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Today, we are in the midst
of a scientific revolution
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in our understanding of the Earth
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and our relationship to it.
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Recently, scientists have begun to
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think of the Earth in a new way -
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almost as a living organism.
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Like a living thing
it is forever on the move,
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driven by the restless energy
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locked up in its interior.
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And as the planet has evolved,
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so has life,
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shaped by the same forces
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that move continents
and change climates.
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In Earth Story we shall
explore this new vision
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of a living planet
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and the essence of this vision
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is an understanding of time.
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The most profound question
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any scientist
can ask about the earth
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is also a simple one -
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how old is it?
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It's a question geologists
have been striving
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to answer for 200 years.
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At the turn of the century
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one such geologist came to
a remote corner
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of Southern Africa
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called the Barberton Mountain Land.
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His name was Alan Hall
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and he had a commission from
the South African government
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to map this area looking for gold.
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The Barberton Mountain Land
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is several thousand square
kilometers of rugged terrain,
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cut through by rivers.
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Rocky outcrops dot the hills,
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signs of the bedrock
hidden beneath the landscape.
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Hall's aim was
to criss-cross the region,
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recording these outcrops,
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and so build up a picture
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of the rocks below the surface.
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It was an immense task.
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But as he worked his way
across the landscape
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Hall slowly realized
that something was missing.
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However hard he looked,
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he could find in the rocks
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none of the usual
signs of fossilized life.
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Could Barberton be a fragment
of the Earth
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from a time before life began?
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Just how old was this place?
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Hall's question came
at a critical moment.
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For a hundred years scientists
had been arguing
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about the age of the Earth
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They were struggling
to overcome ideas
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which had held sway for centuries.
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Ideas sanctioned
by the full authority
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of religious doctrine.
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The book of Genesis relates
how God created the earth
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and everything in it,
including ourselves,
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in just 6 days.
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The implication was that
earth history and human history
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had begun at the same moment
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and this provided
17th century scholars
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with a way to determine
the age of the earth.
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By simply adding up the ages
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of Adam's descendants
as listed in the Bible,
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they concluded that the planet
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must have been created in 4004 BC,
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which meant it was less
than 6,000 years old.
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But it didn't look that
way to geologists.
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when they studied places
like Barberton
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they saw evidence
that the landscape
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had changed over time -
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that it had a long history.
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Hall's modern-day successor
is Maarten de wit.
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He too is fascinated
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by the question
of Barberton's antiquity.
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I really got interested
in this part
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of the world many years ago,
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but the opportunity
to come here didn't arise
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until much later.
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At the end of the 70s
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I came down here to Barberton
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and it turned out to be one of
the best moves of my life.
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It's one of these areas
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that has something extremely special
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to tell about the story
of the earth.
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Maarten, like Hall before him,
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has mapped the rocks
of Barberton in detail.
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when you do this,
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a striking pattern quickly emerges.
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00:07:15,368 --> 00:07:17,893
well once you start mapping
the hills here,
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you'll notice that the landscape
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is dominated by stripes -
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stripes of rocks -
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like that one there.
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And if you get your eye in,
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after a while you'll see, in fact,
all these rock layers,
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all are visible.
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In this case this huge mass here
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has finer vertical rock layers.
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Everywhere in Barberton
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the landscape seems
to be made of layers.
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By the nineteenth century,
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geologists had begun to realize
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that the process
that created these layers
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was still at work all around them.
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Hall and his contemporaries
knew that water
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can be a powerful agent of change,
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eroding rock,
but also creating it... over time.
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well take this river, for example,
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like many rivers,
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cutting through the rocks,
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moving material downstream -
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sand and silt -
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and as it moves down
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that material
will deposit somewhere
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in a quiet spot layer upon layer,
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and as these layers get deposited
on top of one another
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they turn into rock slowly.
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well here you have a slab of rock.
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00:09:18,424 --> 00:09:21,052
Now this slab represents
a river bed.
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00:09:21,193 --> 00:09:23,627
There you can even
see the sand grains.
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These would have been
the sand grains in the river.
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These ridges that you see here,
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they are ripples.
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I can tell that
it would have flowed
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from my hand here
downwards in that direction.
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Now you can see
if you look downwards
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that in fact
there are several of these
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slabs stacked
on top of one another.
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Here's one,
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there you see
another one over here,
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and another one,
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and another one still, and more.
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These are dozens of slabs
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and they're all tilted right now,
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but originally
they would have been horizontal
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and they represent
all history of rivers.
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A long history of deposition.
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00:10:07,173 --> 00:10:08,800
To nineteenth-century scientists
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00:10:08,941 --> 00:10:10,636
a world made up of layers
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00:10:10,776 --> 00:10:12,403
didn't look as
if it had been created
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all in one go as the Bible says.
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It must have been
built up overtime.
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00:10:20,286 --> 00:10:22,277
But how much time?
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00:10:27,026 --> 00:10:28,357
The first person to realise
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the profound importance
of this question
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was a Scotsman, James Mutton.
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At Siccar Point on the east
coast of Scotland
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exposed in the cliff side
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there's a small patch of rock
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which made a deep impression
on Hunt.
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Chris Nicholas is a geologist
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who has made a special study
of his work.
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00:11:05,865 --> 00:11:07,856
So here we are at one of the most
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famous geological localities
in the world.
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This is Hutton's Unconformity
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and what Hutton noticed here
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in this cliff
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is that at the bottom
of the cliff you have these
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vertical strata,
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overlain by horizontal strata
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and between the two
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there was an undulating
erosional surface.
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And what Hutton recognised
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was that well if all rocks
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were deposited horizontally
on the sea-bed,
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what on earth was this grey rock
doing being vertical
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at the base of the cliff
there was something wrong here.
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00:11:39,732 --> 00:11:41,165
And he started to look at rocks
in more detail
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and he came up with this idea
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that what must have happened
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is that the grey rock must
have been twisted and turned
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so that it was vertical,
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uplifted out of the sea,
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eroded off and then drowned again,
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so that the red rock
could be deposited on top.
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00:12:01,187 --> 00:12:03,917
And more than that,
it was then uplifted again
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to form the cliff we now see.
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So there were at least
2 cycles of deposition,
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uplift and then erosion
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that he could see in this cliff.
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And he went on to say
"well, these cycles must have taken
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an immense amount
of time to complete"
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because when he looked around him
and saw rivers
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and the sea eroding today
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it doesn't really erode
very quickly.
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And also he said
"well how many cycles
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could have taken place
before these
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and how many will come after this,
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we just don't know".
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And it led him on to this idea
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of the immensity
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of geological time
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and he came out
with a very famous quote of,
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well, he could see no vestige
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of a beginning
and no prospect of an end.
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For Hutton the earth
was infinitely old.
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00:13:10,556 --> 00:13:14,583
Siccar Point represents
the discovery of geological time
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and it's shaped the way
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00:13:16,929 --> 00:13:20,888
that geologists think
and work ever since.
