Original subtitles

Volcanoes hold a special place in our consciousness.

Stories of the destruction

of the ancient Roman city of Pompeii continue to fascinate,

while terrifying visions of explosive fire and molten rock

play a key part in our nightmares.

But less well known are the horrors of pyroclastic flows:

avalanches of hot volcanic gases, ash and lava bombs

which can descend from steep volcanoes

at blistering speeds of up to 700 kilometers per hour,

vaporizing anything in their path.

A volcanic eruption is one of the most dangerous

and awe-inspiring natural disasters.

When a volcano erupts, it spews out clouds of ash,

lava...

and even volcanic bombs.

These are formed of molten rock

that has been blasted into the air

before hardening into solid lumps

of more than 64 millimeters in diameter

and falling back to earth.

The molten rock that emerges from a volcano

is called lava.

The liquid rock below the surface of the earth

is called magma.

When lava flows, it usually moves quite slowly

but still poses a serious danger

to property and human life.

There are four different types of volcano.

The simplest kind of volcano is called the scoria cone,

also known as the cinder volcano.

They can appear very suddenly

when gases propel lava high into the air,

where it breaks apart into small fragments, or cinders.

As they drop, the particles cool

and fall around the single vent to form conical hills.

Over time, the sides of a cinder cone volcano

can become very steep,

but they rarely grow larger

than about 300 meters tall.

Many cinder volcanoes are monogenetic,

meaning they will only erupt once before becoming dormant.

Famous examples of the cinder cone volcano

are Sunset Crater in Arizona,

a volcano that is 305 meters high

which first erupted around 1065,

and Paricutin, one of the youngest volcanoes on earth,

which appeared suddenly out of a cornfield

in West-Central Mexico in 1943.

The second type of volcano is called the stratovolcano,

also known as the composite volcano.

So there are very different shapes of volcanoes,

and that’s because of the different ways

in which they erupt,

and they build up material differently.

So a stratovolcano is the one that we associate

with the most explosive types of eruption.

And they’re capable of a very wide range of behavior.

But they build up those classic cone shapes

that we might associate with something

like Mount Fuji or Mount St. Helens.

These are the most violent

and dangerous kind of volcanoes.

They can be massive, sometimes reaching heights

of up to 3 kilometers.

The slopes of the composite volcano

tend to rise slowly at first,

and then become very steep with a narrow vent at the top.

They have a system of conduits that channel the molten magma

from deep within the earth to the surface.

Because they can deliver so much magma to the surface,

they can grow thousands of meters tall.

The stratovolcano can explode with extreme violence,

and then go dormant for tens or even hundreds of years

before coming back to life again.

A famous example is Mount St. Helens

in the Pacific Northwest region of the United States.

This stratovolcano last erupted in 1980,

killing 57 people

in what was the deadliest eruption in American history.

Before Mount St. Helens,

it was a reasonable assumption to make

that the big eruptions from volcanoes come out the top.

But Mount St. Helens taught us

that sometimes that’s not the case.

It blew a giant hole out the side.

We’re still analyzing data from Mount St. Helens,

because it’s still valuable to science

and there’s so much more to learn.

What’s special about Mount St. Helens

is that we’ve seen the beginning,

during and after effects of the eruption,

which means that we can piece together warning signals

and the effects of the eruption itself.

Because it’s fairly well studied,

we have a mass of data and understanding

and knowledge to then ask advanced questions upon.

And it’s these advanced questions,

with a context of what we do know about Mount St. Helens,

that allows us to make more progress elsewhere.

The third type of volcano is the shield volcano.

These are broad, dome-like structures,

and when viewed from the air, look like shields,

hence the name.

Mauna Loa and Kilauea in Hawaii

are both examples of shield volcanoes.

The largest volcano known to humanity is a shield volcano,

estimated to be the size

of the entire Hawaiian Island chain.

Fortunately for us, it is not on this planet.

It is a dormant shield volcano found on Mars,

called Olympus Mons.

Its peak is more than twice the height of Mount Everest,

making it the tallest mountain in the entire solar system.

The final type of volcano is called the lava dome.

A lava dome is when you have a type of magma

that comes out as lava,

that’s very, very slow and stiff.

