When did volcanoes start existing?

Volcanoes have been erupting on Earth for BILLIONS of years, and they’re still creating new landscapes today! Volcanoes can seem mysterious and scary, but people all over the world have learned to live in close proximity to active volcanoes. Today we answer questions you’ve sent us about how they form, how they erupt, what magma/lava is, and how volcanologists work to predict when they might erupt. Our guest is Freysteinn Sigmundsson, a volcanologist and professor at the University of Iceland. 

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Episode Transcript

Jane (00:20):
This is But Why
Public. I'm Jane Lindholm. Onthis show, we take questions
from curious kids just like you,and we find answers. You know,
it's been a big summer forvolcanoes. You might have heard
that back in July, a volcanoerupted in Iceland, and then in

(00:41):
August, a big earthquake struckoff the coast of Russia,
triggering multiple volcaniceruptions in the region. While
the eruption in Iceland wasrelated to a couple of years of
ongoing volcanic activity inthat region, the one in Russia
had been dormant - inactive,quiet - for hundreds of years.

(01:01):
And as we're putting thisepisode out in September of
2025, an active volcano in Japanhas been spewing ash into the
air. The SmithsonianInstitution's National Museum of
Natural History in the UnitedStates keeps a list of all the
active volcanoes and volcanicactivity in the world, and says

(01:21):
that at any given time there aretypically 40 to 50 continuing
eruptions, and out of those,generally around 20 will be
actively erupting on anyparticular day. I did not
realize there was that muchvolcanic activity all the time.
You definitely don't want to benear a volcano while it's

(01:43):
erupting, but if you ever get achance to view it from a safe
distance, volcanic eruptions arefascinating. You might see
bright, hot, orange lava flowingdown mountain slopes, making
really cool patterns, and whenyou look up into the sky, you
could see giant plumes of smokefilling the air. Melody, Joey

(02:03):
and I were kind of hoping to getthat safe viewpoint to watch an
eruption while we were inIceland earlier this summer. And
it turns out we just missed one.It was only a couple weeks after
we left that Iceland'sSundhnúkur Crater row erupted
right near where we had been. Ifyou don't live in an area with
volcanoes, they can seem reallymysterious. Why do they erupt

(02:26):
and how? And how can we know inadvance so we can make sure to
stay safe? If you live in areasthat are very volcanically
active, you may already know alot about volcanoes and how to
stay safe around them. You'vesent us a lot of volcano
questions over the years, andsince Iceland has so much
ongoing volcanic activity, wefigured while we were there,

(02:47):
whether we could see a liveeruption or not, we should find
someone who studies volcanoes inIceland who could answer all of
your questions.

Freysteinn Sigmundsson (02:57):
My name is Freystein Sigmundsson. I work
at University of Iceland. We doresearch to better understand
how our planet is working. And Istudy volcanoes.

Jane (03:08):
Does that mean you're a volcanologist?

Freysteinn Sigmundsson (03:10):
Yes, volcanology is a very broad
field. You can study the rockson a volcano. What I try to do
is to study what is inside thevolcanoes.

Jane (03:19):
Iceland has about 30 volcanic systems with about 130
volcanoes within those systems.You can think of a volcanic
system as a network ofvolcanoes. So it's a good place
to be if you're a volcanologist.And living so close to so many
volcanoes when he was youngmadeProfessor Sigmundsson really

(03:39):
curious.

Freysteinn Sigmundsson (03:40):
When I was a young kid, there was a
period of very high activity oferuptions here in Iceland. So I
saw a lot of coverage of that,and I guess that pushed me into
the study of volcanoes.

Jane (03:52):
I did not see volcanoes growing up in New England, the
northeastern part of the US. Andthere's a reason for that. Most
volcanoes form at the boundariesof Earth's tectonic plates,
these large pieces of the outershell, the lithosphere of the
earth. Iceland sits right on topof the Mid-Atlantic Ridge, where

(04:12):
the North American and Eurasiantectonic plates are slowly
drifting apart. And Iceland is ahot spot, meaning the underlying
ground is warmer than thesurface area above. These
factors make for a lot ofvolcanic activity. But to get
volcanic activity, you have tohave a volcano. And what's a

(04:33):
volcano?

Freysteinn Sigmundsson (04:34):
A volcano is, in essence, a crater
that has erupted a magma, and inmost cases we would expect it to
have erupted more than once, soit builds up some kind of a
mountain.

