Original subtitles

NARRATOR: A near perfect circle visible from space

surrounds an ancient mountain.

- There's a deeper story here that needs to be told.

NARRATOR: A mysterious cloud billows up from deep in the ocean.

- It looks like something is moving inside this weird haze.

NARRATOR: Satellites uncover a vast pattern of strange shapes

across dark desert sands.

- Someone must have put these here, but who?

NARRATOR: And invisible for millennia, technology from space

reveals a massive formation beneath the ocean surface.

- This is ground-breaking. This could completely redraw the map.

NARRATOR: Everywhere we look on our planet,

there's evidence of the past.

In nature,

in buildings, in relics.

Each holds a mystery that technology now allows us to see from above.

What new secrets are revealed?

Across our planet, some mysteries are so remote,

so vast, or so strange

that they can only be seen from far above,

by the silent eyes that watch from the sky.

The island nation of New Zealand, Aotearoa,

land of the long white cloud,

is known for its stunning natural beauty.

GEORGE KOUROUNIS: Pretty much every environment that you can think of

is present on New Zealand.

Gorgeous lakes, lush forests,

pristine beaches, even fjords,

but perhaps the most dramatic of all are the mountains.

NARRATOR: One of the most famous on the North Island is Mount Taranaki,

known as "Taranaki Mounga" to the local Maori.

CYLITA GUY: Like many of the mountains on the North Island,

Taranaki Mounga is volcanic.

At around 130,000 years old, it's pretty young for a volcano.

NARRATOR: But when viewed from far above,

satellite images reveal one striking

and very unusual feature at the foot of the mountain.

KAREN BELLINGER: There's a huge and perfectly round dark feature

just plunked into this lush green landscape.

- This is weird. It's like a perfect circle.

TORRI YATES-ORR: The circle around the mountain is dark green,

with a paler green surrounding it.

The peak of the mountain is right in the centre of the circle.

- What could possibly make such a huge imprint?

I mean, the diameter is 19 kilometres.

- Is this caused by some kind of natural phenomena?

- Or is this human-made? How long has this circle been here?

- It's around a volcano, so is this a sign of some kind of eruption?

- Taranaki Mounga is something called a stratovolcano.

They build up into this cone shape from the layers of lava that erupt,

and then cool, and then harden over and over again.

NARRATOR: So what could that mean for the circle?

There could be a clue over 7,000 kilometres away in the Philippines.

And what might be the most perfect volcanic cone in the world.

KOUROUNIS: This is Mount Mayon,

the most active volcano in the Philippines.

And if you look at it from space,

you can see its base is almost a perfect circle.

- And the frequent volcanic activity is the key to the symmetry.

The cone builds faster than the land can erode,

so it leaves this almost perfect shape.

GUY: It makes sense to wonder if the circle around Taranaki Mounga

is what we see here,

really just a dramatic footprint of a symmetrical stratovolcano.

KOUROUNIS: But Taranaki is a dormant volcano.

It hasn't erupted since the 18th century.

By contrast, Mount Mayon last erupted

only a few years ago, in 2018.

NARRATOR: And a closer look from above reveals

another important difference.

RISKIN: At Taranaki Mounga, the change in colour between the inside

and the outside of the circle is way more pronounced.

- So are there any other natural circular formations

that stand out dramatically from the surrounding landscape?

NARRATOR: From lush green islands

to one of the biggest deserts in the world,

perhaps a clue lies in the Western Sahara.

KOUROUNIS: This eerie phenomenon is known as the "Eye of Africa",

and when you're looking straight down at it, it's easy to see why.

YATES-ORR: This set of concentric rings is

an unbelievable 45 kilometres across.

It's so huge and distinct,

it's something of a landmark for astronauts.

BELLINGER: When you look at it from the side,

you can see that it's slightly domed,

which gives a clue to what caused it.

- Millions of years ago, a bubble of magma rose

through the Earth, pushing up layers and layers of rock,

creating this huge dome on the surface.

GUY: Over vast lengths of time,

that dome was eroded by wind and water,

revealing the layers in this bullseye formation.

The oldest rocks are in the centre,

and then they get younger as you move outwards.

NARRATOR: Is the circle at Mount Taranaki

signs of geologic formations made over millions of years?

KOUROUNIS: It makes sense to assume this is an ancient rock formation

of some kind, but when we take a closer look,

there's another crucial clue.

- The circle is actually made by vegetation.

YATES-ORR: There's what looks like grass on the outside,

and then it turns into this dense, lush forest

that grows up the side of the mountain.

But what does it mean?

GUY: Is there something about the plant life here

that is naturally making this divide?

