Journey to the Centre of the Earth - Phil Wang, Ana Ferreira and Chris Jackson

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BBC Sounds, music, radio, podcasts.

You're about to listen to the Infinite Monkey Cage.

Episodes will be released on Wednesdays, wherever you get your podcasts from.

But if you're in the UK, the full series is available right now, first on BBC Sounds.

Hello, I'm Brian Cox.

I'm Robin Insect.

And this is the Infinite Monkey Cage.

Today we journey to the middle of the earth, which I think is a wonderful place to go because I do actually see Brian as a kind of a gandalf-like figure, really, this kind of wizardy person talking magical nonsense about ridiculous ideas of the behaviour of subatomic particles, all made up as he talks to his staff.

I'm kind of more of a bilbo, I like to think of myself.

But this is the weird thing, actually, even though I do see myself as more of a bilbo, it's actually Brian who has very, very hairy feet.

And apparently, it was because he was genetically altered after his first TV series because they were so worried he might lose the hair on his head that they've now made these incredibly fertile feet of his.

And if you actually see him from below the waist, he looks not dissimilar to Pan.

And that's for everyone who'd like to have a nice dream about Brian tonight.

Surprisingly,

for the first time in a very long time, Robin's introductory reference to Middle-earth is not actually far from the the theme of today's show.

Today, we're looking at what lies beneath the surface of the Earth.

If you could slice through the Earth, like a Victoria Sponge, or maybe a Fuerro Rocher.

If you could slice through the Earth, what would you find?

From the crust to the mantle to the core, what do we know about the deep structure of our planets and what mysteries await as we journey to the center of the earth?

To act as our tourist guides as we drill down, we are joined by a seismologist, an earth scientist, and a wang splainer.

And they are.

My name is Chris Jackson.

I am a geoscientist.

And the most exciting thing I've ever dug up was the phone number of an ex-girlfriend who's now my wife.

My name is Anna Ferreira.

I'm a professor in seismology at University College London.

And one of the most exciting things I dug up indirectly was a very deep collision at about a thousand kilometers depth between very hot and very cold materials.

Oh, I'm Phil Wang.

I'm a comedian, and the most intriguing thing I've dug up was a piece of Roman pottery in Vindalanda, which is an old Roman fort in Northumbria.

And all the pottery is all in shards because they were very careless.

And I wonder why they're all broken and why they're all smashed.

Why aren't there any complete vases?

Because it's not like the Roman Empire ended like Pompeii all at once.

They had time to pack.

And this is our panel.

I just want to check, Chris.

So did you physically dig up?

No, it was kind of metaphorically digital.

It was a metaphor.

Yeah, sorry.

I didn't like bury her phone number in the ground.

I thought it was.

Well, because I'd assumed she was trying to hide her number from you.

That's not unreasonable.

Now, imagine it's like that blue Peter.

You remember that memory box that they had?

Yes, yes.

Where Where it was like and they dug it up 30 years later, but it had all gone damp and everything had gone rotten.

But that idea, if I've still been able to read that number in 30 years,

Phil, I love your idea about why the Roman Empire ended, which was due to a lack of crockery to serve their geese on.

And so they went, they're just starved to death.

They were really hungry.

It's like, where's the plates, Titinius?

Oh, smashed again.

So, Chris, if we were to slice through the earth, could you go through from the surface through to the core and describe what we'd see?

I think that one of the best analogues which fails in terms of the shape is probably a Cadbury's cream egg.

And that you cut it open.

Let me just qualify that the earth's not an oval.

But it's basically a series of broadly concentric rings of different

kinds of compositions or different materials.

So I think that's a really good starting point.

Or think of an egg, which again is egg-shaped because it's an egg.

But it's got these different layers, and inside each layer, there's different features.

So, what about scotch egg?

Those are scotch eggs.

Oh my goodness.

That's it's not vegan or vegetarian compliant, but yeah, scotch egg.

But you have vegetarian scotch egg?

That's true.

That's one to you, Phil, in this quiz.

I've come up with a much better metaphor than the professional geologist.

So as we go in, could you describe those layers?

So, you know, you have more than just the simple layers, but let's start simple.

So as you say, you've got the crust, which is this thin, very brittle layer where we all live.

And for instance, earthquakes happen when that brittle layer breaks.

And then beneath that, you have something called the mantle, which at our time scales it's solid, but over millions of years, it actually flows a little bit like glass, for instance.

You might have seen that very old glass is going to be thicker in the bottom and thinner in the top.

So it's exactly the same sort of phenomena that happens in the mantle.

