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There's an Eighth Continent?

It took 375 years for scientists to discover the world's eighth continent, which had been hiding in plain sight all along. Mysteries, however, still remain.



It was 1642 and he was on a mission with Abel Tasman. The experienced Dutch sailor, who sported a flamboyant mustache, bushy goatee, and a penchant for rough justice, who later tried to hang some of his crew on a drunken whim, was confident and determined to discover the existence of a vast continent in the southern hemisphere.


This portion of the globe was still largely mysterious to Europeans at the time, but they had an unshakeable belief that there must be a large landmass there to balance out their own continent in the North, pre-emptively called Terra Australis. The fixation dated back to the Ancient Roman era, but it was only going to be tested now.


And so, on 14 August, Tasman set sail with two small ships from his company's base in Jakarta, Indonesia, heading west, then south, then east, eventually ending up on New Zealand's South Island. His first encounter with the local Māori people did not go well: a few paddled out on a canoe on the second day and rammed a small boat that was passing messages between the Dutch ships. Four Europeans have perished. The Europeans later fired a cannon at 11 more canoes, and what happened to their targets is not known.


Tasman named the fateful place Moordenaers (Murderers) Bay, with little sense of irony, and sailed home several weeks later without even setting foot on this new land. And that was the end of his mission. While he believed that the great southern continent had indeed been discovered, obviously, it was hardly the commercial utopia that he had envisioned. He hasn't returned.


(Australia was already known by this time, but the Europeans thought it was not the legendary continent they were looking for. Later, when they changed their minds, it was named after Terra Australis).


Little did Tasman know, all along, he was right. There was a continent that was missing.


In 2017, when they announced their discovery of Zealand-Te Riu-a-Māui in the Māori language, a group of geologists hit the headlines. It is around six times the size of Madagascar, a vast continent of 1.89 million sq miles (4.9 million sq km).


Even though the encyclopedias, maps, and search engines of the world had been adamant that for some time there were only seven continents, the team confidently informed the world that this was wrong. After all, there are eight, and the latest addition breaks all records, as the world's smallest, thinnest and youngest. The catch is that 94% of it is underwater, with just a handful of islands thrusting out of its oceanic depths, such as New Zealand. It was all along there hiding in plain sight.

"This is an example of how something very obvious can take a while to uncover," says Andy Tulloch, a geologist at the New Zealand Crown Research Institute GNS Science, a team member of the team that discovered Zealandia.

But this is just the start. Four years on and the continent is as enigmatic as ever, under 6,560 ft (2km) of water, its secrets jealously guarded. How has it been formed? What was the use of living there? And for how long was it underwater?


A discovery that was laborious!

In reality, studying in Zealand has always been difficult.

The British map-maker James Cook was sent on a scientific expedition to the southern hemisphere more than a century after Tasman discovered New Zealand in 1642. In order to determine how far away the Sun is, his official orders were to observe the passage of Venus between the Earth and the Sun.


But he also brought a sealed envelope with him, which he was told to open after the first mission had been accomplished. This included a top-secret plan to explore the southern continent before reaching New Zealand, which he arguably sailed straight over.


The first real clues to the nature of Zealand were obtained by the Scottish naturalist Sir James Hector, who in 1895 took a trip to survey a series of islands of New Zealand's southern coast. He concluded, after researching their geology, that New Zealand is "the remnant of a mountain-chain that formed the crest of a great continental area that stretched far to the south and east, and which is now submerged."


The knowledge of a potential Zealandia remained elusive, despite this early breakthrough, and very little happened until the 1960s. "Things happen pretty slowly in this field," says Nick Mortimer, a GNS Science geologist who led the 2017 report.

Then, in the 1960s, geologists finally settled on a description of what a continent is, a high elevation geological region, a large range of rocks, and a dense crust in general. It has to be big as well. "You just can't be a tiny piece, "You just can't be a tiny piece. If they could gather the facts, they could show that the eighth continent was true. This gave geologists something to work with.


Even, the project stalled-it is complicated and costly to explore a continent, and Mortimer points out that there was little urgency. In 1995, Bruce Luyendyk, the American geophysicist, again identified the area as a continent and proposed naming it Zealand. Tulloch characterizes its discovery from there as an exponential curve.



