This may have already been posted here, but I didn't
see it.
The missing continent that took 375 years to find
It took scientists 375 years to discover the eighth
continent of the world, which had been hiding in plain
sight all along. But mysteries about the land mass
still remain.
As we head towards the end of another extraordinary
year, BBC Future is taking a look back at some of our
favourite stories for our Best of 2021 collection.
Discover more of our picks here.
It was 1642 and Abel Tasman was on a mission. The
experienced Dutch sailor, who sported a flamboyant
moustache, bushy goatee and penchant for rough justice
he later tried to hang some of his crew on a drunken
whim was confident of the existence of a vast
continent in the southern hemisphere, and determined to
find it.
At the time, this portion of the globe was still
largely mysterious to Europeans, but they had an
unshakeable belief that there must be a large land mass
there pre-emptively named Terra Australis to
balance out their own continent in the North. The
fixation dated back to Ancient Roman times, but only
now was it going to be tested.
And so, on 14 August, Tasman set sail from his
company's base in Jakarta, Indonesia, with two small
ships and headed west, then south, then east,
eventually ending up at the South Island of New
Zealand. His first encounter with the local Māori
people (who are thought to have settled there several
centuries earlier) did not go well: on day two, several
paddled out on a canoe, and rammed a small boat that
was passing messages between the Dutch ships. Four
Europeans died. Later, the Europeans fired a cannon at
11 more canoes its not known what happened to their
targets.
And that was the end of his mission Tasman named the
fateful location Moordenaers (Murderers) Bay, with
little sense of irony, and sailed home several weeks
later without even having set foot on this new land.
While he believed that he had indeed discovered the
great southern continent, evidently, it was hardly the
commercial utopia he had envisaged. He did not return.
(By this time, Australia was already known about, but
the Europeans thought it was not the legendary
continent they were looking for. Later, it was named
after Terra Australis when they changed their minds).
Little did Tasman know, he was right all along. There
was a missing continent.
In 2017, a group of geologists hit the headlines when
they announced their discovery of Zealandia Te Riu-a-
Māui in the Māori language. A vast continent of 1.89
million sq miles (4.9 million sq km) it is around six
times the size of Madagascar.
Though the world's encyclopaedias, maps and search
engines had been adamant that there are just seven
continents for some time, the team confidently informed
the world that this was wrong. There are eight after
all and the latest addition breaks all the records,
as the smallest, thinnest, and youngest in the world.
The catch is that 94% of it is underwater, with just a
handful of islands, such as New Zealand, thrusting out
from its oceanic depths. It had been hiding in plain
sight all along.
"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, who was part of the team that discovered
Zealandia.
But this is just the beginning. Four years on and the
continent is as enigmatic as ever, its secrets
jealously guarded beneath 6,560 ft (2km) of water. How
was it formed? What used to live there? And how long
has it been underwater?
A laborious discovery
In fact, Zealandia has always been difficult to study.
More than a century after Tasman discovered New Zealand
in 1642, the British map-maker James Cook was sent on a
scientific voyage to the southern hemisphere. His
official instructions were to observe the passing of
Venus between the Earth and the Sun, in order to
calculate how far away the Sun is.
But he also carried with him a sealed envelope, which
he was instructed to open when he had completed the
first task. This contained a top-secret mission to
discover the southern continent which he arguably
sailed straight over, before reaching New Zealand.
The first real clues of Zealandia's existence were
gathered by the Scottish naturalist Sir James Hector,
who attended a voyage to survey a series of islands off
the southern coast of New Zealand in 1895. After
studying their geology, he concluded 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
".
Despite this early breakthrough, the knowledge of a
possible Zealandia remained obscure, and very little
happened until the 1960s. "Things happen pretty slowly
in this field," says Nick Mortimer, a geologist at GNS
Science who led the 2017 study.
Then in the 1960s, geologists finally agreed on a
definition of what a continent is broadly, a
geological area with a high elevation, wide variety of
rocks, and a thick crust. It also has to be big. "You
just can't be a tiny piece," says Mortimer. This gave
geologists something to work with if they could
collect the evidence, they could prove that the eighth
continent was real.
You might also like:
The mystery of the lost Roman herb
How mathematics emerged from a lost Islamic library
The forgotten foods that could excite our tastebuds
Still, the mission stalled discovering a continent is
tricky and expensive, and Mortimer points out that
there was no urgency. Then in 1995, the American
geophysicist Bruce Luyendyk again described the region
as a continent and suggested calling it Zealandia. From
there, Tulloch describes its discovery as an
exponential curve.