There are some places where plants make perfect circles.

NARRATOR: A clue lies on the other side of the world.

Flying across the American Midwest, a pattern begins to emerge.

GUY: Looking down from above, you start to notice these areas

of land with perfectly circular shapes.

KOUROUNIS: They really stand out, because most of the surrounding land

looks like it's been divided into square plots.

So what's going on?

GUY: These are actually fields of crops, and what makes them

this perfect circle is something called "centre-pivot irrigation."

RISKIN: Essentially, it's just a really big sprinkler on wheels

that rotates around a central point in the field.

It's just a really efficient way to water your crops.

BELLINGER: So is this circle around Mount Taranaki

the result of farming technology?

YATES-ORR: New Zealand is known for its farming.

In fact, there are about 50,000 farms in the country.

NARRATOR: A closer look shows that there are farms here,

but they are outside the circle.

Most lead right up to the perimeter of the mountain forest.

But why?

KOUROUNIS: It's a line created by a sharp division

between farmland and thick forest.

But why is it even there at all?

NARRATOR: To find the answer, the investigation takes us

into the past, and uncovers something shocking.

- This circle actually has its roots

in some of the darkest moments in New Zealand's history.

British colonists arrived in New Zealand in increasing numbers

in the early 19th century.

KOUROUNIS: They met the Maori, who had beaten them there

by about 500 years or more.

RISKIN: Soon, the new European settlers were fighting

with the Maori over land use and ownership.

NARRATOR: In 1860, the Crown government declared war

on the Maori.

YATES-ORR: The British brought in thousands of troops to battle

the outnumbered Maori, and conflict raged for over ten years.

It was brutal.

NARRATOR: And perhaps most vicious of all

was the retaliation off the battlefield.

KOUROUNIS: The government used the wars as an excuse

to confiscate huge amounts of land from the Maori as "punishment".

- They then sold the land to settlers to raise money for the war.

- One of those confiscations was a vast swathe of land

around Taranaki Mounga.

KOUROUNIS: If you look at maps of this area from the time,

you can see how the British swept in

and just decided to claim everything.

YATES-ORR: By the 1870s, settlers were chopping down the dense forest

around Taranaki Mounga to make way for dairy farms.

GUY: And it's these farms that hold the secret

to the circle around Taranaki Mounga.

NARRATOR: But how did this perfectly circular boundary

between those farms and the mountain forest appear?

RISKIN: This incredible shape, made by natural vegetation,

is actually a mark of a human-made limit.

- In 1881, British government officials decided

that land within a six-mile, or 9.6-kilometre, radius of the summit

would be a forest reserve.

- It was officially named a national park in 1900.

- And over time, those colonial-era farms spread

right up to the edge of that perfectly circular boundary,

creating this crisp break between the pale pastureland

and the darker forest.

KOUROUNIS: And that strange extrusion at the top?

That's the Pouakai and Kaitake ranges.

Extinct volcanoes, hundreds of thousands of years old.

RISKIN: The colour boundary here is clearly much more natural.

It's a function of the changing terrain.

NARRATOR: The circle around Taranaki Mounga is a striking reminder

of a dramatic conflict, with an impact that echoes even today.

YATES-ORR: On the North Island, four million acres were "confiscated"

in the wars, and that paved the way

for another eight million acres taken from the Maori by 1890.

- And the impact is still felt.

In 2000, the Maori only held about 4% of the land on the North Island.

Aside from the devastating loss of resources,

in many ways, it also held a deeper insult,

because of the connection the Maori feel to the land.

BELLINGER: And Taranaki Mounga is incredibly important to the Maori.

They honour it as an ancestor.

NARRATOR: But today, there are steps being made to make amends.

YATES-ORR: A tribunal recognised the confiscation

of Taranaki Mounga as invalid in 1996.

And in 2017, the Taranaki Iwi and the New Zealand government agreed

to protect the mountain by recognising it as a person in law,

that is, it will own itself.

NARRATOR: Today, this dormant volcano is witnessing

a new era begin,

while serving as a powerful reminder of the past.

YATES-ORR: The circle is a monument of a terrible era

of aggressive colonisation,

and a constant reminder of the debt owed to the Maori.

NARRATOR: From lush, green mountains to deep ocean waters,

eyes in the sky uncover mysteries imperceptible from the ground.

Less than 4,000 kilometres to the northwest,

in the tropical waters of the South Pacific,

lie the Solomon Islands.

GUY: This paradise on Earth is formed of almost 1,000 islands,

stretching across over 1,400 kilometres of ocean.

RISKIN: And it's just as beautiful under the surface.

