today we're in the midst of a scientific
revolution in our understanding of the
earth and our relationship to it
it's a revolution that's had a big
impact on my own thinking
my name is Aubrey Manning I've spent my
career as a biologist but I now realize
that those of us who study the creatures
that live on the earth have a lot to
learn from those who study the earth
itself as a biologist what I find so
fascinating is that as Earth scientists
learn more and more they're revealing
just how intimately life and the planets
are connected we'll never fully
understand the history of living
organisms unless we first understand
also in the story
recently scientists have begun to think
of the earth in a new way almost as a
living organism
like a living thing it is forever on the
moon
driven by the restless energy locked up
in its interior
and as the planet has evolved so his
life shaped by the same forces that move
continents and change climates
in Earth's story I want to explore this
new vision of a living planet
so I've been learning to see the world
through the eyes of geologists and the
essence of that viewpoint is an
understanding of time
to understand the earth geologists have
had to learn how to travel through time
well are there collecting gases from the
summit of an active volcano or bringing
up mud from the floor of the deep ocean
geologists are always looking back in
time
and as they slowly pieced together the
planets past they've been forced to an
astonishing conclusion that the
timescales of Earth history are almost
inconceivably long the time itself is
far faster than they'd ever guessed yet
as I've learnt this profound insight
flowed from the simplest question one
can ask about the earth how old is it a
question which geologists have struggled
to answer for 200 years
at the turn of the century
one such geologists came to a remote
corner of southern Africa called the
Barberton mountain land his name was
Alan Hall and he had a commission from
the South African government to map this
area looking for gold
the Barberton mountain land is several
thousand square kilometers of rugged
terrain cut through by rivers
rocky outcrops topped the hills size of
the bedrock hidden beneath the landscape
Paul's aim was to record these outcrops
and so build up a picture of the rocks
below the surface
Blu's he worked his way across the
landscape all strongly realized that
something was missing
however hard he looked he could find in
the rocks none of the usual signs of
fossilized life could Barberton be a
fragment of the earth from a time before
life began just how old was this place
Paul's question came in a critical
moment for a hundred years scientists
have been arguing about the age of the
earth as they challenged ideas which had
held sway for centuries two hundred
years ago most people in the Western
world wouldn't believe quite literally
in the biblical story of the creation in
Genesis it tells us how God created the
earth and all the living things in it
including ourselves in just six days
of course the biblical account of the
creation implies that Earth history and
human history began at the same moment
and indeed the first attempts to
estimate the age of the earth came from
scholars who went to the Bible and took
the descendants of Adam with their
different ages and simply added them up
and came out with the authoritative
statement that the earth had been
created in 4,000 of 4 BC which meant
that it was just under 6,000 years old
but it didn't look that way to
geologists when they study places like
Barberton they saw evidence that the
landscape had changed over time that
they had a long history
holes modern-day successor is Martin
DeWitt
he too is fascinated by the question of
Barr Burton's antiquity the end of the
70s came down here to Barberton these
special to tell about the story of the
earth
Martin like halt before him has mapped
the rocks of Barberton in detail when
you do this a striking pattern quickly
emerges why don't you stop mapping the
hills here you'll notice that the
landscape was donated by stripes stripes
of rocks like that one there if you get
your eye in after a while you'll seeing
that all these rock layers all are
visible in this case this huge mass here
has finer vertical rock layers
everywhere in Barberton the landscape
seems to be made of layers
by the 19th century geologists had begun
to realize that the process that created
these layers was still at work all
around them
aughter can be a powerful agent of
change
destroying rock but also creating it
over time as the kamati River flows
through the heart of Barberton it cuts
down through the rocks eroding them into
sand and silt which it carries
downstream where the river flows slowly
the silt falls to the bottom layer upon
layer eventually to turn into new rock
well here you have a slab of rock now
this slab represents a riverbed well
yeah there you can just even see the
sand gang these are moving the sand
grain in the river these ridges that you
see here they are ripples I can tell
that a rooted flow from my hand here
downwards in that direction now you can
see if you look downwards in fact there
are several these slabs stacked on top
of one another
here's one don't see another one over
here and another one and another one
still warm
he's a dozens of slabs all tilted right
now but originally that would have been
