Scientists from New Zealand, New Caledonia, and Australia have published a new paper which claims that the southwestern Pacific Ocean harbours an almost entirely submerged continent—Zealandia.
Geologists and geographers don’t entirely agree on what actually makes a continent: for a geographer, Europe and Asia are two separate entities, while geologists lump them together as ‘Eurasia’.
By convention, our planet has seven continents, but there’s no international body or committee that decrees which landmasses of the Earth’s crust should be defined as such.
“Continents are Earth’s largest surficial solid objects, and it seems unlikely that a new one could ever be proposed,” the authors write in the latest issue of Geological Society of America Today.
However, the researchers are proposing exactly that. According to their latest analysis, Zealandia is a 4.9 million-square-kilometre expanse of continental crust that’s 94% underwater, with only New Zealand and New Caledonia sitting above the ocean’s surface. For comparison, the world’s smallest continent Australia is 7.6 million square kilometres.
“If you could pull the plug on the world’s oceans, then Zealandia would probably long ago have been recognised as a continent,” lead author Nic Mortimer from GNS Science in Dunedin told Nature News.
This map shows the outline of Zealandia (red dashed line), based on several geoscience data sets.
IMAGE FROM FIG. 2, MORTIMER ET AL., GSA TODAY
According to the researchers, Zealandia is not a shock discovery by any means; in fact, the name was first proposed in a paper in 1995, although the author did not provide a detailed analysis.
Researchers have been gathering data on this continental crust for the past ten years, and the latest publication is an attempt to “formally put forward a scientific case for the continent of Zealandia.”
This does not make New Zealand an “island continent.” The two islands are simply the highest points of Zealandia, with earthquakes in the region governed by the intersection of the Australian and Pacific tectonic plates.
Previously, it was thought that the crust underneath the ocean in this area was fragmented into various bits. But according to new satellite-based gravity maps of the ancient seafloor, it is now clear that the whole region is a continuous whole.
“The scientific value of classifying Zealandia as a continent is much more than just an extra name on a list,” the authors write.
“That a continent can be so submerged yet unfragmented makes it a useful and thought-provoking geodynamic end member in exploring the cohesion and breakup of continental crust.”
Header image: The two islands of New Zealand as seen from space. IMAGE CREDIT: TE AWAMUTU SPACE CENTRE