Jane (04:46):
The crater is at the top of the volcanic mountain, but
it'll look a little bit likesomebody's taken a big scoop
out, leaving a bowl-shaped,round hole right at the top.
That's the crater. Do you knowwhat magma is? I. Here's how
Professor Sigmundsson explainsit.

Freysteinn Sigmundsson (05:03):
What is inside volcanoes. We call it
magma, molten rock. You canthink of it as a human body. We
have blood inside our humanbody. Volcanoes have magma.

Jane (05:16):
This molten rock, magma, is extremely hot. So hot that it
has become liquefied. It getsthat hot because the core of the
Earth is really, really hot. Aneruption happens when more and
more magma accumulates under thesurface, building pressure. The
magma can move upwards throughcracks or weakness in the

(05:39):
material around it, making itsway up and then breaking through
the top layer of the Earth'ssurface, and boom! That liquid
rock plus gas and ashes come outonto the surface in an eruption.

Freysteinn Sigmundsson (05:51):
We have basically two types of volcanic
eruptions. In one type oferuption, magma comes out of
volcano and flows on the surfaceof the Earth like a liquid. The
magma changes into lava, and itjust solidifies as black rock on
the surface. The other type oferuption is explosive, and they

(06:12):
are often more dangerous. Liquidthat is inside the volcanoes,
when it comes to the surface ofthe Earth, it explodes into tiny
particles and goes up into theair. And it can stop air
traffic. And there can be somuch of this particles that it
becomes completely dark.

Fritz (06:28):
My name is Fritz. I am five years old, and I live in
Fairview Park, Ohio. What wasthe first ever volcano to
explode and turn into magma?

Luca (06:40):
I'm Luca from Pasadena. How many years did volcano
starting existed?

Jane (06:47):
Luca is wondering how many years ago did volcanoes start
existing? And Fritz is wonderingif we know what the first ever
volcano to explode was.

Freysteinn Sigmundsson (06:57):
The existence and evolution of our
planet is all about volcanoes.So the first volcanoes were
really born when the planet wasforming. We don't have a name
for the first volcano, so wecannot say what was the first
volcano, but we can ask otherquestions, like, if you are in

(07:18):
some specific region, we canask, when did the first
volcanoes form in this region?And often the time scale, or the
time for that is measured inmillions of years. Like, I live
in Iceland. Iceland is an islandin the middle of the ocean, and

(07:38):
the reason Iceland exists arevolcanoes. And Iceland started
to form as an island about 20million years ago. That is when
the first volcanoes appearedhere. And typically a volcano
here in Iceland is about half amillion years. So mankind, we

(08:01):
are very small in comparison tothe lifetime of volcanoes.

Navy (08:07):
My name is Navy. I live in Meridian. How do volcanoes
erupt?

Boaz (08:13):
My name is Boaz. I'm from Israel. I'm eight years old.
What is the pressure that makesa volcano erupt?

Oliver (08:21):
My name is Oliver. I live in Watertown,
Massachusetts, and I'm six yearsold. How do volcanoes erupt?

Zoe (08:27):
My name is Zoe. I'm seven years old, and I live in
Singapore. How do volcanoeserupt?

Rosemary (08:34):
My name is Rosemary. I live in Canada. I'm six years
old. Why do volcanoes form?

Jane (08:42):
How do volcanoes form? And how do they erupt?

Freysteinn Sigmundsson (08:46):
Volcanoes form because of this heat that
needs to escape from theinterior of the Earth. So there
is somewhere rock is melted,there's a liquid inside the
Earth. This liquid wants to riseup to the surface because it is
buoyant. It is less dense. It islike if you jump into a swimming

(09:07):
pool, you float up. The same ishappening with the magma inside
the Earth. And therefore theyform because this liquid is
coming towards the surface ofthe Earth. And often when there
has been sort of one path formagma, it is utilized by more
magma. So there are repeatedoutflow of this liquid and the

(09:29):
eruptions, when do they occur,exactly? Well, pressure is
building up inside where magmais accumulating in a very
similar manner as what happensif you, if you have a balloon
and you blow air into it, andyou continue to blow, you see,
it gets always more and moredifficult. That's because there

(09:50):
is more pressure inside theballoon. Same happens with
volcanoes. More new liquid thatflows into a volcano, the
pressure increases. But if youcontinue very hard to blow into
your balloon, it may explode.That is the same thing that
happens for a volcano. Theeruption starts when the
pressure is too much inside theballoon that is collecting magma

(10:15):
inside the volcano, and there wego. We have an eruption.