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00:13:21,033 --> 00:13:21,965
One of Hutton's colleagues,
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00:13:22,101 --> 00:13:23,659
John Plafare,
who was a mathematician
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00:13:23,803 --> 00:13:25,634
came to Siccar Point with Hutton
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and Plafare wrote afterwards
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of his experience here
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and he said that
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00:13:30,376 --> 00:13:31,866
"For those of us who
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saw the rocks at Siccar Point
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their impact was not lost on us
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00:13:36,582 --> 00:13:39,278
and we grew giddy
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00:13:39,418 --> 00:13:42,581
looking so far
into the abyss of time".
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But geologists knew
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00:13:49,728 --> 00:13:53,425
Hutton's abyss was not empty.
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00:13:56,135 --> 00:13:57,124
Beneath their feet
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00:13:57,269 --> 00:14:00,568
lay clues to the entire history
of the planet
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00:14:00,706 --> 00:14:02,936
locked up in the rock layers.
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00:14:03,075 --> 00:14:05,509
Yeah,
we're going down to 128 level,
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00:14:05,644 --> 00:14:08,704
somewhere between
8 and 10 meters per second.
219
00:14:08,848 --> 00:14:10,315
I mean,
it's nothing to be scared about?
220
00:14:10,449 --> 00:14:12,781
No, it's like the Empire State
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00:14:12,918 --> 00:14:14,886
Building's elevator system.
222
00:14:15,020 --> 00:14:16,146
Yeah.
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00:14:16,288 --> 00:14:19,314
Not as smooth and probably
a bit quicker.
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00:14:20,359 --> 00:14:23,920
200 miles west of Barberton
lie the Rand goldfields,
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00:14:24,063 --> 00:14:27,396
where they sink
the world's deepest mine shafts.
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00:14:27,533 --> 00:14:28,522
For Maarten de wit,
227
00:14:28,667 --> 00:14:33,127
it's an opportunity to
travel back in time.
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00:14:46,619 --> 00:14:48,018
OK, now you should be able to
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00:14:48,153 --> 00:14:50,815
get the impression of
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00:14:51,824 --> 00:14:54,156
at a fairly rapid rate
231
00:14:54,293 --> 00:14:55,487
and you'll also feel your ears
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00:14:55,628 --> 00:14:58,153
go from the pressure.
233
00:15:00,366 --> 00:15:02,391
can feel it now.
234
00:15:08,774 --> 00:15:10,765
That's the other cage
going on the way up.
235
00:15:10,910 --> 00:15:12,810
On the couple drum system
236
00:15:12,945 --> 00:15:14,640
if the hoist driver
gets it all wrong
237
00:15:14,780 --> 00:15:17,749
and he snaps the brakes
on too suddenly,
238
00:15:17,883 --> 00:15:19,441
you can feel the stretch now.
239
00:15:19,585 --> 00:15:20,051
Unbelievable.
240
00:15:20,185 --> 00:15:22,517
He got his braking a bit wrong.
Scary.
241
00:15:22,655 --> 00:15:25,488
Oh you get used to it.
242
00:15:26,091 --> 00:15:30,221
So we're travelling through
6,000 meters of sediment
243
00:15:30,362 --> 00:15:31,761
backwards in time?
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00:15:31,897 --> 00:15:33,558
we are now in a part of the world
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00:15:33,699 --> 00:15:36,725
where we are old enough
to be pre-life.
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00:15:38,103 --> 00:15:41,630
No wriggling organisms
were present at this point.
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00:15:46,412 --> 00:15:49,074
No matter how far back
in time you go,
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00:15:49,214 --> 00:15:51,512
every rock contains
a detailed picture
249
00:15:51,650 --> 00:15:54,244
of the environment it formed in -
250
00:15:54,853 --> 00:15:57,720
if you know how to look at it.
251
00:15:59,825 --> 00:16:00,985
OK, what we have here now
252
00:16:01,126 --> 00:16:03,253
is a collection of gravel layers
253
00:16:03,395 --> 00:16:06,523
and what we are mining
from top to bottom
254
00:16:06,665 --> 00:16:08,530
is the selected reef cut
255
00:16:08,667 --> 00:16:11,101
and associated with the pebbles
256
00:16:11,236 --> 00:16:13,261
and the pyrite that you see here,
257
00:16:13,405 --> 00:16:15,839
obviously there are
concentrations of gold,
258
00:16:15,975 --> 00:16:17,636
which is the source
of our business.
259
00:16:17,776 --> 00:16:19,038
well it looks to me
260
00:16:19,178 --> 00:16:20,509
like we're looking at
a section here
261
00:16:20,646 --> 00:16:23,615
that's sliced through
a series of river beds.
262
00:16:23,749 --> 00:16:25,376
I mean,
we can clearly see the pebbles,
263
00:16:25,517 --> 00:16:26,950
you can see them rounded
264
00:16:27,086 --> 00:16:28,553
and of course we can see
265
00:16:28,687 --> 00:16:30,086
the heavy mineral concentration
266
00:16:30,222 --> 00:16:31,450
at the bottom of the bed.
267
00:16:31,590 --> 00:16:32,522
It looks like we're looking at
268
00:16:32,658 --> 00:16:34,023
a stack of river bed.
what do you think?
269
00:16:34,159 --> 00:16:36,525
That these have been
meandering rivers of some sort?
270
00:16:36,662 --> 00:16:37,651
Yeah, exactly that.
271
00:16:37,796 --> 00:16:39,593
what one could actually describe
272
00:16:39,732 --> 00:16:43,327
is a series of gravel bars
273
00:16:43,469 --> 00:16:45,334
in their depositional mode
274
00:16:45,471 --> 00:16:47,166
which have inter-fingered
with each other.
275
00:16:47,306 --> 00:16:48,568
So some sort of meandering river
276
00:16:48,707 --> 00:16:49,867
over a flat plane.
277
00:16:50,009 --> 00:16:52,637
And we're sitting here
a kilometer down now
278
00:16:52,778 --> 00:16:54,439
for these beds have been buried
279
00:16:54,580 --> 00:16:55,842
by later rivers
280
00:16:55,981 --> 00:16:57,642
and more rivers and we know
281
00:16:57,783 --> 00:16:58,715
we can go down in places
282
00:16:58,851 --> 00:17:01,445
even another 4, 5 kilometers,
283
00:17:01,587 --> 00:17:04,181
so we know that
this is a huge stack
284
00:17:04,323 --> 00:17:05,915
of just river bed after river bed
285
00:17:06,058 --> 00:17:07,787
after river bed after river bed.
286
00:17:07,926 --> 00:17:09,757
And as you can see
all this shiny stuff,
287
00:17:09,895 --> 00:17:11,692
iodine sulphite, pyrite,
288
00:17:11,830 --> 00:17:12,922
which should have oxidized -
289
00:17:13,065 --> 00:17:14,396
it should have rusted by now -
290
00:17:14,533 --> 00:17:15,522
but it's still shining.
291
00:17:15,667 --> 00:17:16,861
So the pyrite are telling us that
292
00:17:17,002 --> 00:17:18,469
we must have had much less oxygen
293
00:17:18,604 --> 00:17:19,628
in the atmosphere at the time.
294
00:17:19,772 --> 00:17:21,672
That's correct.
It probably was the atmosphere
295
00:17:21,807 --> 00:17:24,640
which was dominated
by carbon dioxide.
