September 5, 2025 • 27 mins
But Why went somewhere really cool - literally - and we’re taking you along! We visited Sólheimajökull, a glacier in southern Iceland and then talked with University of Iceland glaciologist Guðfinna Aðalgeirsdóttir to discover how glaciers are formed, why they can be different colors, and how they shape the land. (Do you know the difference between a V-shaped valley and a U-shaped valley? Glaciers!) Plus we’ll talk a little bit about why glaciers around the world are retreating at such a fast pace.
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Episode Transcript
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Jane (00:21):
This is But Why
Lindholm. On this show, we takequestions from curious kids all
over the world, and we find coolpeople who can offer answers.
Today, I'm at Solheimejokull.That's a glacier in southern
Iceland. It's been around for400 to 600 years. We're visiting
(00:42):
it to see what a glacier lookslike. But you have sent us a lot
of glacier questions over theyears, so we're going to go now
to the University of Iceland totalk with somebody who can
actually explain what they are.
Guðfinna Aðalgeirsdóttir (00:55):
My name is Guðfinna
Aðalgeirsdóttir. It's a verylong Icelandic name.
Jane (01:01):
As you may have figured out by now, But Why went to
Iceland! That's an islandcountry in the north Atlantic
Ocean, a little closer to Europethan it is to North America. One
of the things we wanted to learnmore about while we were
visiting was glaciers. So afterwalking around, looking at an
amazing glacier calledSolheimejokull, we went in
(01:21):
search of someone who couldexplain this geological
phenomenon to us. But to dothat, we had to leave the
glacier go into the capital cityof Reykjavik, where we walked to
the University of Iceland andinto the bright and sunny
science building. That's wherewe found Guðfinna
Aðalgeirsdóttir in her officewhere she works as a professor
(01:42):
when she's not out walkingaround on glaciers herself.
Guðfinna Aðalgeirsdóttir (01:45):
So I'm a glaciologist, and I became a
glaciologist because I'm reallyinterested in skiing, and I
found this way of traveling onice and snow as a job through my
interest and because I foundthis group of people who were
researching glaciers. So Ididn't know that this existed
(02:07):
when I started, but I learnedgeophysics, so I was interested
in math and physics, and what Ido now is I measure the
glaciers, I model them.
Jane (02:19):
That might sound like she spends her days sculpting models
of glaciers out of air clay orsomething. But sadly, no. Or
maybe not sadly, becauseGuðfinna Aðalgeirsdóttir seems
to really like her job. What shemeans by modeling is that she
uses math and physics to createcomputer models for glaciers,
(02:40):
which are paired with climatemodels. Those models can help
researchers figure out whatmight happen to glaciers under
different conditions over thenext many years. And of course,
as a professor, she also teachesstudents, and she does get to
ski.
Guðfinna Aðalgeirsdóttir (02:55):
No, I ski a lot, so I take every
opportunity I have. For example,this spring, we were on
Mýrdalsjökull, and then we driveon the glacier, and then I had a
rope, and I could be towedbehind the car in that trip. So
then I didn't have to sit in thecar, but I was on the skis
behind the car, towed by a rope.And then we traveled to the
(03:16):
measurement location. And thenwhen we gone and we did the
measurement, we drilled thethickness of the snow layer to
measure how much it was snowingduring the wintertime, and then
I was towed to the nextmeasuring place on the skis. And
then when everybody went home, Iskied down the glacier. So that
was a great ski trip, but ameasuring trip at the same time.
Jane (03:37):
I have to just say, right now, it is not safe for you to
be towed behind a car on skis,unless this is something you're
specifically doing as an adultfor your job in a very
controlled way. Do not try thatat home.
Guðfinna Aðalgeirsdóttir (03:51):
Well, that's true, yes. So we should
be very careful, and you have totrain a lot to be able to do
this. Yes.
Jane (03:56):
But wait, we're getting out over our skis. That's an
expression people use to mean"we're getting ahead of
ourselves and might fall over."We haven't really explained yet
what a glacier is. So let's dothat now.
Eana (04:09):
My name is Eana. I'm nine years old. I live in Victoria,
British Columbia, and myfavorite season is winter,
because it's close to mybirthday, and I love snow. And
my question is, how are glaciersformed?
Kira (04:21):
My name is Kira. I live in Barrie, Ontario. I am six years
old. How do glaciers get therein the first place?
Jane (04:29):
What is a glacier?
Guðfinna Aðalgeirsdóttir (04:32):
That's a good question. So glacier is
ice, and the ice is formedbecause the precipitation of
last winter didn't melt in thefollowing summer. So that means
that there was a positive massbalance there. This region
gained and when there is asequence of year where there is
(04:55):
snow left in the autumn, buriedthen under next winter snow
layer, then that accumulatedsnow is compacted. And when once
that has become densified, sothat the snow that was like
fluffy and flurry in thebeginning is compacted into
glacier ice, then it can startto flow. And the flowing happens
(05:20):
because the thickness of the iceis high enough or large enough.
So once the thickness is largeenough that the ice can start
deforming under its own weight.And you can think of this as
honey. If you put a honey on thetable, and it may be, may be
like a pile, and the pile thenkind of floods out because the
(05:42):
thickness is too high for thesurface tension, if you like.
Jane (05:46):
So a glacier is snow that forms on top of land and gets
squished down year after year asmore snow falls, and not all of
it melts. Over time, that snowpack gets so heavy and compacted
that it turns to ice, and thenthat ice starts to move under
the force of its own weight.That is a glacier. And one of
(06:08):
the most important things isthat glaciers aren't really
glaciers until they start tomove.