You have this movement, motion, flow

in the mantle.

And then beneath that, you have the outer core, which is liquid, and then actually generates our magnetic field of the Earth.

And then deep, deep inside, you have the so-called inner core, which is solid.

You have lots of heterogeneity.

You have lots of lateral variations within those layers.

So if you have to drill down, so what depths do you find those transitions?

So essentially, the crust.

If it's within the oceans, it's very thin, maybe about seven, six, seven kilometers.

If it's within the continents, it can be up to something like 70 kilometers, so really much thicker.

And then as you go to the mantle,

the boundary between the mantle and the core is at about 3,000 kilometers depth.

And then, that boundary between the outer liquid core and the solid core is at about 5,200 kilometers depth.

The bit we experience, which is very real and tangible to us and brings us so many resources but also presents so many challenges to life on Earth, it's incredibly volumetrically an incredibly small part of the Earth.

So, the crust is about 1%

of the, you know, the bit we live on is about 1% of the total earth volume.

So it is strange when you were giving those numbers of thousands of kilometers.

What we experience of it is so infinitesimally small.

And how does the composition change as you go down?

We have at the top we have in the crust we have rocks, so that's the kind of rocks you'd find

on the beach or the rocks we drill into if we were drilling a borehole into the earth.

Then as we go down into the mantle we have effectively rocks, but as Anna described, these are rocks which are not like rocks as we know it.

These are rocks which actually flow like a what we call a viscous fluid, like something that's sticky, but it moves over millions of years very, very slowly.

So it's different in terms of how it behaves to the crust.

But if you held a piece of mantle material in your hand, it would essentially be a rock.

And then as we go down into the outer core, you know, you probably wouldn't want to touch that, would be my guess.

Yeah, so it's mostly iron, liquid iron, that's the main, and also some nickel possibly, but mostly liquid iron that is basically moving and hence generating currents and hence then the Earth's magnetic field of the Earth.

This is the internal source for that.

And then when you have the inner core is also mostly made from iron and nickel, but solid.

Solid, yeah.

The outer core, the bit that's moving, it's under such high pressure that actually if you brought it to the surface of the Earth, I heard, it basically would flow like water.

Really?

So it's so hot, it's so highly pressured, but if you removed it from that environment and put it to the surface of the earth, the viscosity would basically be as runny as water, which is kind of amazing to think.

It's mind-blowing.

It's very difficult to imagine it at our scales.

So just to complete that picture, so in terms of temperature and pressure, as you go down, can you describe those temperature and pressure gradients down to the centre?

Yeah, so for instance, you know, when you are at the sea floor, say five kilometers deep sea, you're at about 500 times the pressure that you have at the atmosphere.

And can you imagine you're 500 times, you would just collapse, basically, you know.

And then when you are at the discontinuity between the crust and the mantle, you're at about a thousand times.

By the time you're at the bottom of the mantle, you're at one million times the pressures that you have at the surface.

I mean, this is crazy.

And by the time you are at the center, it's like three million times.

It's just.

I think the earth is kind of hard to describe to people like that because the only kind of physical experience you could ever have of increasing pressures if you've dived to the bottom of a swimming pool, right?

As you dive down on anybody who's been scuba diving, you feel that pressure a bit, right?

But like, what does it mean, like, the thousand times that?

It's just so incomprehensible.

Or a million atmospheres pressure.

And that's why these materials behave in a strange way, because iron flowing like water is an odd concept.

Exactly.

And I think as well, the other, like, as the temperature as it changes, in addition to the change in pressure that Anna just described, we have what we call the geothermal gradient.

So, this is the rate at which the Earth warms as we go down into it.

And the average geothermal gradient for continental crust around the world is between 25 and 32 degrees Celsius per kilometer.

So that's why it gets hotter.

You know, the movie journey to the center of the earth.

But just again, just to add some numbers to that.

You know, you're talking about hundreds of degrees Celsius, you know, relatively shallow in the mantle, but as you go deeper, we're talking about like 3,000 degrees Celsius at the bottom of the mantle.

So that's why people are sweating in that movie.

It's really,

it's mind-blowing.

It's something completely beyond our human scales.

I just wanted to ask Phil something just about you.

You studied engineering before you gave it all up for showbiz.

And

was this the kind of world that you, because some of the machinery that we see and some of these things which are able to start exploring, was that ever part of the interest in engineering?

It was a big part.

The day I decided I wanted to do engineering was when I went on a school trip to CERN in Switzerland.

And the depth of the hole and the size of the hole they've made to put the accelerator in, I thought was so incredible.

