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This is geology B with all of us
trampled. 

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We know the Earth was born as a 
baking in finow. 

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So the presence of a relatively 
cool surface today suggests that

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the Earth has cooled a lot since
it formed but the very thin 

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crust on which we subsist is not
representative of the Earth as a

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whole. 
And although some heat must be 

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escaping from the earth. 
There are also ongoing sources 

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of heat. 
So the answer to the question as

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to whether Earth is cooling down
is not Forward. 

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Claude, your power is Professor 
of geophysics at the université 

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De Paris and Institute the 
physic do Globe, his research 

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aims to understand the physics 
of igneous processes. 

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In the earth, such as those 
occurring, in volcanic, 

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eruptions magma Chambers and the
mantle, he's especially 

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interested in how heat flows out
of the earth, particularly in 

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continents. 
He is measured heat flow in the 

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field. 
Mostly in remotest. 

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Canada, where he discovered 
surprisingly low heat flow. 

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Claude Joe, Parr welcome to 
geology B. 

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Thank you, Oliver. 
In my introduction. 

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I said that, we know the Earth 
was once a baking Inferno. 

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They can't be much. 
Direct evidence left from the 

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very beginning of the earth. 
So do we simply in furthest from

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our knowledge of the sources of 
heat? 

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Yes, there are two main 
mechanisms that are involved. 

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First, you must gather material 
Outer space. 

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And all these material comes in 
through meteorites and fragments

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of other planets that come 
crashing down and each one of 

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these impacts releases heat. 
So there's an enormous amount of

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heat that's released this way. 
And there is another phenomenon 

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because we know that the Earth's
has differentiated now there is 

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an iron core right in the 
middle. 

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And this core formed when the 
Earth was young and hot because 

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you have to separate the heavy 
iron-bearing minerals. 

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So that they could sink to the 
Center of the Earth. 

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And this very process, the 
sinking of these are enriched 

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material is also releasing heat 
because it's friction involved. 

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When a one material moves with 
respect to another. 

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So these two sources of heat up 
enough to have a limited Earth's

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temperatures to above melting 
point. 

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What about the giant impact? 
That formed the moon? 

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There was an impact by a planet,
which was about the size of 

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Mars, and that's the impact just
Shred the bit of the earth out. 

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And this form the moon and this 
impact was so energetic, that it

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also raised temperatures way 
above the melting point. 

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So at that point to this impact,
in fact sets the clock back to 

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zero because there was enough it
to remove everything that had 

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been happening since the earth 
was formed in the first place, 

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we believe that tidal forces are
keeping some of the moons of 

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Jupiter such as IO and Europa 
and Saturn's moon Enceladus. 

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Halt is Is that something that 
keeps the earth warm as well? 

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Knowing the u.s. it's 
negligible, a lot of the title 

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for his come from the Moon. 
There's a bit from the Sun as 

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well, but these are small and 
that all of this gets dissipated

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in the oceans, a bit of it gets 
distributed in the solid earth 

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because the solidus is also 
moving up and down just as the 

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ocean surface does. 
But there's a very tiny amount 

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of energy that's released this 
way. 

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Leaving aside the question as to
whether the Earth is cooling 

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down for a moment. 
BF must be losing some heat 

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today, it can't be very much 
because apart from near 

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volcanoes or hot springs, the 
surface of the Earth is not 

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discernibly. 
Warm about how much heat are we 

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actually talking about if you 
average out all the heat that's 

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been released of the Earth 
because that varies from point 

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to point, the total average is 
about 18 million watts per 

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square meter. 
That is over an area of 1000 M2 

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your Using 80 watts and 80 watts
is basically what it takes to 

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light up a light bulb. 
So you can see the the not a lot

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of energy by our standards, but 
of course, geology doesn't work 

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on seconds, but human beings do.
So in fact, you must not worry 

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about the rate of heat per 
second, but the rate of heat 

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release per million years. 
And if you scale up this number 

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that, I just caught it to 
million years. 

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That's an absolutely enormous 
amount of energy. 

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That's the energy. 
That's Go to generate volcanic 

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eruptions and that's also the 
energy that's able to drive 

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continental drift. 
It feels warm when you go down a

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coal mine or something like 
that. 

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Presumably, we're feeling the 
heat flow from the Earth's 

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interior. 
When we feel that warmth, are 

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we? 
Yes, it was very clear to 

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earlier researchers that the 
years was hot inside. 

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Simply because as they went down
in mines, the temperature kept 

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rising and the. 
So it was very clear that the 

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Earth was hot. 
Okay, let's talk about how we 

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measure the Heat flour. 
We use a basic law of heat 

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conduction. 
That is the mechanism that 

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carries heat through a solid and
it's analogous to Ohm's law for 

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electric current in our case, 
the potential is the temperature

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and when there's a temperature 
difference between two points 

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heat is Flowing from hot to cold
and the heat flow is analogous 

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to the electrical current. 
So, what we do is we measure not

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only the temperature difference 
between two points, but we 

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measure the temperature gradient
and then we measure the Ability 

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of rocks to carry that heat 
which is measured by 

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conductivity which is the 
inverse of resistance. 

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So the heat flux then is simply 
the conductivity times the 

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temperature gradient. 
Now, conductivity is measured in

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the lab. 
You take Rock samples from the 

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field and subject them to a 
known heat flux and measure the 

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temperature difference. 
So you can work out, what is the

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conductivity? 
And then, in the field, you 

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measure the temperature. 
Gradient in a very deep bore 

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holes and this is done Drilling 
holes in the ground and measure 

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the temperature structure. 
When you go down, these 

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measurements are not easy 
because you don't control the 

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environment. 
And as we discussed in the 

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previous question, the D flow is
very small so it can be 

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perturbed by many processes. 
So you have to go very deep to 

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have very large temperature 
difference so that you're sure 

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that you're really measuring the
heat flow that's coming out of 

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the earth, is it very variable? 
I mean, does it vary on small 

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time scales and space scales 
when you go down the bore hole? 