The ocean around the islands is full of life.

NARRATOR: But in 2022, flying far above the planet,

a NASA satellite spots something alarming

off the coast of one of the islands.

SHEILA HOFFMAN: There is something strange curling upward

towards the surface of the ocean.

- This is from a satellite, so you know it must be enormous.

- I mean, it could be about, what, ten,

fifteen kilometres long. That's pretty big.

YATES-ORR: It almost looks like a plume of smoke.

What's going on here?

- Is this a natural phenomenon or some kind of human-made disaster?

- I can think of at least one case

where I've seen something like this before.

NARRATOR: Almost 13,000 kilometres away,

in the Gulf of Mexico, tragedy strikes.

HOFFMAN: It's 10PM, April 20th, 2010,

and suddenly, flames appear over the quiet waters of the gulf.

- The Deepwater Horizon oil rig exploded.

- (explosion)

KOUROUNIS: It was absolutely devastating.

Eleven people were killed, and the rig sank two days later.

- But that was just the beginning. 1,500 metres underwater,

oil and gas gushed out of a broken wellhead.

YATES-ORR: It took months before the leaking well could be sealed,

and over three million barrels of oil escaped.

GUY: This formed a massive slick on the surface of the gulf,

covering over 100,000 square kilometres.

It was the largest marine oil spill in history.

NARRATOR: And NASA satellites captured the disaster from above.

WALTERS: What you can clearly see is that silvery-grey cloud of oil

just swirling around in the ocean currents.

KOUROUNIS: It looks a lot like this strange plume

near the Solomon Islands, so is this a man-made crisis?

An oil spill emptying into the pacific?

- But there aren't any offshore oil rigs in this area.

- So what else could be going on here?

GUY: There is another kind of ocean cloud

that can be caused by human activity.

NARRATOR: On the other side of the world, between the Caribbean

and West Africa, NASA satellites spot a growing problem.

YATES-ORR: A huge, massive algae growing across the Atlantic Ocean,

almost 9,000 kilometres long.

- It's called sargassum.

And over the past few years, it's been growing like crazy.

It forms these enormous mats that float along the ocean surface.

YATES-ORR: In 2018, it grew to around 20 million tonnes.

That's a lot of seaweed.

RISKIN: This is not good news. Out in the open ocean,

these islands of sargassum are important habitats

for lots of animals. But when that all moves to the coastline

in these huge amounts, it smothers everything.

NARRATOR: But what's behind this sudden explosion of seaweed?

The view from above provides a crucial clue.

GUY: Satellites have recorded plumes of algae

around the mouth of the Amazon River.

That's a sign of a flow of nutrients coming out of the river

and gushing into the ocean.

RISKIN: But don't let the name fool you,

these nutrients aren't necessarily good news.

The Amazon River carries nutrients from the rainforest

out into the Atlantic Ocean,

and rising deforestation could be sending

more and more of this stuff out every year.

GUY: And it's creating a 24-hour buffet for the sargassum.

It's a massive difference,

and it shows that the chemistry of the ocean is changing.

NARRATOR: And algal blooms caused by human activity can be found

all over the world.

KOUROUNIS: They create these swirling clouds

in lakes and oceans that can be clearly seen from satellites.

NARRATOR: Is this strange plume

off the coast of one of the Solomon Islands

another sign of algae growing out of control?

- But there are no huge piles of sargassum

sweeping up on the beaches here.

KOUROUNIS: So it doesn't make sense

for this to be an algal bloom from human activity.

- But it's not just human carelessness

that can cause these events.

NARRATOR: Could a clue lie in another part of the Pacific Ocean?

Perhaps on the island of Hawaii,

when the Kilauea volcano shakes up the ocean.

WALTERS: In the summer of 2018,

the Kilauea volcano spewed out

200 billion gallons of lava.

- When extremely hot molten rock hits the ocean,

it forms this billowing plume of hydrochloric acid and glass shards.

HOFFMAN: But this time, it also created

something totally unexpected,

and clearly seen from above.

RISKIN: It's a huge phytoplankton bloom, and this is baffling

cos you would expect lava would be this brutal killing force.

But you gotta ask yourself, how could this area possibly support

so much life all of a sudden?

GUY: Researchers think that lava plummeted

deep into the coastal water, around 300 metres or more.

And at that depth, cold water is full of nutrients

that don't usually reach the surface.

RISKIN: But the lava would suddenly heat up the cold water,

which would then push it and the nutrients in it up to the surface,

making an excellent lunch for all of these algae.

GUY: It's really amazing, and tells us about a kind of fertilisation

of the ocean that we didn't know about before.