horizontal represent all history of
rivers a long history of deposition
to 19th century scientists a world made
up of layers didn't look as if it had
been created all in one goes the Bible
says it must have been built up over
time
but how much time
the first person to realize that by
studying the rocks you could learn about
the age of the earth with a Scotsman
James Hutton 200 years ago he came to
this place sicker point about 20 miles
down the coast from Edra and the
discovery he made here change forever
the way that geologists think about time
at siccar point I was joined by Chris
Nicholas a geologist who's made a
special study of James happens work
Chris wanted to show me a small patch of
cliff side famous to geologists as
happens unconformity what happened saw
was that the gray rock that's down
towards the bottom of the cliff stands
vertically but on top of it is this
horizontal red rock between the two is
this undulating surface what do you make
of it what did he do deuce from that
well if all rocks were deposited
horizontally he couldn't work out why
this growing one was vertical underneath
how they form they're doing that and the
way he answered this was to say well
what must have happened to this grey
rock is that it must have been deposited
on the seabed at one time and it must
then have been twisted and brought up so
that it's sitting vertically and it must
then have been eroded off so it must
have been land it must then have been
drowned under the sea again for this red
rock to come in over the top and be
deposited and even that there's also
been lifted up to give us the cliff face
now what he was suggesting here is that
we really have at least three cycles of
deposition on seabed then uplift then
erosion three cycles
but Hutton could see that the water eats
away at the land only very slowly each
one of his cycles must have taken a long
period of time to complete and he could
see no reason why there were not many
cycles prior to these ones he could see
in the cliff face here and who knows how
many will come after this these endless
cycles meant the for Hutton Earth's
history was to all intents and purposes
infinite
siccar point represents for us the
discovery of geological time the idea
that the history of the earth is
infinitely longer than human history
this idea this sense of time has
informed everything that geologists have
done and thought since they recognized
that there is time enough for
unimaginably slow processes to have
enormous effects on the earth the
significance of this discovery wasn't
lost on Hutton's contemporaries one of
them John Playfair and mathematician
whom he brought here to siccar point
writes most memorably on us who saw
these phenomena for the first time the
impression made will not be easily
forgotten the minds seemed to grow giddy
by looking so far into the abyss of time
but geologists knew Hutton's abyss was
not empty
dick beneath their feet lay close to the
entire history of the planet locked up
in the rock layers
200 miles west to Barberton lie the rand
gold fields where they sink the world's
deepest mine shafts for Martin DeWitt
it's an opportunity to travel back in
time
now you should be able to get the
impression of
traveling through 6000 meters of
sediments back in time
no matter how far back in time you go
every rock contains a is associated with
these two Emmy geologists these rocks
are bursting with information about what
the world was like when they were laid
down you can see all this shiny stuff
iron sulphide pyrite which shouldn't
oxidize it should have rusted by now but
it's still shining sub-ether art of
telling us that we must have had a much
less option in the atmosphere at the
time it's correct it probably was
atmosphere which was dominated by carbon
dioxide
as 19th century geologists explored the
bedrock in different parts of the world
they slowly built up a collection of
random snapshots of the past isolated
fragments of the planet's history but
how did these fragments be linked
together to form a complete story of the
earth
at the regency resort of Lyme Regis I
met oceanographer and Rachel Mills who
showed me other clues locked up in the
rocks together
this is really exciting about goodness
marvellous fossils wonderful this was
living in the ocean died sank to the sea
for each layer of limestone in fact has
its own characteristic set of fossils in
it
ironically the first people to take a
real interest in these strange shapes in
the rocks were not scientists but fossil
hunters like Chris Moore who made a
living selling them to tourists fossil
hunters have a knowledge of ammonites to
rival that of any paleontologist over a
thousand different species have been
found here each one with its own
particular characteristics this one for
example these lines across here we call
them suture lines this fern shape
pattern separated each different chamber
these varying every different species of
a man I and also the general shape of
the ammonite the number of ribs the
shell structure
fossil hunters soon notice that the
ammonites weren't scattered at random
through the rocks
instead each rock layer seemed to
contain its own particular types which
weren't found elsewhere if I pick out a
specimen say like this one you can tell
me pretty exactly where that comes yes
exactly it comes from the lower part of
the sequence in fact the lowest part
this is siliceous plan Albus he's got