And so instead of flowing away from the volcano top,

it piles up at the top of the volcano

and creates these big features

that are as tall as they are wide.

To a sort of untrained observer,

going up to a lava dome might be slightly disappointing,

because it can look a little bit

like a giant gray mass of rubble.

But when you fly over it,

you can see cracks into the interior.

So only a few tens of centimeters down,

it’s glowing red, and you can see steam coming off it.

And when they collapse, they generate things

called pyroclastic flows.

So they feel powerful, lava domes.

So it’s a pretty intense experience

going that close to one.

And the thing about lava dome eruptions

is that they can suddenly change their behavior.

So if you’re quite close to them,

there’s always this sense of approaching menace,

and we have to be really careful about how we approach them

and make sure that the people who are further away

and monitoring the volcano are in contact with us.

A good example of a lava dome volcano

is Mount Pelée, an active volcano

on the Caribbean island of Martinique.

Its last major eruption was in 1902,

when it destroyed the port of Saint-Pierre

and killed 30,000 people,

some 15 percent of the island’s population.

There are over 500 volcanoes in the world

that have erupted at least once.

Fifty of them are in North America.

An index was devised in 1982

to measure the force of an eruption

so that different events could be compared.

Called the Volcanic Explosivity Index, or VEI,

it is determined using a range of factors,

including the amount of material

vented from the volcano,

the height of the eruption cloud

and how long the eruption lasts.

This is expressed on a scale of zero to eight,

with each number representing a tenfold increase

in the explosive power of the eruption.

One of the most terrifying and deadly phases of an eruption

is undoubtedly the pyroclastic flow.

Sometimes referred to as a "glowing avalanche,"

the pyroclastic flow is formed of many different components.

There are rock fragments

following the volcanic explosion,

particles of lava and magma that are mixed with air,

water and gas from the eruption,

as well as water vapor from melted snow and ice.

This extremely hot fluidized mixture

can reach temperatures of 1000 degrees Celsius

and surge down the slopes of the volcano

at astonishing speeds of up to 200 meters per second.

A pyroclastic flow will instantly incinerate

anything in its path.

And when you consider the heat of the flow,

its speed and its reach,

it is one of Mother Nature’s most terrifying

and deadly forces.

Another deadly event resulting from volcanic eruptions

is the ash landslide called a lahar.

Lahars are a hot or cold combination

of volcanic debris and water

which advance down the slopes of a volcano,

often moving down a river valley.

They tend to occur on or near stratovolcanoes.

While its initial flow may be quite small,

a lahar can quickly grow in volume

as it sweeps up soil, trees and rocks,

even bridges and buildings.

Lahars can easily grow

to more than 10 times their initial size

as they roar downhill.

In steep areas, lahars can travel

faster than 200 kilometers per hour.

Pyroclastic flows can trigger lahars

when super-hot rock debris melts snow and ice

as it rushes down the volcano’s flanks.

Torrential rain during or after an eruption

can mix with the fine particles of ash and other debris

on the volcano’s slopes and quickly turn

into a dangerous and fast-moving lahar.

Rain can cause lahars

a long time after an eruption,

especially if vegetation has not managed

to consolidate the deposits on the slopes of the volcano.

There are many volcanoes in the world

that have not erupted in years,

while others are in a very active phase,

perhaps not erupting violently,

but with smoke, steam,

ash and lava constantly venting.

It’s the simplicity of the characterization

of extinct, dormant and active that holds value,

because they have different issues with each state.

If you have an active volcano in your back garden,

you need to pay attention to it all the time.

If you have a dormant volcano in your back garden,

maybe you should be keeping it in mind,

but it might not change

the day-to-day activities that you have.

If you have an extinct volcano in your back garden,

then you’re pretty happy that it’s not going to erupt.

And if an eruption happens, it won’t be from that point.

But as we learn more about volcanoes,

and particularly as we apply new technology,

more sensitive technology, more sophisticated technology,

the line between dormant and active

is becoming a little blurred.

And that’s because the new technology can hear things

that we couldn’t before.

So if we deploy this technology

and we get signals from a dormant volcano,

is it waking up or was it never truly asleep?

