Latest / Daniel and Kelly’s Extraordinary Universe / What drives the movement of Earth’s continents?

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What drives the movement of Earth’s continents? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Daniel, are your kids as tall as you are yet?
• 0:11
  Speaker 2: Oh? Not yet. I've still got an inch on my
• 0:13
  Speaker 2: fifteen year old, but he's already past my wife. How
• 0:16
  Speaker 2: about you. Are your kids taller than you are?
• 0:18
  Speaker 1: Not yet, but my son is taller than my wife. No,
• 0:22
  Speaker 1: by a lot.
• 0:23
  Speaker 2: It's amazing that you never see them actually grow, and
• 0:26
  Speaker 2: yet one day they're going to look down on us.
• 0:28
  Speaker 1: You mean physically, not figuratively. That's been happening for years
• 0:32
  Speaker 1: for me. But at this rate they'll be there. Should
• 0:34
  Speaker 1: be twice our height in about five years, right.
• 0:38
  Speaker 2: There definitely be twice as smart as we are. I
• 0:40
  Speaker 2: mean I'm already forgetting things faster than they're learning them.
• 0:44
  Speaker 1: I think my son is already smarter than me. Does
• 0:46
  Speaker 1: that mean you've peaked in terms of your brain and
• 0:49
  Speaker 1: your height?
• 0:49
  Speaker 2: Yeah? I think it's just downhill from here, and I'm
• 0:51
  Speaker 2: really not looking forward to incontinental drift.
• 0:54
  Speaker 1: Wait, do you mean continental drift?
• 0:56
  Speaker 2: No, I mean the inevitable drift into incontinents.
• 0:59
  Speaker 1: That would be earth shaking. Hi Am Hoham cartoonists and
• 1:17
  Speaker 1: the author of Oliver's Great Big Universe.
• 1:20
  Speaker 2: Hi, I'm Daniel. I'm a particle. Physicist and a professor
• 1:23
  Speaker 2: at UC Irvine. And I've eaten astronaut ice cream, but
• 1:26
  Speaker 2: I've never worn astronaut underwear.
• 1:28
  Speaker 1: Why not haven't we all? Wait? Are you talking about
• 1:31
  Speaker 1: used Austronauts underwear or brand new Austronauts underwear?
• 1:34
  Speaker 2: No, I'm talking about the kind that lets you drive
• 1:36
  Speaker 2: cross country without having to stop for a rest break.
• 1:39
  Speaker 1: Oh you mean diapers. Wait, why are you bringing up
• 1:43
  Speaker 1: astronaut underwear? Is that the topic of today's podcast?
• 1:45
  Speaker 2: No, today, we're not talking about incontinents. We're talking about continents, which,
• 1:49
  Speaker 2: weirdly are not the opposite of incontinence.
• 1:52
  Speaker 1: Yeah, that's the grammar for you, I guess. But anyways,
• 1:54
  Speaker 1: welcome to our podcast Daniel and Jorge Explain the Universe,
• 1:57
  Speaker 1: a production of iHeartRadio.
• 1:59
  Speaker 2: Where we dig in the crazy motions of everything in
• 2:02
  Speaker 2: the universe, things swirling around black holes, stuff flowing inside
• 2:06
  Speaker 2: our own planet, and the particles moving between our toes.
• 2:09
  Speaker 2: Physics in the end is about understanding the movement of things,
• 2:13
  Speaker 2: why they move, how they move, where they are going
• 2:15
  Speaker 2: to move to, and we want to understand all of it.
• 2:18
  Speaker 1: Yeah, it is a motion filled universe full of things
• 2:21
  Speaker 1: that are moving fast and things that are moving slow,
• 2:23
  Speaker 1: which are all moving nonethe less, and it's up to
• 2:26
  Speaker 1: us to try to catch those patterns and see why
• 2:29
  Speaker 1: things are doing the things that they are doing.
• 2:31
  Speaker 2: And because we live a certain amount of time and
• 2:33
  Speaker 2: our life happens at a certain speed, we tend to
• 2:35
  Speaker 2: notice things that happen on our time scales, things that
• 2:38
  Speaker 2: happen in seconds or days or maybe even years. But
• 2:42
  Speaker 2: there's lots of things in the universe that happen on
• 2:44
  Speaker 2: much shorter and much faster time scales. Quantum particles operated
• 2:49
  Speaker 2: like ten to the negative twenty three seconds, and galaxy
• 2:52
  Speaker 2: spend over hundreds of millions of years. So it's easy
• 2:56
  Speaker 2: to overlook these very slow moving but very important processes,
• 3:00
  Speaker 2: even though they literally shape our world.
• 3:02
  Speaker 1: Yeah. I guess we're used to like a certain rhythm
• 3:05
  Speaker 1: of time, right, kind of like our brains maybe have
• 3:08
  Speaker 1: a certain clock to them.
• 3:09
  Speaker 2: Yeah. Probably. And until recently, most humans lives were very
• 3:13
  Speaker 2: similar to the lives of their parents and grandparents and
• 3:16
  Speaker 2: great grandparents. Right, Culture and technology moved so slowly that,
• 3:20
  Speaker 2: you know, five thousand years ago, you could be pretty
• 3:23
  Speaker 2: sure that your kid's life was going to be basically
• 3:25
  Speaker 2: the same as yours, and you could imagine that life
• 3:27
  Speaker 2: had been like this forever, that fast changes had never occurred,
• 3:31
  Speaker 2: that the universe was basically static.
• 3:34
  Speaker 1: Yeah, it's amazing how fastings changed. I feel like within
• 3:36
  Speaker 1: our lifetime the world has changed several times now. Like
• 3:40
  Speaker 1: when I was growing up, we didn't even have email
• 3:42
  Speaker 1: or cell phones.
• 3:43
  Speaker 2: Is that why you never got used to answering email? Yeah?
• 3:46
  Speaker 1: I haven't. I haven't picked up with that yet. See,
• 3:48
  Speaker 1: I I worked that fine. Some things you don't have
• 3:50
  Speaker 1: to learn.
• 3:51
  Speaker 2: We do live in a really fascinating era where we
• 3:53
  Speaker 2: know that our kids' lives will be different from our
• 3:55
  Speaker 2: lives and fundamental ways that we can't really anticipate. That's
• 3:59
  Speaker 2: pretty exciting, but I think it also narrows our view
• 4:02
  Speaker 2: and makes us focus on rapid changes in our environment.
• 4:05
  Speaker 2: It makes it harder even to see the slow moving,
• 4:08
  Speaker 2: big changes that frame everything around us.
• 4:11
  Speaker 1: Yeah, we live almost in like this giant clockward of
• 4:14
  Speaker 1: a universe, right with galaxy spinning and galaxy clusters churning
• 4:18
  Speaker 1: and turning and planets spinning out there. It's kind of
• 4:22
  Speaker 1: hard to notice that all of these things are happening,
• 4:24
  Speaker 1: But they are happening, and there's a lot happening.
• 4:26
  Speaker 2: Yeah, and we tend to think about things out there
• 4:29
  Speaker 2: in space happening sort of slowly on unstately time scales.
