- Geologists used to think Earth had six continents, but a new study adds a seventh: “Zealandia.”
- Recent satellite data and rock samples are behind the conclusion.
- New Zealand and New Caledonia are part of the new continent, which is about as big as greater India.
- The new continent could have economic and geopolitical implications.
Now its time to refresh your GK and we are requesting all geography books authors that it time to really write something new ……mmmm…. Sarcasm?
Kids are frequently taught that seven continents exist: Africa, Asia, Antarctica, Australia, Europe, North America, and South America.
Geologists, who look at the rocks (and tend to ignore the humans), group Europe and Asia into its own supercontinent – Eurasia – making for a total of six geologic continents.
But according to a new study of Earth’s crust, there’s a seventh geologic continent called “Zealandia,” and it has been hiding under our figurative noses for millennia.
The 11 researchers behind the study argue that New Zealand and New Caledonia aren’t merely an island chain. Instead, they’re both part of a single, 4.9-million-square kilometer (1.89 million-square-mile) slab of continental crust that’s distinct from Australia.
The concept of Zealandia isn’t new. In fact, Luyendyk coined the word in 1995.
But Luyendyk says it was never intended to describe a new continent. Rather, the name was used to describe New Zealand, New Caledonia, and a collection of submerged pieces and slices of crust that broke off a region of Gondwana , a 200 million-year-old supercontinent.
“The reason I came up with this term is out of convenience,” Luyendyk says. “They’re pieces of the same thing when you look at Gondwana. So I thought, ‘why do you keep naming this collection of pieces as different things?'”
Researchers behind the new study took Luyendyk’s idea a huge step further, re-examining known evidence under four criteria that geologists use to deem a slab of rock a continent:
- Land that pokes up relatively high from the ocean floor
- A diversity of three types of rocks: igneous (spewed by volcanoes), metamorphic (altered by heat/pressure), and sedimentary (made by erosion)
- A thicker, less-dense section of crust compared to surrounding ocean floor
- “Well-defined limits around a large enough area to be considered a continent rather than a microcontinent or continental fragment”
Over the past few decades, geologists had already determined that New Zealand and New Caledonia fit the bill for items 1, 2, and 3. After all,
they’re large islands that poke up from the sea floor, are geologically diverse, and are made of thicker, less-dense crust.
This eventually led to Luyendyk’s coining of Zealandia, and the description of the region as “continental,” since it was considered a collection of microcontinents, or bits and pieces of former continents.
The authors say the last item on the list – a question of “is it big enough and unified enough to be its own thing?” – is one that other researchers skipped over in the past, though by no fault of their own. At a glance, Zealandia seemed broken-up. But the new study used recent and detailed satellite-based elevation and gravity maps of the ancient seafloor to show that Zealandia is indeed part of one unified region.
The data also suggests Zealandia spans “approximately the area of greater India,” or larger than Madagascar, New Guinea, Greenland, or other microcontinents and provinces.
“If the elevation of Earth’s solid surface had first been mapped in the same way as those of Mars and Venus (which lack […] opaque liquid oceans),” they wrote, “we contend that Zealandia would, much earlier, have been investigated and identified as one of Earth’s continents.”
The geologic details
The study’s authors point out that while India is big enough to be a continent, and probably used to be, it’s now part of Eurasia because it collided and stuck to that continent millions of years ago.
Zealandia, meanwhile, has not yet smashed into Australia; a piece of seafloor called the Cato Trough still separates the two continents by 25 kilometers (15.5 miles).
Complete Article Credits – Business Insider