Kind: captions
Language: en
[Music]
the
Arctic the
Antarctic our planet's ice
worlds vast Frozen and
empty yet hidden in these
rocks buried under the oceans Pro B
board and trapped in the ice
are clues that reveal a totally
different past oh my God look at this
full of surprises it's like a whole
Forest I'm Kirk Johnson and I'm headed
out on an adventure back in time just
walking around carrying a mammoth tusk
and around the
globe from one polar extreme to the
other to discover an earth totally
different it just looks like Mars from
the planet we know today
this place is so totally
amazing an Arctic that was once a warm
humid
swamp Antarctica Full of
Dinosaurs and a time when ice sheets
extended from pole to pole turning Earth
into a giant
snowball what powerful forces drove the
poles to such
extremes and what does it mean for our
planet's future
find out the true power of ice this is
amazing out here polar
extremes right now on Nova
[Music]
we're right at the mouth of the Ulus at
ice
fiord this place is a
[Music]
dream it's almost unimaginable to think
that I can paddle a kayak around in a
landscape of floating Frozen
ice think about all the other places you
could be right now and then think about
where you actually
are these icebergs are
amazing and they come in all sizes from
they size of little tiny ice cubes all
the way up to the size of
mountains believe it or not we live on a
planet whose fate is determined by Ice
you wouldn't think it living in mid
latitudes but here in Greenland it's
really
obvious there is so much ice in glaciers
and ice caps mostly up here in the
Arctic and down in the
Antarctic when you add it all up it's
70% of Earth's fresh
water I'm paddling towards two of the
most spectacular icebergs I've ever seen
in my
life this stuff looks so solid so vast
so
permanent but looking around at these
Giant floating mountains you've got to
wonder how did all this ice get here how
long did it take to
form and of course how long will it
last for the whole time that humans have
been on this planet around 300,000 years
there's always been ice at the poles
but if you look at the entire history of
Earth Homo sapiens existence has
happened in just a blink of an
eye if we could travel back in time
hundreds of millions of years what would
the Arctic and Antarctic look
like ice at the polar extremes is vital
to the health of our planet if it
disappears what can the past tell us
about the future
how close are we to a Tipping
Point that took me by
surprise to answer these questions I'm
joining scientists working around the
world oh yeah
digging there's a perfect 3 milliony old
clam this is like a window to the Past
drilling you can actually see the annual
ERS even at this level and probing first
we're going to load the probe probe
deployed to unlock the hidden history
okay so it's cold you're better than me
TI of the Polar
extremes oh yes I'm a
paleontologist you get get this Edge
right here I love finding fossils of all
kinds but I have a special place in my
heart for fossil
plants like this palm frond I found in
Alaska a few years ago
wow my first stop on this journey is one
of the most remote places on
Earth with some surprising Secrets
locked in its
rocks I'm on my way to elmir Island high
in the Canadian Arctic next next door to
Greenland and it's only 800 M from the
North Pole we just crossed over latitude
77 and we just left gree fiord which is
the northernmost town in North America
and we're going
north there just clouds and ice and rock
it just looks like Mars it's a magical
place this far north there are no roads
no airports and definitely no runways
he's coming in right now landing on
Uncharted ground is a nail-biting
experience old tight go tight even for a
seasoned Arctic guide like Jason
[Music]
hiler there we go that's what we call
that's a that's an artic Landing right
there he hit the brakes pretty hard
that was awesome
terraferma
oh you got to have a really good reason
to want to land a plane here it's a
great place to be I mean this is the
most beautiful
[Music]
spot there's always a moment when that
twin otter leaves and you're standing
here realizing that there's nobody for
hundreds of miles around
you're all alone out in the amazing wide
world time to get down to business I
know I've come here to try and figure
out what life was like in the Arctic
millions of years ago there's a
two-month Long window in summer when
conditions are right for fossil
hunting this is also a trip back in time
for me I first came here in 1984 when I
was only 23 years
old my first to elmir Island changed the
way I looked at Planet Earth and it
sealed my fate after that trip I knew I
had to become a
paleontologist yeah these are good
memories it's great to be back
here in addition to Jason Dave Briggs is
here to protect us from any stray polar
bears and completing the team is fellow
paleontologist jayen
Eberly once campus set up Jason is going
to help me find a special sight that I
never got to see the last time I was
here it's just straight Northwest for 4
km right just a little bit of a hike
then we uh sort of head Northwest I
guess the beds are dipping pretty
steeply
here yeah it's definitely something we
have to be careful of with this mud
[Music]
and there's a bit of a precipice over
there although it's genuinely in the
direction of where we're
going our Target is several hours hike
from our
camp this frozen tundra may look
Barren but for me as a
paleobotanist this is geologic
Heaven There are a few small Arctic wild
flowers and some Scrappy ground cover
but the nearest living tree is a th000
miles south of here I know the
coordinates are they our best guests are
somewhere in this
vicinity finally we reach what I've been
looking for
wow oh my God there's some amazing
stumps here look at
this sticking out of the hillside are a
bunch of weird brown rocks these are
petrified tree stumps wow one 2 three 4
five 6 78 9 10 11 12 13 14 15 16 17 18
in one view 18 trunks in
place a this is incredible man this is a
whole forest look at that one that one
is just
perfect you can see the whole shape of
the
trunk amazing
thing just
insane this is a stone tree trunk it's a
a petrified tree it used to be a growing
tree then it got buried and turned to