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And in the shallow parts of 
balls, the rocks are permeable. 

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So there's water going through. 
The if water is flowing through 

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the rock, it carries heat. 
And that's something we don't 

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measure by the technique. 
We have been discussing and so 

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you must avoid this at all costs
because that's not hit that you 

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can account for. 
So you must go deeper. 

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Then the parts where there's 
water circulation and basically 

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water circulates in pores and 
cracks that get close with 

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increasing confining pressure. 
So you just have to GP enough. 

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So that all these interstitial 
spaces through which water can 

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circulate get closed and in 
practice, you must go down to at

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least 200 meter depth, suppose 
600 feet and by then there's no 

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detectable water motion. 
We can check that because we 

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measure temperature with a very 
high accuracy, one thousandth of

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a degree. 
So at this Precision, any small 

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water motion or any disturbance,
gets recorded in temperature. 

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Ian. 
So, when we measure temperatures

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in a bowl hole, we make sure the
temperature is absolutely steady

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over time. 
That is sufficiently long in 

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practice that's about 10 to 15 
minutes and if temperature does 

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not change by one thousandths of
a degree, were pretty sure that 

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nothing is happening there. 
Another factor that we need to 

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take into account, is that the 
Earth has been exchanging heat 

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with the atmosphere? 
And as we all know this been, 

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climatic changes in the past a 
One but also a much longer the 

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one associated with the glacial 
cycle so in the shallow part of 

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a bowl, the Earth is still 
equilibrating with the current 

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temperature and as a record of 
the past temperatures, so we 

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need to go sufficiently deep. 
So that we are not sensitive to 

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those changes which are not 
linked to the Earth, heat loss, 

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how deep do you go in fact, in 
some of these bottles? 

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Well for us, the deeper, the 
better because the deeper we 

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Ego. 
We can check that everything is 

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okay. 
What do I mean by everything is?

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Okay, if you have a sufficiently
very deep Bowl, you can measure 

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the heat flow through say, one 
part of the bowl and comparing 

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to the through, through another 
part of the borehole. 

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And if these two heat flows are 
the same, then you're sure 

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that's the heat that's being 
lost out of the interior of the 

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arrows. 
If there's a difference when 

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something has happened between 
these two different parts of the

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borehole. 
So that's why when we go very 

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deep, then we have many, many 
different ways. 

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Checking, that's the Heathrow is
basically the same, whether you 

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are at a kilometer depth or you 
had 500 meters depth in 

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practice. 
We measure balls that are 

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typically more than 600 meters 
deep and we are able to measure 

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the temperatures down. 
Bowls that could be as deep as 

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2.5 km. 
Wow. 

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Now I presume you're not 
drilling these boreholes 

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yourself. 
Oh no, a kilometer deep borehole

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is about a million dollars. 
So we use bones that have been 

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drilled for other purposes. 
The main source of balls for us 

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is the mining industry. 
When the explore for mineral 

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deposits. 
They drill holes to make sure 

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that there is the deposit that 
they're looking for an 

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underground. 
You're basically piggybacking on

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the exploratory, boreholes that 
other people have drilled for 

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prospecting purposes. 
Exactly. 

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Another reason, is that the very
operation of drilling, a hole 

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will perturb the rocks, it heats
up the rock because there's 

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friction between the drill bit 
and The Rock. 

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So we The bowl to cool down and 
they collaborate again with all 

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the Rocks around it. 
And so that takes something like

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several months. 
So where we to drill our holes 

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have cells. 
We would have to go to the 

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field. 
Get permission to drill the hole

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and drill it. 
And then with several months 

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before we can record it and 
that's clearly not very good for

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an academic. 
Research team will use bones 

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that have been drilled a long 
time ago. 

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Sometimes we are able to 
penetrate holes that were as old

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as 50 years. 
I know you've done a lot of 

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work. 
Work in the Canadian Shield and 

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to get good coverage. 
You go to extremely remote 

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places. 
How do you get there? 

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Well, in Canada, we go to remote
places simply because we just 

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want to get the heat through 
map. 

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And that's absolutely 
independent of whether they are 

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roads or easy access to those 
places, so we get drop by drop 

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planes or helicopters. 
So we end up in places that 

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sometimes our completely Away 
From Any Road, the people who 

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drilled the holes go in the 
winter, So, everything is 

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frozen, so that trucks can go 
very easily, but we can't do 

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this ourselves because making 
measurements in the Canadian 

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00:11:12,900 --> 00:11:15,200
cold winter. 
It's too complicated and would 

201
00:11:15,300 --> 00:11:18,400
require a lot of equipment. 
So by the time we go in 

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everything has sold. 
And so we're working through 

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marshes and wet areas and get 
dropped in the middle of 

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nowhere. 
So that leads to Cole, 

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interesting things. 
That's one of the things I 

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enjoy. 
Because you always get 

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surprises, we make measurements,
for example, in the very 

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00:11:32,600 --> 00:11:36,400
Northern tip of Canada near the 
Hudson strait There's no one 

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there, it's a beautiful and we 
set up our measuring gear. 

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It takes us about a day to log a
ball. 

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So you're sitting here and 
waiting. 