Guðfinna Aðalgeirsdóttir (06:14):
You can have snow packs that are
just sitting there, but as soonas the thickness of that ice is
large enough that the weight ofthat ice column is really
pushing it to flow and deformunder its own weight. And
specifically, if the slopeunderneath, so the bedrock
underneath is maybe steep, thenthe glacier can start flowing
(06:36):
downhill, and then it has becomea glacier. So it's ice that
flows, and then you have aglacier.
Jane (06:44):
And glaciers can only form on land, right? We're not
talking about icebergs.
Guðfinna Aðalgeirsdóttir (06:49):
Well, some icebergs are carved off
glaciers, so they are formed ona glacier. And there are many
icebergs. For example, theTitanic, the iceberg that caused
the Titanic to sink was breakingoff Greenland ice sheet. That's
another thing that I findinteresting, the glacier ice
flowing off and breaking off inthe fjords, for example, in
Greenland, that's the oldestice, because that has been
(07:13):
formed somewhere way up and hasbeen transported down to the
axis of the glacier and isbreaking off.
Jane (07:19):
So it's almost like a conveyor belt where the new snow
gets buried and goes down anddown and down, and then
eventually it comes out at thesnout, and that's the older ice.
And that newer snow is pushingdown from the top and sort of
pushing that older icecontinually downwards or
outwards. How old are glaciers?
Guðfinna Aðalgeirsdóttir (07:40):
That's very dependent on the location,
like we're in the world, butalso we're on the glacier, like
we were saying, the conveyorbelt. So the youngest ice is on
the top in the accumulationarea, and then the oldest is at
the snout. And the glacier icein Iceland is probably up to
800, 900 years old. So that'sthe time that it takes for the
(08:02):
ice to be transported with aconveyor belt that the ice
itself down towards the axis.There are places that are much
older, much, much older. TheGreenland ice sheet and the
Antarctic ice sheet. They aremuch bigger. There are, like
whole continents covered withice, and the ice in Greenland,
(08:23):
it's about 130,000 years old,and they have found around 1
million year old ice inAntarctica.
Jane (08:32):
Ice that is a million years old? Imagine putting that
in your glass of water. Justkidding. Scientists do collect
some of that ice, but they don'tjust let it melt in a glass.
Professor Aðalgeirsdóttir saysthat ice is like a time capsule.
It contains a record of theprecipitation, the snow and rain
that fell a million years ago,and the bubbles trapped inside
(08:56):
the ice are a time capsuletelling us about the air a
million years ago, so we canlearn a lot about the past from
glaciers.
Coco (09:04):
Hello. My name is Coco. I'm eight years old. I'm from
St. George, Utah, and myquestion is: how does algae get
into glaciers and turn thempink?
Guðfinna Aðalgeirsdóttir (09:16):
Yes, this is a very interesting
question, and the surface of theglacier can't be variable. And
the question about the algae, Idon't actually know, but I
think, and that's my wild guess,now. I think that algae are
blown onto the glacier and startgrowing, and then they can,
well, you can think, well, whatcan grow on a surface that is
(09:39):
freezing at the freezing point,even, and very cold, and there
is no soil to grow. Butapparently those algae quite
like the cold surface, and theremay be the solar radiation give
them enough energy to grow, andthat causes kind of like a
reddish hue.
Jane (09:57):
We checked on this, and the color is coming from algae.
The algae itself is green, butit has a secondary red pigment
called a carotenoid. In thesummer, the algae can turn on
their red pigments as aprotective barrier against UV
radiation from the sun. It'skind of like sunscreen. But this
red color causes the algae toabsorb heat instead of
(10:19):
reflecting it, and that leads toglaciers that melt faster than
white ones. Pink isn't the onlycolor you can see in a glacier.
Sometimes a glacier looks blue.The more dense the ice, meaning
it has fewer air bubbles and ispacked down under its own
weight, the more likely it is tolook blue. Those large, dense
ice crystals are absorbing somewavelengths of light and
(10:41):
scattering the blue light backto your eyes so it looks blue.
Generally speaking, the olderthe glacier ice, the more likely
it is to appear blue. Butglaciers can be other colors,
too. They can be white, blue,pink, brown, black and more.
Guðfinna Aðalgeirsdóttir (10:57):
In Iceland, that color changes can
be because dust is blown. It'svery windy in Iceland and in the
highlands is basically a desert.And our sand, because it's a
volcanic island, our sand isvery black. So the black sand is
blown onto the glacier, and thatcauses like a dark, darkening of
the surface. There can be evensand dust from Sahara on, some
(11:20):
places in the Alps, and thatsand is kind of yellowish and,
and then the algae contains thesurface color. And anything that
is blown onto the glacier willhave an effect.
Jane (11:33):
The darker the surface of the glacier, the faster it
melts. Speaking of which, whenwe come back, we'll talk a
little bit about how increasingglobal temperatures are
affecting glaciers around theworld. And did you know you can
find glaciers in the tropics?
This is But Why (11:49):
A Podcast for Curious Kids. I'm Jane Lindholm.
We're learning about glacierswith scientist and professor,
Guðfinna Aðalgeirsdóttir, aprofessor and glaciologist at
the University of Iceland.Remember at the beginning of
this episode, when I said I wasstanding at a glacier? You can
see glaciers from a lot ofIceland. Even though only about
(12:11):
10% of the country is covered byice, these glaciers are a very
striking feature of thelandscape, and some of the
glaciers are pretty easy to walkright up to and touch, like the
one we visited. I askedProfessor Aðalgeirsdóttir to
tell us about the glacier we hadvisited before we went to her
office. It's calledSolheimejokull. It looks like a
(12:32):
big pile of dirty black ice andsnow tumbling down in between
two valleys and piling up onitself. It actually starts
higher up in the IcelandicHighlands as part of a much
larger glacier, an ice capcalled Mýrdalsjökull. That ice
cap is on flatter land and kindof spreads out in all
directions. And Solheimajokullis an outlet glacier, where the
(12:55):
ice is heading downwards towardthe sea.