The 'United Nations Convention on the Law of the Sea' came into effect at about the same time and eventually offered some significant inspiration. It notes that nations will expand their legal territories to claim their "extended continental shelf" outside their Exclusive Economic Zone, which extends 200 nautical miles (370 km) from their coastlines, with all the mineral resources and oil that it entails.


If New Zealand were able to show that it was part of a larger continent, its territory could be increased six times over. There was suddenly an abundance of funding for trips to survey the area, and the evidence gradually grew. The argument for Zealand strengthened with every rock sample that was gathered.


The final flourish came from satellite knowledge, which can be used to map the seafloor to track tiny variations in the gravity of the Earth across various sections of the crust. Zealand is clearly evident with this technology as a misshapen mass almost as wide as Australia.


The continent of Zealand, which appears as a light blue upside-down triangle east of Australia, can be visualized using this satellite data below.



When the continent was eventually revealed to the world, one of the world's most powerful maritime territories was unlocked. "It is kind of cool," says Mortimer, "If you think about it, every continent on the planet has different countries on it, [but] there are only three territories on Zealandia."


The continent contains the island of New Caledonia, a French colony famous for its sparkling lagoons, and the tiny Australian territories of Lord Howe Island and Ball's Pyramid, in addition to New Zealand. One 18th-century explorer described the latter as appearing "not to be larger than a boat."


A strange stretching


Originally, Zealand was part of Gondwana's ancient supercontinent, which was formed about 550 million years ago and essentially encompassed all the land in the southern hemisphere. On the eastern side, it occupied a corner, surrounding a few others, including half of West Antarctica and much of eastern Australia.


Then, about 105 million years ago, Zealand began to be pulled away because of a process that we do not yet fully understand, says Tulloch.

Usually, the continental crust is about 40 km deep, considerably thicker than the oceanic crust, which tends to be about 10 km. Zealand ended up being stretched so much as it was strained, that its crust is now only 20 km (12.4 miles) down. Eventually, the wafter-thin continent sank and disappeared under the sea, though not quite to the level of normal oceanic crust.


Despite being thin and submerged, geologists know that, because of the kinds of rocks found there, Zealand is a continent. Igneous, metamorphic and sedimentary rocks such as granite, schist, and limestone tend to make up the continental crust, while the ocean floor is usually just made of igneous rocks such as basalt.


But many unknowns are still there. For geologists, the unusual origins of the eighth continent make it especially intriguing, and more than a little baffling. How Zealand managed to stay together when it is so thin and not disintegrate into tiny micro-continents, for instance, is still not clear.


Another mystery is precisely when Zealand ended up underwater-and whether it ever consisted of dry land in reality. The sections that are currently above sea level are ridges that formed as the tectonic plates of the Pacific and Australia crumpled together. Tulloch argues that opinion is divided as to whether, apart from a few small islands, it was always submerged or, once, completely dry land.


This raises the question of what was living there, too.


Gondwana itself was home to a vast array of flora and fauna with its mild climate and 39 million-sq-mile (101 million-sq-km) range, including the first four-limbed land animals and later an abundance of titanosaurs, the largest ever to live. So, could the rocks of Zealand with their preserved remains be studded?


A Twist


You will find another remaining mystery in the form of Zealand.

"If you look at a geological map of New Zealand, there are two things that really stand out," says Sutherland. One of these is the Alpine Fault, a plate boundary that runs along the South Island and can be seen from space since it is so important.




The second is that, as well as that of the broader continent, New Zealand's geology is strangely distorted. A horizontal line, which is where the Pacific and Australian tectonic plates cross, splits them into two. It looks like someone has taken the lower half at this very point and bent it away, so not only do the previously-continuous rock ribbons no longer line up, but they are almost right-angled.


A simple explanation for this is that the tectonic plates changed, deforming them out of shape somehow. But it is still totally unresolved exactly how or when this happened.

"There are various interpretations, but this is quite a large unknown thing," says Tulloch.

The continent is unlikely to give up all its secrets any time soon, Sutherland explains. "It's quite hard to make discoveries when everything is 2km (1.2 miles) underwater, and the layers that you need to sample are 500m (1,640ft) beneath the seabed as well," he says. "It's really challenging to go out and explore a continent like that. So, it just takes a lot of time, money, and effort to go out and ships and survey regions."

If nothing else, the eighth continent of the world certainly indicates that there is still plenty to be found, almost 400 years after Tasman's hunt.


 

Source BBC



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