stone geologists have dated these trees
to around 50 million years
ago back then this treeless Hillside
would have been completely
different there's a lot of Clues here to
how this Forest got to be the way it is
the first is that all these Stone trunks
are surrounded by coal Black Rock which
is a very strong signal that these trees
when they are growing we growing in a
swamp the second clue are these
radiating roots in swamps Roots grow out
and not
down but what kind of trees were
these these rocks are just chunky silt
stones that are quite near the petrified
forest and I'm breaking them apart
because I'm looking for fossil leaves I
can find the leaves that go with those
trees I can put that Forest Back
Together Again Come to
Papa a now here we
go here's a closeup of that thing what
you got this is meta sequa little
needles it's the Dawn Redwood said
connifer these whole sprigs will fall
off as they've done here and land in the
mud this used to be
mud now it's a rock that would go with
those trunks the Petrified
Forest together these leaves and tree
trunks give us a window into the
past 50 million years ago this dried
Barren Tundra was a warm humid
swamp covered with lotus plants
Ferns and medaa trees that were as tall
as 150 ft
[Music]
the area covered in ice today was once a
massive
Forest that stretched all the way up to
the edge of the Arctic
ocean water ran off the land forming a
surface layer of fresh
water instead of sea ice the North Pole
was covered in subtropical floating
ferns
[Music]
the elmir we see today looks very
different but one peculiarity of the
Arctic summer Remains the
Same one of the things about working in
the Arctic is the sun literally never
goes down it just goes around and around
in the sky that means there's never any
night and it never gets dark it's
midnight right now take a look outside
my tent Yep looks pretty bright out
there but I want to go to sleep so I'm
going to go to sleep here's that we
do close the tent
zip up the sleeping
bag and put on the face mask good
night in the morning I head out to join
Jaylen
Eberly while I've been out looking for
fossil plants she's been hunting for the
animals that lived in this warm polar
swamp 50 million years
ago maybe through here and then up and
over and then back down the other side
I think so yeah I put my boots on then
you boots I've got sandals all right
you're better than me
tire we're
going okay so it's
cold I wouldn't want to be any
deeper there we go you beauty all
right Jaylen spent many Summers up here
searching for
fossils I do love the Arctic I've been
coming up for oh wow I think 10 field
Seasons now and almost everything you
pick up is undiscovered that's something
that doesn't to me uh ever get old
that's exciting searching for animal
fossils in the permafrost is really
tough they're little bits and pieces so
they're not going to show up a lot I
think we're going to need to crawl the
annual freezing and thawing break up the
bones into tiny
fragments uh probably not but um could
be a little piece of bone tooth of
anything right now actually would be
great cuz they're pretty rare uh even
the bits of pieces are pretty rare at
this site after around 4 hours of
crawling
about today
NADA but over the years jaylen's team
has Unearthed a fantastic collection of
creatures these guys are pretty
impressive looks like two jaw bones
missing their teeth yes that's right and
those come from a mamal called cidon and
uh there are no codons living today an
analogy you could use today would be
something like a pyy hippo and living in
in the rivers and stuff like that yeah
probably living in the rivers and the
swamps and munching on aquatic plants
and peridon was a hippol likee mammal
with short tusks and a tiny brain that
weighed just 3
o standing around 3 ft high and 8 ft
long cryodon was a vegetarian that
rooted around the swamp for its
food paleontologists have found fossils
of all sorts of animals here with warm
temperatures all year round back then
there were
turtles taper and even
alligators the fossils we find here on
ilmir island tell a remarkable
Story the Arctic was warm and wet with
no ice in sight
it was filled with plants and animals
similar to ones you might see today in
the swamps of Louisiana or the
Amazon the Frozen North was a completely
different world 50 million years
ago and that's got to make you
wonder if it was like this at a North
Pole what was happening at the other end
of the Earth
10,000 miles south of elmir is the
world's wildest
continent the most extreme place on the
planet there's one word that describes
Antarctica and that word is
ice and the entire continent is one
icebound
mass in fact 90% of the ice on planet
Earth is here in Antarctica
with a record low temperature ofus
128° F this continent is officially the
coldest place on
Earth even in summer the temperatures
rarely ever get above
freezing Antarctica is the size of all
the United States plus Mexico and it's
covered with a sheet of ice that in some
places is almost 3 mil
thick that's a lot of ice
but has Antarctica always been deep
Frozen like
this to investigate I've come to Nelson
island off the Antarctic
Peninsula I'm joining paleontologist
Marcel Lepe from the Chilean Antarctic
Institute Marcelo is taking me to a
small
island one of the few spots with exposed
land where he and his team have been
hunting for fossils after a week we
didn't find a a fossil wow you looked
for a whole week and found nothing yeah
we started to make a hole in the ground
just close to the to the Sea and we
found the the out just by accident think
you can find it today uh I I I hope
so the out crop after is only accessible
at low tide so we've had to time our
Landing just right
Dr our gear here
H yeah
I
yes just like on Emir Island the Bedrock
on this beach is tens of millions of
years
old ah not a great one but it's
definitely a fossil we're in the right
spot
crawling around on this Rocky landscape
today it's hard to believe that anything
could ever grow
here Antarctica has no trees at all just
mosses and lyans and only two species of
flowering plants so when you find a
fossil plant here is telling you about a
very different world
indeed but after just 10 minutes of