Guðfinna Aðalgeirsdóttir (12:57):
So Solheimajokull is flowing
towards south, towards the coastin Iceland. And this outlet
glacier is like a long tongue,and it's bending a little bit
down into this valley, and theend of it is now in a lake, and
(13:17):
the lake formed only maybe 15,20 years ago. I'm not exactly
the same the exact date of it.And that lake is forming because
the glacier is getting shorter.And the glacier is a little bit
like a conveyor belt, and it'stransporting the snow
accumulated on the big ice cap,Mýrdalsjökull, down into the
(13:38):
lower region. And the glacier isalso like your bank account, a
little bit, that you putsomething in, in it in the
wintertime. So the snow comes inthe winter time and that certain
amount, and we go and measurethat in the springtime, how much
was coming into the glacier. Andthen during the summertime, at
the lower region, and but alsohigh up, is ablation. So
(13:59):
ablation is how much is melting,and the ablation is then also a
certain amount. And then comethe bank account that you can
say that mass balance of theglacier, if you take more out
than you put in, the glacier isgoing to get shorter.
Jane (14:15):
And solheimajokull has been shrinking recently.
Guðfinna Aðalgeirsdóttir (14:19):
Yes, since 1995, so now 30 years,
it's getting shorter, sometimes50, up to 100 meters a year. And
we know this because we go andmeasure every year the position
of the snout. So we call it thesnout where the glacier ends,
and the snout is now in thelake. So it's not only melting
(14:43):
on the surface, at the snout,but it's also breaking off into
the lake. So then that's calledcalving, because it's kind of
like calf being broken off theof the snout of the glacier. So
so the ablation possibilitiesare breaking off into the lake
and melting at the surface,because the high temperature.
Jane (15:05):
given how cold it needs to be for a glacier to form, you
might be surprised to learn youcan actually find glaciers in a
lot of places on earth. You caneven have a glacier in the
tropics or near the equator, butyou need to have more snow that
falls than the snow that meltsyear after year after year. So
for that to happen in reallywarm parts of the world, you
(15:28):
usually need to go up. If thereare very tall mountains where
the air is cold, even if it'stropical, down below, you might
be able to find a glacier.
Guðfinna Aðalgeirsdóttir (15:37):
In Africa. There is the Mount
Kilimanjaro, and we find aglacier there that is actually
shrinking quite fast at themoment. But in the tropics, if
you get high enough, you canfind glaciers.
Chet (15:49):
My name is Chet. I'm five years old. Ontario, Canada, and
my question is (15:57):
why glaciers are formed, and they shape the land?
Jane (16:05):
Sometimes, where we live in North America, people will
talk about the landscape andsay, "Oh, that was formed in the
last ice age when the glaciersreceded." And here in Iceland,
we often hear, "this is alandscape that has been shaped
by volcanoes and glaciers." Howdo glaciers shape a landscape?
Guðfinna Aðalgeirsdóttir (16:25):
They are really like bulldozers. So
in areas where there is sandunderneath a glacier, they're
basically just shoveling thesand like bulldozer in front of
them, and they create what wecall frontal moraines. And those
moraines are then like markingof a bulldozer that has pushed
the material in front of it.They also carve the valley. So
(16:48):
valley is V-shaped, kind of likea V if there is only a river at
the bottom that is carving thelandscape, but if a glacier then
starts to fill that valley, thenit carves and create, kind of
more like U-shape, and it kindof grinds the bedrock underneath
(17:08):
it and transport it. Remember,it's a conveyor belt, so it
transports the rocks that theygrounded from the sides. And
then we can see that V-shapedvalley haven't seen the glacier,
but the U-shaped valley, thoseare the valleys that the glacier
has formed.
Jane (17:26):
And if we think of it as that bulldozer and it's pushing
that material forward, thensometimes it also leaves that
material there, and does thatform new hills or mountains?
Because, again, we're thinkingof like a bulldozer for a giant,
not a bulldozer that any of uscould drive so you could see a
hill or a mountain that was sortof left behind, like pushed over
(17:46):
there, and then just discardedby the glacier?
Guðfinna Aðalgeirsdóttir (17:48):
Exactly. And this is how we know how big
the Laurentide ice sheet was inNorth America. And the
Scandinavian ice sheet, how bigthey were, because we see those
land forms that exactly thosebulldozed hills that are then
the leftovers off that bigbulldozer that is now gone.
Jane (18:09):
I think that's kind of amazing to think about someone
like you can go walk outside andsee into the past, because you
know how this landscape wasformed. And I wonder if in your
head, you can almost picturewhat it might have looked like
1,000 years ago, or 10,000 yearsago.
Guðfinna Aðalgeirsdóttir (18:28):
Yes, and even shorter distances,
because we see, for example, inSolheimejokull, where you were,
we can see now how big theglacier was because the
vegetation hasn't come yet. Soin areas where the glacier has
recently been removed orretreated from, there are not
vegetation yet, but in areasthat have been uncovered or
(18:49):
released from the glacier longertime ago, we see that there is
moss and maybe some grassvisible. So the landscape is
really telling us how big theglaciers were and how extensive
they were, and that's what weare using to read the landscape
and of course, the climate tellsus that we understand this
(19:13):
relationship, that if you getcooler climate, the glacier can
grow, and when it gets warmer,the glacier can shrink.