this so preserved in this lovely
mother-of-pearl and it's one of the
earliest ammonites so this is fairly a
fairly simple analyte at the beginning
of their evolution yes yes so we go to
another one which is rather different in
form where that one's fit in fact I'm
about the middle part of a sequence here
it's a straw straw sub twosome he's his
name his characters got very strong ribs
with a heavy keel around the outside and
usually here the preserved in this
beautiful yellow calcite
because different layers contain
different fossils geologists found they
could classify rocks by their fossil
content many scientists in the 19th
century made a very important intuitive
leap they suggested that where you found
the same fossils in layers of rocks then
those layers were the same age
now that gave them some kind of sequence
some kind of measure across happens a
bit of time there gave names to these
epochs names we're fairly familiar with
Permian Triassic Jurassic Cretaceous and
so on and they were able to say that
Jurassic rocks here in Dorset are older
than Cretaceous rocks in Kent or what
they couldn't yet say was how old they
were
the problem of putting a figure to the
age of the earth soon became the most
pressing question in science and it
attracted one of the century's most
brilliant physicist Lord Kelvin
Kelvin believed that he had hidden away
of calculating the Earth's age with some
rigor his method was based on the
experience of Victorian cool - however
deep they go all - face a common hazard
I think it's about 27 degrees right
anywhere in the world you are the deeper
you go the hotter yes what kind of
temperature increase we see here as we
go down oh we have something like 11
degrees per kilometre as 19th century
miners had already discovered the
interior of the earth is hot where was
this heat coming from Kelvin believed
that it was a relic of the planets birth
heat trapped inside the earth since his
formation
Killman deduced that the earth must have
been formed by the steady accumulation
of smaller rocks the force of their
impact as they were pulled into the
growing planet release an immense amount
of energy enough to keep the entire
globe molten
Kelvin's idea was very simple any hot
body will unless you're continuously
eating it cool over time I could get an
idea of how long that coffee's been
there from its temperature Kelvin
applied the same principles to
estimating the age of the earth he
collected information about how
temperature increases you went down mine
shaft how heat was transmitted through
rocks and what temperature rocks melted
at and he applied all this to estimating
how long it was since the earth had last
been molten he worked for many years
then he came up with his best estimate
that the earth couldn't be much more
than 20 million years old
for most scientists killed his argument
appeared watertight but to feel
geologists like Hall his number felt far
too small all around them was layer upon
layer of rock even 20 million years
seemed too short a time to lay them down
then just this whole prepared to leave
Barberton his commission complete back
in London a stunning announcement began
a revolution in geology and resolved the
paradox
in 1904 britain's scientific elite were
gathering at the Royal Institution a
young New Zealand physicist Ernest
Rutherford was to reveal to the world
what he had discovered about the new
phenomenon of radioactivity the human
understanding of the earth and the time
itself was about to change forever
tonight
the eminent scientists addressing the
members is Professor Dan Mackenzie
obviously one of the central issues is
how old it is and one of the first
physicists to try and make a decent
estimate of the age of the earth was
Lord Kelvin and he came up with a number
which was 20 million years earlier this
century and some consternation Lord
Kelvin was in the audience as he says in
his memoirs I came into the room which
was half dark and presently spotted both
Kelvin in the audience and realized that
I was in for trouble at the last part of
the speech where my views conflicted
with his to my relief Kelvin fell fast
asleep
Rutherford realized that various
elements inside the earth radioactive
like uranium and thorium and potassium
and that these generated an important
amount of heat and that this completely
changed the basis of kelvins calculation
because instead of the earth cooling all
the time it actually had heat sources in
it and that you couldn't any longer use
that argument to estimate the age of the
earth Rutherford had removed a central
plank of kelvins argument not all the
heat inside the earth was left over from
its formation instead he was
continuously being generated within the
planet by radioactive decay but on the
other hand what this then allowed you to
do was to use the decay of these things
to don't make an estimate but actually
measure the age of the earth
Releford
realized that radioactivity was slowly
transforming the Earth's crust hidden
inside every rock were minerals
containing elements such as uranium
as time passed radioactive decay was
gradually turning the uranium into lead
changing the chemical composition of the
rock
this inexorable process begins the
moment of rock forms and new minerals
crystallise within it rather than
suggested that by carefully measuring
the chemistry of these minerals
scientists should be able to tell how