digging we find something incredible oh
wow just like that that a beautifully
preserved Leaf from an ancient Beach
tree that one looks like a modern Beach
it's the size of a beach leaf wow and
it's large you can see that it's the
middle section there's the main vein the
lateral veins Leaf would have been about
that long and about that wide and these
very straight secondary veins are
typical of the beach family a northern
temperate forest tree tree that's
deciduous you see it growing in New York
City in in London and here is a chunk of
it from the beach in Antarctica next to
an
iceberg on a very cold
day oh look at that one that's great
we're finding Forest tree leaves and
they're found in great numbers
altogether like Leaf litter implying the
forest was right here where we're
standing or kneeling right
now these fossil leaves reveal a very
different picture of n Island from the
landscape we see
today 83 million years ago this frigid
place was covered in a verdant Forest of
Southern Beach ginkos and tree
ferns with mild temperatures rarely
dropping below
freezing and it wasn't just this one
spot we've just been on the beach found
these amazing fossil
leaves these leaves on the other hand
are from a different place they're from
southern Chile we're here here's a 700
mile Gap and here is southern Chile this
Leaf is from Southern South America and
it's very characteristic of the beach
family as this Leaf from Antarctica that
we just collected this morning so we
have Chile and Antarctica pretty strong
evidence that these two places were
connected we've known for a while that
Earth's TR is broken into plates that
slide and Collide on top of hot flowing
rocks deep beneath the surface evidence
like matching fossils from South
America
Antarctica and even
Australia tells us that these three
continents were once joined together and
covered with a vast Forest stretching
across the South
Pole so with all these trees and a nice
warm climate
what kinds of creatures lived on this
ancient Southern
continent although fossils have been
found in Antarctica some of the biggest
Clues are in
Patagonia at a remote site in
Argentina a team of paleontologists has
just discovered the remains of a forest
dweller that must have had a very large
appetite
this guy was you know all scattered
around all the
[Music]
bones the leader of the Expedition is
Diego
Paul we found the entire for L and then
the other h l and then some to and the
tail so
on all these parts add up to a 69
milliony old
dinosaur it's going to start chipping
away at this thing
yeah the keep thing to not destroy a
dentist or fossils do not let a
paleobotanist in the dentist or Quarry
CU we tend to break big rocks with
pickaxes and sledgehammers and these
guys use little tiny picks and
brushes we're not trying to expose the
bone we're just trying to undercut it
gently and get the rock removed so I'll
just carefully pick around here at the
base see how delicate I am know I'm
doing a beautiful job of carefully
extracting this bone from its Rocky tomb
where it's laying undisturbed for 69
million
years I need to watch my hammer with
this specimen because it's pretty unique
this is a dinosaur without a name it's a
new species of dinosaur and that's a
really cool
thing Diego's team has just discovered a
new species of
titanosaur a plant eating
dinosaur with a long tail long neck and
small head titanosaurs could become so
big because there was so much vegetation
and some species grew to be the biggest
animals that ever walked on
[Music]
land some people estimate these animals
were eating like 1,000 lb pletal per day
1,000 lb a day th000 lb a day that's
half a ton of vegetables a day the
original vegans oh my God yeah these
animals probably have a pretty big home
range they go in and Destroy one forest
for a while they go destroy another
forest with South America and Antarctica
connected into one continuous continent
these munching monsters had plenty of
forest to roam in search of a good
meal did they have any titanosaurs from
Antarctica yeah yeah actually there is
one I mean they found a single bone it
was found in the Antarctic Peninsula
single bone a tailbone wow what a lucky
find that was amazing so we're really
looking at an animal that could have
walked easily to Antarctica absolutely
for a good sandwich
yeah this fossil is a fantastic find but
in 2014 not far from here Diego and his
team uncovered a creature even more
awesome
this is the femur we collected yesterday
it's big but it's nothing compared to
the biggest dinosaurs this one is the
largest one ever
found check out the size of those
vertebrae each single backbone is about
4T
tall I'm a big
guy but this bone dwarfs me I'm lying
next to the 8ot long titanosaur thigh
bone that Diego's team Unearthed
and just in case you can't picture how
big this
was this thing is absolutely immense
there's a life-size model of this 75 ton
Beast that greets you when you drive in
from the local
airport I've seen the bones but I
haven't seen the Reconstruction
before how to go Titan
the world's largest
dinosaur it's incredible to realize that
animals like this once roamed between
South
America and
Antarctica so what's going on here
dinosaurs near the South
Pole and swampy forests in the
north were the poles really that warm
back then
or could there be another
explanation what about those tectonic
plates that move the continents around
could this be the reason that we find
all those warm weather fossils in the
polar regions
today sometimes people tell me that oh
wait PL tectonics means that land masses
can move around and maybe those fossils
you're finding were deposited at Mid
latitudes then brought to the Arctic by
continental drift it's a good thing to
think about but we actually know where
the continents were when they were there
we actually know those positions and we
know for sure that Antarctica was down
by the South Pole and the lands on ell
Island were up by the North Pole when
they were forested by these warm forests
so it's a good idea but the science says
Nope there really were polar warm
forests the entire planet really was
warmer and all the polar ice we see
today didn't exist tens of millions of
years
ago that is pretty
weird but there's an even weirder part