Jane (19:18):
And shrinking is What many glaciers are doing right now.
Glaciers are always changing,growing and shrinking over time.
But right now, they're shrinkingall over the world, and at a
fast rate, because our climateis getting warmer. Some glaciers
are even disappearing. But ifglaciers have gotten bigger and
(19:38):
smaller, appeared anddisappeared over the whole long
history of the earth, why doresearchers like Professor
Aðalgeirsdóttir think thatwhat's happening to glaciers now
is a problem and not just partof a normal cycle?
Guðfinna Aðalgeirsdóttir (19:53):
They grow and shrink as a response to
temperature changes andprecipitation changes, and they
are very sensitive, actually.But what they also are, they
have a long memory, so they arekind of integrating their
climate over long periods, andtheir response is telling us how
(20:15):
the climate has been changing.And we see records from
different regions in the world,and and more and more
information from the ice cores,from the big ice sheets,
indicate and sort of confirmthis idea of ice ages and and
interglacial periods, so thosewarmer periods in between, and
(20:36):
those are natural, and those arekind of because of the distance
of the earth to the sun ischanging, and that is causing
the ice ages to form. Also thetilt of the earth axis and the
wobbling speed is also changing,and that combination causes the
(20:56):
ice ages and the warmer periods.And those are happening on long
time scales, like 40,000 yearsand 100,000 years time scales.
So now, if we think of thosetimescales, like 100,000 years,
and compared to the time sincewe started burning fossil fuels,
(21:17):
that's only 150 years ago, andalso building up that amount of
fossil fuel that we are burningout that takes millions of
years, like the reservoirs thatwe are using now for our energy
consumptions have been formedover millions of years. And in
(21:38):
the span of 150 years, and I say150 because often, often we talk
about 1850 as the beginning ofthe Industrial Revolution, and
when we started having, likefuel engines, and started
burning coal for heating ourhouses and and fuel and gas. And
(21:58):
of course, there's a lot oftechnical evolution, really
rapid evolution of technology,and we managed to start flying
between the continents and usinga lot of energy. And in that
period, we have emitted byburning the fossil fuels, the
CO2 in the atmosphere, and thatis causing the temperature at
(22:21):
the surface to warm up. And nowwhat has been natural and maybe
variable over the differentregions in on the surface of
Earth, we are now seeing veryclear signals. All the glaciers
in the world are responding. Wehave already warmed the planet
on average, 1.1 degree. And allthe glaciers are telling us that
(22:46):
they can feel that. So the clearsignal everywhere, from
Patagonia to Svalbard Icelandicglaciers, the Himalayan
glaciers, and, of course, thebig ice sheets in Greenland and
Antarctica, they are starting toshrink. So let's just make that
thought experiment and say thetemperature rise stopped at 1.1
(23:06):
degree, the glaciers, and itdepends on how... size or the
bit how big the glaciers are,they will take few decades to
adjust. So the conveyor belt hasto kind of figure out what the
new size should be, and thenthey would be about 40% smaller,
or the amount of the volume,amount of current glacier will
(23:27):
be about 40%. If we continue towarm, the more of this ice will
be lost. So the message from theglaciers is really stop the
warming as fast and as soon aspossible and as much as
possible.
Jane (23:45):
There have been agreements made among many countries to
limit greenhouse emissions, thegasses we put into the
atmosphere that are contributingto a warming climate. Countries
have worked to reduce emissionsso we can limit that average
climate warming to two degrees.But those agreements don't seem
to be making a difference sofar, and countries sometimes
(24:07):
change their mind about whatthey're willing to do, depending
on who's the president or primeminister or political leader at
any given time. Sometimes,countries or governments even
decide they no longer want to bepart of the agreements, like the
United States did at thebeginning of 2025 with something
called the Paris ClimateAgreement. Pretty much every
(24:29):
scientist agrees climate changeis happening at an alarming
rate, and it's going to affectall of us. But governments
disagree about what to do.Professor Aðalgeirsdóttir says
she thinks all countries aregoing to have to deal with it
one way or another, whether welike it or not, and the ways we
change our policies could windup happening very quickly as the
(24:51):
climate forces us to thinkdifferently.
Guðfinna Aðalgeirsdóttir (24:54):
Many places are using renewable
energy, and they're calledrenewable energy because they
are not using their fossilfuels, their coal and oil and
the gas that are burning andemitting CO2 in the atmosphere,
and replacing it with solarenergy or wind energy and and I
think we could use tidal energyas well. There are a lot of
energy sources, geothermal, andthere are energy sources that we
(25:18):
know how to harness, and we knowthat they're not emitting CO2,
but it's kind of likecomfortable to still use and it
all the systems are built on thefossil fuels. But I think the
decision, once we make thedecision to say, "Okay, we
really need to swap," I thinkthat will happen fast. We are on
the verge of transition, andthis is why we are talking about
(25:40):
the transition. We really needto move into this renewable
energy regime, because weunderstand that the regime that
we have had in the last 150years is both not good for the
climate and it's also notsustainable, because we're going
to run out of those fossil fuelsanyway.
Jane (25:59):
And glaciers are helping us understand the urgency needed
to move in a new direction.That's it for this episode.
Thanks so much to ProfessorGuðfinna Aðalgeirsdóttir at the
University of Iceland fortalking about glaciers with us.
As always, if you have aquestion about anything, have an
(26:19):
adult record you asking it on asmartphone using an app like
voice memos, then have youradult email the file to
questions@butwhykids.org. ButWhy is produced by Melody
Bodette, Sarah Baik and me, JaneLindholm at Vermont Public and
distributed by PRX. Our videoproducer is Joey Palumbo, and
(26:40):
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please have your adults help yougive us a thumbs up or a review
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families find us. We'll be backin two weeks with an all new
episode. Until then, stay curious!