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And suddenly, you see, an arctic
fox that stayed with us for the 

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00:11:47,100 --> 00:11:50,300
whole day, it was very curious 
and was apparently happy to have

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00:11:50,300 --> 00:11:53,300
some company. 
There's also disappointments 

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because in Canada, there's 
beavers and beavers are very bad

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for us, because sometimes the 
Iraq dams and then they flood 

217
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all area. 
So, in several cases, we had 

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these fantastic balls that were 
just located where we wanted to.

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The measurements. 
And by the time we get there, 

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they will just beneath a pool of
water and we could not therefore

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make the measurements. 
What about measuring the heat 

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flow under the oceans? 
Drilling a hole in the bottom of

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the sea, is time-consuming and 
very costly. 

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So what we do is we use the fact
that they're sediments and 

225
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sediments are Loosely 
Consolidated. 

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They can be penetrated. 
So, what you do is you drop a 

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probe, deep probe. 
It's just like the thin cylinder

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that goes through the sediment. 
And in this scenario, you have 

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00:12:35,200 --> 00:12:38,300
several Thermistors. 
There are thermometers that 

230
00:12:38,300 --> 00:12:41,300
record temperatures and then you
can record the temperature 

231
00:12:41,400 --> 00:12:44,300
profile through the sediment. 
There must be quite a few 

232
00:12:44,400 --> 00:12:48,400
challenges to measuring the heat
flow at the bottom of a deep 

233
00:12:48,400 --> 00:12:51,100
ocean. 
Well, it's a terribly difficult 

234
00:12:51,100 --> 00:12:56,600
Enterprise because you have to 
shove probe down to sediments. 

235
00:12:56,900 --> 00:12:59,900
Those sediments are lying at 
depths which might be four 

236
00:12:59,900 --> 00:13:03,200
kilometers or even more. 
So you have to shove the probe 

237
00:13:03,200 --> 00:13:06,500
you have to make sure that it's 
vertical because if it's Not 

238
00:13:06,500 --> 00:13:09,200
vertical, then you're not 
recording the vertical, gradient

239
00:13:09,200 --> 00:13:11,600
of temperature. 
You recording the gradient at an

240
00:13:11,600 --> 00:13:13,700
angle, which is not what you're 
looking for. 

241
00:13:14,600 --> 00:13:17,000
Furthermore, your probe cannot 
move. 

242
00:13:17,000 --> 00:13:19,900
Once you've shoved it into the 
sediments, it must remain 

243
00:13:19,900 --> 00:13:23,500
absolutely mobile because any 
small motion of the probe will 

244
00:13:23,500 --> 00:13:26,600
generate some heat because you 
have friction of the probe 

245
00:13:26,600 --> 00:13:29,700
against the sediments. 
Given that we are making 

246
00:13:29,700 --> 00:13:31,900
measurements are very small 
temperature differences. 

247
00:13:31,900 --> 00:13:36,600
This minor amount of sheer will 
generate heat that In a mess up 

248
00:13:36,600 --> 00:13:39,400
our measurements and you're 
standing on your ship, which is 

249
00:13:39,400 --> 00:13:41,600
four kilometers above in rough 
Seas. 

250
00:13:41,600 --> 00:13:45,000
Sometimes that might be huge 
waves and you have to make sure 

251
00:13:45,000 --> 00:13:48,100
that your program. 
It's totally mobile for about 

252
00:13:48,300 --> 00:13:51,000
one or two hours because it 
takes one or two hours for 

253
00:13:51,000 --> 00:13:53,800
temperatures to equilibrate and 
for you to be able to make a 

254
00:13:53,800 --> 00:13:57,700
reliable measurements. 
The old saying was never repeat,

255
00:13:57,800 --> 00:14:01,100
he for measurement, twice for 
fear of having a new measurement

256
00:14:01,100 --> 00:14:03,400
that deviates, from the 
previous, one, by more than a 

257
00:14:03,400 --> 00:14:07,400
factor of 10. 
You I've been measuring the heat

258
00:14:07,400 --> 00:14:09,900
flow coming out of the earth 
directly. 

259
00:14:10,600 --> 00:14:14,700
Are there other observations 
that can yield an indirect 

260
00:14:14,700 --> 00:14:18,900
measurement of the heat flux? 
Yes, we use the depth of the sea

261
00:14:18,900 --> 00:14:20,800
floor. 
What happens is that as the 

262
00:14:21,000 --> 00:14:25,200
oceanic lithosphere cools down, 
it contracts and this is what 

263
00:14:25,200 --> 00:14:29,100
explains the fact that we 
observe the seafloor to deepen 

264
00:14:29,100 --> 00:14:31,700
as we go away from a mid-ocean 
ridge. 

265
00:14:32,200 --> 00:14:35,000
That's a deepening is simply D 
to the fact that the little 

266
00:14:35,000 --> 00:14:37,900
circles down and Contracts and 
then gets deeper. 

267
00:14:38,400 --> 00:14:42,400
So the way contracts tells us 
how much heat is being lost and 

268
00:14:42,400 --> 00:14:44,300
therefore, what has been the 
heat loss? 

269
00:14:44,300 --> 00:14:47,900
Of course, when you measure the 
depth of the sea floor, you're 

270
00:14:47,900 --> 00:14:50,500
sensitive to very shallow 
structures. 

271
00:14:50,500 --> 00:14:53,600
That might be a seamount here. 
There might have been some 

272
00:14:54,100 --> 00:14:58,200
turbidity current with an extra 
segment recover there so it is a

273
00:14:58,200 --> 00:15:01,100
roughness in the topography but 
by and large over a large 

274
00:15:01,100 --> 00:15:02,800
killed. 
The deepening of the sea floor 

275
00:15:02,800 --> 00:15:05,400
is just a record of the heat 
that's being lost out of the sea

276
00:15:05,400 --> 00:15:09,000
fool. 
And that works on all oceans 

277
00:15:09,000 --> 00:15:13,400
that have spreading ridges which
I guess all of them do right. 