of the story of ice on this
planet this time the evidence isn't at
the
[Music]
polls it's in the hottest place on
Earth Welcome To Death
Valley I'm here at the national Park's
official weather station at the
appropriately named Furnace Creek Ranger
Alex rool is letting me take today's
measurements so this is our rain
gauge it hasn't rained in a while ow
it's always is it hot yeah it's metal
hold this okay yeah we'll see if there's
a any water in it oh that is really hot
metal all right there's nothing in
it
dust this is the
temperature gauge I see so it's in the
shade they say I'm reading like 103 and
a half is that what you get yeah and you
check this every day yeah we do and then
we record it July to August it spent
something like 28 days over 120 this
year so you got a pretty legitimate
claim to be one of the hottest places on
the planet oh we are the hottest place
on the planet all right so that you
actually hold the alltime record here
and you love this place yeah this is the
best national park the best place on
Earth I love it and the hottest place on
[Music]
Earth but has it always been that
way geologist Francis McDonald has spent
many years battling the heat in these
Desert
Hills searching for clues that might
reveal the secrets of death Valley's
past why I really like coming out here
is all of this raw
Rock here in Death Valley you're not
limited by Rock you're limited by how
far you can walk out there in this hot
weather the Rocks here date back to a
Time way before the dinosaurs long
before trees or even plants
existed why in this rock formed 640
million years ago do we have these
Brocks within the rock this one's a
granite and it's surrounded by this pink
sand and silt and mud and here's another
quartzite piece here's a piece of
carbonate the different Rock types
they're telling you about where they
originally formed these rocks came from
a whole bunch of different places all
over the
place what could have brought this
strange mixture of rocks here and encase
them in
Silt we need a process that's just going
to pick up rocks from all over and dump
truck them into a pile of mud and sand
and we do know one process that does
that and that's
glaciers so we're sitting here in Death
Valley and it's about 95°
and you're pointing to a rock and saying
that it was deposited by a giant slab of
glacial ice so work with me here a
little got to use your use your
imagination what these rocks tell us is
that 640 million years ago the climate
here in Death Valley must have been much
colder so cold that what's now a
scorching desert was covered in giant
sheets of ice as big as you'd find in
the polar regions
today the idea of an ice covered Death
Valley is strange
enough but these rocks tell us something
even more astonishing about how far the
ice extended even though here we're
sitting today it's say about
35° north of the equator we know 640
million years ago this was Far further
south and was situated very close to the
equator earth's tectonic place have
shifted quite a bit over the last 640
million
years back then Death Valley was part of
a huge land mass that sat right on the
Equator so if the ice made it to
here it likely stretched all the way
from both North and South until it met
in the
middle making the entire planet a
snowball Earth
[Music]
for me this is a pretty mindblowing
realization wherever you are in the
world by uncovering evidence in the
rocks and fossils you can travel back in
time and reveal that earth's climate has
undergone incredible
[Music]
changes you have to split a huge amount
of rocks to find a
fossil the only way to find them is just
work your way down through the lake
layers so I just sort of chop a
staircase down the hill sometimes an
entire
Hill in fact we can use the chemistry of
rocks and fossils to find the
temperature at the time those rocks
formed piecing together data from sites
across the globe scientists can build a
temperature timeline going all the way
back to 500 million years ago
laying out Earth's temperature like this
you can see a
pattern the climate fluctuates between
long periods when it's warm with no ice
at all Hot House worlds and cooler
episodes with ice caps at at least one
of the
poles Ice House
Worlds the hot climates are three times
as common as cold
climates and yet Perhaps surprising ly
we live in one of the Ice House worlds
today today we live on a planet that has
ice at both poles we think that's normal
because that's our world when we look at
the fossil record we realize that our
planet has only had four episodes where
there's been glacial ice only about 25%
of the last 500 million years has our
planet been like it is today
so why is this why is Earth spent so
much of its past as a hot house much
warmer than it is
now we can find Clues from a close
neighbor in our solar
system I'm looking at Venus it's the
third brightest thing in the sky after
the sun and the moon it's also one of
our nearest planets but Venus has a very
unusual feature it's about 800° Fen on
the surface of Venus it's hot enough to
melt lead
why is Venus so hot it is a little bit
closer to the Sun than we are but not
enough to explain the huge temperature
difference we found the answer back in
1967 when the Soviets sent the venira 4
space probe to
Venus just before it was crushed by the
huge atmospheric pressure the spacecraft
beamed back its precious data
it had identified one critical component
of the planet's atmosphere the reason
Venus is so hot is that its atmosphere
is composed almost entirely of carbon
dioxide
95% this thick atmosphere rich in CO2
acts like an insulating
blanket most energy from the Sun passes
through this
layer but when it radiates back from the
planet's surface the carbon dioxide
traps the
Heat this is the greenhouse effect which
drove Venus to get hotter and
hotter it didn't just heat up it boiled
Venus is a clear example of a runaway
greenhouse climate what happens when you
get too much carbon dioxide in your
atmosphere so if carbon dioxide can warm
up a planet is this what created all
those hot house worlds in Earth's
past how can we know how much CO2 was in
the atmosphere millions of years
ago the answer may be hiding in some
very special
leaves and deep in a forest just outside