This is But Why
Lindholm. On this show, we takequestions from curious kids all
over the world, and we find coolpeople who can offer answers.
Today, I'm at Solheimejokull.That's a glacier in southern
Iceland. It's been around for400 to 600 years. We're visiting
(00:42):
it to see what a glacier lookslike. But you have sent us a lot
of glacier questions over theyears, so we're going to go now
to the University of Iceland totalk with somebody who can
actually explain what they are.
Guðfinna Aðalgeirsdóttir (00:55):
My name is Guðfinna
Aðalgeirsdóttir. It's a verylong Icelandic name.
Jane (01:01):
As you may have figured out by now, But Why went to
Iceland! That's an islandcountry in the north Atlantic
Ocean, a little closer to Europethan it is to North America. One
of the things we wanted to learnmore about while we were
visiting was glaciers. So afterwalking around, looking at an
amazing glacier calledSolheimejokull, we went in
(01:21):
search of someone who couldexplain this geological
phenomenon to us. But to dothat, we had to leave the
glacier go into the capital cityof Reykjavik, where we walked to
the University of Iceland andinto the bright and sunny
science building. That's wherewe found Guðfinna
Aðalgeirsdóttir in her officewhere she works as a professor
(01:42):
when she's not out walkingaround on glaciers herself.
Guðfinna Aðalgeirsdóttir (01:45):
So I'm a glaciologist, and I became a
glaciologist because I'm reallyinterested in skiing, and I
found this way of traveling onice and snow as a job through my
interest and because I foundthis group of people who were
researching glaciers. So Ididn't know that this existed
(02:07):
when I started, but I learnedgeophysics, so I was interested
in math and physics, and what Ido now is I measure the
glaciers, I model them.
Jane (02:19):
That might sound like she spends her days sculpting models
of glaciers out of air clay orsomething. But sadly, no. Or
maybe not sadly, becauseGuðfinna Aðalgeirsdóttir seems
to really like her job. What shemeans by modeling is that she
uses math and physics to createcomputer models for glaciers,
(02:40):
which are paired with climatemodels. Those models can help
researchers figure out whatmight happen to glaciers under
different conditions over thenext many years. And of course,
as a professor, she also teachesstudents, and she does get to
ski.
Guðfinna Aðalgeirsdóttir (02:55):
No, I ski a lot, so I take every
opportunity I have. For example,this spring, we were on
Mýrdalsjökull, and then we driveon the glacier, and then I had a
rope, and I could be towedbehind the car in that trip. So
then I didn't have to sit in thecar, but I was on the skis
behind the car, towed by a rope.And then we traveled to the
(03:16):
measurement location. And thenwhen we gone and we did the
measurement, we drilled thethickness of the snow layer to
measure how much it was snowingduring the wintertime, and then
I was towed to the nextmeasuring place on the skis. And
then when everybody went home, Iskied down the glacier. So that
was a great ski trip, but ameasuring trip at the same time.
Jane (03:37):
I have to just say, right now, it is not safe for you to
be towed behind a car on skis,unless this is something you're
specifically doing as an adultfor your job in a very
controlled way. Do not try thatat home.
Guðfinna Aðalgeirsdóttir (03:51):
Well, that's true, yes. So we should
be very careful, and you have totrain a lot to be able to do
this. Yes.
Jane (03:56):
But wait, we're getting out over our skis. That's an
expression people use to mean"we're getting ahead of
ourselves and might fall over."We haven't really explained yet
what a glacier is. So let's dothat now.
Eana (04:09):
My name is Eana. I'm nine years old. I live in Victoria,
British Columbia, and myfavorite season is winter,
because it's close to mybirthday, and I love snow. And
my question is, how are glaciersformed?
Kira (04:21):
My name is Kira. I live in Barrie, Ontario. I am six years
old. How do glaciers get therein the first place?
Jane (04:29):
What is a glacier?
Guðfinna Aðalgeirsdóttir (04:32):
That's a good question. So glacier is
ice, and the ice is formedbecause the precipitation of
last winter didn't melt in thefollowing summer. So that means
that there was a positive massbalance there. This region
gained and when there is asequence of year where there is
(04:55):
snow left in the autumn, buriedthen under next winter snow
layer, then that accumulatedsnow is compacted. And when once
that has become densified, sothat the snow that was like
fluffy and flurry in thebeginning is compacted into
glacier ice, then it can startto flow. And the flowing happens
(05:20):
because the thickness of the iceis high enough or large enough.
So once the thickness is largeenough that the ice can start
deforming under its own weight.And you can think of this as
honey. If you put a honey on thetable, and it may be, may be
like a pile, and the pile thenkind of floods out because the
(05:42):
thickness is too high for thesurface tension, if you like.
Jane (05:46):
So a glacier is snow that forms on top of land and gets
squished down year after year asmore snow falls, and not all of
it melts. Over time, that snowpack gets so heavy and compacted
that it turns to ice, and thenthat ice starts to move under
the force of its own weight.That is a glacier. And one of
(06:08):
the most important things isthat glaciers aren't really
glaciers until they start tomove.
Guðfinna Aðalgeirsdóttir (06:14):
You can have snow packs that are
just sitting there, but as soonas the thickness of that ice is
large enough that the weight ofthat ice column is really
pushing it to flow and deformunder its own weight. And
specifically, if the slopeunderneath, so the bedrock
underneath is maybe steep, thenthe glacier can start flowing
(06:36):
downhill, and then it has becomea glacier. So it's ice that
flows, and then you have aglacier.