Theodore (10:21):
My name is Theodore. How does the volcano rise up
inside the sea?

Jane (10:26):
Can you talk a little bit about volcanoes that form
underwater?

Freysteinn Sigmundsson (10:29):
Yes, we have super many volcanoes in the
oceans, underwater. Lots ofsubmarine volcanoes, underwater.
What happens is, inside thevolcano, the process is very
similar, but the eruptions aredifferent. Often we form both
lava similar as on the surface,but the lava will be of a little

(10:53):
different types. If theeruptions happen in shallow
water or water depth of a fewhundred meters, it becomes
explosive. So what happens thenis that the lava, when it comes
into the ocean, it can explodeinto fine particles, similar as
an explosive eruption, and thenit can pile off. And eruptions

(11:13):
can create mountains. And wehave had new island created off
the coast of Iceland in aneruption that was first under
ocean water, and the volcanorose out of the sea.

Calvin (11:27):
My name is Calvin. I'm five years old. I live in New
York City. Which one's hotter,the sun or a volcano?

Freysteinn Sigmundsson (11:35):
The red glow of this liquid that comes
out of the volcano means it isvery hot, 1,000 degrees Celsius.
This is about 1,800 degreesFahrenheit. So it is super hot.
But inside the sun, it is muchhotter.

Jane (11:50):
Scientists say the core of the Sun is as hot as 15 million
degrees Celsius. That's 27million degrees Fahrenheit. So
the heat from underneath theearth is definitely hot. But if
we're comparing about 1,000degrees in a volcano to 15
million degrees in the core ofthe Sun, the Sun is much, much

(12:14):
hotter. Coming up, how do weknow when a volcano is going to
erupt?
This is But Why. I'm JaneLindholm, and today on the show,
we're learning all aboutvolcanoes with University of
Iceland professor andvolcanologist Freysteinn
Sigmundsson. So as we justheard, when a volcano erupts,

(12:34):
magma, or hot, molten rock,flows onto the Earth's surface.
And at that point, we give it anew name: lava. We've got some
questions about lava and how itforms.

Alana (12:48):
Hi, my name is Alana, and I'm eight years old, and I live
in Norwalk, California. And myquestion is, why do volcanoes
have lava in them, and how doesthe lava even get in there?

Landis (13:03):
My name is Landis. I'm seven years old. I live in San
Antonio, Texas. Where dovolcanoes get their lava from?

Charlie (13:10):
My name is Charlie. I live in New Zealand. I am six
years old. What is lava made outof?

Freysteinn Sigmundsson (13:17):
Lava is made out of rock that has become
so hot that it melts. And you'llsee many of the features of
volcanoes can be explained bythis heat. So the volcano
scattered magma initially, thatis when the lava is inside the
volcano. Because of heat, therock started to melt and form

(13:39):
liquid. So the liquid inside thevolcano comes to the surface,
and then we call it lava. So itis a hot liquid. And many
volcanoes have a lot of hotliquid inside them, and that's
when we have an eruption. Thisliquid comes to the surface and
we have lava. So that's thestory, basically, of the lava.

(14:00):
It's all about the Earth tryingto release heat from its

Trixie (14:05):
My name is Trixie. I'm four. I live in Virginia. Why
interior.
are volcano lava is orange?

Jane (14:16):
Why is lava orange?

Freysteinn Sigmundsson (14:17):
Yeah, similar reasons the sun is
yellow. It is transmittingenergy. It is so hot that it
starts to radiate energy. Thesun is radiating energy that is
still hotter than the lava thatis yellow. The orange color is

(14:38):
simply radiation from adifferent temperature.

Jane (14:41):
When melody, Joey and I were in Iceland, we didn't see
an eruption, but we did visit asolidified lava field from
volcanoes that had alreadyerupted just a few years ago.
The lava there was no longerbright orange because it had
cooled and hardened back intorock. But I could see the
different textures and patternsof the lava as it had flowed

(15:03):
across the surface. And I wasreally surprised to see that
there was still smoke coming outof the solidified lava field,
even though it had been morethan a year since the last
eruption. We even saw signswarning people not to walk on it
because it might still be veryhot underneath. So I asked
Professor Sigmundsson how longcan it be hot underneath that

(15:25):
hard surface, and how long can alava field be dangerous after an
eruption.