Tasmans ships left New Zealand after a bloody
encounter with the Māori people but he believed that
he had found the legendary southern continent (Credit:
Alamy)
Tasmans ships left New Zealand after a bloody
encounter with the Māori people but he believed that
he had found the legendary southern continent (Credit:
Alamy)
Around the same time, the "United Nations Convention on
the Law of the Sea" came into force, and finally
provided some serious motivation. It states that
countries can extend their legal territories beyond
their Exclusive Economic Zone, which reaches 200
nautical miles (370km) out from their coastlines, to
claim their "extended continental shelf" with all the
mineral riches and oil this encompasses.
If New Zealand could prove that it was part of a larger
continent, it could increase its territory by six
times. Suddenly there was an abundance of funding for
trips to survey the area, and the evidence gradually
built up. With every rock sample that was collected,
the case for Zealandia improved.
The final flourish came from satellite data, which can
be used to track tiny variations in the Earth's gravity
across different parts of the crust to map the
seafloor. With this technology, Zealandia is clearly
visible as a misshapen mass almost as large as
Australia.
Satellite data can be used to visualise the continent
of Zealandia, which appears as a pale blue upside-down
triangle to the east of Australia (Credit: GNS Science)
When the continent was finally unveiled to the world,
it unlocked one of the most sizeable maritime
territories in the world. "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."
In addition to New Zealand, the continent encompasses
the island of New Caledonia a French colony famous
for its dazzling lagoons and the tiny Australian
territories of Lord Howe Island and Ball's Pyramid. The
latter was described by one 18th-Century explorer as
appearing "not to be larger than a boat."
A mysterious stretching
Zealandia was originally part of the ancient
supercontinent of Gondwana, which was formed about 550
million years ago and essentially lumped together all
the land in the southern hemisphere. It occupied a
corner on the eastern side, where it bordered several
others, including half of West Antarctica and all of
eastern Australia.
Then around 105 million years ago, "due to a process
which we don't completely understand yet, Zealandia
started to be pulled away", says Tulloch.
Continental crust is usually around 40km deep
significantly thicker than oceanic crust, which tends
to be around 10km. As it was strained, Zealandia ended
up being stretched so much that its crust now only
extends 20km (12.4 miles) down. Eventually, the wafter-
thin continent sank though not quite to the level of
normal oceanic crust and disappeared under the sea.
Despite being thin and submerged, geologists know that
Zealandia is a continent because of the kinds of rocks
found there. Continental crust tends to be made up of
igneous, metamorphic and sedimentary rocks like
granite, schist and limestone, while the ocean floor is
usually just made of igneous ones such as basalt.
When the supercontinent of Gondwana broke up, fragments
drifted all across the globe. Many of its ancient
plants still live in the Australian Dorrigo forest
(Credit: Getty Images)
When the supercontinent of Gondwana broke up, fragments
drifted all across the globe. Many of its ancient
plants still live in the Australian Dorrigo forest
(Credit: Getty Images)
But there are still many unknowns. The unusual origins
of the eighth continent make it particularly intriguing
to geologists, and more than a little baffling. For
example, it's still not clear how Zealandia managed to
stay together when it's so thin and not disintegrate
into tiny micro-continents.
Another mystery is exactly when Zealandia ended up
underwater and whether it has ever, in fact,
consisted of dry land. The parts that are currently
above sea level are ridges that formed as the Pacific
and Australian tectonic plates crumpled together.
Tulloch says opinion is split as to whether it was
always submerged apart from a few small islands, or
once entirely dry land.
This also raises the question of what lived there.
With its mild climate and 39 million-sq-mile (101
million-sq-km) range, Gondwana itself was home to a
vast array of flora and fauna, including the first
four-limbed land animals and later, an abundance of the
largest to ever live the titanosaurs. So, could the
rocks of Zealandia be studded with their preserved
remains?
A debate about dinosaurs
Fossilised land animals are rare in the southern
hemisphere, but the remains of several were found in
New Zealand in the 1990s, including the rib bone of a
giant, long-tailed, long-necked dinosaur (a sauropod),
a beaky herbivorous dinosaur (a hypsilophodont) and an
armoured dinosaur (an ankylosaur). Then in 2006, the
foot bone of a large carnivore, possibly a kind of
allosaur, was discovered in the Chatham Islands, about
500 miles (800km) east of the South Island. Crucially,
the fossils all date to after the continent of
Zealandia split from Gondwana.