• 4:33
  Speaker 2: But that's just because we're not used to thinking about
• 4:35
  Speaker 2: things in terms of millions and millions of years. If
• 4:38
  Speaker 2: you looked at a time lapse of the universe over
• 4:41
  Speaker 2: billions of years, it would seem very chaotic, very dramatic
• 4:43
  Speaker 2: to you. It would be turbulent, it'd be violent, it
• 4:46
  Speaker 2: would be really impressive to watch. And the same thing
• 4:49
  Speaker 2: happens not just out there in the universe, but also
• 4:51
  Speaker 2: under our feet.
• 4:52
  Speaker 1: Yeah, I kind of have trouble thinking in terms of
• 4:54
  Speaker 1: weeks or months. I'm more of a live by the
• 4:57
  Speaker 1: day kind of person, live in the moment. What are
• 5:00
  Speaker 1: you talking about again?
• 5:02
  Speaker 2: But as we piece together the story of how our
• 5:05
  Speaker 2: planet got here, how our solar system formed, how the
• 5:08
  Speaker 2: planets did their dance to end up in this configuration,
• 5:11
  Speaker 2: we also see signs on Earth that there is a
• 5:14
  Speaker 2: larger story to tell, that things have not always looked
• 5:17
  Speaker 2: the way that they do now.
• 5:18
  Speaker 1: Yeah, our planet is pretty big, at least compared to us,
• 5:21
  Speaker 1: and it moves in pretty slow ways, and in earth
• 5:24
  Speaker 1: moving ways.
• 5:25
  Speaker 2: And by understanding how that works. We can hope to
• 5:27
  Speaker 2: gain some understanding for whether it happens on other planets,
• 5:30
  Speaker 2: and whether aliens out there also feel their Earth moving
• 5:34
  Speaker 2: beneath their feet.
• 5:35
  Speaker 1: Yeah, and whether they live in the moment or if
• 5:37
  Speaker 1: they think in terms of eons.
• 5:39
  Speaker 2: And whether they'll ever answer our email so to be.
• 5:42
  Speaker 1: On the podcast, we'll be asking the question what drives
• 5:50
  Speaker 1: the movement of Earth's continents?
• 5:53
  Speaker 2: It's not geographers or geologists.
• 5:56
  Speaker 1: And I guess we're talking about the actual movement of
• 5:58
  Speaker 1: earth continents, not like the people redrawing the lines of
• 6:02
  Speaker 1: them or renaming them.
• 6:03
  Speaker 2: I'm pretty sure the maps follow the continents rather than
• 6:05
  Speaker 2: the other way around. I don't think Earth checks our
• 6:08
  Speaker 2: maps to decide where Asia is going to slide over to.
• 6:11
  Speaker 1: Oh yeah. Is there a clear line between Asia and
• 6:14
  Speaker 1: Europe or is it political?
• 6:16
  Speaker 2: I think there actually is a division in the techtonic
• 6:18
  Speaker 2: plates between them.
• 6:19
  Speaker 1: Hmmm. Does that mean that there are countries that are
• 6:22
  Speaker 1: in both continents? Clearly this is not a geography podcast.
• 6:25
  Speaker 2: There's a massive Eurasian plate that most of Europe and
• 6:28
  Speaker 2: most of Asia is on. But like Saudi Arabia, for example,
• 6:31
  Speaker 2: which is considered to be part of Asia is on
• 6:34
  Speaker 2: its own plate, and India is on its own plate
• 6:37
  Speaker 2: as well.
• 6:37
  Speaker 1: So you're saying it is sort of like a subjective
• 6:40
  Speaker 1: kind of or at least for some continents.
• 6:42
  Speaker 2: I think the definition of a continent is a little
• 6:45
  Speaker 2: bit subjective. Yeah, but the definition of a continental plate,
• 6:48
  Speaker 2: these things are scientific and geological, Like we can see
• 6:51
  Speaker 2: where the edges are of these cracks in the crust.
• 6:54
  Speaker 1: You mean it's kind of leaky or definition, it's a
• 6:56
  Speaker 1: little incontinent.
• 6:58
  Speaker 2: A little incontinent, exactly, all right.
• 7:00
  Speaker 1: Well, as usual, we're wondering how many people out there
• 7:02
  Speaker 1: had thought about the question of what drives the movement
• 7:04
  Speaker 1: of earth technic plates and continents, And so this time
• 7:08
  Speaker 1: Daniel went out there into the wild of the UC
• 7:10
  Speaker 1: Irvine campus to ask people this question.
• 7:13
  Speaker 2: That's right, And today's episode is dedicated to TJ, a
• 7:16
  Speaker 2: listener out there in recovery from a stroke who requested
• 7:19
  Speaker 2: this topic specifically. So thanks very much everybody who answers
• 7:23
  Speaker 2: these questions, and thanks to everybody in the USA irun
• 7:25
  Speaker 2: campus who put up with a weird physicist with a
• 7:27
  Speaker 2: phone in their face.
• 7:28
  Speaker 1: So think about it for a second, what do you
• 7:30
  Speaker 1: think drives the movement of Earth's continents. Here's what people
• 7:33
  Speaker 1: have to say.
• 7:34
  Speaker 2: Do you know what makes the continents move, of the
• 7:36
  Speaker 2: ocean continents drift?
• 7:38
  Speaker 3: Yeah, probably because we have this plates, geological plates that
• 7:43
  Speaker 3: are constantly moving.
• 7:45
  Speaker 1: But I'm not a geologist, so actually, to be honest,
• 7:47
  Speaker 1: I don't know.
• 7:48
  Speaker 3: It's not like because like the liquid and the Earth,
• 7:50
  Speaker 3: like the Earth center is still liquid and therefore, like
• 7:52
  Speaker 3: the plates on top are like moving along because there's
• 7:55
  Speaker 3: I'm not sure if there are currens going on and
• 7:57
  Speaker 3: that's why we are like plates are moving.
• 8:00
  Speaker 2: I'm not sure what it makes the continents move. Do
• 8:02
  Speaker 2: I know what causes the continents to drift?
• 8:05
  Speaker 3: I mean, they call it continental drift, but I don't
• 8:07
  Speaker 3: know what started them moving.
• 8:09
  Speaker 1: Uh yeah, So I understand that that is caused because
• 8:13
  Speaker 1: the plates are sitting pretty much on malten rock, so
• 8:16
  Speaker 1: one one across the other, they're kind of like crumpling,
• 8:20
  Speaker 1: So that's what's moving.
• 8:22
  Speaker 2: The stuff that's on top right.
• 8:23
  Speaker 1: Well, I just I know that the malten rock is
• 8:25
  Speaker 1: like revolving right inside the core.
• 8:27
  Speaker 2: But that's about what I know.
• 8:29
  Speaker 1: I don't understand that tectonic plates.
• 8:32
  Speaker 2: For those are the plates, why do they move? The
• 8:34
  Speaker 2: Magma movement, anybody else.
• 8:37
  Speaker 1: I have no idea. All right, it kind of seems
• 8:42
  Speaker 1: like you took a lot of people by surprise. They're like,
• 8:45
  Speaker 1: what are you doing? Why are you putting a microphone
• 8:48
  Speaker 1: in my face? How do you approach people by the way?