The achievement, I thought,

I'm going to learn how to do that.

And then a year into uni, I discovered dick jokes and I never turned back.

I'm fickle, basically.

I'm fickle.

And my head is easily turned.

You went from one deep darkness to another.

I see.

I like that moment where you're thinking now I could be part of the true understanding of why the universe is as it is, but I've come up with the pun chilly, chilly, wang, wang.

And I feel that that might be a better direction direction to go in.

Well, I think also the headlines of all jobs are quite cool, like science, medicine.

The headlines are pretty dramatic.

But the reality of the day-to-day work is the same as all work.

It's emails, isn't it?

I mean, it's emails and waking up early and office politics and just grind and spreadsheets.

Misery.

Yeah, there you go.

Yeah, so I think once you hit the reality of what a cool job is.

Are there any young children listening who thinks a drug into science?

This is

it.

Just so you know, we're 198 episodes in, and we forgot to tell you back in 2009, science is boring.

Anyway,

I disagree.

I was just about to add, coincidentally, last week I went down.

We have a laboratory in the UK called the Bowlby Underground.

Oh, wow.

Which is Bowlby Mine.

And I think it's the deepest mine in Britain.

It's over a kilometre deep.

And what you said about the temperature, it's about 35 to 40 degrees down there.

And it's in Weatherby.

So in Weatherby, in November, you go down one kilometre and you suddenly it's 35 degrees.

You can almost not touch the sides of that mine.

And that mine is absolutely mind-blowing in that it actually goes out under the North Sea.

So it goes so far east with the Bowlby mine.

If you access the drifts that go out in this layer called the Zechstein, it's a halite rock, a salt rock.

It goes out under the North Sea.

So when you're in those distant parts of that mine, you're not only under a kilometre or so of rock, you're actually beneath the North Sea.

Yeah, and what was interesting to me is it goes to the, we're going to talk about the dynamic nature of the Earth, because we described it just as a fixed thing, but of course it isn't.

Yeah, yeah, so it was when the UK was a lot further south in terms of latitude than where we are now.

There was a higher evaporation rate than there was an inflow of fresh brine, so fresh seawater.

So we built up these great thicknesses of salt.

So, and that's the incredible thing about the geological record: is that it has this little window into this dramatic history of the earth, and even somewhere as humdrum as the northeast of England, you know, it has sampled such a different diversity of climates and different tectonic settings.

Very quickly, Gunners, I'd like to apologise to all listeners in Sunderland, Newcastle, South and North Shields.

I think you're really smashing, and there's a lot of great stuff that happens there.

I do not find you humdrum.

Hannah.

I was just going to add that what we were discussing before, the scales are so mind-blowing and so beyond us.

Not just the spatial scales, the temperatures, the pressures, but also the time scales.

We are talking about movements at the best of a few centimeters per year, often of millimeters per year.

So it's again, you know, very...

very different.

It's a completely different mindset when we think about these processes.

Yeah, and I think as well with geology and the way our planet works is that oftentimes the public's kind of exposure to the the planetary dynamics is when it's kind of the earth is trying to kill them, right?

A volcanic eruption, an earthquake, and they're really dramatic, aren't they?

The earth shakes, something comes out of a big hole in the ground.

But a lot of the time the earth is kind of doing its thing, but just in a much more kind of modest and humble and quiet way.

And and nobody wants to make T V shows about all the ordinariness of the planet.

And I think that's a loss.

How far, first of all, has a human being actually managed to go down?

How far have they been able to explore?

Oh, humans, it's really just meters, basically.

Yeah, yeah, you know, humans, because of the pressures and all of that.

Yeah, yeah.

So, in terms of meters, how many meters would we?

I think the deepest mines on Earth go to about three and a half kilometers, some of the deepest mines, and I think they're in South Africa.

So, that's the deepest I think a human's ever been in terms of entering the crust.

Yeah, but then it's open, right?

I was thinking things like, you know, for instance, diving.

Yeah, diving, I guess, you know, there's Mariana's trend, Mariana Trench, and places where people have tried to go deeper.

So

there is that sort of thing.

So it depends whether you mean whether people going under the water or going actually into the Earth's crust.

Going into the Earth's crust is so much cooler than digging a hole.

Next time I'm digging a hole and someone says, Phil, what are you doing?

I'm going to say, I'm going into the Earth's crust.

That's so much more dramatic.

I remember as a kid, I was always told about how comparatively thin the Earth's crust was.

And I thought it was like a warning.

I got really scared of how thin the crust was.