According to the definition of "extinct,"

it means no activity in the last 10,000 years.

Now, 10,000 years is a long time, even for a volcano.

Normally, they erupt more frequently than that.

So if you go to the volcano

and measure the age of the youngest rock

and that’s more 10,000 years,

then it’s declared extinct.

When experts assess

which volcanoes are the most dangerous in the world,

they take several things into consideration:

How many people live nearby,

the types of magma that emerge during eruptions

and each volcano’s eruption history.

A volcano that has laid dormant for a long time

can pose a higher risk

because of the mounting pressure inside it.

Taking all this into account means that Mount Vesuvius,

a stratovolcano located just 14 kilometers away from Napoli,

is also one of the most dangerous.

While experts disagree

on the precise number of incidents,

it is clear that Vesuvius has erupted at least 30 times

since its iconic eruption in 79 A.D.

The last eruption occurred in 1944

when 26 people were killed.

For the Romans, there wouldn’t really have been

a living memory of it as an erupting volcano.

But in Italy, there are other volcanoes

that erupt pretty frequently,

so probably they knew it wasn’t entirely benign.

And in the run up to the eruption,

we do know there were known signals

that things weren’t quite right down below.

There was a big earthquake,

and then we think there were sequences

of these smaller, little earthquakes

as that magma’s trying to make its way up towards the surface

in the run-up to the eruption.

And the Romans would have felt those,

and they would have been fairly intense, I would imagine,

in the few days leading up to the eruption itself.

There are plans in place to evacuate 600,000 people

should Vesuvius show signs of erupting again.

Active volcanoes in densely populated areas

obviously pose the biggest threat to life.

In other places around the world,

there are volcanoes that erupt very frequently.

So the big contrast from Vesuvius is Stromboli,

which the Romans called

the Lighthouse of the Mediterranean.

And that’s a little island that had a little eruption

that happens every 10, 15 minutes.

It erupts extremely regularly.

So the populations who live with those sorts of volcanoes

tend to live with it in a different way.

The Volcano de Fuego,

a stratovolcano situated less than 44 kilometers

from Guatemala City,

the capital of Guatemala in Central America...

has erupted 600 times since 1542,

including the last explosive eruption in 2012

that forced 11,000 people to flee the area

but luckily did not result in any loss of life.

For many people living in the shadow of the volcano,

it was an uncomfortable reminder

of the awesome power of the Volcán de Fuego

sitting right at their doorstep.

But when the volcano suddenly exploded

just before midday on the 3rd of June, 2018,

many of them had no time to evacuate.

It spewed a cloud of ash and lava

10 kilometers into the air.

The explosion caused the rocky surface of the volcano

to shatter into dust.

It mixed with ash and superheated gas

into a pyroclastic cloud of death

that engulfed the villages

of San Miguel Los Lotes

and El Rodeo,

instantly killing more than a hundred people.

The 3700-meter-high volcano

continued to erupt for more than 16 hours.

After the initial explosion,

a stream of lava spewed down the side of the mountain.

Guatemala’s coast was also hit by an earthquake,

though there were no reports of damage.

Hundreds of emergency and military personnel

faced appalling conditions to retrieve bodies from the lava.

The ash and lava was still so hot

that the soles of some firefighters’ boots

were melted away.

The firefighters were unable to reach people

they knew were trapped in villages

on the slopes of the volcano,

because roads leading to the area

were cut off by pyroclastic flows.

It suddenly dawned on them

that the volcano’s activity

had started to increase again after the initial blast.

Gas, mud and ash flowed down the slopes of the volcano.

As stones hailed down on them,

darkness fell as the sun became obscured

by more ash clouds spewing into the air.

Emergency personnel were forced to retreat from the villages

until early the next morning.

Guatemalan President Jimmy Morales

declared a state of emergency

and ordered the population

to heed warnings from emergency officials.

He also declared three days of national mourning.

Rescuers that reached the town of El Rodeo

reported that it had been buried in heavy ash

which could have reached temperatures

of up to 700 degrees Celsius.

They poked metal rods into the ground,

releasing clouds of smoke into the air,

showing that temperatures below the surface

were still extremely hot.