• 8:50
  Speaker 1: Do you just walk up to them or do you
• 8:52
  Speaker 1: bring out the microphone later?
• 8:55
  Speaker 2: You know. The very first time I did it, I
• 8:56
  Speaker 2: brought my kids with me so I would seem less
• 8:58
  Speaker 2: weird and threatening, because I was expecting most people say no.
• 9:02
  Speaker 2: But what I discovered is that most people say yes,
• 9:04
  Speaker 2: no matter what. And so I walk up to them
• 9:07
  Speaker 2: and I say, I'm a professor interested in what people
• 9:09
  Speaker 2: know about some questions in science. Can I ask you
• 9:11
  Speaker 2: a random science question? And I think ninety nine percent
• 9:15
  Speaker 2: of the time people say, sure, no problem.
• 9:17
  Speaker 1: Hmm.
• 9:18
  Speaker 2: Interesting.
• 9:18
  Speaker 1: I wonder if they think you're doing it for scientific purposes.
• 9:21
  Speaker 2: Aren't we isn't this part of science?
• 9:23
  Speaker 1: Or like, I mean, like you're running an experiment? Like
• 9:26
  Speaker 1: anytime you open like, hi, I'm a professor, I'm interested
• 9:28
  Speaker 1: in They're probably thinking you're running an experiment.
• 9:31
  Speaker 2: Maybe I am. Maybe this whole podcast project is actually
• 9:34
  Speaker 2: just an experiment. I'm writing up the paper right now,
• 9:37
  Speaker 2: what's your hypothesis a physicist and a cartoonist can actually
• 9:40
  Speaker 2: talk about science for five hundred episodes.
• 9:43
  Speaker 1: Sounds like a more of a there than an experiment there. Implausible,
• 9:50
  Speaker 1: I know, But anyways, it's an interesting question what drives
• 9:53
  Speaker 1: a movement of Earth's continents? Because, first of all, I
• 9:56
  Speaker 1: guess Earth's continents are moving. Maybe a lot of people
• 9:58
  Speaker 1: don't know that they're moving.
• 10:00
  Speaker 2: Yeah, they are moving very very slowly, so slowly that
• 10:03
  Speaker 2: it took us a long time to figure it out.
• 10:06
  Speaker 2: And even once we had the idea, it took decades
• 10:08
  Speaker 2: before people believed it because it seems like such a
• 10:11
  Speaker 2: crazy notion.
• 10:12
  Speaker 1: Yeah, it's pretty wild that a whole continent can move,
• 10:15
  Speaker 1: and I guess it happens slower than anyone can notice
• 10:18
  Speaker 1: in their lifetime, right.
• 10:19
  Speaker 2: You would think so. But actually the motion of the
• 10:21
  Speaker 2: continents is pretty dramatic. I mean they move like centimeters
• 10:25
  Speaker 2: per year, which is definitely something that you could measure.
• 10:28
  Speaker 2: I think it just took a long time for people
• 10:30
  Speaker 2: to wrap their minds around the idea that an entire
• 10:32
  Speaker 2: continent could be floating on an ocean of liquid magma
• 10:36
  Speaker 2: and sliding around the surface of the Earth is just
• 10:38
  Speaker 2: so far from what anybody conceived of that the data
• 10:41
  Speaker 2: really had to be screaming at us in our face
• 10:43
  Speaker 2: before we figured it out.
• 10:45
  Speaker 1: Well, let's maybe one of you take us back into
• 10:48
  Speaker 1: the history of this idea. How do we actually know
• 10:51
  Speaker 1: that the continents are moving? And when do we notice?
• 10:53
  Speaker 2: So around the turn of last century, like nineteen hundred,
• 10:56
  Speaker 2: there were a bunch of unexplained phenomena, things people couldn't
• 10:59
  Speaker 2: figure out. They didn't have a story to tell that
• 11:02
  Speaker 2: explained the stuff that they saw. And looking back, it
• 11:05
  Speaker 2: seems sort of obvious because we know the answer. But
• 11:07
  Speaker 2: remember that, you know, science is always running up against
• 11:10
  Speaker 2: the boundary of our ignorance, and there's always lots of random,
• 11:13
  Speaker 2: weird ideas and pass not taken. So it's very easy
• 11:16
  Speaker 2: to look back and see how the story came together.
• 11:18
  Speaker 2: It's much harder when you're standing at the forefront of
• 11:20
  Speaker 2: human ignorance to figure out what the clear path is.
• 11:23
  Speaker 2: But basically, about one hundred years ago, we saw all
• 11:25
  Speaker 2: these continuities between the continents, like connections between the continents
• 11:31
  Speaker 2: that you couldn't explain if the continents really were separate
• 11:34
  Speaker 2: and had always been separate. The most famous example is
• 11:38
  Speaker 2: how the shapes of the continents are similar. You know,
• 11:41
  Speaker 2: like the tip of South America the east coast matches
• 11:44
  Speaker 2: pretty well Africa's west coast, Like you could just imagine
• 11:47
  Speaker 2: sliding them together and they would like click together like
• 11:50
  Speaker 2: puzzle pieces. There's lots of examples of that in many
• 11:53
  Speaker 2: areas of research.
• 11:55
  Speaker 1: I mean, they're sort of like jigs or puzzle pieces
• 11:58
  Speaker 1: that seemed to fit together.
• 12:00
  Speaker 2: So there's geographic continuities where the continents can fit together.
• 12:03
  Speaker 2: And it's not just South America and Africa, Like it's
• 12:06
  Speaker 2: not too hard to imagine India and Antarctica and Australia
• 12:09
  Speaker 2: like clicking together. But also if you look at the
• 12:12
  Speaker 2: rocks on the shores of those continents, you see continuities,
• 12:16
  Speaker 2: Like there are layers of rock you can see in
• 12:18
  Speaker 2: Scotland and Ireland, and then you go to like Newfoundland
• 12:21
  Speaker 2: across the Atlantic and you see the same layers of rock.
• 12:24
  Speaker 2: It really looks like somebody, you know, cut a cake
• 12:27
  Speaker 2: and slid the two halves apart.
• 12:29
  Speaker 1: But I wonder if that's only a weird mystery if
• 12:31
  Speaker 1: you don't look underwater, like it's only weird if you
• 12:33
  Speaker 1: don't imagine that maybe that continuity continues onto the seafloor,
• 12:38
  Speaker 1: Like did they check for that or did they just
• 12:40
  Speaker 1: notice that it was the same.
• 12:41
  Speaker 2: The rocks under the sea floor definitely do not contain
• 12:44
  Speaker 2: all those same layers, And the sea floor is mostly basalt,
• 12:47
  Speaker 2: different kind of rock, whereas on the continent it's mostly granite.
• 12:50
  Speaker 2: So it's like different kinds of rock and deffinitely different layers,
• 12:53
  Speaker 2: and you can really fit them together, like they find
• 12:55
  Speaker 2: these layers on one continent and you can sign the
• 12:58
  Speaker 2: same kind of rocks the other side of the Atlantic.