I thought they were telling me that, like, sort of be careful out there and not play wrestling too hard or something.

Crack through this crust.

I feel a bit betrayed to learn that it's hundreds of meters.

It's important for us that it's quite thin, isn't it?

Because

there is access to the mantle below.

There's a cycle.

Could you describe actually, if we were just to have a snapshot of the way that the Earth moves, the way that this system, the dynamics of the Earth.

So essentially, the way things happen is that you have all the time new Earth, if you want, or new crust being formed, and also new crust, new Earth dying.

And the way that works is that you basically have new crust at so-called mid-ocean regions.

So this is typically, you know, in the Atlantic, in the Pacific, but also in some continental settings, where you have this very hot magma rising, you know, typically quite passively.

You have molten rock that comes from quite deep inside the Earth, hundreds of kilometers deep inside the earth, that basically as it's hot, it rises, and then it spreads laterally.

And as it spreads laterally, it cools, it ages, it gets denser, and then when it gets very, very old, it eventually sinks down again inside the earth.

These are so-called in subduction zones.

And some of those areas where you have this cold, old material is actually where you also have some of these very big earthquakes, such as in Japan or in South America.

Material plunges down, so we say, you know, the crust is dying, let's say, then goes into the mantle, it has quite a few transformations, and often it kind of stops halfway inside the mantle because you have some transformations going on, but in other cases it plunges all the way down to the boundary between the mantle and the core.

And then it might stay there.

So we call it some graveyards basically

of the crust.

It might stay there for quite some time, millions of years.

But then also

at this core-mantle boundary, there are these continent-sized structures that we still do not fully understand exactly their origin.

They are very low-velocity regions, hot regions,

and from there, because you have the core that is being hit from beneath, you have stuff that starts coming up.

And we call these upwellings or sometimes also called mantle plumes that might come all the way up to the surface as well, creating some of the islands that we have, such as, for example, maybe Hawaii.

Yeah, and the cycle just carries on through over millions and millions of years.

And where are the subduction zones?

Yeah.

So that's like in Japan, for instance.

That's in South America.

So these are plate boundaries.

Let's put it like this.

Most of this activity, new crust coming, old crust plunging, it's mostly at these boundaries of different tectonic plates.

But magma can come in through the plates.

Yeah.

So there's holes in the plates.

This is wow.

This is how you can see it.

Again, this old fear, I'm going to fall in the class.

I'm going to handle this carefully.

Yeah, yeah.

So I say, well done, though, Phil, because one of the things that really increases ratings is a sense of panic.

So we've added now possibly a million new listeners going, my God, the world might end.

It's all cracked and broken.

You're totally right, though.

So you go, so there's holes in the plates?

You leave on a hole in the plate.

I mean, there's no, I mean, a volcano is a hole in a plate, depending on the source of the magma, right?

So if you fell it, I mean, if you fell in a volcano, you wouldn't get very far.

But I mean, at least theoretically, if the volcanic throat was empty of magma, you'd go all the way down to where that magma had been sourced from, if that makes sense.

So

there are holes in the...

I don't know how to answer this without panicking you.

This sounds absolutely terrifying, and perhaps it might even threaten areas like Peterborough and Ottomans at this very moment.

So tell us more about why these people might be about to be destroyed.

There's no volcanoes in Peterborough, but like, yeah, I think what Anna described is very kind of exciting as well, because there is this slow grind of basically what you're describing is what we refer to as plate tectonics.

It's the movement of the Earth's plates as a function of the addition and loss of material and the thermal gradients, you know, the way energy is distributed around the Earth.

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To that process.

You mentioned that the plates, plate tectonics.

How many plates are there?

How do they fit together?

I'm having like undergraduate trauma now.

Well, there's a bunch of plates and then there's micro plates.

Yes.

And then, so I don't know, like, is there like 10, 11?

Around it, yeah.

These plates are all sort of moving around in constant motion.

So there is that dynamics, and it's very slow, it's very gradual, but it's ultimately those processes which lead to the really immediate and dramatic events we see happening because it's the slow grind of the plates that accumulate stress, and that stress is released in the form of earthquakes every so often.

So that's why we have most of the drama happens at plate boundaries.

And Phil, you know, be reassured,

we live in what we refer to as an intra-plate setting.

So we're away from those boundaries where all the drama is, which is why the earthquakes in the UK are relatively small and we don't have any actual business.

Well,

I've been in an earthquake in Bath.

You know, and I've been to the West Coast of America, I've been to Japan, but the place I've experienced an earthquake was in my mum's living room in Bath.