296
00:17:27,780 --> 00:17:28,804
As nineteenth-century
297
00:17:28,947 --> 00:17:32,314
geologists explored the bedrock
in different parts of the world,
298
00:17:32,451 --> 00:17:34,316
they slowly built up a collection
299
00:17:34,453 --> 00:17:36,819
of random snapshots of the past,
300
00:17:36,955 --> 00:17:40,447
isolated fragments
of the planet's history.
301
00:17:40,592 --> 00:17:42,457
But how could these fragments
be linked together
302
00:17:42,594 --> 00:17:45,620
to form a complete story
of the Earth?
303
00:17:53,338 --> 00:17:55,806
Here at the Regency resort
of Lyme Regis
304
00:17:55,941 --> 00:17:58,068
on Britain's south coast,
305
00:17:58,210 --> 00:17:59,575
19th century scientists
306
00:17:59,711 --> 00:18:02,111
found the key to this puzzle.
307
00:18:07,886 --> 00:18:10,252
Every year oceanographer,
Rachel Mills,
308
00:18:10,389 --> 00:18:12,914
brings her students here
to see a place
309
00:18:13,058 --> 00:18:17,119
where the past is vividly etched
into the rock layers.
310
00:18:21,733 --> 00:18:24,031
These rocks hold
a different sort of clue
311
00:18:24,169 --> 00:18:26,160
to the earth's history.
312
00:18:32,010 --> 00:18:33,705
The beach is a great place
to come and do geology
313
00:18:33,846 --> 00:18:34,870
because here we have the sea
314
00:18:35,013 --> 00:18:36,002
eating away continuously
315
00:18:36,148 --> 00:18:38,207
at the cliffs exposing the rocks
316
00:18:38,350 --> 00:18:40,375
that normally
are under our feet in dorset,
317
00:18:40,519 --> 00:18:42,043
but here we can
walk along the beach
318
00:18:42,187 --> 00:18:43,950
and actually see the rocks
that were laid down
319
00:18:44,089 --> 00:18:46,148
millions of years ago.
320
00:18:46,291 --> 00:18:48,259
The striking thing about
these rocks is that
321
00:18:48,393 --> 00:18:50,554
here we have a cliff which seems
to have this alternating
322
00:18:50,696 --> 00:18:52,163
light/dark, light/dark, light/dark,
323
00:18:52,297 --> 00:18:54,959
which is repeating
in a sort of regular basis
324
00:18:55,100 --> 00:18:57,500
as we move up through
geological time,
325
00:18:57,636 --> 00:18:59,069
up this cliff.
326
00:18:59,204 --> 00:19:01,934
Now if we look at these rocks
in a bit more details
327
00:19:02,074 --> 00:19:05,043
we can see there's a lot of
interesting information
328
00:19:05,177 --> 00:19:07,907
in here which we can
pull out as geologists
329
00:19:08,046 --> 00:19:11,641
to tell us about the conditions
under which they formed.
330
00:19:11,783 --> 00:19:12,977
Now the dark, soft layers,
331
00:19:13,118 --> 00:19:15,279
have been laid down
in an ocean environment,
332
00:19:15,420 --> 00:19:16,785
a shallow sea.
333
00:19:16,922 --> 00:19:18,617
I can break this with my fingers,
334
00:19:18,757 --> 00:19:20,156
so you can see
it falls apart very easily
335
00:19:20,292 --> 00:19:22,726
and that's why it erodes
very easily here on the beach.
336
00:19:22,861 --> 00:19:25,352
And essentially
it's made from clay particles
337
00:19:25,497 --> 00:19:27,863
that have been transported
by rivers to the ocean
338
00:19:28,000 --> 00:19:31,265
and then very little
has happened to it since then.
339
00:19:31,403 --> 00:19:32,893
The light layer
is strikingly different.
340
00:19:33,038 --> 00:19:34,596
It's much, much harder
341
00:19:34,740 --> 00:19:36,298
and that's why it stands out
342
00:19:36,441 --> 00:19:38,534
in these platforms across the beach.
343
00:19:38,677 --> 00:19:40,372
Basically this rock is limestone
344
00:19:40,512 --> 00:19:42,912
and it is formed
by the shelly remains of organisms
345
00:19:43,048 --> 00:19:44,845
that lived in the ocean
at that time,
346
00:19:44,983 --> 00:19:47,315
but later on it has been cemented,
347
00:19:47,452 --> 00:19:49,511
which makes it hard.
348
00:19:49,655 --> 00:19:51,646
But what's most exciting
about these rocks
349
00:19:51,790 --> 00:19:54,224
is what we find in them.
350
00:19:54,927 --> 00:19:57,157
And so this layer which
I'm walking across at the moment
351
00:19:57,296 --> 00:19:59,161
is one of these limestone pavements
352
00:19:59,298 --> 00:20:03,496
which is full of hundreds
and thousands of fossils.
353
00:20:03,635 --> 00:20:05,262
And this is
a really nice example here
354
00:20:05,404 --> 00:20:07,304
of a fossil ammonite.
355
00:20:07,439 --> 00:20:09,031
And this organism lived
in the ocean
356
00:20:09,174 --> 00:20:10,471
millions of years ago.
357
00:20:10,609 --> 00:20:12,372
It died, sank to the sea floor,
358
00:20:12,511 --> 00:20:15,412
and then has been preserved
for geological time.
359
00:20:18,150 --> 00:20:21,244
Ironically, the first people
to take a real interest
360
00:20:21,386 --> 00:20:23,047
in these strange shapes
in the rocks
361
00:20:23,188 --> 00:20:26,214
were not scientists
but fossil-hunters
362
00:20:26,358 --> 00:20:30,590
who made a living selling
these beautiful objects to tourists.
363
00:20:46,011 --> 00:20:47,569
Fossil hunters at Lyme Regis
364
00:20:47,713 --> 00:20:49,544
soon acquired an intimate knowledge
365
00:20:49,681 --> 00:20:52,775
of the different ammonites
they found along the beach.
366
00:20:54,920 --> 00:20:56,888
There were over
1,000 different species
367
00:20:57,022 --> 00:20:59,547
in this locality alone.
368
00:21:03,629 --> 00:21:07,121
Significantly these
fossils increased in size,
369
00:21:07,266 --> 00:21:09,291
complexity and diversity
370
00:21:09,434 --> 00:21:11,959
as you moved higher up the cliff.
371
00:21:12,104 --> 00:21:15,870
In other words they seemed
to evolve through time
372
00:21:25,484 --> 00:21:27,111
Now each layer of limestone
373
00:21:27,252 --> 00:21:29,777
has a characteristic assemblage
of fossils in it
374
00:21:29,921 --> 00:21:30,979
which allows geologists
375
00:21:31,123 --> 00:21:32,613
to go anywhere else in the world
376
00:21:32,758 --> 00:21:34,726
and if they find
the same assemblage of fossils
377
00:21:34,860 --> 00:21:35,588
they then can say
378
00:21:35,727 --> 00:21:38,059
"That rock was laid down
at exactly the same
379
00:21:38,196 --> 00:21:40,562
as these rocks here
in Lyme Regis".