Two days after the initial explosion,

volcanologists reported that the eruptions

seemed to have ended for the moment.

Soldiers and firefighters continued searching

for those missing, but the death toll had climbed to 69.

By now, the ash from the eruption

was covering a radius of 19 kilometers

around the volcano.

Satellite footage of Fuego revealed

that the massive dark-gray cloud from the eruption

was visible from space.

By Wednesday, the death toll had climbed

to 75 people, and a further 200 were still missing.

Officials were worried that a downpour

of additional rock and debris could destabilize the slopes,

sending lethal lahar flows of water

mixed with volcanic ash and debris

hurtling down the volcano.

They called everyone off the mountain,

halting the recovery effort for a whole day.

Some relatives of the missing defied police roadblocks

and went to their family’s houses.

They tried to dig through the rapidly hardening ash,

which they feared had buried their relatives,

using whatever tools they could get their hands on.

There were concerns that the government’s focus

seemed to be on getting the highway cleared

and not recovering the bodies of the dead.

By the time the authorities could get

heavy digging machinery to the buried towns,

it became clear how little chance of survival

there had been for anyone trapped in the path

of the pyroclastic flows.

Amid scenes of apocalyptic devastation,

the death toll reached 112,

with 197 still missing.

Many people didn’t accept

the government’s official death toll.

They were convinced that the scale of fatalities

was being underreported.

It emerged that scientists

at the National Institute of Seismology, Volcanology,

Meteorology and Hydrology had warned officials

in the early morning on the day of the eruption.

But despite these warnings,

the national coordinator for disaster reduction

did not issue a red alert and evacuate communities.

Even though nearly 200 people died there,

the area around the volcano will continue to be inhabited.

The deaths in the Fuego eruption

were mainly attributed

to the lightning-quick pyroclastic flows

typical of the stratovolcano.

And although it brought death and destruction to a wide area,

Fuego’s reach was not nearly as far

as an event that occurred in April 2010,

when a volcano in Iceland suddenly erupted,

spewing a vast plume of ash

that spread across much of Europe.

The eruption of Eyjafjallajökull

became an international event,

as around 20 countries closed their airspace

and forced flight cancellations

that affected 10 million travelers

as well as thousands of businesses

that relied on air freight.

The volcano Eyjafjallajökull

had been dormant for nearly 200 years

when it burst into life in March.

Although relatively small,

at a rating of one on the Volcanic Explosivity Index,

it was a mere suggestion of the violent activity

that was to come.

On the 14th of April, 2010, earth tremors were reported

under the summit of the Eyjafjallajökull glacier,

in the south of Iceland.

In the lead-up to the eruption,

one of things that you’re gonna be most aware of

is that space problem the magma’s creating.

So it will generate lots of earthquakes and shaking,

there’s maybe bulging.

But that kind of slow run,

the slow time scale of volcanoes erupting,

becomes really fast once the volcano starts to erupt.

So if it’s an explosion,

there will be a sudden change.

And you will start to see a huge pulse

of gas, ash,

and bits of solid magma

flying out of that volcano.

And there’s been slow-motion footage taken

that’s shown there’s even a sound wave

that comes out ahead of this because this happens so quickly.

The force of the volcanic eruption

under the Eyjafjallajökull glacier

sent a plume of ash 8.5 kilometers into the air.

Heavy ash fell over the areas to the south,

with police reporting that visibility

had been severely reduced, in some places down to zero.

Icelandic air-traffic control received two reports

from commercial aircraft

of steam plumes rising from the glacier.

But because the glacier remained covered in cloud,

it was impossible to see the extent of the volcanic activity

occurring on the ground.

But there were alarming clues

about the severity of the eruption.

The water level in two nearby rivers

had suddenly risen by over half a meter,

showing that there had been substantial melting

of the volcano’s glacier.

Concern grew about the ash plume,

which by now was engulfing much of Northern Europe.

It contained large amounts

of microscopic abrasive particles of silicates,

or glass fibers, capable of clogging jet engines.

Once ingested, the particles can melt,

causing the engine to flame out and stall.

Because of the danger of catastrophic failure

of any aircraft flying into the ash

and to ensure the safety of passengers,

aircraft were left idle on the tarmac

of some of Europe’s busiest airports.