I was home alone.

I was just sitting watching TV and the whole house just went

like that, just back and forth.

And I just texted mum saying, like, is there a new washing machine or something there?

And is it massive?

And she's like, no.

And then a couple of, like an hour later, there was a news story about all along the west of the UK, there was an earthquake.

So yeah,

what I'm saying is I'm right to be terrified at all times.

Also, it does lead to more broken crockery.

And thousands of years' time when they return to your mother's home and they'll think, why did the great Bath Spa Empire collapse?

Look at all these broken plates.

I'm finding a link.

All these plates made by IKA.

She must have been the most amazing artist.

But the question then, so it's quite...

There aren't that many of them.

You said 10, 11,

how you define them.

So the obvious question is, why?

Why is the planet like that?

It's like my mum saying, Chris, why did you do that thing?

Plate tectonics has evolved over 4.5 billion years.

There's been more and less plates than that number.

And it just so happens we live on a planet where 11 is energetically, if I want to describe it in that way, the optimal number.

I've always wondered, are the plates always just rubbing up against each other?

Are they right next to each other, or are they sort of floating around and bumping like bumper cars?

The moment you have a gap, it's a new plate.

Oh, or because stuff comes up to fill it, and that's a new plate.

Yeah.

Oh, okay.

So Brian was telling me earlier on, because without the tectonic plate, you won't have

life on Earth.

So

you were saying Venus doesn't have life.

Part of the regulation system of our atmosphere is plate tectonics, volcanoes.

The bringing of

carbon, so in the form of carbon dioxide, into the atmosphere is what gives us some of the

ozone layer, which actually shields us from incoming radiation, but also keeps the Earth at a kind of hospitable temperature for us our species right you know so actually volcanoes are a fundamental regulator of the earth's kind of climate and therefore you know plate tectonics which is the the basically the underlying process which dictates how many volcanoes we have and what they bring up is the fundamental driver for life on earth and yeah it's it's a you know plate tectonics as a as a resource almost you know

it's first reflecting on venus the runaway greenhouse effect 90 atmospheres pressure what 450 degrees Celsius or so.

In part, that's because there's no way of getting the greenhouse gases out and back into the planet.

Yeah, so we have this constant carbon cycling.

So we liberate this carbon and in the form of carbon dioxide through these volcanoes, but then we consume that carbon at subduction zones.

And often we consume that carbon, weirdly, in the form of small fossils, so planktonic foraminifera.

These are animals that live in the the sea microscopic.

They use the calcium carbonate, the CO2, to build their shells.

But the poor suckers, when they die, they go down a subduction zone and get re-entered back into the mantle.

So we have volcanoes and fossils are fundamental to life on Earth.

Can you believe that?

Never thought of it being it having a role to play in the atmosphere as well.

They seem like very separate things to me.

There's the air, the crust and the goo and the air.

Yeah.

But now I'm hearing about subduction zones, so that's another thing to worry about.

Are you a warrior, Phil?

Are you genuinely a warrior?

Yeah, big time.

Yeah, ultimate warrior.

I'm always

looking out for ways I'm going to perish or get sucked into the earth.

It's my ultimate nightmare.

Would you get sucked in or you'd just fall in?

Wouldn't you?

Descend.

Knowing Phil's luck, you'd probably get sucked in, though.

I'll be off chasing plankton, and obviously, I want to follow it into subduction zone because they're just too tasty to leave alone.

How do we know these things?

How far have we gone physically down?

And below that?

I mean, so we've never accessed the core, for example.

So how do we know it's there?

How do we know what it's made of?

Yeah, so the deepest borehole that's ever been drilled is in northern Russia.

I think it was called the Kola borehole.

And they drilled to 12,000, I think it's 12,365 meters

down into the Earth's crust.

So it's the deepest borehole ever drilled.

They eventually abandoned it, but it's an incredible kind of feat of engineering and daring do, if you will, around like what we're kind of capable of doing.

Why, I don't know, but like

you know, they did it for scientific reasons and everything.

That's effectively the deepest point on Earth constructed by humans, is that borehole, as I understand it.

There's a borehole being drilled in China, and I think it's called Sendikan 1.

I think it's in the Tarim Basin in northern China.

They started drilling last year, and the last news story I could find was the 23rd of March, I think it was this year, and they'd reached 10,000 meters in 278 days of drilling.

See, that's what I find threatening, Phil, because I imagine what if they go, oh my god, the Earth's core, it's not made of that at all.

It's just filled with air.

That would have been the perfect end, I think, to the way that we're going.