long ago the rocket formed
so after 200 years of controversy and
speculation the age of the earth would
be found in a few grains of dust as a
story that when Rutherford was working
in Canada he went up to a colleague one
day with a sample of rock how old you
think this is he inquired Oh about 10
million years was the reply I can prove
to you said rather wooden glee that this
rock is more than 500 million years old
and that was far older than current
estimates of the age of the earth and it
is indeed remarkable how as radioactive
dating techniques developed how quickly
scientists estimate of geological time
in the age of the earth expanded
rather for the attributive stroke was to
lengthen geological time by a factor of
something like a hundred and this was
greeted by the Georges with a great sigh
of relief and it is really one of the
major achievements right of the 20th
century that we now can date rocks and
minerals and things of that kind with
greater and greater accuracy and see how
the whole history of the solar system
and the earth is unrolled the techniques
that Rutherford pioneered have been
extended and refined by scientists like
Stephen Moore baths at Oxford University
radioactive dating has become the
geologists most powerful tool and you've
got really here an atomic clock I mean
which runs at a very constant rate you
know that uranium would always decay to
MIT at the same rate no matter what the
temperature or the pressure or
absolutely constant it never changes and
no known physical or chemical process or
coal there's nothing at all it's
completely invariable the rate of
radioactive decay is always the same
it's a universal clock and that's vital
because to finally determine the age of
the earth scientists needed a rock with
a very special history a rock left over
from the time when the earth was forming
this rather inconspicuous looking object
it's part of a meteorite which fell in
Mexico at a place called IND in February
1969 and it is actually the oldest known
object that we know of that exists on
earth
it's the oldest object that can be held
by human hand
it has an age of 4566 plus or minus two
million years actually most meteorites
that hit the earth are only just
slightly younger they're all within
quite a narrow in the Narrows they round
about 4550 million years and this is
regarded as part of the material from
which the solar system our Sun and
planets actually came together accreted
they are the remnants of the raw
material from which the solar system is
made so this meteorite gives us an idea
of the age of which the solar system and
the earth was forming yes it does
believe that the earth formed at this
time also and by a kind of indirect but
very strong reasoning it's believed that
the earth is also about 4550 million
years old so in the way the meteorites
give us an absolute age for the earth
yes it's the limiting aromatics 'as old
as you can get yes
if you wanted anything older you'd have
to get outside the solar system
meteorites tell scientists when the
earth started to form
but to know what the infant planet was
like they needed to find a remnant of
the early crust miraculously preserved
at the surface the search was on for the
oldest place on earth that quest took
Stephen more baths to the edge of the
great greening the icecap
in 1971 big McGregor and I heard about
this area which is about 150 kilometers
northeast of look the capital of
Greenland and the mining company was up
there exploring a big iron ore deposit
and Vic and I were very keen to see this
area Vic made the first reliable
geological map and he suggested that
some of these rocks might be very old
indeed this place is called issue.i for
Steven it was to prove the discovery of
a lifetime we're standing right in the
middle of the oldest known rock Sonia
and they extend from the lake there over
to the other Lake here
but back in 1971 when we first came up
here we collected many of the rock types
and then took them back to our
laboratory to do the radioactive dating
analysis and we found that many of these
rock types around here have ages of
nearly three thousand eight hundred
million years which is still the oldest
age of any terrestrial rocks which are
sort of as extensive as this well it
comes quite a surprise it's the age
itself is is very old in relation to the
age of the earth but also what's
interesting is what these rocks can tell
you about the environment of the early
Earth 1 outcrop in particular Port
Stephens I as you can see it's full of
thousands and thousands of round pebbles
set in a fine-grained matrix of mud clay
and chow and this sort of rock which
geologists call a conglomerate were
formed at a beach or shoreline and the
the erosion by water has rounded these
pebbles and it shows without any doubt
that water existed at the surface of the
earth three thousand eight hundred
million years ago which at that time
came as a complete surprise
at issuer the ice has uncovered a
tantalizing glimpse of the early Earth
but the search for a place where rocks
might yield a more detailed picture of
the young Pere it took geologists to the
other side of the globe to the Barberton
mountain land in South Africa field area
of Martin DeWitt well it turns out that
the oldest rocks are barbels are about
3,500 million years old
someone's slightly older up to 3,700
million years there are all the rocks