• 13:02
  Speaker 2: It really is very clear that these things clicked together
• 13:05
  Speaker 2: in that.
• 13:05
  Speaker 1: Way, like in the way that they also match as
• 13:08
  Speaker 1: jigsaw puzzle.
• 13:09
  Speaker 2: Pieces, like the rocks in South America on the coast
• 13:11
  Speaker 2: match the rocks on the coast of Africa the west coast.
• 13:15
  Speaker 2: And there's other weird continuities, like there are fossils of
• 13:18
  Speaker 2: animals that appear in South America and in Africa, and
• 13:23
  Speaker 2: it's like very clearly the same animal that was one community,
• 13:26
  Speaker 2: you find them across the Atlantic. So either you had
• 13:30
  Speaker 2: like exactly the same animals evolve totally independently because the
• 13:34
  Speaker 2: contents were always separate or they used to be together,
• 13:37
  Speaker 2: the animals died a long time ago and then the
• 13:40
  Speaker 2: continents split.
• 13:41
  Speaker 1: Or maybe there was a lost continent of a planets
• 13:44
  Speaker 1: in the middle it was full of this animal. I mean,
• 13:47
  Speaker 1: I just brainstorm you here.
• 13:49
  Speaker 2: Right right, Maybe its ancient aliens.
• 13:52
  Speaker 1: Right, yeah, there you go. No, but that's what I mean,
• 13:55
  Speaker 1: Like I'm just trying to put my head in those
• 13:57
  Speaker 1: in that time, Like could that have been a possibility
• 13:59
  Speaker 1: for there to have been a bridge or something or
• 14:01
  Speaker 1: a continent in the middle of the tank.
• 14:02
  Speaker 2: Perhaps, But there's lots of different examples. It's not just
• 14:05
  Speaker 2: like South America to Africa, Like this fossil evidence of
• 14:08
  Speaker 2: this land reptile called Listrosaurus, which you see in Antarctica
• 14:13
  Speaker 2: and in India and in Africa because those pieces used
• 14:16
  Speaker 2: to click together. And then there's like fossils of this
• 14:19
  Speaker 2: fern called Glysopteris, which is found in all the southern
• 14:23
  Speaker 2: continents to show that they were once joined. And then
• 14:25
  Speaker 2: there's this like fresh water reptile to Mesosaurus, which is
• 14:28
  Speaker 2: connected from the south of Africa to the south of
• 14:30
  Speaker 2: South America. So like one single bridge wouldn't do it.
• 14:33
  Speaker 2: You need like a lot of bridges or you just
• 14:36
  Speaker 2: got to stick the continents together.
• 14:37
  Speaker 1: Hmmm. All right, So those were some clues. What were
• 14:40
  Speaker 1: some other clues.
• 14:41
  Speaker 2: Another really fascinating clue was looking underwater. They did study
• 14:45
  Speaker 2: the rocks on the seafloor, and what they found were
• 14:48
  Speaker 2: these weird stripes of magnetism. Like the rocks on the
• 14:52
  Speaker 2: sea floor sometimes contain this stuff called magnetite, which is
• 14:55
  Speaker 2: very magnetic material and it's influenced by the magnetic field
• 14:59
  Speaker 2: of the Earth. And they looked to the magnetic field
• 15:02
  Speaker 2: of these rocks and they found this weird zebra striping,
• 15:05
  Speaker 2: Like there's a stripe that's pointing one way, and then
• 15:08
  Speaker 2: another stripe that's pointing the opposite way, and then another
• 15:10
  Speaker 2: stripe that's pointing back the first way. So it's like
• 15:13
  Speaker 2: the rocks have these alternating stripes of magnetic field sort
• 15:17
  Speaker 2: of frozen into them.
• 15:18
  Speaker 1: They have like a pattern the writ in the magnetism.
• 15:22
  Speaker 2: Yeah, they're like these zebra stripes, you know, like a
• 15:24
  Speaker 2: stripe pointing towards the north pole, and then a stripe
• 15:26
  Speaker 2: pouring towards a south pole, and then stripe pointing towards
• 15:29
  Speaker 2: the north pole. So there are all these weird things
• 15:31
  Speaker 2: that nobody could explain all these weird clues that, like,
• 15:34
  Speaker 2: you know, we couldn't tell a story that made sense
• 15:36
  Speaker 2: of what we were seeing. The geographic clues, the geological cues,
• 15:40
  Speaker 2: the biographic clues, the magnetic field clues, all of these
• 15:43
  Speaker 2: things didn't make sense.
• 15:45
  Speaker 1: How wide were these stripes? Like are they huven size
• 15:48
  Speaker 1: or are they like miles wide?
• 15:50
  Speaker 2: These things are not tiny, you know, they're like kilometers
• 15:53
  Speaker 2: wide in some cases, but they show weird patterns. They're
• 15:56
  Speaker 2: like not like exactly perfect stripes. They show some ridges
• 15:59
  Speaker 2: and some twists, which we'll talk about later, but they're
• 16:02
  Speaker 2: pretty big, m I see.
• 16:03
  Speaker 1: So it was really kind of like there were all
• 16:06
  Speaker 1: these puzzle pieces lying around in the table, and like,
• 16:09
  Speaker 1: if you thought about it, you start to figure out
• 16:11
  Speaker 1: that not just the shapes can fit, but like maybe
• 16:13
  Speaker 1: like the picture of the pattern in the puzzle pieces
• 16:16
  Speaker 1: seemed to make sense if you spect them together.
• 16:19
  Speaker 2: Yeah, exactly. And it was nineteen twelve when a guy
• 16:23
  Speaker 2: named Weggner first proposed this idea. He's like, I can
• 16:25
  Speaker 2: explain all of these things with the simple idea that
• 16:28
  Speaker 2: the continents were once all together, that they drifted apart.
• 16:33
  Speaker 2: So he proposed this concept of Pangaea that a couple
• 16:36
  Speaker 2: of one hundred million years ago, all the continents we know
• 16:39
  Speaker 2: now were actually congealed into one big super continent and
• 16:43
  Speaker 2: they've drifted apart over those years.
• 16:46
  Speaker 1: M like they were once part of a super band,
• 16:49
  Speaker 1: but then they disbanded and they of course they played
• 16:51
  Speaker 1: rock music right exactly.
• 16:53
  Speaker 2: And now we know actually that that's only the most
• 16:55
  Speaker 2: recent example. Like Pangea existed around two hundred and fifty
• 16:59
  Speaker 2: million years ago, but we reconstructed even further back into
• 17:02
  Speaker 2: the past. There were super continents like a billion years
• 17:05
  Speaker 2: ago and two billion years ago. It's really a crazy
• 17:08
  Speaker 2: chaotic story. Pangaea is only the most recent super continent. Whoa.
• 17:14
  Speaker 2: But at the time people were like, what your bonkers?
• 17:17
  Speaker 2: How could the continents move? They're like these huge piles
• 17:20
  Speaker 2: of rock. There's no way to like slide them around.
• 17:23
  Speaker 2: You know, when you're doing a puzzle on a table,
• 17:25
  Speaker 2: you have gaps between the pieces so you can slide
• 17:27
  Speaker 2: them around. If all the pieces were like already stuck together,
• 17:30
  Speaker 2: it'd be pretty hard to move them around to adjust
• 17:33
  Speaker 2: their locations.