I just want to recall, you know, the audience, that we're really talking about such high pressures.

Yeah, it's incredibly challenging to,

you know, firstly, there's two, well, there's two main things.

One is the temperature we've already talked about.

It's just bloody hot down there.

So you get down there and it's several hundreds of degrees Celsius and pressure, as Anna described, is incredibly high down there.

So just keeping that hole open

or basically circulating mud in that hole to keep the hole open by imposing pressure against the borehole wall.

So it's an incredibly difficult thing to do.

Are there a set of kind of tenets of this is why we're doing it, or is it like we just need to and we will discover?

It's a bit of a mix, you know.

Of course, if you really want ultimately to understand all of these impacts on humans, like we were talking about, you know, the process of earthquakes, the you know, the phenomena behind volcanoes, how mountains build, you know, ultimately you really need to understand how the mantle works.

But of course, you know, I have to be fair, it's quite indirect.

You know, it's a very ultimate type of analysis.

So it tends to be more really about understanding how our planet has evolved over time.

Can we then use this understanding for understanding other planets?

So that tends to be really more, you know, it's a more exploratory, you know, overall idea.

But a lot of the work that we do

at the scale of the planet, you know, really, for instance, trying to image the planet as a whole, a lot of the techniques that actually we develop, and we work really quite hard on imaging techniques, like people in medical teams, you know, hospitals, when you go to do a scan of your body, we use that type of techniques to image the Earth, but we apply them at the global scale really to understand these very fundamental questions, but then they can be transferred to small scales.

And for instance, to understand geothermal potentials, so for energy applications.

But for instance, the work I do, it's really, I want to understand how our planet works.

So, for instance, maybe for about a decade, more than a decade now, we are really intrigued by these continent-size structures that we have imaged.

I mentioned them briefly before, at the boundary between the mantle and the core.

These are really massive structures.

We call this region the anti-crust.

So we know that essentially they are.

That's when I thought the crust was enough danger.

Now you have an anti-crust 3,000 kilometers deep beneath your feet.

And

we don't really know exactly what they are made of.

There are lots of ideas, but it's really intriguing.

We know that a lot of these upwellings that I was talking about seem related with them.

These upwellings, in turn, then create islands, like we were saying.

They actually created, they led to massive eruptions in the past that caused these so-called igneous provinces.

We are talking about regions with thousands of kilometers full of magna.

Thankfully, we don't have those mega eruptions now.

But this is just an example.

You know, understanding really how these big structures that we see inside the Earth then link with the surface and with the behavior of our planet is ultimately what we try to understand.

And you mentioned the imaging there.

So,

how do we image?

So, essentially, you have earthquakes that occur around the world, and those earthquakes generate seismic waves that propagate inside the Earth.

And they propagate in many different directions and they probe many different depths inside the Earth.

And then we have at the surface of the Earth so-called seismometers.

So these are basically like you are listening to the sounds coming from the Earth.

And we have them all around the world.

And also I must say we have actually access to this data freely.

So we put together all the data, these waves that propagate through many different directions.

So they saw the Earth, the waves, and we disentangle the reading, so we do lots of advanced data analysis, we do modeling as well, to then convert those recordings into images of the Earth's interior.

So, from hearing the sounds of our Earth, in this case the earthquakes, we basically convert those sounds with mathematical and physical models into images of the Earth's interior.

Because I work with cosmologists, we joke that they look up, I look down, but we use the same type of imaging techniques.

And yeah, really fundamental to that is that those waves are of different types and they move in different ways through different materials.

So the way those waves move are different through solids and some of them don't move through liquids.

So one of the kind of underpinning reasons why we know that the

outer core is liquid is because these shear waves don't travel through that region of the Earth's crust.

So that's how we found out that the outer core was liquid.

So we're really reliant on these physics-based tools to see down.

So I often describe them as CT scans of the Earth.

And I'd like to just scare Phil some more because he does look great.

So I'd like to talk about extinction events.

You mentioned, actually, Annie, you mentioned, so with the Deccan Traps in India, that kind of region, what do we know about those extinction events?

For Phil, when is the next one going to happen?

Just like we're living out for.

In or near Peterborough,

so we have these things called large igneous provinces.

We call them lips.

And the Deccan Traps is one of these lips.

And these are events in Earth history.

And these are really voluminous outpourings of lava that go on for probably tens of thousands of years.

So, huge volumes in terms of cubic kilometers of material expelled onto the Earth's surface.

The lava itself is not the problem, it's the gas that comes with it.