380
00:21:40,699 --> 00:21:42,860
This was a great leap
forward for geologists
381
00:21:43,001 --> 00:21:44,025
in the 19th century
382
00:21:44,169 --> 00:21:47,297
because it allowed them
to divide up geological time
383
00:21:47,439 --> 00:21:50,067
into the familiar time-scales
that we now use -
384
00:21:50,208 --> 00:21:53,405
the Triassic, the Jurassic,
the Cretaceous -
385
00:21:53,545 --> 00:21:56,912
and so with this understanding
of how fossils evolve
386
00:21:57,049 --> 00:21:58,482
and change through time
387
00:21:58,617 --> 00:22:01,609
we can put together a timescale.
388
00:22:02,988 --> 00:22:04,319
By classifying rock layers
389
00:22:04,456 --> 00:22:06,424
according to their fossil content,
390
00:22:06,558 --> 00:22:08,526
scientists were able
to tell how layers
391
00:22:08,660 --> 00:22:10,093
in one part of the world
392
00:22:10,228 --> 00:22:12,719
related to layers found elsewhere,
393
00:22:12,864 --> 00:22:15,424
whether they were younger or older.
394
00:22:15,567 --> 00:22:17,398
But what they still couldn't say
395
00:22:17,536 --> 00:22:20,369
was how old they were.
396
00:22:25,177 --> 00:22:26,508
The problem of putting a figure
397
00:22:26,645 --> 00:22:28,078
to the age of the Earth
398
00:22:28,213 --> 00:22:31,979
soon became the most
pressing question in science -
399
00:22:32,117 --> 00:22:33,277
and it attracted one of
400
00:22:33,418 --> 00:22:36,182
the century's most
brilliant physicists-
401
00:22:36,321 --> 00:22:38,255
Lord Kelvin.
402
00:22:39,925 --> 00:22:41,415
Kelvin believed that he had hit
403
00:22:41,560 --> 00:22:43,892
on a way of calculating
the Earth's age
404
00:22:44,029 --> 00:22:45,929
with some rigour.
405
00:22:47,232 --> 00:22:49,393
His method was based on
the experience
406
00:22:49,534 --> 00:22:52,526
of Victorian coal miners.
407
00:22:53,438 --> 00:22:54,962
However deep they go,
408
00:22:55,107 --> 00:22:57,302
all miners face a common hazard.
409
00:22:57,442 --> 00:23:00,172
wow, it's hot down here.
Hey! How hot is it here?
410
00:23:00,312 --> 00:23:02,803
well I think it's about 27 degrees.
411
00:23:02,948 --> 00:23:04,279
Anywhere in the world you are,
412
00:23:04,416 --> 00:23:06,611
the deeper you go,
the hotter it gets.
413
00:23:06,752 --> 00:23:07,810
what kind of temperature increase
414
00:23:07,953 --> 00:23:10,251
do we see here as we go down?
415
00:23:10,389 --> 00:23:14,052
we have something like
11 degrees per kilometer.
416
00:23:14,192 --> 00:23:17,389
As nineteenth-century miners
had already discovered
417
00:23:17,529 --> 00:23:20,828
the interior of the Earth is hot.
418
00:23:22,434 --> 00:23:25,130
where was this heat coming from?
419
00:23:25,270 --> 00:23:29,001
Kelvin believed that it was a relic
of the planet's birth -
420
00:23:29,141 --> 00:23:32,975
heat trapped inside the Earth
since its formation.
421
00:23:38,150 --> 00:23:40,448
Kelvin deduced that the Earth
must have been formed
422
00:23:40,585 --> 00:23:43,713
by the steady accumulation
of smaller rocks.
423
00:23:43,855 --> 00:23:44,879
The force of their impact
424
00:23:45,023 --> 00:23:47,014
as they were pulled
into the growing planet
425
00:23:47,159 --> 00:23:49,457
released an immense
amount of energy -
426
00:23:49,594 --> 00:23:52,722
enough to keep
the entire globe molten.
427
00:23:59,971 --> 00:24:02,269
But Kelvin knew that any hot body,
428
00:24:02,407 --> 00:24:04,500
unless it's being
continuously heated,
429
00:24:04,643 --> 00:24:07,134
will cool overtime.
430
00:24:07,279 --> 00:24:08,644
The longer the earth
had been cooling,
431
00:24:08,780 --> 00:24:11,112
the colder it would be.
432
00:24:14,219 --> 00:24:15,982
So he set about
collecting information
433
00:24:16,121 --> 00:24:19,852
about how temperature increases
as you go down mine shafts,
434
00:24:19,991 --> 00:24:22,221
how heat was transmitted
through rocks
435
00:24:22,360 --> 00:24:25,454
and what temperature rocks melt at.
436
00:24:25,597 --> 00:24:28,430
He applied all this to estimating
how long it was
437
00:24:28,567 --> 00:24:31,468
since the earth had
last been molten.
438
00:24:33,605 --> 00:24:35,698
After many years of calculation
439
00:24:35,841 --> 00:24:38,674
Kelvin finally concluded
that the earth
440
00:24:38,810 --> 00:24:43,270
couldn't be much more than
20 million years old.
441
00:24:49,254 --> 00:24:53,247
For most scientists Kelvin's
argument appeared watertight.
442
00:24:53,391 --> 00:24:55,757
But to field geologists like Hall,
443
00:24:55,894 --> 00:24:58,454
his number felt far too small.
444
00:24:58,597 --> 00:25:01,532
All around them was layer
upon layer of rock -
445
00:25:01,666 --> 00:25:04,157
even 20 million years
seemed too short a time
446
00:25:04,302 --> 00:25:06,327
to lay them down.
447
00:25:08,340 --> 00:25:11,571
Then, just as Hall prepared
to leave Barberton,
448
00:25:11,710 --> 00:25:13,075
his commission complete,
449
00:25:13,211 --> 00:25:15,338
back in London
a stunning announcement
450
00:25:15,480 --> 00:25:18,210
began a revolution in geology...
451
00:25:18,350 --> 00:25:20,580
and resolved the paradox.
452
00:25:23,555 --> 00:25:25,216
In 1904
453
00:25:25,357 --> 00:25:26,756
Britain's scientific elite
454
00:25:26,892 --> 00:25:29,759
were gathering
at the Royal Institution.
455
00:25:31,596 --> 00:25:34,793
A young New Zealand physicist,
Ernest Rutherford,
456
00:25:34,933 --> 00:25:37,265
was to reveal to the world
what he had discovered
457
00:25:37,402 --> 00:25:41,771
about the new phenomenon
of radioactivity.
458
00:25:44,576 --> 00:25:46,476
The human understanding
of the Earth,
459
00:25:46,611 --> 00:25:48,135
and of time itself,
460
00:25:48,280 --> 00:25:50,976
was about to change forever.
461
00:25:53,552 --> 00:25:56,715
Tonight, the eminent scientist
addressing the members
462
00:25:56,855 --> 00:25:59,449
is Professor Dan McKenzie.
463
00:26:00,325 --> 00:26:02,793
Professor McKenzie, we're ready.
464
00:26:13,238 --> 00:26:16,173
Obviously one of the central issues
465
00:26:16,308 --> 00:26:18,173
for the Earth is how old it is
466
00:26:18,310 --> 00:26:20,574
and one of the first
physicists to try
467
00:26:20,712 --> 00:26:22,680
and make a decent estimate
of the age
468
00:26:22,814 --> 00:26:25,214
of the Earth was Lord Kelvin.