278
00:15:13,800 --> 00:15:15,700
Yes. 
That's one of the beauty of the 

279
00:15:15,700 --> 00:15:18,300
physics is this has been done. 
The fact that there was a 

280
00:15:18,308 --> 00:15:20,800
mid-ocean ridge was known since 
the 19th century. 

281
00:15:21,000 --> 00:15:24,700
It was one of the big questions.
What is the origin of? 

282
00:15:24,700 --> 00:15:27,900
The oceanic Mountain belts and 
it's quite different for what 

283
00:15:27,900 --> 00:15:30,200
happens in the continents. 
In the oceans. 

284
00:15:30,200 --> 00:15:33,600
What is happening is simply the 
cooling and we only realized 

285
00:15:33,600 --> 00:15:36,500
that in the 1960s 1970s. 
Geez. 

286
00:15:37,000 --> 00:15:41,100
But by then we knew that the 
deepening of the seafloor away 

287
00:15:41,100 --> 00:15:42,900
from a rich. 
We measured it as a function of 

288
00:15:42,900 --> 00:15:44,700
distance was absolutely the 
same. 

289
00:15:44,900 --> 00:15:48,600
In all oceans you could measure 
it in the Atlantic Ocean or in 

290
00:15:48,600 --> 00:15:52,800
the Pacific Ocean or in the 
Indian Ocean and you had exactly

291
00:15:52,800 --> 00:15:56,100
the same deepening. 
So that was telling us that 

292
00:15:56,100 --> 00:15:59,000
there was a single physical 
mechanism at work there. 

293
00:15:59,900 --> 00:16:04,000
What do the results of all these
heat flow measurements? 

294
00:16:04,200 --> 00:16:08,500
Tell us we Know how much heat is
being lost by the Earth's? 

295
00:16:08,500 --> 00:16:11,800
That's one aspect and it's 
telling us two things. 

296
00:16:11,800 --> 00:16:15,500
One, is that larger fraction of 
the Earth's heat losses, don't 

297
00:16:15,500 --> 00:16:18,600
shoot the ocean and they're very
big contributor for two reasons.

298
00:16:18,600 --> 00:16:21,600
One is that it's the largest 
surface which is losing heat. 

299
00:16:21,600 --> 00:16:25,000
So, that's one aspect but also 
per unit surface. 

300
00:16:25,000 --> 00:16:27,100
It's also where the flow is 
largest. 

301
00:16:28,000 --> 00:16:31,000
Then if you go to countenance, 
it's a different story because 

302
00:16:31,000 --> 00:16:33,200
there are young continents, 
where you're sitting next to a 

303
00:16:33,208 --> 00:16:35,000
volcano. 
Clearly you're going to have a 

304
00:16:35,000 --> 00:16:38,100
large heat flow. 
Because the magma that's been in

305
00:16:38,100 --> 00:16:40,100
place beneath the volcano is 
cooling down. 

306
00:16:40,100 --> 00:16:43,300
So that's extra eat. 
But when you go to very old 

307
00:16:43,300 --> 00:16:46,300
places, such as the Canadian 
Shield, the Canadian Shield on 

308
00:16:46,300 --> 00:16:49,000
average is more than 2.5 billion
years old. 

309
00:16:49,400 --> 00:16:53,800
And we know that by this time, 
every transient heat loss due to

310
00:16:53,800 --> 00:16:56,000
the formation of the continent 
has decayed away. 

311
00:16:56,000 --> 00:17:00,500
So we still measure differences 
of heat flow, simply because 

312
00:17:00,800 --> 00:17:02,600
coconut oil. 
Rocks are full of radioactive 

313
00:17:02,600 --> 00:17:05,700
elements and is radioactive 
elements release heat as they 

314
00:17:05,900 --> 00:17:07,800
DK. 
Depending on which work you're 

315
00:17:07,800 --> 00:17:11,000
standing on, there's more or 
less energy, that's being 

316
00:17:11,000 --> 00:17:13,400
produced, and that is reflected 
in the heat flow. 

317
00:17:13,700 --> 00:17:16,300
So incontinence. 
What we are measuring is by and 

318
00:17:16,300 --> 00:17:19,400
large the amount of heat that's 
released by radioactivity in 

319
00:17:19,400 --> 00:17:23,599
crustal rocks. 
Does the heat flow we measure 

320
00:17:24,000 --> 00:17:26,700
very on quite small, spatial 
scales. 

321
00:17:26,700 --> 00:17:29,500
You mentioned the presence of 
volcanoes do we see that kind of

322
00:17:29,500 --> 00:17:33,900
variation elsewhere as well, 
equal varies on all sorts of 

323
00:17:33,900 --> 00:17:37,100
scale on a very large scale. 
New content, for example, North 

324
00:17:37,100 --> 00:17:41,400
America, if you measure heat 
flow close to the west, then you

325
00:17:41,400 --> 00:17:44,400
have active volcanoes. 
You have also extension the 

326
00:17:44,400 --> 00:17:47,500
Basin and Range is the province 
where the Earth's lithosphere 

327
00:17:47,500 --> 00:17:50,600
and cross are being thinned. 
So, that's a very active region.

328
00:17:50,600 --> 00:17:53,300
Where the flow is large. 
When you go to the Colorado 

329
00:17:53,300 --> 00:17:57,000
Plateau, the Colorado Plateau 
itself was a site of magnetic 

330
00:17:57,000 --> 00:17:59,100
activity about 100 million years
ago. 