Washington DC is an experiment to try
and unlock their
secrets the experiment is being run by
one of my former students Rich bark
hey Rich oh hey Kirk Let's It Go man hey
welcome to the fossil atmospheres
experiment he's investigating the gko
tree the Geto is pretty special because
fossils tell us that this species has
survived almost unchanged for the last
200 million
years since all plants use carbon
dioxide to grow a plant that's been
around that long might be able to tell
us how CO2 levels have
changed rich is is growing them in
customade atmospheres to see how
different amounts of carbon dioxide
affect the
leaves so each of the chambers in here
has a a different CO2 concentration this
is a control tree at 400 parts per
million 600 the next treatment up 800
parts per million the final tree 1,000
parts per million can we go in the we
can go into the into the chamber Yep
this tree is growing at 1,000 parts per
million you put a tag around the branch
so you can just wrap that around the
branch and I take the leaf that's right
above that one yep that one right there
is fine so what we do with the leaf is
we take it back to the lab and we can
look at the the details of the leaves
under a microscope the leaves all look
pretty much the same to me but put them
under a microscope and you see something
really
cool this is the service of a genko leaf
from this experiment you have to go in
about 200 times magnification now you
can see that the leaf from today's
atmosphere is perforated with tiny holes
called
stomata this is where the plants take in
the carbon dioxide they need for
photosynthesis and what rich is
discovering is that adding extra CO2
does something striking to the stomata
then I've got this one and it's really
obvious to me that there's far fewer
pores on this one that one's from the
1,000 PPM Chambers as CO2 increases they
don't need as many stamata they can
become more efficient more CO2 less more
CO2 fewer
stamata this happens with all kinds of
plants that take in carbon
dioxide but because genos have been
around for 200 million years they can
preserve a snapshot of Earth's CO2
levels in the Deep
past this is a fossil of genko it sure
is it's it really looks like gko I mean
this leaf and that leaf are are almost
identical how old is this one this
fossil is 56 million years old old and
when you take that you can put it under
a microscope and seen the exact same
features as you find on the
modern right there on the fossil is the
pattern of stamata many fewer than on
the leaves
today fossils from all around the world
help us estimate CO2 levels going back
more than 400 million
years if we look back on our temperature
timeline we see that when CO2 levels are
high it's it's hot and when CO2 levels
drop it
cools when this gko was alive 56 million
years ago about the same time that
swampy forests were growing on elmir
island in the Arctic the amount of CO2
in the air was roughly four times what
it is
today so where did all that CO2 come
from
[Music]
one possibility is from deep inside the
earth here at Mammoth Lakes in
California the ground is belching out
Steam and
gas and the pools are literally boiling
beneath our
feet because right under these mountains
is one of the largest super volcanoes in
America wow this place is pretty cool
yeah it's amazing isn't it geologist
Kayla yovino studies volcanoes all over
the world we don't want to get too close
to the edge of the water here the ground
is quite unstable if you did fall
through that would be very very bad news
okay I won't do that do you want to hold
on to this read off all right here we go
Kayla is taking measurements to monitor
the volcano's activity starting with
temperature it's like trout fishing you
sneak up to the edge of a creek you
lower the line over the edge and you
wait you waiting yeah next she needs to
measure the composition of the gas
rising out of the ground
you want to use this little tiny Mud Pot
yes looks like a good one this is a CO2
meter and it can tell us the
concentration of carbon dioxide in the
gases that we measure the level of
carbon dioxide in the air is around 410
parts per
million but the reading from the Mud Pot
is much higher there we go 3,000 parts
per million of
CO2 the magma that sits deep within the
Earth contains lots of carbon
when this magma gets close to the
surface at a volcano that carbon is
released into the air as carbon
dioxide Kayla is part of a team of
scientists measuring how much CO2 is
being released from volcanoes all over
the
world so it's based on Volcano by
Volcano by volcano that's how it's done
they actually look at individual
volcanoes yep and they kind of add them
up together even volcanoes encased in
ice like Mount arabus and Antarctica are
spewing out carbon
dioxide Mount Etna in Italy is built on
carbon-rich rocks and buches out more
CO2 than almost any other
volcano when geologists estimate all the
CO2 coming out of volcanoes today the
total is around 300 million tons a
year that might sound like a lot but
it's not enough to significantly change
Global
temperature the amount of CO2 coming out
of volcanoes today just doesn't even
come close it's tiny compared to the
amount of CO2 that humans are putting
out for example what it takes to
actually warm the planet from a volcano
from volcanic CO2 is a massive amount of
CO2 put out over a very long period of
time today Earth's volcanoes are
relatively quiet and aren't cooking up a
whole lot of
CO2 but in the past it's been a very
different
story this 10 m wide Basin looks
peaceful
today but many thousands of years ago it
was the sight of a huge eruption that
speed at 150 cubic miles of lava and Ash
and this is just one spot we know that
at certain points throughout Earth's
long history volcanoes and other
geologic activity released much more CO2
into the atmosphere than
today and sometimes this Ed for millions
and millions of
years that's what geologists think must
have kept the planet so warm during all
those long periods when Earth was a hot
house giving us warm polar forests
teeming with
life but if volcanic activity keeps
releasing carbon
dioxide why hasn't CO2 built up in our
atmosphere making our planet overheat
like Venus
[Music]
Earth must have something Venus doesn't