• 17:34
  Speaker 1: Yeah, I guess like the mechanism for how those continents
• 17:37
  Speaker 1: are moving is kind of hard to fathom right, because
• 17:40
  Speaker 1: the Earth we at least at the time, No, it's
• 17:44
  Speaker 1: all made out of rock, right, even under the ocean
• 17:46
  Speaker 1: it's rock, And so like, how do you move dying
• 17:48
  Speaker 1: mountains exactly?
• 17:49
  Speaker 2: People knew that the Earth's crust was solid, and like
• 17:52
  Speaker 2: fifty or so years ago, people had figured out that
• 17:54
  Speaker 2: the Earth was solid underneath. It was very dense and
• 17:57
  Speaker 2: there's probably a liquid core. Were actually talked about that
• 18:00
  Speaker 2: our episode about how to measure the gravitational constant. In
• 18:03
  Speaker 2: order to do that, we basically had to measure the
• 18:04
  Speaker 2: density of the Earth and understand that it was not
• 18:07
  Speaker 2: like hollow, it was actually filled with rock. But yeah,
• 18:10
  Speaker 2: the basic question is if you have a solid crust,
• 18:12
  Speaker 2: even if it's liquid underneath, how do the pieces of
• 18:15
  Speaker 2: the solid crust slide right, like you have a balloon
• 18:18
  Speaker 2: it's filled with liquid, doesn't mean that like the surface
• 18:20
  Speaker 2: of the balloon can slide around and rearrange the pieces, right,
• 18:23
  Speaker 2: There's no like room for things to move. So there
• 18:26
  Speaker 2: was a lot of skepticism about this idea.
• 18:29
  Speaker 1: M They thought it was crazy.
• 18:30
  Speaker 2: Yeah, and at the time that had an even more
• 18:32
  Speaker 2: bonder sounding idea for like how mountains formed right now
• 18:36
  Speaker 2: of course, we understand mountains form often when plates smash
• 18:39
  Speaker 2: into each other, like the Himalayas are from India slamming
• 18:42
  Speaker 2: into the Eurasian plate. At the time, they thought that
• 18:45
  Speaker 2: mountains formed vertically as the planet was cooling. It was
• 18:49
  Speaker 2: like shrinking as it was cooling, and things like bubbled up.
• 18:53
  Speaker 1: Hmmm, sort of like shrink rab what was left after
• 18:56
  Speaker 1: U shrink wrap something?
• 18:57
  Speaker 2: Yeah, exactly, that it wasn't that mountain and so rising,
• 19:00
  Speaker 2: but that the rest of the surface was sort of
• 19:02
  Speaker 2: like shrinking as the planet cooled, revealing these mountains.
• 19:06
  Speaker 1: Well, it sounds like today we know a little bit better,
• 19:09
  Speaker 1: and so let's get into how these continents are actually
• 19:12
  Speaker 1: able to move around the planet and what is powering
• 19:15
  Speaker 1: this movement. But first let's take a quick break. All right,
• 19:32
  Speaker 1: we're asking the question what drives the movement of Earth's continents,
• 19:35
  Speaker 1: and we talked about how they are moving and how
• 19:37
  Speaker 1: we sort of figured that out because they are sort
• 19:39
  Speaker 1: of like puzzle pieces. The continents, the shape of them
• 19:42
  Speaker 1: and also the rocks and the patterns on top of
• 19:44
  Speaker 1: them are like a giant jigsaw puzzle, which I guess
• 19:48
  Speaker 1: makes me ask the question, which is the corner piece
• 19:50
  Speaker 1: Daniel in a spherical puzzle, how do you even get
• 19:54
  Speaker 1: started if you don't have corner pieces?
• 19:55
  Speaker 2: Antarctica? Always start with Antarctica.
• 19:58
  Speaker 1: But it's all white and it looks the same as
• 20:01
  Speaker 1: the pieces in the North Pole.
• 20:04
  Speaker 2: Yeah, that's true. It's a puzzle, but.
• 20:06
  Speaker 1: It sounds that we sort of figured it out. So
• 20:08
  Speaker 1: we know that the continents are moving, and they have
• 20:11
  Speaker 1: been moving, and before only about two hundred and something
• 20:14
  Speaker 1: million years ago, all the continents that we know today
• 20:17
  Speaker 1: were all crushed together into one super continent.
• 20:20
  Speaker 2: Yeah, around two hundred and fifty million years ago, And
• 20:23
  Speaker 2: this was a really revolutionary idea at the time. You know,
• 20:26
  Speaker 2: this is an example science historians talk about a scientific
• 20:29
  Speaker 2: revolution where a concept is intuitive and ingrained and widely
• 20:34
  Speaker 2: accepted and then eventually overthrown by the data. You know
• 20:38
  Speaker 2: that we're confronted with the facts and forced to change
• 20:42
  Speaker 2: the way we think about the universe. And you know,
• 20:44
  Speaker 2: people who talk about like science conspiracies and all this stuff.
• 20:47
  Speaker 2: This is a great example of how science really does
• 20:50
  Speaker 2: change when faced with the data. It takes a while,
• 20:52
  Speaker 2: and it takes a lot of data. But scientists like
• 20:55
  Speaker 2: to be right. They like to explain what we are seeing.
• 20:57
  Speaker 2: A don't likes to cover things up or gauge in
• 21:00
  Speaker 2: planet wide conspiracies. Everybody wants to be Wagoner, the guy
• 21:03
  Speaker 2: who came up with a revolutionary idea that changed the
• 21:06
  Speaker 2: way we think about the entire history of our planet.
• 21:09
  Speaker 1: Yeah. I think it's more like a Scientists like to
• 21:12
  Speaker 1: prove others wrong. Yo.
• 21:13
  Speaker 2: Yeah. Scientists are people, which means they are motivated by
• 21:18
  Speaker 2: the same things people are motivated by, sometimes pettiness and
• 21:21
  Speaker 2: sometimes glamor. Yeah.
• 21:22
  Speaker 1: And I think in this case you're saying like their
• 21:24
  Speaker 1: motivation sort of aligns with the idea of finding out
• 21:26
  Speaker 1: what the truth is exactly.
• 21:28
  Speaker 2: Scientists want to be right.
• 21:29
  Speaker 1: Yeah, they gained nothing by a worldwide conspiracy.
• 21:33
  Speaker 2: I mean, maybe we gain like cool robes and a
• 21:35
  Speaker 2: secret handshake, but that doesn't seem to be worth it. Yeah.
• 21:38
  Speaker 1: Secret handshakes, Yeah, like.
• 21:40
  Speaker 2: Pales in comparison to discovering the truth about the universe.
• 21:43
  Speaker 1: You just want to be part of the club.
• 21:45
  Speaker 2: I don't actually care about being part of the club.
• 21:47
  Speaker 2: I just want to know the truth.
• 21:48
  Speaker 1: You just want to prove others wrong.