331
00:17:59,600 --> 00:18:03,000
And so there's a big jump in the
Heathrow when you go from the 

332
00:18:03,000 --> 00:18:05,000
Basin and Range under Corrado 
Plateau. 

333
00:18:05,400 --> 00:18:08,900
Then when You go further east. 
Then you go to the older parts 

334
00:18:08,900 --> 00:18:11,900
of North American continent and 
you still have variations of 

335
00:18:11,900 --> 00:18:14,800
heat flow but on a smaller scale
that is the scale of an 

336
00:18:14,800 --> 00:18:18,300
individual Rock. 
For example, from one pluton to 

337
00:18:18,700 --> 00:18:23,500
sedimentary Basin the change of 
geological setting will be 

338
00:18:23,500 --> 00:18:25,300
reflected in the change in heat 
flow. 

339
00:18:25,500 --> 00:18:28,400
So you have a large-scale 
operation which is due to the 

340
00:18:28,400 --> 00:18:31,700
story of the continent, a young 
continent, or an old continent 

341
00:18:31,800 --> 00:18:34,800
and within a content of a given 
age, then you have smaller scale

342
00:18:34,800 --> 00:18:37,300
variations that are due. 
The juridical fabric of the 

343
00:18:37,300 --> 00:18:40,000
continent. 
Do you see much higher heat flow

344
00:18:40,000 --> 00:18:43,400
in the tens or hundreds of 
kilometers around Yellowstone? 

345
00:18:43,400 --> 00:18:46,800
For example, Yellowstone is a 
place where the Earth is losing,

346
00:18:46,800 --> 00:18:50,900
an enormous amount of heat and 
not by this mechanism, we were 

347
00:18:50,900 --> 00:18:54,000
talking about conduction. 
It's mostly releasing heat 

348
00:18:54,000 --> 00:18:56,600
because there's film roles, 
that's hot gases. 

349
00:18:56,900 --> 00:18:59,800
And as a gigantic amount of 
Magma's that has been in place 

350
00:18:59,800 --> 00:19:01,600
in the Earth's crust beneath 
Yellowstone. 

351
00:19:02,100 --> 00:19:07,600
So when we measure heat flow, we
close to the axis of activity. 

352
00:19:07,600 --> 00:19:10,300
We still measure a high heat 
flow but we only measuring part 

353
00:19:10,300 --> 00:19:12,900
of it because most of it is 
actually being lost through 

354
00:19:12,900 --> 00:19:16,900
hydrothermal circulation in 
cracks but as we go away from 

355
00:19:16,900 --> 00:19:19,800
Yellowstone we measure decrease 
in the Heathrow simply because 

356
00:19:19,800 --> 00:19:22,300
we're getting away from the big 
heat source which is the magma 

357
00:19:22,300 --> 00:19:26,000
Reservoir that's beneath 
Yellowstone overall averaging 

358
00:19:26,000 --> 00:19:31,700
for the f is a whole are we 
currently losing more heat than 

359
00:19:31,700 --> 00:19:34,100
we're generating from 
radioactive sources? 

360
00:19:34,900 --> 00:19:38,900
The story of the heat sources 
and the Heathrow is a complex 

361
00:19:38,900 --> 00:19:42,900
one so we can measure this today
and then we can infer what 

362
00:19:42,900 --> 00:19:46,300
happens in the past remodeled, 
but let's talk about what we do 

363
00:19:46,300 --> 00:19:49,000
today. 
So today I have all these 

364
00:19:49,000 --> 00:19:51,900
measurements in the oceans and 
the continents and I can't 

365
00:19:51,900 --> 00:19:54,000
figure out how much the Earth is
losing heat. 

366
00:19:54,200 --> 00:19:57,200
We talked about on average was 
80 million watts per square 

367
00:19:57,200 --> 00:20:00,700
meter and now I can calculate 
how much heat is being produced 

368
00:20:00,700 --> 00:20:04,300
by redirect ability because I 
have some idea about the total 

369
00:20:04,300 --> 00:20:06,800
amount Amount of radioactive 
elements that I've indiarose. 

370
00:20:07,200 --> 00:20:13,100
All the geochemical evidence and
all the models for the arose 

371
00:20:13,400 --> 00:20:16,900
construction are such that the 
radioactivity can only 

372
00:20:16,900 --> 00:20:19,400
contribute half of what we're 
losing today. 

373
00:20:19,400 --> 00:20:23,400
So we're losing today twice as 
much heat as we're producing. 

374
00:20:23,600 --> 00:20:26,300
So we have a net loss of equal 
to 0. 

375
00:20:26,300 --> 00:20:30,400
So the Earth is cooling down. 
Does that translate into a 

376
00:20:30,400 --> 00:20:33,200
temperature loss rate of the 
earth? 

377
00:20:33,800 --> 00:20:36,600
Yes, if you For this to 
temperature with cooling down at

378
00:20:36,600 --> 00:20:40,100
a rate of about 100 degrees per 
billion years. 

379
00:20:40,600 --> 00:20:43,500
Okay? 
So well over 1,000 degrees now, 

380
00:20:43,500 --> 00:20:46,000
so we've got a long way to go 
before we cool down. 

381
00:20:46,600 --> 00:20:50,000
In fact, it is a very small rate
of cooling and this is why 

382
00:20:50,000 --> 00:20:52,700
geological activity has been 
sustained for so long. 

383
00:20:52,700 --> 00:20:56,900
Because a deer has been cool 
down much faster than everything

384
00:20:56,900 --> 00:21:00,000
would be dead by. 
Now, as we go back in time, 

385
00:21:00,000 --> 00:21:03,800
there must have been more and 
more radioactive heat 

386
00:21:03,800 --> 00:21:04,700
generation. 
Ian. 