elsewhere in the world but what's so
special about that it's so incredibly
well
holls original suspicion turned out to
be correct
Barberton is the oldest extensive piece
of the Earth's ancient surface here the
rocks at last
really begin to speak and it's not to
leave war for weeks and weeks and all of
a sudden you find one tiny little our
couples have bingo you have got it
that's what they be trying to tell me
that's not natural siding that's why I
am a geologist off the rocks of
Barberton reveal is that 3.5 billion
years ago the earth was a world of
volcanoes as amazing little globules
physics information is very like
formation of hailstones he's globular
form of volcanic clouds where very large
volcanoes erupted violently black
mountain islands from Zhang
the positronic hailstone form they fall
back to earth in this case on the layer
in a lake the biggest ones settle to the
bottom and the smallest ones fall out
and as in Greenland there's abundant
evidence that the volcanoes were
surrounded by water okay these are the
volcanic rocks that are so
characteristic on all over Barberton and
it's these funny shapes these bulbs and
these contorted things and we see all
over his face here that tells us that
these volcanic rocks were wrapped it
underwater and the shape is a reaction
of the larvae are that the wraps on the
Warford against the cool water that
wants to cool it down
how's it freezes it forms as barrel
there's like squeezing toothpaste out
and piling it up with one another
everywhere in Barberton we look it is
these kind of rocks that allow us to
reconstruct that there were huge tracts
of ocean in this part of the world at
that time but where was all this water
coming from
see these textures on the ruffles very
delicately preserved almost has it good
to be walking on this there are actually
little crystals
they almost look man-made but they're
really natural crystals growing these
rocks came from very high temperatures
crystallized out from Magnus that came
from deep in the earth very rapidly to
the surface high in in volatile contents
high in water the volcanoes erupting
here were producing vast quantities of
water vapor with the lava it was this
water which was condensing to form the
primitive ocean
the combination of volcanic activity and
water produce an environment where a
fascinating new process could begin my
core piece structured by accident and
when I looked at them I never seen
anything like this before
that same year I went on a conference to
New Zealand and during that conference I
had a chance to sit around some of the
mock polls in New Zealand and when I was
looking nothing while I was looking at
this bubbling mud I all of a sudden
remember these structures are Wow
that's it that's gotta be what it is
ancient metal structures frozen in the
rock here and what gives it away as a
mat cause of course all these
intersections
what is it even more interesting to
think about is the warmth of this area
and sort of nice it might have created
for bacteria for example in swimming
around and this is of course warm of the
site we might be thinking about where
life I have started and in fact just
recently Martin has made another
remarkable find
well these sedimentary rocks have locked
inside them the very earliest signs of
life on this planet they're very tiny
and when you look through the microscope
of these rocks you'll see tiny little
bacteria that's these bacteria there are
the first well-preserved signs of life
on this planet from the unique rocks of
Barberton Martin has been able to build
up an extraordinarily vivid picture of
the young earth looking back as far as
they can see more than three and a half
billion years scientists have found a
planet studded with volcanic islands
the intense heat of the unearthed meant
the volcanoes were much more active than
volcanoes today
as the lava cooled it's steadily added
to the growing land masses
but there were no plans to soften the
contours of the newly created land and
without plants no oxygen in the
atmosphere
but around bubbling volcanic pools
bacteria thrived
and the volcanoes also produce vast
quantities of water vapour as it rained
back to the surface it eroded the new
rocks sedimentary layers started to form
and gradually the shallow ocean that
covered the young planet grew deeper
since the scientific study of our planet
began geologists have been learning to
travel through time
thanks to places like easier and
Barberton
they've been able to achieve something
quite remarkable to show us our world
being born
this is the earth as it is at the very
limit of our scientific imagination
as far as the record in the rocks is
concerned this is the beginning of the
earth story
a planet shape throughout its history
are the same forces of heat and water
still at work
how those forces have transformed the
earth from a planet covered by a single
shallow ocean dotted with volcanic
islands to the world we know today
that's the story we'll be telling over
the next few programs we'll start next
time with the place where the Earth's
crust is formed as we our voyage to the
bottom well be following the journey of
the research submarine Alvin as it
ventures thousands of meters below the
waves on board a scientists intent on
studying at firsthand a strange volcanic
realm where new ocean floor is
continuously being created the next
stage in Earth's story