Practically all flights

over mid, north and Eastern Europe

were canceled until further notice.

It’s really a bit strange to think

that a volcano would affect a flight.

But, yeah, so...

It’s not something you expect to happen.

Other flights were either rerouted north over Greenland

or south over Spain to avoid the cloud,

which now stretched 1930 kilometers

from Iceland to Northern Spain.

The plume of ash was further carried along

by Atlantic winds and later forced the closure

of 15 airports in northern Spain,

and was expected to expand into parts of France.

More than 100 flights were canceled

at Portugal’s three international airports.

It was the most serious disruption

of European air traffic since the Second World War.

As the eruption continued,

meltwater from the summit of Vatnajökull,

one of the largest glaciers in Europe,

increased dramatically.

It was estimated that the volcano was ejecting

about 750 tons of magma every second,

much of it through a fissure

that was already 2 kilometers long.

Tuesday, the 20th of April,

most of the ice in the crater appeared to have melted.

But it was another month until the eruption had subsided

to the point that no further lava or ash was being produced.

Finally, in October 2010,

scientists monitoring the volcano declared

that the eruption had officially ended,

although the area was still geothermally active

and might erupt again.

The explosive activity might drop down for a period time,

but then we will have, over an extensive period of time...

Months to even years.

...intermittent explosive eruptions.

Taking stock of the devastation caused by the eruption,

experts estimated that at least 55 million cubic meters of ice

melted during the eruption.

It’s a scientist’s job to report the facts

and explain what would happen if there were an eruption,

and then recommend a course of action

that will provide more information to decision makers.

Now governments will invest more in monitoring

and volcanology in general

because the risk to society is growing.

Our world is more interconnected now.

Look at what happened in Eyjafjallajökull.

If that happened 200 years ago,

it wouldn’t have had nearly the same impact

as it did on the world economy,

through airlines, et cetera.

So now disruption,

indirect disruption from volcanoes,

has a large impact.

And that just underscores

that we need to urgently understand what happens

before a volcano erupts

so we can put in place plans

to mitigate against those hazards.

Every volcanic eruption is different.

Eyjafjallajökull caused mayhem because of its ash cloud,

and Fuego with its terrifying pyroclastic flows.

But when Kilauea,

a shield volcano on the island of Hawaii,

erupted in May 2018,

it demonstrated a very different kind of behavior.

Kilauea is the youngest volcano on the island of Hawaii

and looks like a bulge on the side of Mauna Loa,

a much bigger volcano.

It rises 1227 meters above sea level

and makes up about 14 percent

of the land area of the Big Island.

Legend supposes that the lava lake at its summit

is home to Pele, the Hawaiian goddess of volcanoes,

indicating the significance of Kilauea

to the people of Hawaii.

It provides us a window of a deeper level than usual,

because it hasn’t been modified on its way to the surface.

The fact that it’s coming up so rapidly means

that’s it preserving the information

that it carries from depth.

Although it had been erupting continually since 1983,

the people on Big Island

had learned to live with the volcano.

In fact, it was seen in a very positive light,

attracting tourists eager to see

such a dangerous force of nature close up.

Obviously the geothermal energy around volcanoes

is a wonderful benefit that they bring,

with an infinite supply of power and hot water.

But also, for many populations,

these geothermal areas are fantastic tourist attractions.

In places, people could get so close to the lava

that it became a tradition to take postcards

and burn one corner in the flow before sending them off.

But that all changed when a magnitude 5 earthquake

struck the Big Island

and triggered a violent and dramatic eruption,

turning the tourist volcano

into a dangerous threat to life and property.

The day before, on Wednesday, the 2nd of May,

seismologists had noticed significant volcanic activity

coming from Kilauea.

As the volcano blasted solid and molten rock fragments

and gases into the air,

the authorities immediately told residents

in the surrounding area to make preparations to leave.

So at 1:30, after we all kind of got up and said, "Okay, well,"

I opened the door to see if I could see anything.

And, of course, I could see the orange glow

coming through the forest.

And, um, I said, "Wow!"