Jane (06:44):
And glaciers can only form on land, right? We're not
talking about icebergs.
Guðfinna Aðalgeirsdóttir (06:49):
Well, some icebergs are carved off
glaciers, so they are formed ona glacier. And there are many
icebergs. For example, theTitanic, the iceberg that caused
the Titanic to sink was breakingoff Greenland ice sheet. That's
another thing that I findinteresting, the glacier ice
flowing off and breaking off inthe fjords, for example, in
Greenland, that's the oldestice, because that has been
(07:13):
formed somewhere way up and hasbeen transported down to the
axis of the glacier and isbreaking off.
Jane (07:19):
So it's almost like a conveyor belt where the new snow
gets buried and goes down anddown and down, and then
eventually it comes out at thesnout, and that's the older ice.
And that newer snow is pushingdown from the top and sort of
pushing that older icecontinually downwards or
outwards. How old are glaciers?
Guðfinna Aðalgeirsdóttir (07:40):
That's very dependent on the location,
like we're in the world, butalso we're on the glacier, like
we were saying, the conveyorbelt. So the youngest ice is on
the top in the accumulationarea, and then the oldest is at
the snout. And the glacier icein Iceland is probably up to
800, 900 years old. So that'sthe time that it takes for the
(08:02):
ice to be transported with aconveyor belt that the ice
itself down towards the axis.There are places that are much
older, much, much older. TheGreenland ice sheet and the
Antarctic ice sheet. They aremuch bigger. There are, like
whole continents covered withice, and the ice in Greenland,
(08:23):
it's about 130,000 years old,and they have found around 1
million year old ice inAntarctica.
Jane (08:32):
Ice that is a million years old? Imagine putting that
in your glass of water. Justkidding. Scientists do collect
some of that ice, but they don'tjust let it melt in a glass.
Professor Aðalgeirsdóttir saysthat ice is like a time capsule.
It contains a record of theprecipitation, the snow and rain
that fell a million years ago,and the bubbles trapped inside
(08:56):
the ice are a time capsuletelling us about the air a
million years ago, so we canlearn a lot about the past from
glaciers.
Coco (09:04):
Hello. My name is Coco. I'm eight years old. I'm from
St. George, Utah, and myquestion is: how does algae get
into glaciers and turn thempink?
Guðfinna Aðalgeirsdóttir (09:16):
Yes, this is a very interesting
question, and the surface of theglacier can't be variable. And
the question about the algae, Idon't actually know, but I
think, and that's my wild guess,now. I think that algae are
blown onto the glacier and startgrowing, and then they can,
well, you can think, well, whatcan grow on a surface that is
(09:39):
freezing at the freezing point,even, and very cold, and there
is no soil to grow. Butapparently those algae quite
like the cold surface, and theremay be the solar radiation give
them enough energy to grow, andthat causes kind of like a
reddish hue.
Jane (09:57):
We checked on this, and the color is coming from algae.
The algae itself is green, butit has a secondary red pigment
called a carotenoid. In thesummer, the algae can turn on
their red pigments as aprotective barrier against UV
radiation from the sun. It'skind of like sunscreen. But this
red color causes the algae toabsorb heat instead of
(10:19):
reflecting it, and that leads toglaciers that melt faster than
white ones. Pink isn't the onlycolor you can see in a glacier.
Sometimes a glacier looks blue.The more dense the ice, meaning
it has fewer air bubbles and ispacked down under its own
weight, the more likely it is tolook blue. Those large, dense
ice crystals are absorbing somewavelengths of light and
(10:41):
scattering the blue light backto your eyes so it looks blue.
Generally speaking, the olderthe glacier ice, the more likely
it is to appear blue. Butglaciers can be other colors,
too. They can be white, blue,pink, brown, black and more.
Guðfinna Aðalgeirsdóttir (10:57):
In Iceland, that color changes can
be because dust is blown. It'svery windy in Iceland and in the
highlands is basically a desert.And our sand, because it's a
volcanic island, our sand isvery black. So the black sand is
blown onto the glacier, and thatcauses like a dark, darkening of
the surface. There can be evensand dust from Sahara on, some
(11:20):
places in the Alps, and thatsand is kind of yellowish and,
and then the algae contains thesurface color. And anything that
is blown onto the glacier willhave an effect.
Jane (11:33):
The darker the surface of the glacier, the faster it
melts. Speaking of which, whenwe come back, we'll talk a
little bit about how increasingglobal temperatures are
affecting glaciers around theworld. And did you know you can
find glaciers in the tropics?
This is But Why (11:49):
A Podcast for Curious Kids. I'm Jane Lindholm.
We're learning about glacierswith scientist and professor,
Guðfinna Aðalgeirsdóttir, aprofessor and glaciologist at
the University of Iceland.Remember at the beginning of
this episode, when I said I wasstanding at a glacier? You can
see glaciers from a lot ofIceland. Even though only about
(12:11):
10% of the country is covered byice, these glaciers are a very
striking feature of thelandscape, and some of the
glaciers are pretty easy to walkright up to and touch, like the
one we visited. I askedProfessor Aðalgeirsdóttir to
tell us about the glacier we hadvisited before we went to her
office. It's calledSolheimejokull. It looks like a
(12:32):
big pile of dirty black ice andsnow tumbling down in between
two valleys and piling up onitself. It actually starts
higher up in the IcelandicHighlands as part of a much
larger glacier, an ice capcalled Mýrdalsjökull. That ice
cap is on flatter land and kindof spreads out in all
directions. And Solheimajokullis an outlet glacier, where the
(12:55):
ice is heading downwards towardthe sea.
