The Breakdown: Scientists Take to the Sea to Study a Lost Land: Zealandia

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It’s about half the size of the United States, and it’s been hiding under everyone’s noses — or more precisely, under the waves — for millions of years. Now, scientists are setting sail to finally help solve the mystery of Zealandia, the lost undersea landmass being billed as the world’s eighth continent.

Zealandia, an expanse of 1.9 million square miles, extends from far south and east of New Zealand up to New Caledonia and west to an area off Australia’s northeast coast. It was part of Australia until about 75 million years ago, when it started to break away and move northeast. That movement stopped 53 million years ago, and scientists have slowly discovered the landmass, almost entirely submerged, over the past two decades.

“It’s a long way from anywhere,” said Rupert Sutherland, a Victoria University of Wellington professor who will be on the monthslong voyage from Australia to Zealandia, which began Friday. “A few missions have been going there to look for some specific things, but there hasn’t really been a coordinated plan of attack.”

He continued, “It is quite exciting, this Zealandia exploration. We’ve got an entire continent that has not been explored.”

Scientists who are part of the drilling expedition said sediment would be collected to help answer lingering questions about Zealandia — such as how and when it formed and what has happened in the area over time. They also hope to better understand how the Pacific Ring of Fire, a hot spot for volcanoes and earthquakes, formed.

“What we hadn’t realized until fairly recently was that the formation of the Pacific Ring of Fire greatly modified the continent of Zealandia,” Dr. Sutherland said. “It greatly changed the water depth, and it created topography.”

Earlier this year, in a study published by the Geological Society of America, scientists argued that Zealandia should be assigned continent status, despite the fact that it’s mostly underwater, because of its distinctive geology. The study outlined all that was known about Zealandia and went through all of the criteria used to define a continent and evaluated Zealandia against that criteria. The findings have been widely accepted, said Dr. Sutherland, who was a co-author of the study.

“The scientific value of classifying Zealandia as a continent is much more than just an extra name on a list,” the study concluded. “That a continent can be so submerged yet unfragmented” makes it useful for “exploring the cohesion and breakup of continental crust.”