And I can hear crackling,

and we’re all kind of just going, "Whoa."

I said, "Well, we’re not leaving until we hear the siren."

And the moment I finish the sentence,

the siren went "whoop!"

We all looked at each other and says,

"Yep, everybody in the car."

And out we went.

When the volcano started to spew lava

into residential subdivisions

in the Puna district of the Big Island,

compulsory evacuation orders were released.

The volcano became increasingly active.

There were quakes, with hundreds of tremors

of magnitude 2.5 or higher.

But shortly after midday,

a quake measuring 6.9 knocked out power

to thousands of islanders,

causing sea-level fluctuations which terrified residents,

fearful that it would generate a tsunami.

Fortunately, the sea remained relatively calm,

but lava flowed down the sides of the volcano

and gases spewed into the air.

Homes were destroyed as eruptions increased.

During the 2018 eruption,

the magma moved and created pressure

that then resulted in the opening of new vents

for that magma to pour out of

during the course of its eruption,

sometimes right in the middle of a road.

On a volcano like that in the Big Island in Hawaii,

there’s an almost continuous supply of magma

coming into the base.

But what-- It’s one of the best monitored volcanoes

in the world, if not thebest monitored volcano in the world,

and what they picked up were signs

that new magma was coming into the system,

causing pressurization and causing the ground to move up.

As news of the eruption

and dramatic footage showing houses being engulfed

by red-hot flows of molten lava was beamed around the world,

people began to wonder why anyone would choose

to live near an active volcano.

Volcanoes and their immediate environment

offer a lot of benefits to people who live around them.

So they create soil that can be more fertile

than surrounding area.

There’s a lot of volcanoes in the tropics,

and they are a little bit of higher land

that’s a little bit more pleasant to live in.

They provide geothermal energy

and soil and rock resources as well.

And when you think about how often volcanoes erupt, it’s--

In the grand scheme of things, it’s not very often.

So I think often people live around volcanoes

because it’s worth enjoying all of those benefits

for the small but finite risk

that it’s going to erupt during their lifetime.

One of the things that’s very challenging

about volcanic eruptions

is that they aren’t just instantaneous.

A volcano can be in eruption

for many days and weeks and months.

And so sometimes what we’re doing

is we’re asking people to move away permanently

or for very long periods of time,

and that’s a difficult thing to do.

People are attached to where they live,

but also in many volcanoes around the world,

people are dependent on that area for their livelihoods.

Once a volcano’s erupted,

it obviously creates a lot of damage,

and people may want to build

quite close to where that damage was created.

And I think one of the things

that we are doing now as volcanologists

is we’re recognizing we have to work in partnership

with the communities who are impacted,

to try and work out the best way to choose the place

that it’s going to be the safest to build back

and try to ensure that they’re ready,

as much as they can be, for future eruptions.

A week after the first new eruption,

12 more fissures opened up in Leilani Estates

on Hawaii’s Big Island.

The new points of lava flow

showed that the eruption of Kilauea was ongoing.

There were now major disruptions

to life on the island, with more evacuations needed.

On Wednesday, the 9th of May,

Kilauea volcano erupted again

as two new vents released toxic gases into the atmosphere.

The Civil Defense Agency ordered

the immediate evacuation of residents

from Lanipuna Gardens

on the east side of the Big Island.

Scientists noticed a drop in the lava lake

at the summit of the volcano.

They warned that this might create conditions

for an explosion that could send ash

and refrigerator-sized boulders shooting into the air.

The following day, the authorities warned

that mass evacuations might be required.

Levels of sulfur dioxide reached dangerous levels,

which could prove fatal if inhaled,

and residents were at risk

from magma bursting out of the ground.

People who are frail or who have underlying COPD,

that’s chronic lung disease,

we worry about them quite a lot.

That can be made much worse by spikes in sulfur dioxide.

So checking people’s lungs,

making sure they have medications,

making sure we evacuate them further away if they’re bad.

By the following weekend,

there were now 17 open fissures

since the lava flows began on the 3rd of May.

On Wednesday, the 16th of May,

following the rise of an ash plume

several thousand meters into the air,

the Hawaiian Volcano Observatory issued a code red,

warning residents that additional activity

could be expected.