387
00:21:05,800 --> 00:21:09,500
What's that actually a time when
the Earth was heating up before 

388
00:21:09,500 --> 00:21:12,800
it started cooling down? 
Well, that's the billion-dollar 

389
00:21:12,800 --> 00:21:14,700
question. 
There is some evidence that we 

390
00:21:14,700 --> 00:21:17,600
reach the temperature maximum 
sometimes in US history. 

391
00:21:18,200 --> 00:21:21,900
So it's clear that today we're 
losing mojito real producing. 

392
00:21:22,600 --> 00:21:26,300
It's clear also that because the
radioactive decay we had to lose

393
00:21:26,300 --> 00:21:29,200
more heat in the past because 
the radioactive elements are not

394
00:21:29,200 --> 00:21:32,400
decayed as much as they've 
decayed today, but we also know 

395
00:21:32,400 --> 00:21:35,000
that heat flux should also go up
as we go back in time. 

396
00:21:35,200 --> 00:21:38,800
Simply because as the earth cut 
after it became easier to 

397
00:21:38,800 --> 00:21:42,400
deform, then it could lose more 
heat it was more efficient that 

398
00:21:42,400 --> 00:21:46,800
mixing up its interior and 
shedding its eat so we have both

399
00:21:47,200 --> 00:21:49,900
the heat loss and the heat 
production that go up 

400
00:21:50,100 --> 00:21:54,600
simultaneously with time. 
As of now we have clear evidence

401
00:21:54,600 --> 00:21:57,600
that the Earth has been cooling 
down for between two and three 

402
00:21:57,600 --> 00:22:00,600
billion years. 
And we reach apparently some 

403
00:22:00,600 --> 00:22:02,600
Maximum at about 3 billion years
ago. 

404
00:22:03,200 --> 00:22:07,800
Do we have any observations That
we can use to corroborate these 

405
00:22:07,800 --> 00:22:11,500
conclusions that the F was 
hotter in the past. 

406
00:22:11,900 --> 00:22:15,500
Yes, we can use the composition 
of lavas, the Earth's mantle, 

407
00:22:15,500 --> 00:22:18,700
which is producing the Primitive
lavas that eventually feed all 

408
00:22:18,700 --> 00:22:22,300
sorts of volcanic activity. 
It's the Earth's mantle that's 

409
00:22:22,300 --> 00:22:24,800
melting. 
Now, the Earth's mantle is not a

410
00:22:24,800 --> 00:22:28,700
pure substance, so just does not
melt at one temperature. 

411
00:22:28,800 --> 00:22:30,600
It melts over a temperature 
range. 

412
00:22:31,100 --> 00:22:34,100
Now, depending on the 
temperature at which you are 

413
00:22:34,100 --> 00:22:37,100
melting, therefore, you're 
melting different proportions of

414
00:22:37,100 --> 00:22:41,100
the mental and hence you're 
generating liquids that have 

415
00:22:41,100 --> 00:22:46,800
different compositions. 
So the hotter, the mental, the 

416
00:22:47,300 --> 00:22:51,000
more primitive. 
The lava is so by looking at the

417
00:22:51,000 --> 00:22:55,600
lava composition in terrains of 
different ages, we get a record 

418
00:22:55,700 --> 00:22:59,300
of the temperature at which the 
Earth's mantle got molten and so

419
00:22:59,500 --> 00:23:05,000
we can transform composition of 
lava into mental temperature. 

420
00:23:05,600 --> 00:23:10,100
And when we do this, we observe 
that as we go back in time, the 

421
00:23:10,300 --> 00:23:14,100
mental temperature goes up and 
it goes up to about 3 billion 

422
00:23:14,100 --> 00:23:19,100
years as the calculations tend 
to indicate it's consistent with

423
00:23:19,100 --> 00:23:22,600
what we observe these lava 
compositions but for ages that 

424
00:23:22,600 --> 00:23:25,900
are older than 3 billion years 
first, we don't have that many 

425
00:23:25,900 --> 00:23:29,800
samples as we go back in time. 
There's not a lot of lava flows 

426
00:23:29,800 --> 00:23:32,300
that are still around and 
they've been altered being 

427
00:23:32,300 --> 00:23:36,300
exposed to the winds and to the 
waters and they've been Sewed up

428
00:23:36,300 --> 00:23:40,500
in a mountain belt. 
So for older than 3 billion 

429
00:23:40,500 --> 00:23:43,100
years, we're not quite sure. 
There's data that suggests that 

430
00:23:43,100 --> 00:23:46,400
the temperature doesn't change 
much and that's about it. 

431
00:23:46,900 --> 00:23:50,800
So you mentioned that the fact 
that the Earth is still very hot

432
00:23:51,000 --> 00:23:56,200
explains that it's still very 
geologically active and it's 

433
00:23:56,200 --> 00:24:00,300
driving that activity. 
So, to our measurements, in our 

434
00:24:00,300 --> 00:24:05,200
understanding of heat flow help 
us understand how plate. 

435
00:24:05,300 --> 00:24:10,600
Onyx works pretty tunics is in 
fact the major agent for losing 

436
00:24:10,600 --> 00:24:12,600
heat. 
You cool, a plate at the surface

437
00:24:12,700 --> 00:24:16,100
during Place material at the 
surface, it's coming from the 

438
00:24:16,100 --> 00:24:19,100
Earth's interior, it's hot, then
it cools down and this is what 

439
00:24:19,100 --> 00:24:22,200
is responsible for. 
The deepening of the sea floor 

440
00:24:22,200 --> 00:24:25,300
with age and then by the time, 
you've cooled quite a lot of 

441
00:24:25,300 --> 00:24:29,800
material then you subtract it, 
you shove it in the Earth's 

442
00:24:29,800 --> 00:24:33,400
interior and that of course, is 
acting to cooling the Earth's 

443
00:24:33,400 --> 00:24:35,200
interior because you just carry 
cool stuff. 