Guðfinna Aðalgeirsdóttir (12:57):
So Solheimajokull is flowing
towards south, towards the coastin Iceland. And this outlet
glacier is like a long tongue,and it's bending a little bit
down into this valley, and theend of it is now in a lake, and
(13:17):
the lake formed only maybe 15,20 years ago. I'm not exactly
the same the exact date of it.And that lake is forming because
the glacier is getting shorter.And the glacier is a little bit
like a conveyor belt, and it'stransporting the snow
accumulated on the big ice cap,Mýrdalsjökull, down into the
(13:38):
lower region. And the glacier isalso like your bank account, a
little bit, that you putsomething in, in it in the
wintertime. So the snow comes inthe winter time and that certain
amount, and we go and measurethat in the springtime, how much
was coming into the glacier. Andthen during the summertime, at
the lower region, and but alsohigh up, is ablation. So
(13:59):
ablation is how much is melting,and the ablation is then also a
certain amount. And then comethe bank account that you can
say that mass balance of theglacier, if you take more out
than you put in, the glacier isgoing to get shorter.
Jane (14:15):
And solheimajokull has been shrinking recently.
Guðfinna Aðalgeirsdóttir (14:19):
Yes, since 1995, so now 30 years,
it's getting shorter, sometimes50, up to 100 meters a year. And
we know this because we go andmeasure every year the position
of the snout. So we call it thesnout where the glacier ends,
and the snout is now in thelake. So it's not only melting
(14:43):
on the surface, at the snout,but it's also breaking off into
the lake. So then that's calledcalving, because it's kind of
like calf being broken off theof the snout of the glacier. So
so the ablation possibilitiesare breaking off into the lake
and melting at the surface,because the high temperature.
Jane (15:05):
given how cold it needs to be for a glacier to form, you
might be surprised to learn youcan actually find glaciers in a
lot of places on earth. You caneven have a glacier in the
tropics or near the equator, butyou need to have more snow that
falls than the snow that meltsyear after year after year. So
for that to happen in reallywarm parts of the world, you
(15:28):
usually need to go up. If thereare very tall mountains where
the air is cold, even if it'stropical, down below, you might
be able to find a glacier.
Guðfinna Aðalgeirsdóttir (15:37):
In Africa. There is the Mount
Kilimanjaro, and we find aglacier there that is actually
shrinking quite fast at themoment. But in the tropics, if
you get high enough, you canfind glaciers.
Chet (15:49):
My name is Chet. I'm five years old. Ontario, Canada, and
my question is (15:57):
why glaciers are formed, and they shape the land?
Jane (16:05):
Sometimes, where we live in North America, people will
talk about the landscape andsay, "Oh, that was formed in the
last ice age when the glaciersreceded." And here in Iceland,
we often hear, "this is alandscape that has been shaped
by volcanoes and glaciers." Howdo glaciers shape a landscape?
Guðfinna Aðalgeirsdóttir (16:25):
They are really like bulldozers. So
in areas where there is sandunderneath a glacier, they're
basically just shoveling thesand like bulldozer in front of
them, and they create what wecall frontal moraines. And those
moraines are then like markingof a bulldozer that has pushed
the material in front of it.They also carve the valley. So
(16:48):
valley is V-shaped, kind of likea V if there is only a river at
the bottom that is carving thelandscape, but if a glacier then
starts to fill that valley, thenit carves and create, kind of
more like U-shape, and it kindof grinds the bedrock underneath
(17:08):
it and transport it. Remember,it's a conveyor belt, so it
transports the rocks that theygrounded from the sides. And
then we can see that V-shapedvalley haven't seen the glacier,
but the U-shaped valley, thoseare the valleys that the glacier
has formed.
Jane (17:26):
And if we think of it as that bulldozer and it's pushing
that material forward, thensometimes it also leaves that
material there, and does thatform new hills or mountains?
Because, again, we're thinkingof like a bulldozer for a giant,
not a bulldozer that any of uscould drive so you could see a
hill or a mountain that was sortof left behind, like pushed over
(17:46):
there, and then just discardedby the glacier?
Guðfinna Aðalgeirsdóttir (17:48):
Exactly. And this is how we know how big
the Laurentide ice sheet was inNorth America. And the
Scandinavian ice sheet, how bigthey were, because we see those
land forms that exactly thosebulldozed hills that are then
the leftovers off that bigbulldozer that is now gone.
Jane (18:09):
I think that's kind of amazing to think about someone
like you can go walk outside andsee into the past, because you
know how this landscape wasformed. And I wonder if in your
head, you can almost picturewhat it might have looked like
1,000 years ago, or 10,000 yearsago.
Guðfinna Aðalgeirsdóttir (18:28):
Yes, and even shorter distances,
because we see, for example, inSolheimejokull, where you were,
we can see now how big theglacier was because the
vegetation hasn't come yet. Soin areas where the glacier has
recently been removed orretreated from, there are not
vegetation yet, but in areasthat have been uncovered or
(18:49):
released from the glacier longertime ago, we see that there is
moss and maybe some grassvisible. So the landscape is
really telling us how big theglaciers were and how extensive
they were, and that's what weare using to read the landscape
and of course, the climate tellsus that we understand this
(19:13):
relationship, that if you getcooler climate, the glacier can
grow, and when it gets warmer,the glacier can shrink.
Jane (19:18):
And shrinking is What many glaciers are doing right now.
Glaciers are always changing,growing and shrinking over time.