• 21:50
  Speaker 2: But in this case, it took like fifty years for
• 21:53
  Speaker 2: people to really come around to this idea because there
• 21:56
  Speaker 2: were a lot of puzzles before people figured out how
• 21:58
  Speaker 2: it all worked. There were a few more piece of
• 22:00
  Speaker 2: evidence that started to sway people towards the direction of
• 22:04
  Speaker 2: this idea. More things we learned about what was happening
• 22:08
  Speaker 2: on the surface of the Earth that made the continental
• 22:10
  Speaker 2: drift theory make more sense.
• 22:12
  Speaker 1: Yeah, And I guess it's not something that you can
• 22:14
  Speaker 1: like test right or make a prediction about, right, It's
• 22:17
  Speaker 1: somebody you can see, Like, I think the continents are moving,
• 22:19
  Speaker 1: and in a hundred million years, this is what the
• 22:22
  Speaker 1: Earth is going to look like, and you'll see I'll
• 22:24
  Speaker 1: be right. You just kind of have to like look
• 22:27
  Speaker 1: at the data and be convinced by the data, right, Yeah.
• 22:30
  Speaker 2: Actually, I think there is a prediction for what the
• 22:32
  Speaker 2: continents are going to look like, and they put it
• 22:34
  Speaker 2: up on a satellite orbiting the Earth. The idea being
• 22:37
  Speaker 2: that if humans all die out and aliens come to
• 22:40
  Speaker 2: visit in a hundred million years and find this satellite,
• 22:44
  Speaker 2: it would be like evidence that we knew what we
• 22:46
  Speaker 2: were doing or not.
• 22:48
  Speaker 1: I feel like that it's pretty risky. We could be
• 22:50
  Speaker 1: totally off and then we'll be known throughout the trinity
• 22:53
  Speaker 1: in the cosmic community. How wrong we were.
• 22:57
  Speaker 2: Yeah, that's why they died out because they failed to
• 22:59
  Speaker 2: predict the coal drift right.
• 23:01
  Speaker 1: Yeah, they couldn't even get that right, something as small
• 23:04
  Speaker 1: as continent's moving.
• 23:05
  Speaker 2: Well, it's a really fun story because along the way
• 23:07
  Speaker 2: we learned so much about our planet. One mental obstacle
• 23:11
  Speaker 2: people had to accepting the idea of a continental drift
• 23:14
  Speaker 2: was the idea of the age of the Earth. People
• 23:16
  Speaker 2: had this concept that the Earth was pretty old, but
• 23:18
  Speaker 2: the current thinking of the time was like the Earth
• 23:20
  Speaker 2: was only around maybe ten million years old or so.
• 23:24
  Speaker 2: They did this calculation to estimate how long it would
• 23:26
  Speaker 2: take the Earth to cool from a ball of hot
• 23:29
  Speaker 2: magma to its current temperature. And if you just think
• 23:33
  Speaker 2: about like radiating heat out into space, then it only
• 23:36
  Speaker 2: takes like a few tens of millions of years to
• 23:39
  Speaker 2: cool the Earth down to where it is today. So
• 23:41
  Speaker 2: the continental drift theory required a much older Earth, and
• 23:44
  Speaker 2: that was hard to jibe with this idea that the
• 23:46
  Speaker 2: Earth only takes a few tens of millions of years
• 23:49
  Speaker 2: to cool.
• 23:50
  Speaker 1: Well, I guess maybe it depends on your theory or
• 23:52
  Speaker 1: what you know about how the Earth started, Like did
• 23:55
  Speaker 1: the Earth start with a bunch of molten rock or
• 23:59
  Speaker 1: did it start with like free floating rocks that then
• 24:01
  Speaker 1: gathered and melted.
• 24:03
  Speaker 2: It started from pebbles and gas and dust and all
• 24:05
  Speaker 2: this stuff in the very early solar system, which then
• 24:08
  Speaker 2: formed gravitationally. But the gravitational pressure was pretty intense. I mean,
• 24:11
  Speaker 2: it's intense enough to like spark fusion at the center
• 24:14
  Speaker 2: of the Sun. It's not hot enough to get fusion
• 24:17
  Speaker 2: going at the center of the Earth, but it's definitely
• 24:19
  Speaker 2: hot enough to melt those rocks.
• 24:21
  Speaker 1: And so you're saying, like, that's how you assume. And
• 24:23
  Speaker 1: if that's the only thing you assumed that was happening
• 24:26
  Speaker 1: with a giant rock floating in space, then the Earth
• 24:28
  Speaker 1: by now should have been you know, kind of stone
• 24:31
  Speaker 1: cold exactly.
• 24:32
  Speaker 2: But around that same time, like the very end of
• 24:35
  Speaker 2: the eighteen hundreds, very beginning of the nineteen hundreds, we
• 24:37
  Speaker 2: discovered radioactivity like beckerel left blob uranium on a photographic plate,
• 24:42
  Speaker 2: came back after the weekend, saw it was fogged. The
• 24:45
  Speaker 2: cures studied radioactivity was right around that time we understood it.
• 24:49
  Speaker 2: So then people realized that radioactive decay inside the Earth
• 24:52
  Speaker 2: was also keeping the Earth warm. The Earth is like
• 24:55
  Speaker 2: a giant nuclear battery where these nuclear decays are heating
• 25:00
  Speaker 2: up the Earth and keeping it toasty. So actually the
• 25:03
  Speaker 2: Earth had to be much much older than just a
• 25:05
  Speaker 2: few tens of millions of years to have cool this much.
• 25:09
  Speaker 1: Well, let's talk about the continental driss then, I guess,
• 25:12
  Speaker 1: how is it that the continents can move? Like what's
• 25:15
  Speaker 1: going on there? Are they not fixed in place? And
• 25:17
  Speaker 1: what are they moving on top of?
• 25:19
  Speaker 2: So there's a lot of action happening at the edges
• 25:22
  Speaker 2: of these continental plates. So like the Earth has a
• 25:24
  Speaker 2: surface which is a crust. We call it the lithosphere,
• 25:27
  Speaker 2: and it's solid, but it's cracked into pieces, and at
• 25:29
  Speaker 2: the edges stuff can happen. There's some places at the
• 25:32
  Speaker 2: edges where they're being pushed apart. The plates are being
• 25:35
  Speaker 2: pushed further apart, and this is for example, in the
• 25:37
  Speaker 2: middle of the Atlantic Ocean. There's this ridge that was
• 25:41
  Speaker 2: discovered in the nineteen forties where magma is bubbling up
• 25:44
  Speaker 2: from within the Earth and pushing these two plates apart
• 25:47
  Speaker 2: from each other, So the Atlantic Ocean is growing. That's
• 25:50
  Speaker 2: one example of how we get like motion at the
• 25:52
  Speaker 2: edges of these plates.
• 25:54
  Speaker 1: I think you're saying that, like the Earth, it's a
• 25:55
  Speaker 1: little bit maybe like an egg right where it's like
• 25:59
  Speaker 1: it's circulars but the inside, the outside is kind of
• 26:02
  Speaker 1: hard and crusty like a shell, and the inside is
• 26:06
  Speaker 1: sort of soft and liquid in a way.