NARRATOR: Is the strange ocean cloud near the Solomon Islands

the sign of a volcanic algal bloom?

- But on the surface of these islands, the nearest active volcano,

Tinakula, is over 850 kilometres away.

KOUROUNIS: But volcanoes aren't just found on land.

In fact, there are over 5,000 active underwater volcanoes

that we know of.

NARRATOR: Could a staggering underwater explosion

in the Canary Islands provide us with the final piece to this puzzle?

GUY: In the fall of 2011, strange things started happening

in the waters around the island of El Hierro.

RISKIN: The ocean starts bubbling and steaming.

Dead fish washed ashore.

And people at sea spot something they call "lava balloons".

These are black pumice rocks that actually float on the surface.

KOUROUNIS: It's a volcanic eruption.

And activity there goes on for months.

GUY: And seen from satellites far above the Earth,

the shapes the eruption creates in the ocean look familiar.

KOUROUNIS: This looks just like the cloud near the Solomon Islands,

maybe it's not an algal bloom at all.

Maybe there's an erupting volcano under the sea.

NARRATOR: When we take a closer look from above,

footage from previous years shows something explosive.

GUY: About 20 metres below sea level lies the summit of Kavachi,

one of the most active submarine volcanoes in the Pacific.

YATES-ORR: The satellite image of the plume is from 2022,

and must be a sign of a new eruption.

NARRATOR: Underwater volcanoes like Kavachi are an ongoing mystery,

but what we do know is the waters around them are deadly.

- They're blasting out lava and gas, just like above ground,

but they're also under tonnes of pressure from the water.

- When the lava hits the water, the massive temperature change

vaporises the water and solidifies the lava.

It's wild.

- So you've got sudden huge temperature changes

and noxious gases, and because of dissolved metals and sulphur,

the water around the volcanoes becomes more acidic.

YATES-ORR: And of course, there's the risk of an eruption,

you get hit by a burst of lava, you're toast.

NARRATOR: Despite these lethal dangers,

researchers approached these toxic waters in 2015,

sending special cameras down toward the hidden peak of Kavachi.

- They were expecting to find bacteria

that thrive in hot and acidic waters,

and maybe some other small creatures like shrimp or crabs.

- But what they caught on camera was unbelievable.

- You can see all these really big, fast-moving shapes in the water.

- What could possibly withstand the toxic waters

around an underwater volcano?

NARRATOR: A closer look at the footage reveals

the astonishing truth.

- Those are sharks!

- Oh, wow. This place is teeming with sharks.

- Why are they there? What's attracting them to this place?

GUY: For a predatory species, you can understand the appeal.

With all of the small creatures around, there is plenty to snack on.

KOUROUNIS: And if there are other creatures accidentally swimming

into an environment they can't handle,

well, it's another easy meal.

NARRATOR: But how are these rulers of the sea surviving

the dangers of the undersea volcano?

HOFFMAN: This environment could be, should be, deadly.

What's protecting them?

GUY: Some sharks really love warm water.

I mean, not hot lava, of course, but the higher temperatures here

could kind of be like a warm bath for them.

- And sharks have tough skin, which could help protect them

against any pieces of abrasive rock that are floating in the water.

- Plus, sharks have an amazing sense called "electroreception."

This could help them tell when seismic activity increases

and give them enough warning to get out of there before an eruption.

KOUROUNIS: It's amazing, but when you think about it,

sharks have been around for something like 150 million years,

and maybe over 450 million,

compared to around only two million for the earliest humans.

- Sharks have been around on the Earth

for longer than there have been trees on Earth.

They are used to everything the Earth can throw at them.

WALTER: So sharks have had a lot of time

to adapt to things that we've never imagined.

NARRATOR: This stunning discovery leads scientists

to give kavachi a title worthy of a Hollywood blockbuster...

"Sharkcano."

And it gives a glimpse of the staggering secrets

that can only be uncovered from above.

RISKIN: It's one of those perfect moments in science where you realise

the ocean could be hiding anything.

GUY: I mean, sharks are cool. Volcanoes are cool.

Sharkcanoes, though, might just be

the coolest natural phenomena I have ever heard of.

NARRATOR: From mysteries reaching the ocean surface

to strange shapes on dry land,

the view from far above the planet uncovers hidden truths.

In the Middle East, dark volcanic sands stretch

across southern Syria, through Jordan,

Israel, and into northern Saudi Arabia.

This is the Harrat Al-Sham, the Black Desert.

- It's a brutal and unforgiving landscape,

stretching over 40,000 square kilometres.