Freysteinn Sigmundsson (15:30):
For... for years. Because it takes a
long time to cool a lava field.It depends, of course, how thick
it is, but if it is like fewmeters...

Jane (15:44):
As tall as an adult.

Freysteinn Sigmundsson (15:45):
Yes, or twice or three times that. That
is maybe typical for lava fieldshere in Iceland, they can have
really liquid magma inside themfor possibly for months or
years. But there is also anotherdanger simply related to the
rocks. You know, it is liquidthat is transforming into rock

(16:08):
again on the surface of theEarth. And the structure of lava
fields is very intriguing. Manyof the lava fields here in
Iceland are very irregular onthe surface. So you also have
the danger of just falling. Sothey are dangerous, yes. So you
need to be aware of that.

Harper (16:28):
My name is Harper, and I am five years old, and I live in
Scottsdale, Arizona. Why can'twe live on volcanoes?

Freysteinn Sigmundsson (16:38):
Lots of people live on volcanoes, and
lots of people live close tovolcanoes. Here in Iceland, we
live quite close to volcanoes. Imean, the capital of Iceland,
Reykjavik, is not far fromvolcanoes. Here in Iceland,
there are two villages that arepractically on a volcano. But
worldwide, there are many peoplethat live on volcanoes. And the

(16:59):
reason people live on volcanoes,like in Indonesia, is because
the the soil on a volcano can bevery fertile, and you can grow
crops there.

Jane (17:11):
Professor Sigmundsson says living close to volcanoes can
come with other great benefits.In Iceland, for example,
geothermal energy powers about70% of the country.

Freysteinn Sigmundsson (17:21):
We have cold winters, but we heat most
of the houses in Iceland bywater that comes from the
volcanoes, hot water, and itjust goes into a radiator
directly from volcano and heatsour houses. We have very hot
houses here in Iceland, even ifthe winters are cold

Jane (17:37):
And many volcanoes stay dormant, which means they're
inactive, kind of asleep forhundreds or even thousands of
years. So it's entirely possiblefor someone to live close to an
inactive volcano their wholelife and not experience an
eruption. The tricky thing,though, is that volcanoes don't
always stay asleep.

Freysteinn Sigmundsson (17:57):
If they can talk about the volcanoes as
a living creature, in theirlifetime, most of the time they
are sleeping. So they only wakeup occasionally. Some of the
work I do is try to understandwhat happens when a volcano is
trying to wake up. And yeah, itis difficult to forecast. For
example, if you're sick, if youdo not feel very well in your

(18:20):
stomach, you may need to throwup occasionally. And forecasting
when you will throw up if youhave a stomach disease may be
difficult. You almost throw up,but then suddenly it comes, and
maybe we are not prepared. Thesame is with volcanoes. It is
difficult to forecast when theythrow up.

Jane (18:41):
I like that way of thinking about it. And yes, in
my experience, sometimes youthink: Oh, I don't feel good. Oh
my gosh, now I'm throwing up. Itcan be a very surprising thing.

Freysteinn Sigmundsson (18:51):
Same for volcanoes. What volcanologists
are trying to do, some of ourwork is to forecast the activity
and better prepare society. Thatyou're listening to this podcast
is very good, because we need tomore people that understand what
volcanoes are doing.

Soleil (19:08):
Hello. My name is Soleil and I live in Hamden,
Connecticut, and I'm five yearsold and about to be 60,
volcanoes erupt in the winter?

Freysteinn Sigmundsson (19:17):
What you know about volcanoes is that
they are very irregular. Theycan erupt any time of the year.
Volcanoes are not like a clock.

Jennifer (19:26):
My name is Jennifer, and seven years old. I'm from
Ohio. How do volcanologists knowa volcano is going to erupt?

Freysteinn Sigmundsson (19:33):
That is my job, part of my job, to
understand what happens beforethis, yeah. So we need to
measure their activity, and wecan measure what is happening
inside the volcano withdifferent techniques, mainly
three techniques. We can studyearthquakes, how the ground is

(19:53):
shaking in a volcano, becausethe waves from earthquakes come
to the surface. And we canmeasure the waves and then
figure out what is happeninginside. Or we can measure how
the ground of a volcano ismoving, and thereby, maybe, try
to understand how the pressureis building up, like in a

(20:13):
balloon. Or we can measure whatwe can call volcanic gas. That
is like if you smell somethingis burning in your stove, then
something serious may happenunless you stop the process.
It's basically the same thing wecan try to sense or sniff, in a
sense, what the gas that iscoming out of a volcano.