• 26:09
  Speaker 2: The inside is definitely hotter and softer. Just below the
• 26:12
  Speaker 2: crust is the mantle, and the upper mantle is like
• 26:15
  Speaker 2: technically a solid, but because it's under such great pressure,
• 26:18
  Speaker 2: it can actually very slowly flow, and as you go
• 26:21
  Speaker 2: further and further down, it gets to be more and
• 26:23
  Speaker 2: more liquid. So yeah, things can slide and squish underneath
• 26:26
  Speaker 2: the surface of the Earth. But one of the big
• 26:28
  Speaker 2: questions was, you know, even if things are liquid, how
• 26:31
  Speaker 2: do you get room to move? Right, Like, if the
• 26:33
  Speaker 2: pieces are fixed in shape, then how do they move?
• 26:36
  Speaker 2: And the answer is they're not fixed in shape. The
• 26:38
  Speaker 2: plates both grow and shrink, so they grow on sides
• 26:41
  Speaker 2: where there's like creation of new surface, like when you're
• 26:45
  Speaker 2: creating new earth underneath the ocean, it's like magma is
• 26:48
  Speaker 2: bubbling up and becoming new surface. That's like extending the
• 26:51
  Speaker 2: size of those plates. And then on the other side
• 26:54
  Speaker 2: you actually have destruction of the plates, Like the plates
• 26:58
  Speaker 2: are going underneath each other cyclic back into the earth.
• 27:01
  Speaker 2: So it's sort of like very slow moving conveyor belt
• 27:05
  Speaker 2: where you're destroying a plate on one side and creating
• 27:08
  Speaker 2: more plate on the other side.
• 27:10
  Speaker 1: So, going back to our egg analogy, I think what
• 27:13
  Speaker 1: you're saying is that, like the crust of the earth
• 27:15
  Speaker 1: is not one whole piece like an eggshell. It's actually
• 27:19
  Speaker 1: cracked in a lot of places. But then even if
• 27:21
  Speaker 1: you crack it in break it the shell into several pieces,
• 27:24
  Speaker 1: you still have to wonder like how those pieces can
• 27:27
  Speaker 1: move about. The reason is that they're sort of floating
• 27:30
  Speaker 1: on semi liquid mantle right on rock that is fluid.
• 27:34
  Speaker 1: And also they're not just doing that, but they're also
• 27:37
  Speaker 1: sort of like being created and destroyed at the same time.
• 27:40
  Speaker 1: These giant plates.
• 27:41
  Speaker 2: Exactly, each plate is like flowing in some direction on
• 27:45
  Speaker 2: top of liquid, and where it hits another plate, it's
• 27:47
  Speaker 2: being subducted. It's like getting pushed down back into the earth.
• 27:51
  Speaker 2: Those are like the deep trenches in the ocean, like
• 27:54
  Speaker 2: the Baryanas Trench. In other places, on the west coast
• 27:58
  Speaker 2: of South America and on the east coast of Asia,
• 28:01
  Speaker 2: there are these deep trenches where the ocean floor is
• 28:03
  Speaker 2: getting pushed down into the earth, and on the other side,
• 28:08
  Speaker 2: new plate is being created, like the mid Atlantic Ridge
• 28:11
  Speaker 2: is creating new plates. So that's why, like the Atlantic
• 28:14
  Speaker 2: Ocean is growing and the Pacific Ocean is shrinking.
• 28:17
  Speaker 1: Right, So like if you have one of these plates
• 28:19
  Speaker 1: that let's say like you live in an island on
• 28:21
  Speaker 1: top of one of these plates, and let's say the
• 28:23
  Speaker 1: whole plate is flowing to the right, that means that
• 28:26
  Speaker 1: like on the left side of your plate, there's more
• 28:30
  Speaker 1: plate growing. Right, there's like more more of it coming
• 28:33
  Speaker 1: up from the ground being created, pushing the whole plate
• 28:36
  Speaker 1: to the right. But then on the right side of
• 28:38
  Speaker 1: the plate it's running into another plate and so then
• 28:40
  Speaker 1: it's getting destroyed there or maybe it might not be right.
• 28:43
  Speaker 1: It's usually like one of them goes under.
• 28:45
  Speaker 2: Yeah, the subduction, so one of them goes under. Exactly
• 28:48
  Speaker 2: where they meet, and we can tell where the edge
• 28:51
  Speaker 2: of these plates are, where the cracks are on the
• 28:53
  Speaker 2: Earth's surface because we can measure the seismic activity. Basically
• 28:57
  Speaker 2: there's earthquakes where these plates meet because they're grinding and
• 29:00
  Speaker 2: sliding away from each other, or one is going under
• 29:03
  Speaker 2: the other one, or there's like huge volcanoes underground creating
• 29:08
  Speaker 2: new surface. And so if you look at like this
• 29:10
  Speaker 2: seismic activity pattern, you just ask like where are all
• 29:13
  Speaker 2: micro earthquakes on the Earth. Then they don't just happen
• 29:16
  Speaker 2: randomly all over the Earth to happen in these lines.
• 29:20
  Speaker 2: If you put a dot on the Earth wherever there's
• 29:22
  Speaker 2: an earthquake, they come out to make these patterns that
• 29:25
  Speaker 2: show you the edges of the plates, like the cracks
• 29:28
  Speaker 2: in the eggshell.
• 29:29
  Speaker 1: You can hear the continents crunching.
• 29:31
  Speaker 2: Kind of Yeah, it's actually interesting bit of history. In
• 29:34
  Speaker 2: like the nineteen sixties, the US and the USSR, we're
• 29:37
  Speaker 2: doing underground testing of nuclear weapons and one of the
• 29:41
  Speaker 2: best ways to detect underground testing is to build a
• 29:43
  Speaker 2: worldwise network of seismographs to see when testing is happening.
• 29:48
  Speaker 2: And so that's why the US invested in a huge
• 29:51
  Speaker 2: network of these seismographs, and that's one of the ways
• 29:53
  Speaker 2: that we learned about all of these micro earthquakes that
• 29:56
  Speaker 2: showed us where the plates were mmmmm.
• 30:00
  Speaker 1: But then we use that for sign.
• 30:03
  Speaker 2: Well. As usual, the science budget is a tiny, tiny
• 30:06
  Speaker 2: fraction of like the military budget or the intelligence budget,
• 30:10
  Speaker 2: or even like the consumer electronics budget. So we're always
• 30:13
  Speaker 2: trying to be clever in ways to like leverage the
• 30:16
  Speaker 2: huge resources of other sectors the economy for the benefit
• 30:20
  Speaker 2: of science.
• 30:20
  Speaker 1: I think you can also tell where these plates meet
• 30:22
  Speaker 1: by looking at more volcanoes, right, Like most volcanoes are
• 30:26
  Speaker 1: where two plates intersect.