a way of taking carbon dioxide out of
the atmosphere and putting it somewhere
else turns out here in the mountains of
Alaska I'm experiencing it what's
falling in my hands and my face right
now is rain in the mountains and it's
got dissolved CO2 in
it rain absorbs CO2 from the air and
then the raindrops combin to form
streams that eventually become fast
flowing Rivers
the dissolved CO2 makes the water
slightly acidic helping it erode and
weather rocks releasing elements like
calcium magnesium and
silicon riding these Rapids gives me a
sense of just how powerful the river is
yeah off the edge
yes it's like a saw that's cutting right
down and the canyons are just cutting
their way into the mountain range and
chopping them in half the water I'm
rafting on now is full of just the right
chemical elements that will help lock up
[Music]
carbon that was
awesome eventually all the water in this
River will end up in the Pacific Ocean
and with it all of those dissolved
minerals once they reach the ocean the
dissolved elements are taken in by tiny
sea creatures and used to build their
shells
over millions of years these shells drop
down to the seafloor forming layers of
limestone locking the carbon that used
to be in the atmosphere into
rocks It's the final stage of a process
that's been driving our climate for
millions of years the carbon
cycle there's a finite amount of carbon
on planet Earth when that carbon is in
the ground locked up in rocks or
sediments then the planet is cool and
when that carbon is up in the atmosphere
as carbon dioxide the planet warms and
the climate history of our planet is
this tug and pull between carbon in the
ground and carbon in the
atmosphere we can see how this balance
plays out on the planet's southernmost
active
volcano Mount
arabus here in Antarctica this mountain
terrain is encased in ice year
round there is no rain and there are no
Rivers the weathering part of the carbon
cycle is
stalled meanwhile the volcano continues
to spew out
[Music]
CO2 Mount arabus is a window into what
it was like 640 million years ago during
snowball Earth when the planet was
covered in
ice with CO2 from ice covered volcanoes
building up the planet eventually got
warm enough to melt the
snowball if adding Co to is how we melt
a frozen planet then how do we freeze a
warm
[Music]
one about 50 million years ago after
more than 200 million years in a hot
house carbon dioxide levels started to
drop and the Earth began to
cool eventually gigantic ice sheets
began to
form first in the
Antarctic and then the
Arctic a new era had begun that we still
live in today the ice
house but where did all this ice come
from how do you build an ice sheet a
mile or two thick when you start with
[Music]
nothing to take a closer look at how ice
sheets form I'm going to climb down into
a
glacier a little help from Mountaineer
Brian rouie perfect wish me luck yeah
have fun down
there there's actually an overhang yeah
get your butt as low as you feel
comfortable and then take a step down
first I have to hop over this year's
snow layer it's quite a step
nice that's like a foot and a half
overlap man nice work beneath the
overhang are snow layers from previous
years pretty amazing to be hanging out
here in this ice world and to imagine
how this ice even got here in the first
place each year it snows in the winter
in most places snow melts in summer but
here the summers are so cold the ice
never fully melts and next year's
snowfall piles up on top snows falls in
the winter and it stays there throughout
the summer and the next summer and the
next summer and the next
summer over many Winters the snow pile
gets
higher and heavier compressing the
snow the weight of the snow pushes down
and compacts the underlying layers into
ice over thousands of years these layers
build up until they form an ice
sheet and that's exactly what happened
at our
[Music]
poles when carbon dioxide levels fell
around 50 million years ago the
temperature started to
drop and Ice eventually took hold at the
bottom of the
planet our Ice House world started 34
million years ago here in
Antarctica but carbon dioxide wasn't the
only culprit responsible for the deep
freeze it turns out there was something
special about
Antarctica its position on the globe
globe in that direction 700 Mi is the
southern tip of South America in between
me in South America is what's called
Drake
Passage this stretch of water is one of
the most feared passages in the world
it's got tremendous
storms I feel really lucky to be on a
boat where I'm not actually seasick cuz
it's a nice flat calm day here but if we
uh wait just a few hours is things get
pretty
ugly the reason it's almost always
stormy here is because there's a
powerful current that constantly runs
from west to east through this Gap but
it hasn't always been this
way we know from fossils dating back to
the dinosaurs that Antarctica used to be
connected to South America but around 30
to 40 million years ago the giant
tectonic plates beneath the continents
gradually pulled
apart eventually creating Drake
Passage once Antarctica was free
powerful currents started circling
around the entire
continent this is the circumpolar
current and it keeps the cold in
Antarctica and it keeps the warm from
Antarctica so it sort of keeps the
refrigerator door closed on this Mighty
icy continent because the current was
then allowed to go right around the
continent endlessly around endlessly
around keeping it cold and
Frozen we think it's right around this
time that Summers down here got colder
so cold that the Winter's snow wouldn't
melt beginning at the South Pole the
snow piled up and Glaciers grew and
slowly Antarctica started to freeze
over but it would take millions of years
more for the Arctic to get its ice
mainly because at the North Pole
there is ocean rather than
land and it's hard to form ice sheets on
water but eventually it cooled enough
that ice began to form on the
surrounding
land and once it was there ice sheets
could spread
quickly sometimes even reaching Seattle
my
hometown this is my old neighborhood I
lived here when I was was 8 years old
until I went away to
college used to play in these forests my
house is only about a block
away walking around now I see things I