469
00:26:25,350 --> 00:26:27,511
And he came out with a number
470
00:26:27,652 --> 00:26:30,246
which was 20 million years.
471
00:26:31,022 --> 00:26:33,422
Earlier this century
Rutherford came here
472
00:26:33,558 --> 00:26:35,822
to give a talk about radioactivity
473
00:26:35,961 --> 00:26:38,896
and somewhat to his consternation
474
00:26:39,030 --> 00:26:41,362
Kelvin was in the audience.
475
00:26:41,499 --> 00:26:43,967
And he says in his memoirs,
476
00:26:44,102 --> 00:26:45,899
"I came into the room
477
00:26:46,037 --> 00:26:47,698
which was half dark
478
00:26:47,839 --> 00:26:50,364
and presently spotted Lord Kelvin
in the audience
479
00:26:50,508 --> 00:26:52,806
and realised
that I was in for trouble
480
00:26:52,944 --> 00:26:54,775
at the last part
of the speech dealing
481
00:26:54,913 --> 00:26:56,380
with the age of the Earth
482
00:26:56,514 --> 00:26:59,483
where my views conflicted with his.
483
00:26:59,618 --> 00:27:03,486
To my relief Kelvin
fell fast asleep.
484
00:27:06,558 --> 00:27:10,085
Rutherford realised
that various elements
485
00:27:10,228 --> 00:27:12,128
inside the Earth were radioactive,
486
00:27:12,263 --> 00:27:14,527
like uranium and thorium
and potassium
487
00:27:14,666 --> 00:27:16,429
and that these generated
488
00:27:16,568 --> 00:27:18,365
an important amount of heat
489
00:27:18,503 --> 00:27:20,869
and that this completely
changed the basis
490
00:27:21,006 --> 00:27:22,439
of Kelvin's calculation
491
00:27:22,574 --> 00:27:24,542
because instead of the Earth
cooling all the time
492
00:27:24,676 --> 00:27:26,439
it actually had heat sources in it.
493
00:27:26,578 --> 00:27:28,808
And that you
couldn't any longer use
494
00:27:28,947 --> 00:27:32,508
that argument to estimate
the age of the Earth.
495
00:27:32,651 --> 00:27:33,583
Rutherford had removed
496
00:27:33,718 --> 00:27:36,653
a central plank of
Kelvin's argument.
497
00:27:36,788 --> 00:27:38,346
Not all the heat inside the Earth
498
00:27:38,490 --> 00:27:40,424
was left over from its formation.
499
00:27:40,558 --> 00:27:42,685
Instead,
heat was continuously being
500
00:27:42,827 --> 00:27:44,317
generated within the planet
501
00:27:44,462 --> 00:27:46,930
by radioactive decay.
502
00:27:47,065 --> 00:27:48,657
But, on the other hand,
503
00:27:48,800 --> 00:27:50,631
what this then allowed you to do
504
00:27:50,769 --> 00:27:53,237
was to use the decay
of these things,
505
00:27:53,371 --> 00:27:55,601
right, to not make an estimate
506
00:27:55,740 --> 00:27:59,301
but actually measure
the age of the earth.
507
00:27:59,444 --> 00:28:01,002
Rutherford had laid the foundations
508
00:28:01,146 --> 00:28:04,138
for an entirely new branch
of the Earth sciences,
509
00:28:04,282 --> 00:28:05,909
geochronology -
510
00:28:06,051 --> 00:28:09,578
the direct measurement
of the ages of rocks.
511
00:28:09,721 --> 00:28:12,087
One of its most
distinguished practitioners
512
00:28:12,223 --> 00:28:14,248
is Stephen Moorbath.
513
00:28:14,392 --> 00:28:16,053
what Rutherford suggested
514
00:28:16,194 --> 00:28:18,253
was that you could actually use
515
00:28:18,396 --> 00:28:22,162
the phenomenon of radioactivity
to date rocks
516
00:28:22,300 --> 00:28:25,599
and he suggested that
if you had a rock
517
00:28:25,737 --> 00:28:29,833
which has a certain
amount of uranium in it,
518
00:28:29,974 --> 00:28:31,908
the uranium would
in the course of time
519
00:28:32,043 --> 00:28:33,840
decay to the element lead
520
00:28:33,978 --> 00:28:35,843
by radioactive decay
521
00:28:35,980 --> 00:28:39,177
and one could measure
the rate of that process
522
00:28:39,317 --> 00:28:40,682
so that if you took a rock
523
00:28:40,819 --> 00:28:42,184
and measured the amount of uranium
524
00:28:42,320 --> 00:28:43,617
and the amount of lead,
525
00:28:43,755 --> 00:28:45,586
and then you could calculate
526
00:28:45,724 --> 00:28:48,124
the actual age of the rock.
527
00:28:49,794 --> 00:28:52,058
So Rutherford -
528
00:28:52,197 --> 00:28:55,325
well some of his younger
colleagues actually -
529
00:28:55,467 --> 00:28:57,435
started to measure,
530
00:28:57,569 --> 00:29:01,232
take rocks and measure
the uranium and lead content.
531
00:29:08,480 --> 00:29:12,109
Every rock contains
its own radioactive clock.
532
00:29:12,250 --> 00:29:14,912
That clock starts ticking
when the rock forms
533
00:29:15,053 --> 00:29:17,920
and new minerals crystallize
within it.
534
00:29:18,056 --> 00:29:20,991
Immediately the chemical
composition of these minerals
535
00:29:21,126 --> 00:29:22,821
slowly starts to change
536
00:29:22,961 --> 00:29:26,988
as radioactive decay
turns one element into another.
537
00:29:35,607 --> 00:29:39,065
So after nearly two centuries
of scientific endeavour,
538
00:29:39,210 --> 00:29:41,178
the age of the earth
would be revealed
539
00:29:41,312 --> 00:29:44,440
by a few grains of sand.
540
00:29:46,084 --> 00:29:52,580
And they suggested
that they found that rocks
541
00:29:52,724 --> 00:29:56,421
were as old as
a few hundred million years
542
00:29:56,561 --> 00:29:59,428
and then very soon afterwards
543
00:29:59,564 --> 00:30:01,031
it was found that there were rocks
544
00:30:01,166 --> 00:30:04,329
which were 1,500 million years old,
545
00:30:04,469 --> 00:30:07,563
and this is a completely
different order of magnitude
546
00:30:07,705 --> 00:30:11,539
to the estimates of
the age of the earth,
547
00:30:11,676 --> 00:30:12,938
and the age of rocks
548
00:30:13,077 --> 00:30:15,307
that had been given
before radioactivity
549
00:30:15,446 --> 00:30:17,038
which tended to give figures like
550
00:30:17,182 --> 00:30:20,310
10, 20, 30 million years.
551
00:30:20,451 --> 00:30:23,716
what Rutherford
did really at a stroke,
552
00:30:23,855 --> 00:30:26,915
was to lengthen geological time
553
00:30:27,058 --> 00:30:30,858
by a factor of something like 100.