444
00:24:35,400 --> 00:24:37,900
To the interior and just mix it 
with the surroundings. 

445
00:24:38,300 --> 00:24:41,200
So, plate tectonics is a major 
cooling agent. 

446
00:24:41,200 --> 00:24:45,800
So if we understand how the 
Earth is losing seats, there are

447
00:24:45,800 --> 00:24:49,500
two aspects of the same problem.
So if we understand the heat 

448
00:24:49,500 --> 00:24:52,300
loss, and we also understand the
rate at which we've been 

449
00:24:52,300 --> 00:24:55,900
subducting things in the past. 
And so the rate at which 

450
00:24:55,900 --> 00:24:59,400
subtracting has operated in the 
past tells us the intensity of 

451
00:24:59,400 --> 00:25:03,100
mantle convection tells us how 
many plates we were generating 

452
00:25:03,100 --> 00:25:07,600
and other aspects like that. 
So, So yes, the E-class story is

453
00:25:07,700 --> 00:25:10,400
actually providing us with a 
very strong constraint on the 

454
00:25:10,600 --> 00:25:13,900
operation of plate tectonics. 
In the past, the simple-minded 

455
00:25:13,900 --> 00:25:18,700
model of convection of the 
mantle driving the plate motions

456
00:25:18,700 --> 00:25:24,400
has some major challenges such 
as the scale of the plates and 

457
00:25:24,700 --> 00:25:29,800
how subduction actually starts. 
If you look at any system that's

458
00:25:29,800 --> 00:25:33,300
convecting, usually what you 
find is that the horizontal 

459
00:25:33,300 --> 00:25:35,200
scale of motion that is the 
distance. 

460
00:25:35,400 --> 00:25:39,100
Between an upwelling and 
downwelling is about equal to 

461
00:25:39,100 --> 00:25:43,000
the depth of the system that is 
if you have a cup of water which

462
00:25:43,000 --> 00:25:46,700
is 5 cm thick, you will have 
upwelling and downwelling which 

463
00:25:46,700 --> 00:25:50,400
are separated by about 5 cm. 
Now on the earth, we don't have 

464
00:25:50,400 --> 00:25:52,000
this. 
The Earth's mantle is about 

465
00:25:52,000 --> 00:25:55,100
3,000 kilometers thick and we 
have this plate that I 

466
00:25:55,108 --> 00:25:58,000
extraordinarily, large the 
Pacific, Ocean extends, over 

467
00:25:58,000 --> 00:26:00,000
something like, 10,000 
kilometers. 

468
00:26:00,400 --> 00:26:02,600
So, it is much wider than it is 
deep. 

469
00:26:03,000 --> 00:26:06,200
That's a major problem. 
We don't And this very well. 

470
00:26:06,900 --> 00:26:08,700
And the other problem is, we 
don't understand very well. 

471
00:26:08,700 --> 00:26:11,000
I wish abduct, we know it's 
happening. 

472
00:26:11,300 --> 00:26:14,100
We know it essential to cool 
viewers, we know it's bound to 

473
00:26:14,100 --> 00:26:17,500
happen, but why it happens in 
the way, it happens on the 

474
00:26:17,500 --> 00:26:19,900
Earth, where it is so difficult 
to subduct. 

475
00:26:19,900 --> 00:26:23,100
Why do we have to wait for 
10,000 kilometers to see a 

476
00:26:23,108 --> 00:26:25,000
subduction zone in the Pacific 
Ocean? 

477
00:26:25,400 --> 00:26:27,200
This is something we don't 
understand very well. 

478
00:26:27,500 --> 00:26:29,800
And that's the key question. 
Because if you don't understand 

479
00:26:29,800 --> 00:26:32,200
subduction, you don't 
understand, convection. 

480
00:26:32,400 --> 00:26:33,800
I you don't understand heat 
loss. 

481
00:26:34,200 --> 00:26:37,500
Do you have any? 
Ideas as to how we might be able

482
00:26:37,500 --> 00:26:41,200
to explain these puzzles this 
difficult because we don't have 

483
00:26:41,200 --> 00:26:45,000
that many records of Seduction, 
which is a starting we have 

484
00:26:45,100 --> 00:26:48,600
subduction that has been going 
on for a long time and so any 

485
00:26:48,600 --> 00:26:51,200
record of how it started is long
gone. 

486
00:26:51,200 --> 00:26:55,700
So it's not an easy question. 
So the two kinds of theories one

487
00:26:55,700 --> 00:26:58,500
is that the Earth has been 
deforming quite a bit from day 

488
00:26:58,500 --> 00:27:01,400
one. 
So you have zones of weakness 

489
00:27:01,800 --> 00:27:05,000
that are still lying about. 
For example, the collision 

490
00:27:05,000 --> 00:27:08,900
between Three, two continents 
and that will leave a scar and 

491
00:27:08,900 --> 00:27:11,800
the Zone which will remain weak 
for quite some time. 

492
00:27:12,000 --> 00:27:14,900
And by the time you have an 
ocean build up in the same area,

493
00:27:14,900 --> 00:27:17,800
then this area is still weak and
this is maybe how you can 

494
00:27:18,000 --> 00:27:20,200
generate subduction in this 
particular place. 

