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Zealandia, considered the representative of the world’s continents, was mostly lost in the sea.
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Geologists say they have now mapped nearly 2 million square miles of underwater land.
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The research team used rocks from the ocean floor to study and decipher the undersea geology of North Zealandia, the final piece of the Zealandia puzzle.
Zealandia had so much promise as the eighth continent on Earth. Well, anyway—until about 95 percent of its weight sank to the bottom of the ocean.
While most of Zealand may never receive citizenship—perhaps, not citizenship—the would-be continent is now far from lost. Researchers have completed mapping the northern two-thirds of Zealand, documenting nearly two million millimeters of submerged land.
In a study published in Tectonicsresearchers from New Zealand’s GNS Science document their process of excavating rocks from the Fairway Ridge to the Coral Sea in order to analyze the rock geochemistry and understand the underwater structure of Zealandia.
The history of Zealandia is closely tied to the ancient supercontinent of Gondwana, which broke up hundreds of millions of years ago. Zealandia followed – about 80 million years ago, according to current theories. But unlike neighboring Australia or much of Antarctica, Zealandia is largely submerged, leaving only a small portion of what geologists believe is still the eighth continent.
New Zealand is the most famous above-water part of Zealand, although a few other nearby islands are also part of the sub-continent in question.
The research, led by Nick Mortimer, excavated the northern two-thirds of the sunken area, pulling up rock and sandstone, grain sand, mud, bioclastic limestone, and basaltic lava from different periods. By dating rocks and interpreting magnetic anomalies, the researchers wrote, they were able to map major geological features across North Zealandia. “This work completes the geological mapping of the entire continent of Zealandia,” he said.
The researchers found sandstone about 95 million years old from the Late Cretaceous period and a mixture of granite and volcanic rocks from about 130 years ago during the Early Cretaceous period. The salts are relatively new – about 40 million years old and from the Eocene period.
Along with the map, the paper says the internal deformation of Zealandia and West Antarctica shows that the stretching led to the rifting of the plates that received the ocean water to form the Tasman Sea. Then, a few million years later, another Antarctic breakaway continued to stretch the crust of Zealandia until it was thin enough to crack and seal the great seabed of Zealandia. This is contrary to the existing theory of break-slip.
The team believes, respectively Science Alertthat the extension varied as much as 65 degrees, which would have allowed for a great thinning of the continents.
As scientists in New Zealand will tell you, just because Zealandia is underwater, it doesn’t make it any less of a geological wonder.
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