NARRATOR: An area approximately the size of Switzerland.

CHAD HILL: The Black Desert is a stunning environment

in which you have sort of a classic desert,

light-coloured sand everywhere,

and then huge piles of these very black basalt stone.

It's very impressive.

GUY: The rugged basalt terrain makes it difficult to travel,

and it's extremely dry, getting less than 100mm of rain per year.

NATASHA BILLSON: In such a harsh environment,

you wouldn't expect to find anything but sand and rocks.

NARRATOR: But flying high above the sands,

an astonishing sight is revealed.

- From a distance, we can start to see these sorts of lines appearing.

These are amazing.

GUY: There are these strange-looking structures

staring out from the sand.

- They look very organic. Almost like children's drawings.

- From the sky, you can see that they're clearly walls,

they're straight lines that you don't usually find

in this landscape. So you can see

that they look like a human-made thing.

But then when you get on the ground, there's not much there.

They don't look like a wall.

It's a small pile of basalt stones.

NARRATOR: It's only with the view from above

that the scale of these creations can be seen.

- These things are massive, each one stretching over kilometres.

WALTERS: It must have taken a vast amount of effort

to have created these frankly, giant structures.

- So that means someone has put these things here, but who?

- Were these done with modern machinery

or are these a product of more ancient technology?

GUY: They must be for something important.

What are these structures for?

NARRATOR: The first clue can be found decades in the past,

when these eerie constructs were first spotted from the air.

WALTERS: In the 1920s, you have pilots

in the British Royal Air Force

flying an airmail route between Transjordan and Iraq.

- Remember, this is the early days of aviation.

These are the days of biplanes flying under 5,000 metres

at a maximum speed of 180 kilometres an hour.

GUY: It's no wonder they spotted these strange formations

out of the airplane window.

- The pilots called these things "desert kites,"

because they've got these large, kind of angular central shapes,

and then these pairs of long string-like tails.

They reminded them of children's kites.

BILLSON: So we know for sure these must be

at least around 100 years old,

but they look even older.

KOUROUNIS: And the local Bedouins,

when asked about the strange structures,

called them "the works of the old men",

hinting at a much longer history.

So what other clues can we find?

NARRATOR: Early aviation brought these objects to wider attention.

But the latest technology exploring from the sky

has uncovered something even more shocking.

- These things are everywhere!

HILL: With the advent of clear, high-resolution satellite imagery,

we realised that there are thousands of these structures

across the landscape. It's sort of mind-blowing.

BELLINGER: So far, over 6,000 desert kites have been found

all across the Middle East, and even into Asia and Africa.

BILLSON: Have these all been here all along,

and we only now have the technology to see so many?

GUY: When we search across the Arabian Desert,

we can find more potential clues.

NARRATOR: Over 700 kilometres southeast of the kites,

a shock of green interrupts the sands...

the oasis of Khaybar.

KOUROUNIS: There are ruins of an ancient city and fortress here,

likely dating back to the Bronze Age.

But even more intriguing is what lays along the road

leading away from the lush oasis.

NARRATOR: A search from far above reveals

strange geometric formations

that offer a tantalising and ancient clue.

AGRAWAL: There's a whole network of stone shapes lining the roads.

There are circular bullseyes,

many with stone walls that make triangular tails.

BELLINGER: Experts call these fascinating constructs

"keyholes" and "pendants" because of their shape.

KOUROUNIS: And the scale is unbelievable.

Looking down from the sky, researchers have found over 9,000

of these in this area alone.

NARRATOR: And these structures line hundreds

of kilometres of connected roads.

GUY: These vast pathways of geometric stone shapes

seem eerily similar to the kites.

Could they offer a clue to who built them and why?

KOUROUNIS: What have scientists discovered

about these strange geometric formations?

BILLSON: Excavations of these fascinating sites uncovered

stone-lined burial chambers in the circular structures.

So these are actually tombs.

AGRAWAL: Experts have called these "funeral roads".

With so many side by side,

this is kind of live an ancient desert necropolis.

BELLINGER: Radiometric dating indicates

that these structures are 4,500 years old.

That means they date all the way back to the Bronze Age,

just like the nearby Khaybar ruins.

KOUROUNIS: The kites and the keyholes look like they're built

in a similar way and from similar materials.

- And just like the staggering lengths of the kites' tails,

the keyholes line funeral roads that stretch for hundreds of kilometres.

- Could the kites be another form of burial site or monument?

NARRATOR: But there's a crucial element missing.

- These kites don't appear to have anything that is like

the round burial chambers of the keyholes and pendants.

- So if these have nothing to do with burials,

what else could they be?