The elephant bird stood 3 m (9.8 ft) tall and fragments
of its eggshells still litter beaches to this day
(Credit: Alamy)
The elephant bird stood 3 m (9.8 ft) tall and fragments
of its eggshells still litter beaches to this day
(Credit: Alamy)
However, this doesn't necessarily mean there were
dinosaurs roaming over the majority of Zealandia
these islands may have been sanctuaries while the rest
was drowned, as it is now. "There's a long debate about
this, about whether it's possible to have land animals
without continuous land and whether without it, they
would have been snuffed out," says Rupert Sutherland, a
Professor of Geophysics and Tectonics at the Victoria
University of Wellington.
The plot thickens with one of New Zealand's weirdest
and most beloved inhabitants, the kiwi a dumpy,
flightless bird with whiskers and hair-like feathers.
Oddly, its closest relative is not thought to be the
Moa, which is part of the same group the ratites
and lived on the same island until its extinction 500
years ago, but the even-more giant elephant bird, which
stalked the forests of Madagascar until as recently as
800 years ago.
The finding has led scientists to believe that both
birds evolved from a common ancestor that lived on
Gondwana. It took 130 million years to fully break up,
but when it did, it left behind fragments which have
since been scattered all across the globe, forming
South America, Africa, Madagascar, Antarctica,
Australia, the Arabian Peninsula, the Indian
Subcontinent, and Zealandia.
This, in turn, suggests that at least part of now-
submerged Zealandia has remained above sea level the
whole time. Except around 25 million years ago the
entire continent even possibly the entirety of New
Zealand is thought to have been plunged underwater.
"It was thought that all the plants and animals must
have colonised afterwards," says Sutherland. So what
happened?
New Zealand is one of the highest points of Zealandia,
after being pushed up by the movement of tectonic
plates (Credit: Alamy)
New Zealand is one of the highest points of Zealandia,
after being pushed up by the movement of tectonic
plates (Credit: Alamy)
Though it's not possible to collect fossils from the
seafloor of Zealandia directly, scientists have been
plumbing its depths by drilling. "Actually the most
helpful and distinctive fossils are the ones which form
in the very shallow seas," says Sutherland. "Because
they leave a record there are zillions and zillions
of tiny, tiny little fossils that are very
distinctive."
In 2017, a team undertook the most extensive surveys of
the region so far, and drilled more than 4,101ft
(1,250m) into the seabed at six different sites. The
cores that they collected contained pollen from land
plants, as well as spores and the shells of organisms
that lived in warm, shallow seas.
"If you have water, which is only you know, 10m (33ft)
deep or something like this, then there's a good chance
that there was land around as well," says Sutherland,
who explains that the pollen and spores also hint at
the possibility that Zealandia was not quite as
submerged as was thought.
A (literal) twist
Another lingering mystery can be found in Zealandia's
shape.
"If you look at a geological map of New Zealand, there
are two things that really stand out," says Sutherland.
One of these is Alpine Fault, a plate boundary that
runs along the South Island and is so significant, it
can be seen from space.
The red band of rock the Median Batholith should
travel all the way down Zealandia in a diagonal line,
but instead it has been twisted out of shape (Credit:
GNS Science)
The red band of rock the Median Batholith should
travel all the way down Zealandia in a diagonal line,
but instead it has been twisted out of shape (Credit:
GNS Science)
The second is that the geology of New Zealand as well
as that of the wider continent is oddly bent. Both
are split in two by a horizontal line, which is where
the Pacific and Australian tectonic plates meet. At
this exact point, it looks like someone has taken the
lower half and twisted it away, so that not only do the
previously-continuous ribbons of rock no longer line
up, but they are almost at right angles.
An easy explanation for this is that the tectonic
plates moved, and somehow deformed them out of shape.
But exactly how or when this happened is still totally
unresolved.
"There are various interpretations, but this is quite a
large unknown thing," says Tulloch.
Sutherland explains that the continent is unlikely to
give up all its secrets anytime soon. "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 world's eighth continent surely
shows that nearly 400 years after Tasman's quest
there is still plenty to be discovered.
Zaria Gorvett is a senior journalist for BBC Future.
Twitter: @ZariaGorvett
--
Join one million Future fans by liking us on Facebook,
or follow us on Twitter or Instagram.
If you liked this story, sign up for the weekly bbc.com
features newsletter, called "The Essential List". A
handpicked selection of stories from BBC Future,
Culture, Worklife, and Travel, delivered to your inbox
every Friday.
|
|