But right now, they're shrinkingall over the world, and at a
fast rate, because our climateis getting warmer. Some glaciers
are even disappearing. But ifglaciers have gotten bigger and
(19:38):
smaller, appeared anddisappeared over the whole long
history of the earth, why doresearchers like Professor
Aðalgeirsdóttir think thatwhat's happening to glaciers now
is a problem and not just partof a normal cycle?
Guðfinna Aðalgeirsdóttir (19:53):
They grow and shrink as a response to
temperature changes andprecipitation changes, and they
are very sensitive, actually.But what they also are, they
have a long memory, so they arekind of integrating their
climate over long periods, andtheir response is telling us how
(20:15):
the climate has been changing.And we see records from
different regions in the world,and and more and more
information from the ice cores,from the big ice sheets,
indicate and sort of confirmthis idea of ice ages and and
interglacial periods, so thosewarmer periods in between, and
(20:36):
those are natural, and those arekind of because of the distance
of the earth to the sun ischanging, and that is causing
the ice ages to form. Also thetilt of the earth axis and the
wobbling speed is also changing,and that combination causes the
(20:56):
ice ages and the warmer periods.And those are happening on long
time scales, like 40,000 yearsand 100,000 years time scales.
So now, if we think of thosetimescales, like 100,000 years,
and compared to the time sincewe started burning fossil fuels,
(21:17):
that's only 150 years ago, andalso building up that amount of
fossil fuel that we are burningout that takes millions of
years, like the reservoirs thatwe are using now for our energy
consumptions have been formedover millions of years. And in
(21:38):
the span of 150 years, and I say150 because often, often we talk
about 1850 as the beginning ofthe Industrial Revolution, and
when we started having, likefuel engines, and started
burning coal for heating ourhouses and and fuel and gas. And
(21:58):
of course, there's a lot oftechnical evolution, really
rapid evolution of technology,and we managed to start flying
between the continents and usinga lot of energy. And in that
period, we have emitted byburning the fossil fuels, the
CO2 in the atmosphere, and thatis causing the temperature at
(22:21):
the surface to warm up. And nowwhat has been natural and maybe
variable over the differentregions in on the surface of
Earth, we are now seeing veryclear signals. All the glaciers
in the world are responding. Wehave already warmed the planet
on average, 1.1 degree. And allthe glaciers are telling us that
(22:46):
they can feel that. So the clearsignal everywhere, from
Patagonia to Svalbard Icelandicglaciers, the Himalayan
glaciers, and, of course, thebig ice sheets in Greenland and
Antarctica, they are starting toshrink. So let's just make that
thought experiment and say thetemperature rise stopped at 1.1
(23:06):
degree, the glaciers, and itdepends on how... size or the
bit how big the glaciers are,they will take few decades to
adjust. So the conveyor belt hasto kind of figure out what the
new size should be, and thenthey would be about 40% smaller,
or the amount of the volume,amount of current glacier will
(23:27):
be about 40%. If we continue towarm, the more of this ice will
be lost. So the message from theglaciers is really stop the
warming as fast and as soon aspossible and as much as
possible.
Jane (23:45):
There have been agreements made among many countries to
limit greenhouse emissions, thegasses we put into the
atmosphere that are contributingto a warming climate. Countries
have worked to reduce emissionsso we can limit that average
climate warming to two degrees.But those agreements don't seem
to be making a difference sofar, and countries sometimes
(24:07):
change their mind about whatthey're willing to do, depending
on who's the president or primeminister or political leader at
any given time. Sometimes,countries or governments even
decide they no longer want to bepart of the agreements, like the
United States did at thebeginning of 2025 with something
called the Paris ClimateAgreement. Pretty much every
(24:29):
scientist agrees climate changeis happening at an alarming
rate, and it's going to affectall of us. But governments
disagree about what to do.Professor Aðalgeirsdóttir says
she thinks all countries aregoing to have to deal with it
one way or another, whether welike it or not, and the ways we
change our policies could windup happening very quickly as the
(24:51):
climate forces us to thinkdifferently.
Guðfinna Aðalgeirsdóttir (24:54):
Many places are using renewable
energy, and they're calledrenewable energy because they
are not using their fossilfuels, their coal and oil and
the gas that are burning andemitting CO2 in the atmosphere,
and replacing it with solarenergy or wind energy and and I
think we could use tidal energyas well. There are a lot of
energy sources, geothermal, andthere are energy sources that we
(25:18):
know how to harness, and we knowthat they're not emitting CO2,
but it's kind of likecomfortable to still use and it
all the systems are built on thefossil fuels. But I think the
decision, once we make thedecision to say, "Okay, we
really need to swap," I thinkthat will happen fast. We are on
the verge of transition, andthis is why we are talking about
(25:40):
the transition. We really needto move into this renewable
energy regime, because weunderstand that the regime that
we have had in the last 150years is both not good for the
climate and it's also notsustainable, because we're going
to run out of those fossil fuelsanyway.
Jane (25:59):
And glaciers are helping us understand the urgency needed
to move in a new direction.That's it for this episode.
Thanks so much to ProfessorGuðfinna Aðalgeirsdóttir at the
University of Iceland fortalking about glaciers with us.
As always, if you have aquestion about anything, have an
(26:19):
adult record you asking it on asmartphone using an app like
voice memos, then have youradult email the file to
questions@butwhykids.org. ButWhy is produced by Melody
Bodette, Sarah Baik and me, JaneLindholm at Vermont Public and
distributed by PRX. Our videoproducer is Joey Palumbo, and
(26:40):
our theme music is by LukeReynolds. If you like our show,
please have your adults help yougive us a thumbs up or a review
on whatever podcast platform youuse. It helps other kids and
families find us. We'll be backin two weeks with an all new
episode. Until then, stay curious!
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