NARRATOR: Perhaps a clue can be found in southern Africa,

where a view from above captures a common village feature

that may provide a hint.

GUY: In many African villages, you find these rounded structures

made of strong wood branches.

These are enclosures known as "kraals",

and they're used to corral livestock like cows.

AGRAWAL: These structures secure and protect the animals at night.

In some cases, these kraals are encircled by huts,

creating a defensive formation.

NARRATOR: Is it possible that the desert kites were built

for a similar purpose?

- It's a good question, because we know that sheep,

and goats, and cattle were all domesticated

in the Middle East from around, what, 8,000 years ago.

So it would make a lot of sense that there would have to be structures

to corral all these animals.

KOUROUNIS: But many of these kites are far larger

than these animal pens,

some cover several kilometres.

And they're not exactly in the middle of a village.

They're scattered all across the desert.

- To figure out what these kites really are,

we need to figure out when they're from.

That would tell us something about what humans of that time

might have been doing with them.

NARRATOR: To determine the age of the kites,

experts need to take a closer look.

And the latest research suggests an astonishing age.

HILL: There aren't very many dates that we have for kites yet,

but the ones that we have suggest

that they were built sometime around 8,000 years ago.

- These kites were likely built in the Stone Age.

- The question is, what on Earth are these stone structures for?

NARRATOR: More ancient artefacts discovered nearby

reveal a clue to how Stone-Age humans

used these massive structures.

BELLINGER: Petroglyphs, or rock drawings, have been found

near kites, and what they depict is amazing.

AGRAWAL: These ancient drawings show shapes

that look an awful lot like desert kites appear from the sky.

HILL: If you don't have a plane, it's very hard to tell

what these structures look like on the ground.

The fact that we find depictions of kites at least strongly implies

that those depictions were made by people who were building,

operating, maintaining the kites.

KOUROUNIS: And what's really interesting

is that some of these petroglyphs show humans

and animals around these kites together.

NARRATOR: And on-the-ground excavations around some kites

have uncovered a critical clue...

..bones.

HILL: Archaeologists have found gazelle remains

at the bottom of these structures.

Finding animal remains, in the correct context,

is some of the best evidence for what these structures were used for.

Humans have been hunting gazelle in this region

for thousands of years before the kites are being built.

And so, the development of the kites appears to be

this sort of development of improving

the efficiency of hunting.

NARRATOR: Researchers believe that these kites are signs

of a stunning hunting technology from the Stone Age.

- The people living in the past were very smart.

RISKIN: These hunter-gatherers, after centuries and centuries

of chasing gazelles for food,

learned to predict their prey,

and then figured out this amazing plan.

HILL: They started building these structures,

making these really impressive decisions

with the technology they had at hand

to build these really impressive machines.

- The theory is that kites are absolutely massive traps.

- Experts believe the long "kite-strings" were used

as guiding walls that helped to kind of lead migrating herds of animals

into an enclosure, kinda like a giant funnel.

NARRATOR: The structure of the kites on the ground reveals

astonishing detail about the prey the humans were trapping.

HILL: A gazelle could literally walk over these walls

for at least a long stretch of where they're being guided into these.

And we think that the reason these worked

was taking advantage of gazelle psychology.

I think of it as being maybe similar to the fact that you can draw

a box of tape on the ground, and your cat will go and sit in it

because they like to be in enclosed spaces, even though

there's not actually a box there.

NARRATOR: And even more unexpected is the stunning connection

between these kites, only visible from above.

KOUROUNIS: These massive structures are actually connected!

Thousands of kites, across hundreds of kilometres, all linking together.

HILL: This is all one thing that people built.

And it's not just individual, separate structures.

This is like an infrastructure-level project.

BELLINGER: This indicates a ground-breaking level of cooperation

in this era, moving far beyond

individual subsistence hunting and foraging.

HILL: The idea that, instead, people are building

permanent structures on the landscape

over probably a long period of time

that they're revisiting every year, that create

and mark, probably, control of the landscape.

It sort of wildly changes how we think about

what people were doing out there at the time.

NARRATOR: A new drone exploration from above uncovers

more Stone-Age secrets.

HILL: We began visiting this region to use drones

because they can provide us with a high level of mapping data

that we can't get in any other way.

With the drone data, we can really get a clear picture

of how people who were building these kites,

that are very clearly almost everywhere.

That they build them using the shape of the landscape

to inform how they build the structures

and how they're going to help trick the gazelle

into getting to the part that they want to get them to.

We think, at least, that the idea is that you might try

to place the enclosure in a way that would make it

less visible to the gazelle

as they're approaching the final part of the trap.