They cautioned that at any time,

activity could become more explosive,

producing ballistic projectiles near the vents.

The following day, another 2000 people

were forced to abandon their homes.

Several schools closed because of the risk

from high levels of sulfur dioxide.

I, uh-- I’ve already evacuated everything.

I just came down to say, um, goodbye to my neighborhood

one last time.

There were also earthquakes around the volcano

which damaged many roads, including Highway 11

near the entrance of the Hawaii Volcanoes National Park.

Fast-moving lava spewed into a region

southwest of Leilani Estates,

cutting off about 40 homes in a remote region.

Hawaii’s County Civil Defense warned

that brushfires caused by the burning lava

were threatening homes in the Malama-Ki Forest Reserve.

Residents were immediately evacuated.

Then scientists noted something worrying.

The lava spattering out of fissures in lower Puna

seemed to be different.

It was coming out faster and more dramatically.

That contrasted with the first two weeks of the eruption,

when activity was largely a slow oozing

of a very thick, pasty lava that wasn’t moving very far.

Scientists explained that the lava

of the first two weeks was probably from magma

stored underground making its way onto the surface

as a result of the fresh magma

pressing down from Kilauea’s summit.

The lava now coming out of the latest fissures was different.

Scientists braved noxious fumes and spattering lava

to gather samples that would be crucial for research.

One of the most important things for volcanologists

in these sorts of situations is really teamwork.

So it’s making sure that there’s people

who have their eyes on the instruments

and that you are not doing anything that is too risky

and that you think about it very carefully in advance.

And so when something like that happens,

what you’re really thinking is, "This is quite scary,"

but you have to have strong trust and reliance

in the team that are around you

so that you’re going to get out in time.

A chemical analysis of the samples showed

that the fresh, more violent magma

had come down from the summit of Pu’u O’o,

a volcanic cone situated in the eastern rift zone of Kilauea.

This was fresher and hotter magma

with the potential to produce lava flows

that moved with greater ease

and therefore covered a wider area.

A wall of lava blocked part of a coastal road,

cutting off a key escape route for residents

and hampering evacuations.

Fresh lava flows overwhelmed more houses

while the ash plume continued to ground flights in the area.

The situation for residents on Big Island

was steadily worsening.

Lava flows forced the shutdown of a geothermal energy plant

that normally provides about a quarter

of the island’s electricity.

By now, the lava had reached Big Island’s south coast.

As the lava plunged into the ocean,

it caused some of the 1000-degree-Celsius

molten rock to explode into lava bombs

that shot hundreds of meters into the air.

The lava also reacted with the salt water

to produce poisonous gases,

and triggered further safety warnings.

When the lava flows reached the Pacific,

it created thick hazardous clouds known as laze,

which is a kind of hot and corrosive gas mixture.

The clouds contain hydrochloric acid

and glass particles, which can cause irritation

and breathing difficulties.

Even the wispy edges of the clouds

can be enough to cause irritation.

Residents were told to stay away from any ocean plume,

since they traveled on wind

that was liable to change direction without warning.

But they need to really pay attention to what’s happening,

because anything can happen.

Mother Nature, Madame Pele, can come out at anytime.

But we don’t wanna cause panic.

We want them to just be well informed.

So volcanology’s a very exciting and dynamic science,

because volcanoes throw all sorts of challenges at us.

They’re capable of erupting in all sorts of different ways,

and they can change how they erupt

during the course of even one eruption,

and also what they can do is erupt for long times.

And that’s what we are trying to face:

the challenge of figuring out how to forecast that,

and forecast those changes

during the course of an eruption.

And all of these mean that there’s all sorts

of new understanding and techniques

that improve how we do that all the time.

The lava flow continued unabated.

A huge river of molten rock

crept several kilometers across the landscape

towards the eastern tip of the island.

It swallowed two entire seaside housing estates.

It took just a matter of days

for a relentless wave of lava

over 4 meters high and 800 meters across

to bury hundreds of homes.

It even vaporized the island’s largest freshwater lake.

Within four hours, the 400-year-old Green Lake,

which was about 60 meters deep

and had been a popular swimming spot,

completely disappeared under a mass of molten rock.