So, a lot of gases come out of all volcanic eruptions, but especially out of these lips, you get large amounts of carbon dioxide.

And that carbon dioxide, as well as greenhouse gases, I should say,

water vapor, and there's other things that are greenhouse gases that come out with these volcanic eruptions.

They then fundamentally change the world's climate over varying time scales.

In the case of Lips, these things go on for long enough to actually lead to a substantial proportion of life on Earth dying.

How much do we know about the potential for such events?

Now we could talk about these big super volcanoes, but also these events.

We have a sense from some of the techniques Anna referred to from global seismology about where on the planet there are large volumes of melt within the mantle or large volumes of melt, so magma within the Earth's crust.

We have a sense as well as to the dynamics, the time scales over which that material is moving and migrating vertically through the Earth's crust.

We can see earthquake swarms, which are effectively the fingerprints of vertically rising magma.

So we can map those things.

And, you know, Yellowstone is one of the very famous examples of the next super volcano because there's a large volume of magma resident underneath that part of the Earth's crust, and so the fears are, you know, what's the what's the likelihood?

Don't don't go there, Phil.

I'm accommodation.

That's why I'm a cancelled, yeah.

Yeah, but those, but those sorts of areas, and so that's why I think

you know, for geoscientists, it's always very hard to communicate with the general public because we do know a lot about these dynamics.

And the question is, is when might it happen again?

And we can't predict.

We could only possibly hope to forecast, and they sound like the same word, but they're actually different things: forecasting and prediction.

We can safely say there will be another large igneous province forming on Earth, and we could possibly take a guess based on the organization of the Earth's tectonic plates and the magma where it is now as to where that might be.

But the likelihood of it happening whilst humans are on the planet are probably

quite small.

Just in case you didn't hear the news, humans are dying out next Thursday.

I was just going to add, I mean, this is exactly one of the purposes of trying to get our images better and better, to really try to understand exactly

where are the regions where there's really potential for these cygnus provinces to to form, and the UK is not one.

Now, Annie, you've done some special research about what lies directly beneath us, haven't you?

What lies beneath us.

So, Phil, we're here at the Radio Theatre.

Any guesses, any kind of predictions?

I mean, it's going to be scandalous.

Let's Let's be honest.

I would like to think an even older radio theatre, maybe

one made of a Stone Age BBC

with like stone versions of all our favorite television shows.

But for stone people.

I don't know.

I mean,

was London just like a big old mucky delta originally?

Is it just like sludge and snails?

It's an old Roman town, so I guess this spoiler alert, gonna be a lot of broken pots.

I imagine basically the same as Weatherby, though, weren't it?

Wouldn't it be if you go to the same depth, so a kilometre or so, do you get to 250 million years?

Does it work like that?

Yeah, beneath London here,

if you go down a few hundreds of meters, you eventually go into the chalk.

So, this is Cretaceous rock, which is

130,

you know, up to 100 million years old, or even a bit younger than that.

And that's where we get our water from.

And then above that, we have something called the Eocene Clay.

So that's a clay stone which was deposited in a seaway.

So that's when London was actually an ocean.

So we do have all this history in the rocks beneath our feet here.

And you mentioned where we get our water from, so where's that in from the Cretaceous chalk.

So it's what we call an aquifer.

So that's why your kettles and showers get loads of calcium carbonate on is because the water in London, this is why northern water is a lot better.

Trying to win them back at the last minute.

This is why the water is stopped and on tees, he said.

Yes, it is a remarkable thought.

I don't think of it very often, that the water that comes out of your taps is coming from

an aquifer that's the in the Cretaceous period that structure was formed.

Even more bizarre, the water that you extract or abstract, we should say, from beneath London for us, you know, for people who live here, is that water is tens of thousands of years old, I think, a few thousand years old, and it comes in in the Chilterns and it comes in the South Downs, well, the North Downs as well.

So it actually is ancient rainwater that's percolated down under London.

I like the fact that Brian's pretending he uses a tap.

As we all know, he's by a magical spring.

He's in right now.

So, Anna, it's time for the reveal then.

What shall we find beneath us?

What lies beneath us?

Shall I show it?

So, first of all, I have to say, I'm sorry to disappoint you.

This is a global model that we have produced, but we have done this cross-section.

So, it's a section going, like if you slice a cake, let's imagine, goes from the surface of the cake to

the outer core, which is here at the bottom.

I must say it was produced by my colleague William Surgeon, who is sitting here.

We are here in London.

That's London.

And then this is Iran, just to give you a scale.

This is really a global scale model.