missed as a kid clues in the landscape
that tell me what happened
here plopped right in the middle of a
nearby neighborhood is something
remarkable this is a huge
Rock I grew up in Seattle and never
heard about this rock that kind kind of
bothers me it's a gigantic
Boulder it's got trees going around it
so it's been here a long time it makes
you ask the question how did they get
here to understand how you need to get
the big picture and luckily I know a
place with a spectacular view a spot I
dreamed of climbing when I was a kid oh
yeah the top of the Seattle Space Needle
this is
fantastic you going to clip me in the
back
there okay I'm ready to go
and okay I'm 600 ft above the street no
place to be if you're scared of
heights but for me it's the perfect way
to check out the city's
Contours oh man what a great place this
is really phenomenal I never thought I'd
be able to climb to the top of the Space
Needle in my
hometown and you really get to
understand the landscape when you view
it from above you can see things you
don't see when you're at human scale The
Hills Have a grain to them north to
south and this case they're all pointing
in One Direction as if something
powerful flowed over
them this is a landscape created by
snow accumulating year after year to
form a massive moving ice sheet big
enough to shape Hills and dump a huge
Boulder on what's now the edge of the
city around 177,000 years ago an ice
sheet once towered 3,000 ft 5 times the
height of the Space
Needle Seattle was at the edge of a vast
ice sheet that covered half of North
America in places the ice was over 2
miles thick
this landscape my landscape of my
childhood but it's also the landscape of
glaciers it's just
killer what a day in
Seattle when you think about this whole
area buried in ice it makes you wonder
how did anything live through this ice
age to find out I'm heading north to dig
up some
Clues buried at the edge of the Canadian
Yukon home of the kondik Gold Rush
they're still mining gold here today but
not with pans and
shovels now they use giant water jets
that make a fire hose seem like a garden
sprinkler these melt away the Frozen
Earth to uncover the gold bearing
gravels
below but there are other Treasures
buried here Ice Age
bones paleontologist Grant suula is
always on call to retrieve
them hey Logan I'm Grant I'm Kirk I'm
Logan good to meet you have a go oh yeah
what what I do just tally hold on yeah
nice slow movements who doesn't love
blasting a fire hose at something this
is really fun there's a buried gravel
layer that's got the gold in it and the
silt that's frozen has all the bones in
it there's a layer of Bones and a layer
of gold bearing gravel if there wasn't
gold in this gravel then we'd have no
ability to actually find any of these
bones because there's no way you're
going to get through that in a Trel you
know look at that that layer of ice is
amazing that i'm exposing that's 25 or
30,000 year old ice in there 25,000 year
old ice yeah this permafrost layer is
ground that's been permanently Frozen
since the last ice age once the hose
breaks it up we go hunting oh here we go
oh yeah wow a little bit of a scapula I
think it's a horse
oh wow yeah permafrost is amazing stuff
because it's cold enough to preserve the
tissue of buried animals as if they were
in a freezer got a big beast over here
Kirk it's a big piece of Mammoth oh it's
huge yeah it is left a shovel on your
side oh it's still it goes in quite a
way wow smells like the pine doesn't it
smells good it's the pelvis of a woolly
mammoth this is still bone it's not like
a dinosaur fossil where has been
replaced by minerals this is still
actual bone even though it's thousands
and thousands of years old we call it a
fossil it's just not a petrified F yeah
absolutely what do you got there too
it's probably a moose antler oh wow a
moose pull it here's a tooth is that a
horse tooth there are fossils everywhere
here and this is oh horse tibia tiia
this is like name that bow oh my God
this is an upper horse horse smaller I'm
not leaving I am not leaving oh what'
you get it's a chunk of uh the skull of
a wolf wolf hey first carnivore three
beautiful MERS in here this is uh like
taking candy from a baby just take my
candy oh here's your
candy oh there's a Tusk right oh he
really cool solid Ivory in there just
found the Tusk of a woolly
mammoth just walking around carrying a
mammoth tusk like nothing's going on on
a summer's day these are Blades of grass
that were collected by an Ice Age Arctic
ground Square 30,000 years ago there a
30,000 year old piece of ground squirrel
poo yeah absolutely
yeah I think everything that could be
found has been
[Music]
found it's an impressive
[Music]
Hall got bison mammoth
horse moose Caribou miscellaneous
carnivores Carnivor is a wolf and a
lion so what can these bones tell us
about life in the last ice
age they're so perfectly preserved we
can figure out how the animals adapted
to survive the harsh cold
climate take woolly
mammoths they would have stood about 10
ft high with giant tusks up to 12T long
they evolve from the same ancestor as
modern-day
elephants but to survive the colder
climate woolly mammoth developed long
hair and small ears that prevented them
from losing too much of their body heat
through their
skin there was no shortage of mammals
living
here 228 bones that's a that's a big
haul for a single day 20 28 bones in 4
hours so how did all these different
mammals survive here when we know that
much of North America was buried under
ice to thrive here they needed to eat
and this means something must have been
different in the
Yukon when you have animals like woolly
mammoth and bison and horses which are
animals that are big grazers they need
to consume a lot of grass this is
telling me that this landscape is
covered by expansive grasslands there's
like there's no Arctic grass lands today
at all no absolutely this is an extinct
ecosystem this is the this is an
ecosystem that we have no analoges to in
the present day
environment but if there was grassland
here during the Ice Age that means
unlike the rest of the north this part
of the continent was Ice
free places like Boston and Seattle and
Chicago were covered by Ice yes most of
