Sunken Zealand is hidden under New Zealand and the surrounding Pacific Ocean. New research suggests this hypothetical eighth continent is 1 billion years old. This is twice as much as the geologists who suggested the existence of Zealand thought.
At a depth of one kilometer in the South Pacific Ocean, there is a 5.2 million km² piece of land. Scientists argue over whether the sunken land mass has been a continent since 2017. Despite this, scientists led by Nick Mortimer, a geologist at New Zealand’s GNS Science, suggested that the continent should have well-defined boundaries, cover an area of more than 1 million km², rise above the surrounding oceanic crust and have a thicker continental crust. Zealand meets all these requirements. If the world’s oceans evaporated, Zealand would look like a well-defined plateau above the ocean floor, scientists say. So, Mortimer calls Zealand “the thinnest, most submerged and smallest continent” on Earth.
Most (approximately 94%) of the continent is located under the waters of the Pacific Ocean; the islands of the New Caledonia archipelago and the New Zealand islands of the North and South are referred to the continental land. Scientists believe that Zeeland was completely flooded 23 million years ago. Researchers believe that it broke away from Australia 60–85 million years ago and from Antarctica between 130 and 85 million years ago.
The problem is that until recently, samples of the oldest crust and rock ever taken in Zeeland were at most 500 Ma. Moreover, all other continents contain crust 1 million years old or more. But recent research has shown that a portion of the submerged continent is twice as old as geologists had previously assumed, which could bolster Mortimer’s argument.
“The new study draws the line,” said Rose Turnbull, a New Zealand geologist and co-author of the study, in a press release. “There is no longer any doubt that we live at the top of the continent.”
The geologists behind the recent study examined 169 chunks of Zeeland granite that were found near the southern tip of New Zealand. The results showed that the crust was once part of another hypothetical supercontinent known as Rodinia, which formed between 1.3 and 900 million years ago. In other words, the geological history of Zealand began much earlier than 500 million years ago.