In mid-July, a tiny island less than 10 meters wide

suddenly appeared off the coast of Big Island.

It wasn’t long before lava filled in the gap

between the new island and the shore,

and it became part of the changing coastline

caused by Kilauea’s eruption.

It was a reminder of how the Hawaiian Island chain

was first formed.

The Big Island of Hawaii is around a million years old,

but it’s part of a chain of volcanoes,

and the oldest chain of those that stretch across the Pacific

is about 80 million years old.

And that observation that the volcanoes seem to get older

as you go west across the Pacific

is part of the evidence

to say that there’s a hot spot in the mantle underneath

that is more or less fixed,

but as the tectonic plate moves across

like a conveyor belt,

the volcanoes that are produced

start traveling off towards the west.

Melt within the earth travels upwards

until such time that it hits the surface.

Now, that could be the surface of a continent

or, in the case of Hawaii,

it’s the bottom of the sea floor.

And it starts a small volcano.

And over time, it builds up and builds up.

And if it builds up fast enough,

it will reach the top of the sea.

Throughout the eruption,

a remarkable transformation had occurred

to the lava lake crater at the top of Kilauea.

The Halema’uma’u crater at the summit

had been rumbling nonstop

since the eruption began in early May.

Then the lava lake began to drain quite suddenly

as the reservoir of magma beneath it

began dumping its contents out of fissures

on the volcano’s slopes.

The United States Geological Survey sent a drone

into the crater to see the dramatic changes.

It showed that the steep walls of the crater

were collapsing inwards,

with large chunks of the rim,

including a parking lot

which served the Hawaii Volcanoes National Park

swallowed by the crater’s collapse.

The powerful activity was triggered

by the flow of magma away from the summit crater

eastwards toward the rift zone.

As the crater got deeper,

the walls began to collapse inwards,

which led to further explosive releases

of gas, ash, and other volcanic debris.

The lava lake in the Halema’uma’u crater

in the volcano of Kilauea

started draining from the inside.

And as each phase of the draining happened,

the eruption site flared up.

And this is part of the evidence to link the two phenomena

and suggest that this is a linked plumbing system

in the lower Eastern Rift Zone of Hawaii.

The magma is interconnected,

and as each cycle of the volcano of Kilauea occurs,

it’s becoming more and more evident

that the behavior of the lava lake can be used

to understand the eruption site itself.

On the 9th of August,

the lava flow finally stopped expanding.

And with the lull in activity on Kilauea continuing,

volcanologists are saying that the eruptive period

which first began in 1983

and continued right through

to the recent and most violent cycle

is over.

So one of the things that was amazing about the eruption

that happened in 2018 is that it was exceptional.

There were huge amounts of material,

we opened up new vents,

and that caused a shift in the magma system.

So before that, it was erupting continuously for decades.

It’s quite likely now

that it may remain quiet for a few years.

That’s what happened the last time it had

one of these really big eruptions.

But what’s for sure is there’s still magma

underneath the ground there,

and that the shift will probably cause it to erupt again,

and probably in the lifetime of the people

who live on the island.

If and when eruptive activity does eventually return,

it will be classified as an entirely new eruption.

A period of constant eruption of Kilauea

lasting over 35 years will have come to an end.

The simple answer is, we don’t know

exactly what will happen to the lava lake.

Will it refill? Will it be a hole in the earth

for times to come?

But what we do know about Kilauea

is that it has gone through cycles

of repeated lava lake formation and draining.

So one reasonable idea about what might happen

is that the lava lake will refill

and an eruption will happen as it drains.

Volcanology is a fairly new science

in that there’s lots of different sciences

that are trying to understand the same phenomena.

You can approach it from a chemical point of view,

you can approach it from an atmospheric point of view,

you can approach it from a geophysical point of view.

And it’s as these fields emerging

and is called volcanology,

that’s only happened in recent decades

as a modern science of volcanology.

One thing we do know

is that volcanoes will continue to cause death and destruction

for as long as there is life on Earth.

And whether it’s the horrors of pyroclastic flows,

the choking gas,

or the molten lava,

volcanoes are truly one of Mother Nature’s

most combustible killers.