So it goes from what, west of Iceland all the way over to Iran.

Exactly.

On this cross-section, And we're in the middle.

We are in the middle here.

This was a special cut for tonight.

And essentially, what you see is beneath London in this area here, there's this hole of this blue stuff, which is pretty much boring stuff.

It's cold.

We did it.

We did it, guys.

We're going to be okay.

It's cold, stable material, so not much happening there.

Maybe it's going to be a twist.

However.

And then you can see this low, again, hot stuff in the lower mantle, very deep, but somehow it avoids London.

So we are quite safe, quite in a very stable region, this blue area here.

Well, I see there was good news.

So, Phil, just to end, in terms of all the things that have terrified you today, what was number one?

Was it the falling into the volcano?

Was it the anticrust?

The anticrust sucks.

The idea that I could keep falling through magma and hit something hard is just creepy, I think.

And I think the holes in the plates scared me the most, because I always assumed the volcanic action happened on the edges of the plates.

But now I learn there are plate holes to look out for as well.

So that's quite scary.

I'm very scared of this giant hole in China that I'm just going to trip and fall down that.

There's a lot to be afraid of.

I'm going to leave tonight terrified, but thankful.

By the way, this map is called the Seismic Velocity Anomaly.

That sounds frightening, doesn't it?

It sounds like one of the 60s science fiction films that you...

Sounds like a button.

Yeah, an anomaly sounds like it's wrong.

Or a Doctor Who thing.

There's been a seismic velocity anomaly.

Yeah.

So, we also asked our audience a question, and we wanted to know what do you think might be found in the centre of the Earth?

So, Brian, what have you got?

I don't know, I'm not good under pressure.

There's Nathan Joyce for the math.

Oh, we can almost pack this up on the first one.

What have you got, Phil?

How can the Earth have a center if it's flat?

Very good question.

Very good question.

I saw actually the security guys wandering around it.

I thought, what are they doing?

They're looking for the flat earth.

The deep state.

I think that's probably the same person as the flat earth.

A viewing platform with overpriced cafe and souvenir shop.

So thank you very much to our fantastic panel, Professor Chris Jackson, Professor Anna Ferreira, and Phil Wang.

So,

very, very excited about next week's show, because next week Brian is going to give me £1 million

so I can start building my dream sea monkey sanctuary in Bucharest.

We're going to do a show about altruism and I thought the best way of proving it was by you because you're very very rich

giving me money to make a sea monkey sanctuary in Bucharest because that's better than the you know normally you just spend it on fine wines and velvet mittens.

Sorry?

Velvet mittens.

You do you've got everyone out here knows the number of velvet mittens you've got.

It's ridiculous.

Velvet on the inside for your pleasure or on the outside for the pleasure of others.

Brian Dubs, he's 360 degrees pleasure, that man.

Yeah, yeah, yeah.

And when you see his alpaca jodpers, you will be really impressed by the way.

Yeah, sitting there with his velvet mittens, thinking of my sea monkey.

What is the jogpa?

Is that the big trousers?

Yeah, the wide at the top, thin at the bottom, kind of horse riding ones, or the Eric von Stroheim director ones, yeah.

And they're just like shaved alpaca, and they're, yeah, it's, it's uh, and it does make him walk weird as well.

It does make him walk a bit bit like an alpaca.

It's like he becomes, so his pan-like legs become possessed by the alpaca-like trousers.

It's going to be one of the harder edits for the end of the show, isn't it?

Thank you very much, everyone, for joining us.

Bye-bye.

In the infinite monkey cage.

In the infinite monkey cage.

Till now, nice again.

I'm Hannah Frye.

And I'm Daro Breen.

And in the all-new series of Curious Cases, things are getting curiouser and curiouser.

We'll be looking the universe squarely in the eye and demanding an answer to your everyday mysteries.

Including, can you actually die of boredom?

Why do some people taste music?

And how many lemons would it take to power a spaceship?

We will shine a light on the world's most captivating oddities.

Brought to us by you, you delightful bunch of weirdos.

I don't think you're allowed to call them that.

But I love them, really.

Curious cases.

On Radio 4.

And available now on BBC Sounds.

Sucks!

The new musical has made Tony award-winning history on Broadway.

We the man to be honest!

Winner, best score.

We the man to be seen!

Winner, best book.

It's a theatrical masterpiece that's thrilling, inspiring, dazzlingly entertaining, and unquestionably the most emotionally stirring musical this season.

Suffs!

Playing the Orpheum Theater October 22nd through November 9th.

Tickets at BroadwaySF.com