554
00:30:30,995 --> 00:30:33,395
And this was greeted
by the geologists
555
00:30:33,531 --> 00:30:35,624
with a great sigh of relief
556
00:30:35,767 --> 00:30:39,828
and it is really
one of the major achievements
557
00:30:39,971 --> 00:30:41,666
of the 20th century
558
00:30:41,806 --> 00:30:45,264
that we now can date
rocks and minerals
559
00:30:45,410 --> 00:30:49,005
and things of that kind
with greater and greater accuracy
560
00:30:49,147 --> 00:30:52,310
and see how the whole history
561
00:30:52,450 --> 00:30:55,510
of the solar system
and the Earth has unrolled.
562
00:31:01,826 --> 00:31:05,057
But to finally determine
when our planet began,
563
00:31:05,196 --> 00:31:07,289
geologists still needed
to find a rock
564
00:31:07,432 --> 00:31:11,061
left over from the time
when the Earth was forming.
565
00:31:19,077 --> 00:31:22,137
This rather inconspicuous
looking object,
566
00:31:22,280 --> 00:31:24,009
it's part of a meteorite
567
00:31:24,148 --> 00:31:26,241
which fell at
a place called Allende
568
00:31:26,384 --> 00:31:30,445
in Mexico in February 1969.
569
00:31:30,588 --> 00:31:35,287
And it is actually
the oldest known object
570
00:31:35,426 --> 00:31:38,259
that we know of,
that exists on Earth.
571
00:31:40,698 --> 00:31:41,892
It's the oldest object
572
00:31:42,033 --> 00:31:45,400
that can be held by human hands.
573
00:32:04,956 --> 00:32:09,359
It has an age of 4,566,
574
00:32:09,494 --> 00:32:12,895
plus or minus 2, million years.
575
00:32:13,031 --> 00:32:14,760
Actually most of the meteorites
576
00:32:14,899 --> 00:32:17,094
are in approximately
the same range -
577
00:32:17,235 --> 00:32:19,999
just a few million years younger -
578
00:32:20,138 --> 00:32:22,572
and its these little
white inclusions here
579
00:32:22,707 --> 00:32:25,767
that give
this fantastically old age.
580
00:32:25,910 --> 00:32:29,346
And it comes from the outer
581
00:32:29,480 --> 00:32:31,175
reaches of the solar system.
582
00:32:31,316 --> 00:32:36,151
It's really a kind of
residue of the material
583
00:32:36,287 --> 00:32:40,314
from which the whole
solar system accreted,
584
00:32:40,458 --> 00:32:42,050
came together, compacted.
585
00:32:42,193 --> 00:32:43,387
It's the building block
586
00:32:43,528 --> 00:32:46,395
of all the planets and the sun
587
00:32:46,531 --> 00:32:50,399
and that formation
of the solar system
588
00:32:50,535 --> 00:32:53,663
and of the earth
happened a few tens,
589
00:32:53,805 --> 00:32:54,931
perhaps a hundred million years
590
00:32:55,073 --> 00:32:57,473
after the formation of this object,
591
00:32:57,608 --> 00:33:08,280
between about 4,550 to
4,450 million years ago.
592
00:33:09,287 --> 00:33:10,686
Meteorites told scientists
593
00:33:10,822 --> 00:33:13,154
when the Earth started to form.
594
00:33:13,291 --> 00:33:15,555
But to know what
the infant planet was like,
595
00:33:15,693 --> 00:33:18,389
they needed to find a remnant
of the early crust
596
00:33:18,529 --> 00:33:21,623
miraculously preserved
at the surface.
597
00:33:21,766 --> 00:33:25,167
The search was on
for the oldest place on Earth.
598
00:33:26,904 --> 00:33:28,929
That quest took Stephen Moorbath
599
00:33:29,073 --> 00:33:32,975
to the edge of
the great Greenland Ice Cap.
600
00:33:39,817 --> 00:33:41,284
In 1971
601
00:33:41,419 --> 00:33:44,877
Vic MacGregor
and I heard about this area
602
00:33:45,023 --> 00:33:49,585
which is about 150 kilometers
north east of Knud,
603
00:33:49,727 --> 00:33:51,695
capital of Greenland,
604
00:33:51,829 --> 00:33:54,059
and a mining company was up there
605
00:33:54,198 --> 00:33:56,928
exploring a big iron ore deposit,
606
00:33:57,068 --> 00:34:01,164
and Vic and I were
very keen to see this area.
607
00:34:01,305 --> 00:34:04,934
Vic made the first reliable
geological map
608
00:34:05,076 --> 00:34:06,805
and he suggested
609
00:34:06,944 --> 00:34:10,778
that some of these rocks
might be very old indeed.
610
00:34:22,627 --> 00:34:25,187
This place is called Isua.
611
00:34:25,329 --> 00:34:29,356
For Stephen it was to prove
the discovery of a life-time.
612
00:34:29,967 --> 00:34:31,958
we're standing right in the middle
613
00:34:32,103 --> 00:34:35,800
of the oldest known
rocks on the Earth.
614
00:34:35,940 --> 00:34:40,309
And they extend
from the lake there,
615
00:34:40,445 --> 00:34:43,471
over to the other lake here.
616
00:34:55,093 --> 00:34:56,651
well back in 1971
617
00:34:56,794 --> 00:34:58,227
when we first came up here
618
00:34:58,362 --> 00:35:00,523
we collected many of the rock types
619
00:35:00,665 --> 00:35:03,498
and then took them
back to our laboratory
620
00:35:03,634 --> 00:35:06,569
to do the radioactive
dating analysis
621
00:35:06,704 --> 00:35:10,435
and we found that many
of these rock types around here
622
00:35:10,575 --> 00:35:14,978
have ages of nearly
3,800 million years
623
00:35:15,113 --> 00:35:19,243
which is still the oldest age
624
00:35:19,383 --> 00:35:21,180
of any terrestrial rocks
625
00:35:21,319 --> 00:35:24,755
which are as extensive as this.
626
00:35:24,889 --> 00:35:26,982
well it came as quite a surprise.
627
00:35:27,125 --> 00:35:30,891
The age itself is very old
628
00:35:31,028 --> 00:35:33,588
in relation to the age of the Earth
629
00:35:33,731 --> 00:35:35,756
but also what's interesting is
630
00:35:35,900 --> 00:35:37,390
what these rocks can tell you about
631
00:35:37,535 --> 00:35:40,402
the environment of the early Earth.
632
00:35:40,905 --> 00:35:43,499
This is a particularly
interesting unit here
633
00:35:43,641 --> 00:35:45,131
because as you can see
634
00:35:45,276 --> 00:35:48,404
it's full of thousands
and thousands of round pebbles
635
00:35:48,546 --> 00:35:51,538
set in a fine grained matrix of mud,
636
00:35:51,682 --> 00:35:53,707
clay and shale.
637
00:35:53,851 --> 00:35:55,375
And this sort of rock
638
00:35:55,520 --> 00:35:58,114
which geologists call a conglomerate,
639
00:35:58,256 --> 00:36:01,885
were formed at a beach
or a shoreline
640
00:36:02,026 --> 00:36:08,659
and the erosion by water
has rounded these pebbles,
641
00:36:08,799 --> 00:36:11,893
and it shows without any doubt
that water existed
642
00:36:12,036 --> 00:36:15,096
at the surface of the Earth
3,800 million years ago,
643
00:36:15,239 --> 00:36:19,539
which at that time came
as a complete surprise.