Jane (20:37):
When something is burning in your stove, that's a very
familiar smell. Like I canpicture the smell of burning
toast. The smell of a volcanothat is getting active, what is
that smell? Is that a sulfuricsmell, which sometimes people
describe as kind of like rotteneggs?

Freysteinn Sigmundsson (20:55):
It can be increased in that. It can
also be increase in gas typesthat has no smell that we need
special instruments to measure.So we need some technology.
Normally, we cannot use our nosefor it.

Jane (21:11):
Are there things that you can look at? If I was looking at
a volcano, and say, oh,something is happening? Or do
you need special tools andspecial maybe even computer
models to be able to understandwhat's happening?

Freysteinn Sigmundsson (21:23):
Sometimes we can see it with our eyes. For
example, if there is new, hotliquid coming into a volcano,
the heat of the rock around itcan increase, and we can start
to have more geothermalactivity, or basically steaming
from a volcano. So we can getvisual steam from a volcano,

(21:45):
basically meaning it is hotter.But we typically need equipment.
We need to study theearthquakes. We need to see how
the ground is moving, or we needto measure the gases that come
out. And typically, tounderstand how volcanoes behave,
both in this time period beforean eruption and during eruption,

(22:07):
we need this monitoring data,and we take it all together and
try to understand what ishappening inside the volcano
during an eruption. And often weneed a computer model for that.
So even if I'm a volcanologist,most of the time I'm in front of
a computer.

Jane (22:26):
Scientists have been studying volcanic activity for a
long time, but there's still alot we don't know about how they
work. For Professor Sigmundsson,he says his goals are to keep
learning more about what'sinside volcanoes and how that
might help him understand betterthe warning signs volcanoes are
giving. That way, people couldbe informed before a volcano

(22:46):
erupts. That's especiallyimportant for people who live
close by, of course. Volcaniceruptions are a forceful release
of extreme heat and energy. Theycan destroy homes, they can make
nearby towns unsafe, requireresidents to evacuate, or leave.
Sometimes, all the ash from aneruption gets high up into the

(23:07):
atmosphere and causes problemslike planes needing to find new
routes or not being able to flyat all. And remember our recent
episode about smoke travelingfrom forest fires. Ash from
volcanoes can, of course, alsoget into the atmosphere and go
very, very far from where thevolcano has originally erupted.
Given all of that, it makessense that we often think of

(23:30):
volcanoes as something kind ofscary and unpredictable and
dangerous and bad. But ProfessorSigmundsson says it's important
to be respectful of the powerand destruction of volcanic
activity, but to also recognizethe beauty.

Freysteinn Sigmundsson (23:45):
If you look at some photographs or
videos of volcanoes, it's abeautiful thing to see a small
eruption. You sese some nice redmagma being thrown up into the
air and flowing. So, so I was ayoung kid that had the
opportunity to see eruptions andhear about them. They caught my

(24:07):
interest. They are beautiful,spectacular, and if you stare at
them for a long time, stare intothe red glow, you can be
charmed.

Jane (24:19):
And volcanoes are also very important. Not only did
they shape the landscape we knowtoday on Earth, but they
continue to do that. New islandsand new terrain is constantly
being formed by volcaniceruptions. Plus, volcanoes are
important for things likegeothermal energy, how we can
heat and cool our homes andbuildings. And they can create

(24:42):
very fertile soils, meaning it'seasier to grow things like
fruits and vegetables. Sovolcanoes are all of those

things at once (24:50):
a little bit mysterious, maybe scary
sometimes, occasionallydangerous, but also beautiful,
interesting and important.Thanks to Professor Freysteinn
Sigmundsson at the University ofIceland for speaking with us
about volcanoes and answeringyour question. As always, if you
have a question about anything,have an adult record you asking

(25:12):
it on a smartphone. You can usean app like voice memos or
recorder. Then have your adultemail the file to
[e-mail]. ButWhy is produced by Melody
Bodette, Sarah Baik and me JaneLindholm at Vermont Public and
distributed by PRX. Our videoproducer is Joey Palumbo, and
our theme music is by LukeReynolds. If you like our show,

(25:34):
please have your adults help yougive us a thumbs up or a review
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episode. Until then, staycurious.