In a study published in the journal Tectonics, scientists led by New Zealand’s GNS Science describe a process of collecting rock samples from the Fairway Ridge to the Coral Sea, which allowed them to analyze the geochemistry of the area and understand the underwater composition of Zealandia, the eighth “lost” continent of our planet. According to specialists, this work completes the offshore geological reconnaissance mapping of the entire continent of Zealandia, which remains almost completely submerged.

Almost entirely under the sea

According to a article Published on Phys.org, previous research has suggested that approximately 83 million years ago the supercontinent Gondwana was divided by geological forces, which gave rise to the beginning of the continents that exist today. He also determined the creation of another continent that is now submerged, an eighth “lost” continent, which would be added to the 7 that we already know: Asia, Africa, North and Central America, South America, Antarctica, Europe and Oceania.

It is believed that this “hidden” continent, called Zealandiait’s found approximately 94% under the sea, while the remaining 6% is made up of New Zealand and nearby islands. Being mostly submerged under the ocean, Zealandia is not as well studied as conventional continents, raising questions about its supposed shape and structure.

In this new effort, the research team composed of specialists from New Zealand, New Caledonia, Australia, the United States, Denmark and Tasmania, compiled a new geological map using a combination of rock samples recovered from the sea and geophysical mapping methods: they achieved cover almost all of the more than 5 million square kilometers that Zealandia ownsaccording to a article published in Forbes magazine.

A progressive sinking

Why was Zealandia almost completely submerged? Scientists explain in the research that, as the ancient supercontinent of Gondwana stretched, its tectonic plates began to crack and allow ocean water to enter. Once Antarctica broke away, Zealandia bark continued to thin: Finally, she was submerged and lost in the depths.

Basalt pebbles, a typical rock associated with underwater volcanism, show that Zealandia was gradually flooded for about 40 million years. From that point on, the entire region sank at least a kilometer to its current depth, perhaps in response to widespread tectonic activity along fault zones surrounding the Pacific.

The existence of this eighth underwater continent has not been postulated for the first time in recent years: in 1642, the Dutch explorer Abel Tasman, after which the Australian island state of Tasmania is named, first identified the island now known as New Zealand. Although he had to quickly return to the Netherlands due to an attack by the Maori, who had settled on the island a few centuries earlier, Tasman was convinced that an unknown continent existed there.

As pointed out by a article Published on Futurism.com, a 2017 study took up this idea from Tasman and noted that Zealandia is different from the continent of Australia in different geological aspects, despite its relative proximity. In fact, New Zealand and its neighboring island group, New Caledonia, were never officially considered part of the Australian continent. These differences are surely based on the conditions that determined the emergence of the eighth submerged continent.

Reference

Reconnaissance Basement Geology and Tectonics of North Zealandia. Nick Mortimer et al. Tectonics (2023). DOI:https://doi.org/10.1029/2023TC007961