Alaska was not and the part of Yukon
that we're in was not covered by
climatologically it's telling us that it
was almost too cold and too dry to
support
glaciers While most of North America was
icing over here in the far Northwest
there wasn't enough snow to build an ice
sheet and with more of the planet's
water now locked up in glaciers sea
levels fell exposing new ice free land
between Alaska and
Siberia the bearing land bridge
this was a great place to be during the
Ice Age there was glaciers only probably
100 kmers away but this was a little
little bit of an Ice Age Oasis for these
animals because it was highly
productive what's now forest in
tundra would have been more like a
prairie covered in Wild grasses and in
summer small flowering plants like
poppies buttercups and
[Music]
Sage the ice of eventually started to
retreat leaving an ice free Corridor
that allowed Ice Age animals and later
people to migrate between Asia and North
[Music]
America we still live in an ice house
world with ice at the
poles but it's obviously nowhere near as
cold as the most extreme ice ages so
what's going
on we can find the answer thanks to a
large
meteorite that struck the Arctic 32
million years
ago creating a 10m wide crater that
became a
lake ever since the lake formed even
when it was covered in
ice sediment all the stuff floating or
living in the water has been settling
down to the lake Bottom forming
layers locked inside the thin layers is
a detailed history of our current Ice
House stretching back 3 and2 million
years today Lake El gitkin lies 60 Mi
north of the Arctic Circle in
Russia back in
2009 scientists set out to unearth the
secrets buried deep beneath the frozen
lake but it wasn't
easy one more Julie Brigham gredy was
the leader of this extreme
Expedition there's lots of lakes in the
world why that one turns out this
meteorite hit right smack dab in the
largest unglaciated area in the entire
Arctic we put a 100 ton drill rig out on
the lake ice and then drilled from that
platform the team only had a short
window in the very depths of winter when
the lake ice was strong enough to
support the drill rig
over 50 scientists from four countries
camped out on the frozen lake working in
temperatures often 30 to 40° below
zero this was one of the most difficult
and dangerous drilling projects ever
attempted slide it just a little bit so
I feel privileged that Julie's letting
me handle these precious cores this is
nice okay yeah so this goes around this
side this 1,000 ft length of core is the
longest continuous record of Arctic
climate we
have so a single layer like this little
layer right here that's telling you what
was happening to the climate on that day
yeah we're extracting the climate
history so you've basically got a mud
record of 3.6 million years of climate
in the Russian Arctic yeah this is just
a small part but we have the entire core
represented here in photographs which
allow us to then look at the entire core
over time that's great you can scroll
through
it layer by layer Julie has pieced
together an astonishing
story we can zoom in on this older part
of the record pollen spores and other
fossils in the mud layers from 3 and 1.2
million years ago reveal a climate
warmer than today back then this Arctic
Lake was surrounded by Hemlock and Hazel
trees and the water was teeming with
life creatures tunneled into the lake
Bottom stirring up the mud layers and
leaving them
smooth but then here around 2.6 million
years ago there's a sudden
change these dark striped layers come
from a time when the lake was completely
frozen over all year round with no
plants or animals living on the lake bed
you could have ice skated across the
Lake in
July that's
cold here Julie can pinpoint the moment
when this part of the Arctic froze over
2.6 million years ago this isn't found
anywhere earlier in the lake history all
of a sudden boom comes the first
glaciation right and here's what's
really cool as we move along the length
of the core these contrasting periods of
warm and cold pop up again and again
the temperature swings between very cold
periods called glacials when the ice
sheets extend down over the
continents and warmer interglacials like
today when there's still ice but it's
confined to the
poles but what causes so much variation
within the Ice House
World why does the ice grow and shrink
in such a regular rhythm
there's some changes in the earth's
climate that are periodic we don't think
anything about
them things like the change of the
[Music]
seasons let's call that fire Sun here's
I got a little bit of a globe right here
and we know that the sun is 93 million
miles away from planet Earth and what
makes the seasons is that the Earth is
tilted so when the northern hemisphere
is tilted towards the sun you have
northern hemisphere summer 6 months
later as the Earth rotates around the
Sun you have the southern hemisphere
summer and that change of the seasons
makes lots of sense to
us but there are longer term variations
in the earth's climate
too and these changes are also driven by
the way our planet moves around the Sun
and receives energy from it our orbit is
distorted by the gravitational pole of
the bigger planets Jupiter and Saturn
those big planets are pulling on Earth
and they're bending and flexing the
Earth's orbit around the
Sun the shape of our orbit gradually
changes from more circular to more
oval and there are two other things that
drive these climate Cycles the tilt of
the earth shifts and it wobbles on its
axis all these changes over time add up
to a repeating pattern of warming and
cooling over tens to hundreds of
thousands of of
years where the ice grows and shrinks
over and over
again these swings in climate can make
it pretty challenging for life to
thrive even for a highly adaptable
species like
[Music]
us the first humans appeared about
300,000 years ago and they had to deal
with very erratic climates cold cold to
hot to cold to hot but around 12,000
years ago something
changed from the depths of the last ice
age our planet warmed and the glaciers
that covered much of North America and
Europe
retreated as the ice melted sea levels
started to rise flooding River mouths
around the world and building up Deltas
like the Nile