GUY: So this shows not just a deep understanding of their prey,

but also the land itself,

and how both can be manipulated to make these traps effective

on an unbelievably massive scale.

NARRATOR: And this is just the beginning.

HILL: Drones have rapidly become a critical tool

that gives us the ability to really map the world

with a level of detail that wouldn't have been possible otherwise.

- And that means that there will be plenty more to discover

about the kites, and the people who built them, from above.

NARRATOR: From ancient deserts to the depths of the ocean,

the view from far above uncovers astonishing riddles

from our distant past.

Thousands of kilometres away, in the waters to the east of Australia,

the South Pacific Ocean holds countless secrets.

RISKIN: The Pacific is the Earth's largest and deepest ocean.

This is where you can find some of the most diverse marine environments

anywhere on the planet.

YATES-ORR: The deep ocean is one of the most mysterious places on Earth.

We know more about the surface of Mars than the depths of the ocean.

NARRATOR: But satellites scanning the deep ocean floor

with advanced technology capture something astonishing,

a vast feature reaching up from the deep...

..around the islands of New Zealand.

YATES-ORR: You can clearly see a solid profile

that's distinctly different from the surrounding ocean.

- There appears to be this raised area underneath the water.

- But it's not just around New Zealand. This is a vast area.

It's over half the size of neighbouring Australia.

RISKIN: This is a discovery that could only have been made

by satellites far above, measuring the ocean floor.

NARRATOR: What is this Pacific mystery

sprawled across nearly five million square kilometres?

- What is this thing? And what could have created it?

- Was it above ground at some point?

WALTERS: The ocean is a really strange place,

so could this be something completely unknown?

HOFFMAN: A mark this big on the planet's surface must be caused

by something immensely powerful.

Have parts of the seabed been forced upwards from a hard-hitting impact?

NARRATOR: A clue could be found far to the west.

Embedded in the Yucatan Peninsula, signs of a massive,

out-of-this-world strike.

YATES-ORR: About 66 million years ago,

a devastating impact event forever altered life on Planet Earth.

HOFFMAN: With the force of 100 million atomic bombs,

a gargantuan asteroid as wide as the grand canyon,

measuring up to 29 kilometres wide, slammed into the Gulf of Mexico.

NARRATOR: This giant fireball burned

at around 10,000 degrees Celsius.

- And the molten debris sparked fires across the world.

- Animals and plants within a 1,000-mile radius were destroyed,

causing the extinction of 75% of all the species

on land and in the sea, including the dinosaurs.

- The result of that event, the Chicxulub crater,

is now buried under the Yucatan Peninsula.

- Could something similar have happened to New Zealand?

GUY: It's a good theory. In fact, in 2005,

experts uncovered something that hints

at an astronomical impact in the waters off New Zealand.

NARRATOR: 2,500 kilometres away,

and two kilometres down, inside the Antarctic ice sheet.

RISKIN: Researchers examined something called

the Siple Dome ice core from Western Antarctica.

Now, this massive ice sample gives us hints

into the far distant past, with the oldest sections

dating back over 95,000 years.

- And what was really weird was that they discovered deformed,

broken and square microfossils.

That's usually the sign of a major event.

- They're most frequently found in places

where bolides have hit the earth.

Things like asteroids, meteors and comets.

- So could there be a hidden impact crater nearby?

NARRATOR: Some experts believe that only 250 kilometres

southwest of New Zealand,

hiding beneath the South Pacific Ocean,

lies an undiscovered site, the Mahuika crater.

YATES-ORR: The Mahuika crater, named after the Maori god of fire,

was believed to represent a major historical turning point

in the 15th century.

HOFFMAN: Maori legends tell centuries' old tales

of powerful tsunamis swallowing entire mountainsides

across parts of New Zealand and Australia.

KOUROUNIS: Is this underwater feature a record

of this long-hidden, cataclysmic impact?

RISKIN: Did the Mahuika comet smash into the South Pacific

with enough force to change the shape of the ocean floor?

NARRATOR: But there's some important evidence missing.

- There's no mention of the Mahuika comet in historical records.

But is it possible that the impact would be hidden

without the marvels of satellite technology?

- Even if this major impact somehow escaped notice,

there's still no direct geophysical evidence of the Mahuika impact.

YATES-ORR: So if it's not the remains of a meteorite strike,

what else could cause this massive shape on the ocean floor?

I mean, it must have been something incredibly powerful.

NARRATOR: There's another possibility

hiding beneath the ocean surface,

and only truly visible through technology looking down from above.

The mid-ocean ridge.

