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Meet Zealandia, Earth’s New Continent

Meet Zealandia, Earth’s New ContinentMost people view the continents and oceans as discrete entities of land and water across Earth’s surface. However, even a cursory look at our world establishes the problem.

Are North America and South America truly separate continents with their connection through the Isthmus of Panama? Where and why does one distinguish Europe, Africa, and Asia considering the Bosphorus and Sinai Peninsula?

One might suggest a geological reason: continents are large, identifiable areas underlain by continental crust.

A new paper by GNS Science geologist Dr. Nick Mortimer and co-authors follows this idea, but then throws a fascinating twist on the subject: Zealandia.

“Several islands, notably New Zealand and New Caledonia, are connected by submerged continental crust across a large area of Earth’s surface,” the authors explained.

“This region has elevated bathymetry relative to surrounding oceanic crust, diverse and silica-rich rocks, and relatively thick and low-velocity crustal structure.”

“Its isolation from Australia and large area support its definition as a continent — Zealandia,” they said.

Zealandia is approximately the area of greater India and, like India, Australia, Antarctica, Africa, and South America, was a former part of Gondwana.

As well as being the seventh largest continent, Zealandia is the youngest, thinnest, and most submerged.

“The identification of Zealandia as a geological continent, rather than a collection of continental islands, fragments, and slices, more correctly represents the geology of this part of Earth,” the scientists said.

“Currently used conventions and definitions of continental crust, continents, and microcontinents require no modification to accommodate Zealandia.”

Roughly 94% of the area of Zealandia currently is submerged.

“It is not unique in this regard: an ice-free, isostatically corrected West Antarctica would also largely be submerged,” Dr. Mortimer and his colleagues said.

“Zealandia and West Antarctica were formerly adjacent to each other along the southeast Gondwana margin and, prior to thinning and breakup, the orogenic belts, Cordilleran batholiths, and normal continental crustal thickness of eastern Australia would have projected along strike into these areas.”

Zealandia once made up approximately 5% of the area of the supercontinent Gondwana, according to the team.

“It contains the principal geological record of the Mesozoic convergent margin of southeast Gondwana and, until the Late Cretaceous, lay Pacificward of half of West Antarctica and all of eastern Australia,” the researchers said.

“Thus, depictions of the Paleozoic-Mesozoic geology of Gondwana, eastern Australia, and West Antarctica are both incomplete and misleading if they omit Zealandia.”

“The importance of Zealandia is not so much that there is now a case for a formerly little-known continent, but that, by virtue of its being thinned and submerged, but not shredded into microcontinents, it is a new and useful continental end member,” they added.

“Zealandia illustrates that the large and the obvious in natural science can be overlooked.”
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