the breakup of the supercontinent Gondwana around 180 million years ago, with evidence from sediment cores revealing its ecological evolution through varying sea levels during ice ages. The region is rich in biodiversity, with species like the kea and kakapo parrots showcasing evolutionary links to Australia. Furthermore, Zealandia's recognition as a continent may have significant political and economic implications, as it holds valuable natural resources including mineral deposits and natural gas fields. The classification impacts maritime boundaries and rights, providing New Zealand with potential drilling and mining opportunities in the underwater regions.
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Zealandia (continent)
Zealandia is a continent in the South Pacific. It is about 1.89 million square miles (4.9 million square kilometers), although only about 6 percent of the landmass is above sea level. These areas include the islands of New Zealand, Lord Howe Island off the coast of Australia, and New Caledonia, which is a French overseas territory comprising dozens of islands.
Satellite data has provided updated, twenty-first-century information about the seafloor that has allowed geologists to understand the size and qualities of Zealandia. After much debate over whether to classify Zealandia as a microcontinent or continent, a paper published in the journal of the Geological Society of America in 2017 declared the landmass the newest continent on Earth. Scientists are free to use any term they wish, however, because no official classification of landmasses exists. In addition to scientific implications, classification as a continent also could have political repercussions, because many treaties are tied to continental and maritime boundaries.
Background
Earth comprises three main layers: core, mantle, and crust. The crust is the location where plate tectonic activity occurs as land plates slowly move over the mantle. The crust may have formed three billion years ago when the land plates shifted, and less-dense rock was pushed upward. This uplift formed supercontinents, which eventually broke up into the landmasses classified as modern continents. Zealandia was probably formed from the supercontinent Gondwana, which broke up about 180 million years ago. The crust includes both dense ocean crust of volcanic rock and continental crust of rocks including granite. At about 4 miles (7 kilometers) thick, the ocean crust is thinner and lower than continental crust, which is on average about 21 miles (35 kilometers) thick.
Geographers—scientists of the earth and its land, features, and inhabitants—generally define continents as large, continuous, discrete masses of land. Some are separated by expanses of water. Geologists—who study the history of the earth and its life—have other conditions for determining the status of a landmass. A continent must be higher than the ocean floor; include a variety of siliceous igneous, metamorphic, and sedimentary rocks; have a thicker crust than the surrounding ocean floor; have well-defined limits; and be of sufficient size to be regarded as a continent. The 2017 paper notes that Zealandia is 9,800 feet (3,000 meters) higher than the surrounding crust and contains continental rock. The last point—size—has not been defined. Nick Mortimer and the other authors of the 2017 report have proposed a minimum continent size of 0.4 million square miles (1 million square kilometers). Zealandia has previously been referred to as a microcontinent, which is a small isolated fragment of a continental crust. (Subcontinents, such as India, fall somewhere between microcontinents and continents in size.) Zealandia appears to meet all of the conditions of a continent, based on the available data. The researchers argue that because it is separated from Australia by a stretch of ocean crust, it is distinct from the continent of Australia and does not meet the conditions of a subcontinent.
Overview
Zealandia straddles two tectonic plates, the Pacific and the Australian. The plates in this region are very active, and earthquakes are common. Northern Zealandia also sees a great deal of volcanic activity, with six major volcanic zones. The Taupo Volcanic Zone on New Zealand's North Island is the largest. This zone also contains numerous natural geysers and hot springs, which are found in many areas of Zealandia.
The amount of Zealandia that is submerged has varied over time. During ice ages, the world's ocean water levels were considerably lower, and more land was exposed. Mortimer and his colleagues studied sediment cores drilled from more than 2,821 feet (860 meters) below the seafloor to determine the ecological and tectonic changes of Zealandia. These cores revealed a wealth of evidence including pollen, shells, and spores.
Studying the evidence helps researchers understand how the plant and animal life of the islands developed. New Zealand and Australia are separated by 2,581 miles (4,155 kilometers) of ocean in modern times. This separation dates to the breakup of Gondwana. When more of Zealandia was exposed during ice ages, the continent would have stretched far enough to allow land animals and plants to freely spread between continents. Scientists have found evolutionary evidence of Zealandia's link to the Australian continent in the DNA of several species, including New Zealand parrots. The kea, a large species of parrot and the world's only alpine parrot, lives in the mountains of the South Island. Another large parrot, the kaka, lives in the forests on the three major islands, while the endangered kakapo, a flightless parrot, lives in a few forested areas. DNA analysis revealed that the three species evolved from an extinct proto-kaka, a large parrot species. The kakapo and kea/kaka lines diverged about sixty to eighty million years ago. During ice ages, sea levels fell and the landmass of Zealandia increased significantly. This allowed species populations to expand. During warmer periods when water levels were higher, the populations on various islands developed in isolation, creating subspecies. For example, during the Pleistocene epoch (the ice age from about 2.5 million to 11,700 years ago), New Zealand was one large island; during the Oligocene epoch (from about 33.9 million to 23 million years ago), it was two considerably smaller, more distant islands. Others continued to diversify. Researchers have found similar results when studying DNA of New Zealand cicadas. DNA has revealed that the ancestors of the modern insects arrived from both Australia and New Caledonia, which is 1,481 miles (2,384 kilometers) northwest of New Zealand.
Recognition of Zealandia could have political and economic implications for the islands of the region. The continent contains a wealth of natural resources. The underwater areas have large mineral deposits, although mining activity is strictly regulated by New Zealand's government. The region also contains large natural gas fields. During the 1990s, New Zealand joined a United Nations treaty, the Convention on the Law of the Sea, which defines maritime zones related to continents. One portion of the treaty allows a nation to claim drilling and mining rights on a continental shelf that is connected to the nation. Already-established offshore drilling projects brought New Zealand about $100 million in royalties annually as of 2017. However, New Zealand banned offshore oil drilling in 2018 but had introduced legislation in 2024 to reverse the ban.
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