644
00:36:27,285 --> 00:36:29,310
At Isua the ice has uncovered
645
00:36:29,453 --> 00:36:32,616
a tantalizing glimpse
of the early earth.
646
00:36:33,191 --> 00:36:35,284
But geologists' search
for a place where rocks
647
00:36:35,426 --> 00:36:38,020
might yield a more detailed picture
of the young planet
648
00:36:38,162 --> 00:36:41,325
took them to the other
side of the globe.
649
00:36:43,167 --> 00:36:44,657
The Barberton Mountain Land,
650
00:36:44,802 --> 00:36:46,599
in South Africa.
651
00:36:48,406 --> 00:36:51,136
Field area of Maarten de wit
652
00:36:54,579 --> 00:36:55,841
well it turns out
that the oldest rocks
653
00:36:55,980 --> 00:36:59,177
at Barberton
are about 3,500 million years old.
654
00:36:59,317 --> 00:37:00,409
Some of them slightly older,
655
00:37:00,551 --> 00:37:02,712
up to 3,700 million years.
656
00:37:02,853 --> 00:37:04,878
There are older rocks elsewhere
in the world
657
00:37:05,022 --> 00:37:06,512
but what's so special
about Barberton
658
00:37:06,657 --> 00:37:09,125
is that it's so incredibly
well preserved.
659
00:37:09,260 --> 00:37:11,285
Almost in a pristine state.
660
00:37:16,701 --> 00:37:19,761
Hall's original suspicion
turned out to be correct.
661
00:37:19,904 --> 00:37:21,963
Barberton is the oldest
extensive piece
662
00:37:22,106 --> 00:37:24,631
of the Earth's ancient surface.
663
00:37:24,775 --> 00:37:28,438
Here, the rocks at last
really begin to speak.
664
00:37:29,113 --> 00:37:30,444
And it's not until you've walked
665
00:37:30,581 --> 00:37:31,980
for weeks and weeks on end,
666
00:37:32,116 --> 00:37:33,743
all of a sudden you find
one tiny little outcrop
667
00:37:33,884 --> 00:37:35,818
and you say "Bingo, I've got it.
668
00:37:35,953 --> 00:37:37,716
That's what
they've been trying to tell me.
669
00:37:37,855 --> 00:37:41,086
That's what makes it exciting.
That's why I'm a geologist. "
670
00:37:44,895 --> 00:37:46,760
what the rocks of Barberton reveal
671
00:37:46,897 --> 00:37:49,866
is that 3.5 billion years ago
672
00:37:50,001 --> 00:37:52,765
the Earth was a world of volcanoes.
673
00:37:55,539 --> 00:37:56,563
That's amazing,
674
00:37:56,707 --> 00:37:58,334
all these little globules.
675
00:37:58,476 --> 00:37:59,374
The physics of the formation
676
00:37:59,510 --> 00:38:01,478
is very like
the formation of hailstones.
677
00:38:01,612 --> 00:38:03,477
These globules form
in volcanic clouds
678
00:38:03,614 --> 00:38:06,378
where very large
volcanoes erupt violently,
679
00:38:06,517 --> 00:38:09,042
like Mount St Helens, for example.
680
00:38:16,093 --> 00:38:18,118
And as the volcanic hailstones form,
681
00:38:18,262 --> 00:38:19,854
they fall back to Earth,
682
00:38:19,997 --> 00:38:22,227
in this case on a layer in a lake.
683
00:38:22,366 --> 00:38:24,334
The biggest ones settled
to the bottom
684
00:38:24,468 --> 00:38:27,266
and the smallest ones follow.
685
00:38:27,838 --> 00:38:30,136
And as in Greenland
there's abundant evidence
686
00:38:30,274 --> 00:38:33,300
that the volcanoes
were surrounded by water.
687
00:38:48,292 --> 00:38:49,816
Look!
These are the volcanic rocks
688
00:38:49,960 --> 00:38:51,154
and they're so characteristic
689
00:38:51,295 --> 00:38:53,126
and all over Barberton.
690
00:38:53,264 --> 00:38:54,891
And it's these funny shapes,
691
00:38:55,032 --> 00:38:56,897
these bulbs
and these contorted things
692
00:38:57,034 --> 00:39:00,094
that we see all over this face here
693
00:39:00,237 --> 00:39:02,000
that tells us that
these volcanic rocks
694
00:39:02,139 --> 00:39:04,232
were erupted under water.
695
00:39:07,745 --> 00:39:10,077
And the shape is a reaction
696
00:39:10,214 --> 00:39:12,512
of the lava onto the rocks
on the water,
697
00:39:12,650 --> 00:39:15,676
against the cool water
that wants to cool it down.
698
00:39:17,054 --> 00:39:19,488
And as that freezes
and forms this bulb
699
00:39:19,623 --> 00:39:21,454
it's like squeezing toothpaste out
700
00:39:21,592 --> 00:39:24,288
and piling it up
on top of one another.
701
00:39:26,497 --> 00:39:29,091
Everywhere in Barberton
we look it is these kind
702
00:39:29,233 --> 00:39:32,361
of rocks that allow us
to reconstruct
703
00:39:32,503 --> 00:39:35,336
that there were
huge tracks of ocean
704
00:39:35,473 --> 00:39:38,306
in this part of the world
at that time.
705
00:39:40,111 --> 00:39:43,171
where was all
this water coming from?
706
00:39:45,483 --> 00:39:47,280
Look at this rock.
707
00:39:48,586 --> 00:39:50,747
See these textures on the rock.
708
00:39:50,888 --> 00:39:53,083
Very delicately preserved -
709
00:39:53,224 --> 00:39:55,385
almost as if birds
have been walking on this.
710
00:39:55,526 --> 00:39:58,086
They're actually little crystals.
711
00:40:02,666 --> 00:40:03,690
They almost look man-made
712
00:40:03,834 --> 00:40:06,962
but they're really
natural crystals growing.
713
00:40:10,207 --> 00:40:12,767
These rocks came from
very high temperatures,
714
00:40:12,910 --> 00:40:14,810
crystallized out from magma
715
00:40:14,945 --> 00:40:16,503
that came from deep
in the Earth
716
00:40:16,647 --> 00:40:18,239
very rapidly to the surface,
717
00:40:18,382 --> 00:40:23,285
high in volatile content,
high in water.
718
00:40:25,055 --> 00:40:26,647
The volcanoes erupting here
719
00:40:26,791 --> 00:40:28,452
were producing vast quantities
720
00:40:28,592 --> 00:40:31,152
of water vapour with the lava.
721
00:40:31,295 --> 00:40:33,263
It was this water
which was condensing to
722
00:40:33,397 --> 00:40:35,957
form the primitive ocean.
723
00:40:46,010 --> 00:40:49,241
The combination of
volcanic activity and water
724
00:40:49,380 --> 00:40:50,677
produced an environment where
725
00:40:50,815 --> 00:40:54,046
a fascinating
new process could begin.
726
00:40:57,721 --> 00:41:01,350
My eye caught
these structures by accident
727
00:41:01,492 --> 00:41:04,052
and when I looked at them
I asked "what is that?"