KOUROUNIS: This is an almost continuous range

of rugged underwater mountains that wrap around the globe.

GUY: It's the longest mountain range in the world,

with an average depth of 2,600 metres.

- We know that these subsurface peaks are created

by sliding tectonic plates.

NARRATOR: So could this undersea anomaly be part

of this worldwide mountain range?

- But when we look at maps of the ridges,

we can see that the closest ones are several kilometres south

of the strange shape around New Zealand.

- But could this be some other type of subsea mountain?

- Is there a potent tectonic zone around New Zealand

strong enough to create this massive site?

NARRATOR: There are impressive volcanic forces nearby.

Could these explosive powers be the secret

to this stunning formation?

- New Zealand has about 24 volcanoes spanning both the north

and south islands, around half of these are submarine.

KOUROUNIS: They're located right on the Pacific Ring of Fire,

an active volcanic zone, which dominates

about 40,000 kilometres of the Pacific Ocean.

YATES-ORR: So is this volcanic zone behind the vast raised plain

around New Zealand?

NARRATOR: But when scientists look closer,

key evidence is missing.

RISKIN: If this underwater landmass was volcanic,

you would expect it to be made out of basaltic rocks

from the fairly recent past, because basalt is a kind of rock

that forms when lava cools.

GUY: But samples drawn from this mysterious mass uncover

completely different types of rock.

It's formed from granite, and limestone, and sandstone.

This is really surprising to find under the ocean.

KOUROUNIS: Usually, this kind of rock is found on dry land,

so what is it doing over 2,000 metres underwater?

RISKIN: This is a fascinating mystery.

Is it possible that this land mass used to be above sea level,

and then it somehow sank?

HOFFMAN: For more than 20 years, geological surveys in this area

collected samples to try and solve the mystery in the South Pacific.

YATES-ORR: They didn't have enough evidence

because they didn't have the technology or the vantage point

we have now.

NARRATOR: In 2017, satellite imagery helped crack this case

with a view from far above.

- With all this evidence about composition, elevation and size,

there's only one thing this could be.

KOUROUNIS: Scientists have identified that this is actually

an eighth continent, and they've called it "Zealandia."

NARRATOR: Even though Zealandia meets a lot

of the scientific criteria to be called a continent,

this isn't an open-and-shut case,

because most of it is underwater.

RISKIN: We can now see from above

that about 94% of this eighth continent

is submerged underwater.

GUY: The remaining 6% above water makes up

New Zealand, Stewart Island, New Caledonia,

and many smaller islets.

- Researchers also found that Zealandia was surprisingly thin,

about 20 kilometres thick.

GUY: And it's that thinness of the continent that hints

at how it became submerged.

Continental crust is generally much thicker than oceanic plates,

around 40 kilometres versus 10 kilometres.

RISKIN: So the idea is that Zealandia broke off

of the continental plate, and got stretched thin

like taffy by tectonic activity,

until it was so short it didn't stick up outta the water anymore.

So it's still on top of the oceanic plate, but most of it is underwater.

KOUROUNIS: Now, Zealandia is believed to be the world's youngest,

smallest, thinnest, and most submerged continent.

It's an absolutely ground-breaking discovery.

NARRATOR: And this unprecedented find sparks more questions

about the secret history hidden on this submerged land.

- What more might Zealandia be able to tell us?

NARRATOR: An expedition searching for clues on the ocean floor

found something astonishing...

three-million-year-old fossils,

clues to life on the lost world of Zealandia.

- These fossils and bones prove

that a previously unknown penguin called "Eudyptes atatu"

lived in New Zealand tens of millions of years ago.

RISKIN: This is amazing because this extinct species could be

the missing link between the ancient penguins

and the modern penguins. And that would mean that Zealandia

is where the whole penguin diversification started.

GUY: It's likely Zealandia was once inhabited

by other sea birds and animals

that were able to migrate to and from other places, and evolve.

- This means that Zealandia is a significant part

of our biological history,

and there could be much more there to discover.

NARRATOR: This hidden eighth continent is a major discovery,

and contains far more mysteries to investigate.

- Zealandia will likely be explored for years and years to come.

- Could Zealandia appear on globes and world maps in the future?

We'll have to wait and see.

GUY: I find it incredible that something this large

and this significant remained hidden for so long.

I think it just goes to show how much we still have to learn

about what hides beneath our ocean surface.

NARRATOR: The sheer size of our planet's vast oceans,

towering mountains, and seemingly endless deserts

can hide countless mysteries.

But hundreds of satellites staring down from far above

can unveil their secrets.

Subtitles by Sky Access Services