495
00:27:21,100 --> 00:27:25,300
Another concept is that we have 
continents and oceans continents

496
00:27:25,300 --> 00:27:29,400
Yukon subduct provide us with 
the ankles to Anchor motion. 

497
00:27:29,700 --> 00:27:32,400
So you do have to make sure that
the Motions that you're 

498
00:27:32,400 --> 00:27:34,900
generating, the oceans are 
consistent with the presence of 

499
00:27:34,900 --> 00:27:38,000
cut. 
So in some models, the contents 

500
00:27:38,000 --> 00:27:42,300
are actually those which force 
the subtraction, what are you 

501
00:27:42,300 --> 00:27:44,100
currently working on a new 
research? 

502
00:27:44,500 --> 00:27:48,000
Well, right now, I'm working on 
the your seat laws. 

503
00:27:48,100 --> 00:27:51,000
I'm interested in the way that 
he loves is connected to 

504
00:27:51,000 --> 00:27:55,000
Continental growth, continents 
today occupy something like 40% 

505
00:27:55,000 --> 00:27:58,600
of the external surface, but in 
the past, we started with 

506
00:27:58,600 --> 00:28:01,500
probably know conference. 
At also contents have been 

507
00:28:01,508 --> 00:28:03,500
growing and continents. 
Do two things. 

508
00:28:03,500 --> 00:28:07,600
One is that this They collect 
radioactive elements and those 

509
00:28:07,600 --> 00:28:10,300
radioactive elements will not 
participate in driving mental 

510
00:28:10,300 --> 00:28:13,600
motions, because they are just 
stuck in these rigid continents.

511
00:28:13,600 --> 00:28:16,600
So that's one aspect, is that 
content will gross act to 

512
00:28:16,600 --> 00:28:19,300
deplete the Earth's mantle in 
radioactive elements. 

513
00:28:20,200 --> 00:28:23,000
The other aspect is that 
continents are thick and they 

514
00:28:23,000 --> 00:28:26,400
don't lose that much heat. 
So, you see, the contents are 

515
00:28:26,600 --> 00:28:29,500
doing two things. 
They reduce the area through 

516
00:28:29,500 --> 00:28:33,100
which you can release a lot of 
it back, Oceanic spreading it 

517
00:28:33,200 --> 00:28:37,000
and then they take real. 
Two lemons out of the mental and

518
00:28:37,000 --> 00:28:39,400
hence out of the engine. 
That's preparing everything. 

519
00:28:39,900 --> 00:28:43,700
So these are two major aspects 
that are intimately linked to 

520
00:28:43,700 --> 00:28:46,500
the her stumble history. 
And that's what I'm working on 

521
00:28:46,500 --> 00:28:48,800
linking. 
The story of content or grows 

522
00:28:49,200 --> 00:28:52,600
with the story of mantle, 
convection and plate tectonics. 

523
00:28:53,600 --> 00:28:59,400
If you had unlimited funds for 
your research, how would you use

524
00:28:59,400 --> 00:29:02,600
them? 
If I had a lot of money, I would

525
00:29:02,600 --> 00:29:05,100
go and explore places that we 
don't know. 

526
00:29:05,200 --> 00:29:07,700
Yet understand quite well. 
What's going on in North 

527
00:29:07,700 --> 00:29:09,600
America. 
But there are large bits of 

528
00:29:09,600 --> 00:29:12,500
North America that we don't know
very well geologically. 

529
00:29:12,800 --> 00:29:16,100
We don't know the Northern parts
of Canada first because it's 

530
00:29:16,500 --> 00:29:19,600
under a lot of snow and ice and 
surprisingly enough. 

531
00:29:19,600 --> 00:29:21,900
This is also where the content 
is the oldest. 

532
00:29:22,100 --> 00:29:26,000
So we missing a big record of 
the early evolution of the North

533
00:29:26,000 --> 00:29:29,000
American continent because we 
don't have a proper geological 

534
00:29:29,000 --> 00:29:31,300
map and we don't have samples 
from those areas. 

535
00:29:31,900 --> 00:29:35,100
Similarly, when you look at the 
oceans, we are very good. 

536
00:29:35,300 --> 00:29:38,800
Jewel of the ocean floor in the 
Pacific or the Atlantic. 

537
00:29:38,900 --> 00:29:41,700
When when you go to the Arctic 
Ocean we don't have that much 

538
00:29:41,700 --> 00:29:44,400
resolution. 
There's a mid-ocean ridge there.

539
00:29:44,800 --> 00:29:46,900
We don't know exactly how its 
structure is. 

540
00:29:47,600 --> 00:29:50,500
And the last but not least, 
there's a big continent that's 

541
00:29:50,500 --> 00:29:53,900
lying in the South Pole 
Antarctica and we don't know it 

542
00:29:53,900 --> 00:29:56,700
George go structure very well. 
There's an active volcano Here. 

543
00:29:56,700 --> 00:30:00,900
Mount Erebus beautiful volcano. 
There's a mountain belt but we 

544
00:30:00,900 --> 00:30:01,700
don't know. 
It's me. 

545
00:30:01,800 --> 00:30:06,400
So we don't have access to a 
current parts of Earth's 

546
00:30:06,400 --> 00:30:08,300
history. 
So what I would do is go and 

547
00:30:08,300 --> 00:30:12,100
explore these unexplored places.
Close your Park. 

548
00:30:12,200 --> 00:30:15,800
Thank you very much. 
Thank you Oliver for more about 

549
00:30:15,800 --> 00:30:20,100
geology b, as well as pictures 
and illustrations, that support 

550
00:30:20,100 --> 00:30:24,500
this podcast, you can go to 
geology B.com