728
00:41:04,195 --> 00:41:05,890
You know, I didn't have
a clue what it was.
729
00:41:06,030 --> 00:41:08,555
I'd never seen anything
like this before.
730
00:41:08,699 --> 00:41:09,461
In that same year
731
00:41:09,600 --> 00:41:13,502
I went on a conference
to New Zealand
732
00:41:13,637 --> 00:41:14,604
and during that conference
733
00:41:14,738 --> 00:41:17,571
I had a chance to sit around some
of the mud pools
734
00:41:17,708 --> 00:41:18,800
in New Zealand
735
00:41:18,943 --> 00:41:20,103
and when I was looking at them,
736
00:41:20,244 --> 00:41:22,405
while I was looking at
this bubbling mud,
737
00:41:22,546 --> 00:41:24,241
I all of a sudden
remembered these structures
738
00:41:24,381 --> 00:41:25,245
and I thought "wow, that's it.
739
00:41:25,382 --> 00:41:27,350
That's got to be what it is. "
740
00:41:28,719 --> 00:41:31,483
Ancient mud pool structures frozen
in the rock here
741
00:41:31,622 --> 00:41:33,249
and what gives it away
as a mud pool
742
00:41:33,390 --> 00:41:35,688
is of course
all these intersections.
743
00:41:43,300 --> 00:41:45,359
what is even more interesting
to think about
744
00:41:45,503 --> 00:41:47,596
is the warmth of this area
745
00:41:47,738 --> 00:41:50,400
and the sort of niche
it might have created
746
00:41:50,541 --> 00:41:52,873
for bacteria, for example,
to be swimming around.
747
00:41:53,010 --> 00:41:55,410
And this is,
of course, one of the sites
748
00:41:55,546 --> 00:41:56,877
we might be thinking about
749
00:41:57,014 --> 00:41:59,710
where life might have started.
750
00:42:02,286 --> 00:42:04,447
And in fact, just recently Maarten
751
00:42:04,588 --> 00:42:07,489
has made another remarkable find.
752
00:42:12,830 --> 00:42:13,819
well these sedimentary rocks,
753
00:42:13,964 --> 00:42:15,397
they've locked inside them
754
00:42:15,533 --> 00:42:18,195
the very earliest signs
of life on this planet.
755
00:42:18,335 --> 00:42:19,825
They're very tiny
756
00:42:19,970 --> 00:42:21,870
and when you look through
the microscope at these rocks
757
00:42:22,006 --> 00:42:24,941
you'll see tiny little bacteria.
758
00:42:30,347 --> 00:42:31,507
And it's these bacteria
759
00:42:31,649 --> 00:42:34,482
that are the first well
preserved signs
760
00:42:34,618 --> 00:42:36,779
of life on this planet.
761
00:42:43,694 --> 00:42:46,060
All geologists are time travellers
762
00:42:46,196 --> 00:42:49,962
but few have travelled as far as
Maarten de wit.
763
00:42:51,035 --> 00:42:52,195
He has ventured back in time
764
00:42:52,336 --> 00:42:55,032
almost as far as the rocks
will take him,
765
00:42:55,172 --> 00:42:59,040
to a planet very different
from the world we know today.
766
00:43:06,717 --> 00:43:09,652
It's quite remarkable to think that
767
00:43:09,787 --> 00:43:11,448
geologists over the last 100 years
768
00:43:11,589 --> 00:43:15,116
have been able to collect
all this data to allow us
769
00:43:15,259 --> 00:43:16,624
to piece together
what the early earth,
770
00:43:16,760 --> 00:43:18,022
the young earth, the juvenile earth
771
00:43:18,162 --> 00:43:22,656
might have looked like
3.5 million years ago.
772
00:43:22,800 --> 00:43:24,267
And in many ways Barberton
773
00:43:24,401 --> 00:43:26,426
has played a very big role in this.
774
00:43:26,570 --> 00:43:30,597
The unique preservations of
all the features in Barberton
775
00:43:30,741 --> 00:43:34,040
allow us to have
to very firm picture
776
00:43:34,178 --> 00:43:35,110
of what that planet,
777
00:43:35,245 --> 00:43:37,839
the skin of the planet,
might have looked like.
778
00:43:37,982 --> 00:43:39,449
There would have been
lots of continents,
779
00:43:39,583 --> 00:43:42,245
little continents, rocks basically,
780
00:43:42,386 --> 00:43:45,184
with lots of volcanoes
reaching the surface.
781
00:43:45,322 --> 00:43:47,813
So we would have seen a tremendous
amount of volcanic activity.
782
00:43:47,958 --> 00:43:50,984
Gasses, lava flows everywhere.
783
00:44:03,207 --> 00:44:05,232
This whole process would have been
784
00:44:05,376 --> 00:44:09,506
driven at a faster rate
than we see today.
785
00:44:09,647 --> 00:44:11,512
There's more energy inside the planet
786
00:44:11,649 --> 00:44:13,378
through this huge amount
787
00:44:13,517 --> 00:44:16,850
of radioactive heat
that's trying to escape.
788
00:44:20,024 --> 00:44:22,515
All this volcanic activity
was constantly
789
00:44:22,660 --> 00:44:26,255
adding new material to
the growing continents.
790
00:44:30,034 --> 00:44:32,332
But there were no plants
to soften the contours
791
00:44:32,469 --> 00:44:34,528
of the newly created land
792
00:44:34,672 --> 00:44:38,631
and without plants no oxygen
in the atmosphere.
793
00:44:47,885 --> 00:44:52,913
But around bubbling
volcanic pools bacteria thrived,
794
00:45:03,734 --> 00:45:08,137
And the volcanoes also produced
vast quantities of water vapour.
795
00:45:10,407 --> 00:45:12,136
As it rained back to the surface,
796
00:45:12,276 --> 00:45:15,143
it eroded the new rocks.
797
00:45:15,279 --> 00:45:17,247
On the bottom
of the primitive ocean
798
00:45:17,381 --> 00:45:20,748
sedimentary layers started to form.
799
00:45:21,285 --> 00:45:25,722
80-90%, 95% perhaps of the planet
would have been ocean
800
00:45:25,856 --> 00:45:27,255
and we know
from our observations that
801
00:45:27,391 --> 00:45:29,154
the oceans must have been shallow.
802
00:45:29,293 --> 00:45:32,228
Shallow oceans over
most of the planet.
803
00:45:32,830 --> 00:45:35,526
Since the scientific study
of our planet began,
804
00:45:35,666 --> 00:45:39,397
geologists have been learning
to travel through time.
805
00:45:39,536 --> 00:45:42,266
Thanks to places
like Isua and Barberton
806
00:45:42,406 --> 00:45:45,432
they have been able to
achieve something quite remarkable -
807
00:45:45,576 --> 00:45:48,704
to show us our world being born.
808
00:45:52,816 --> 00:45:55,148
This is the Earth as it is
at the very limit
809
00:45:55,285 --> 00:45:58,049
of our scientific imagination.
810
00:46:01,759 --> 00:46:04,557
As far as the record
in the rocks is concerned,
811
00:46:04,695 --> 00:46:07,823
this is the beginning
of the Earth's story.
812
00:46:21,470 --> 00:46:24,470
Subtitles: Thor
57445
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