• 30:28
  Speaker 2: Exactly earthquakes and volcanoes. And if you look underwater at
• 30:31
  Speaker 2: the Atlantic you can see this huge ridge which is
• 30:34
  Speaker 2: basically a line of volcanoes where the Earth is cracked
• 30:38
  Speaker 2: and it's seeping up and that magma then becomes new
• 30:41
  Speaker 2: surface of the ocean. And that actually explains what's going
• 30:45
  Speaker 2: on with the magnetic striping, because this new rock is
• 30:48
  Speaker 2: forming and cooling, but it's happening over time, and so
• 30:52
  Speaker 2: as you get further from this mid Atlantic ridge, the
• 30:54
  Speaker 2: rock gets older and older. So what the rocks are
• 30:57
  Speaker 2: doing are tracking the Earth's magnetic over time. I remember,
• 31:02
  Speaker 2: the Earth's magnetic field is not constant. The North Pole
• 31:05
  Speaker 2: today is not where the North Pole has always been,
• 31:07
  Speaker 2: and over the last millions of years it has flipped
• 31:10
  Speaker 2: a bunch of times. So basically this magnetic striping is
• 31:13
  Speaker 2: a record of the flipping of Earth's magnetic field because
• 31:17
  Speaker 2: it's like influenced by the magnetic field and locks in
• 31:20
  Speaker 2: whatever it was at the time, and then it doesn't change.
• 31:23
  Speaker 1: Hmmm. It's like the Earth's magnet field paints on these
• 31:26
  Speaker 1: rocks sort of right, and so as new rocks for
• 31:28
  Speaker 1: coming up to get painted differently, and it logs how
• 31:31
  Speaker 1: many times Santa Claus had to move over the years,
• 31:34
  Speaker 1: which is probably a big pain for him and Missus claws.
• 31:36
  Speaker 2: Yeah, but it's a silver fascinating like measurement of the
• 31:39
  Speaker 2: history of the Earth. It's like rings on a tree, right,
• 31:42
  Speaker 2: It like tells you how many times this has happened.
• 31:45
  Speaker 2: And because these things are not perfect stripes, you can
• 31:48
  Speaker 2: use them to reconstruct how the ocean floor has grown, right,
• 31:52
  Speaker 2: it tells you like where it's grown faster and where
• 31:54
  Speaker 2: it's grown slower. You should totally google a picture of
• 31:57
  Speaker 2: the magnetic field striping of the It's really fascinating. They've
• 32:01
  Speaker 2: used this to reconstruct like the super continents a billion
• 32:04
  Speaker 2: years ago and two billion years ago. It tells you
• 32:07
  Speaker 2: the whole history, the dramatic, violent history of the continents
• 32:11
  Speaker 2: on the surface.
• 32:13
  Speaker 1: Yeah, it's pretty dramatic. I guess if you look at
• 32:15
  Speaker 1: it from a long term point of view, right, Like
• 32:18
  Speaker 1: if you were to take a movie of the Earth
• 32:20
  Speaker 1: and fast forward it, you know, by millions of years,
• 32:22
  Speaker 1: you would see these giant continents like crashing to each
• 32:25
  Speaker 1: other and split apart.
• 32:26
  Speaker 2: Yeah, but the surprising thing to me is that it's
• 32:28
  Speaker 2: not that slow. It moves in centimeters per year. In
• 32:33
  Speaker 2: some places, it's like eleven centimeters per year of subduction.
• 32:37
  Speaker 2: I mean, that's not so tiny. Like if your neighbor's
• 32:39
  Speaker 2: house moved closer to your house by centimeters per year,
• 32:42
  Speaker 2: it wouldn't take very many years.
• 32:43
  Speaker 1: Before you noticed, unless you really like your neighbors and
• 32:47
  Speaker 1: are considered moving in with them. But I think the
• 32:49
  Speaker 1: question that was posted originally was what drives the movement
• 32:53
  Speaker 1: of these continents? And so like the question is like
• 32:56
  Speaker 1: why are they moving? Anyways? Like we know how they're moving.
• 32:58
  Speaker 1: We talked about the mechanism makes a move, but like
• 33:01
  Speaker 1: why are they moving? Is maybe the question? And so
• 33:03
  Speaker 1: let's get into that big question what drives these continental
• 33:07
  Speaker 1: shifts and drifts? But first let's take another quick break.
• 33:23
  Speaker 1: All right, we're asking the question what is making Earth's
• 33:26
  Speaker 1: continents move? Because they're moving, and they're moving none as
• 33:31
  Speaker 1: insignificant rate a few centimeters a year, which doesn't seem
• 33:34
  Speaker 1: like a lot, but over millions of years, it can
• 33:36
  Speaker 1: make continents split apart, crash into each other, make new continents.
• 33:40
  Speaker 1: Pretty dramatic and juicy history there that the Earth has.
• 33:44
  Speaker 1: And so now we're asking the question, what is making
• 33:47
  Speaker 1: these big continental motions, what is powering it? And why
• 33:51
  Speaker 1: isn't the Earth just staying the same.
• 33:53
  Speaker 2: Yeah, it's really amazing how the surface of the Earth
• 33:55
  Speaker 2: reveals what's going on underneath. Beneath the hard crust, this
• 34:00
  Speaker 2: cracked eggshell of a surface of the Earth is a
• 34:03
  Speaker 2: crazy amount of energy of heat and motion of the mantle.
• 34:07
  Speaker 2: So we have the outer mantle, which is pretty solid
• 34:10
  Speaker 2: but actually does flow, but below that things get liquid.
• 34:13
  Speaker 2: And what's happening there is convection, like things heat up
• 34:17
  Speaker 2: and so they rise, things cool down and so they sink.
• 34:19
  Speaker 2: It's sort of like a big bubbling pot of tomato
• 34:22
  Speaker 2: sauce where you have like bubbles coming up and things
• 34:24
  Speaker 2: sinking and things are mixing. Right when you have soup
• 34:27
  Speaker 2: bubbling on the stove, it doesn't just sit there like
• 34:29
  Speaker 2: mixes itself, because things rise, they get hot and sink
• 34:33
  Speaker 2: as they cool, and that same thing is happening inside
• 34:36
  Speaker 2: the Earth, creating these convection cells, which are basically huge
• 34:40
  Speaker 2: spinning currents of magma underneath the Earth that drive the
• 34:44
  Speaker 2: conveyor belt on the surface.
• 34:46
  Speaker 1: I guess it pushes like it creates, like let's say,
• 34:48
  Speaker 1: a giant flow forms or giant bubble forms in the
• 34:51
  Speaker 1: Earth center. That's going to put pressure on the mantle,
• 34:54
  Speaker 1: which is then creating pressure on the eggshell crust. Right.
• 34:58
  Speaker 2: So imagine beneath the center of the plantic for example,
• 35:01
  Speaker 2: there's a hot spot, and so magma gets extra heated
• 35:04
  Speaker 2: there and what happens, Well, it's going to rise, and
• 35:07
  Speaker 2: it's going to bubble up, and there's a crack there
• 35:09
  Speaker 2: between the tectonic plates, so it's going to come out,
• 35:12
  Speaker 2: and so it's pushing those plates apart. And on the
• 35:14
  Speaker 2: other side the subduction where the plates are meeting and
• 35:17
  Speaker 2: banging into each other and getting pushed below, those are cooler, right,
• 35:21
  Speaker 2: and so as that cooler surface gets pushed into the magma,
• 35:24
  Speaker 2: it falls, it sinks, right. Because it's cooler, cold things
• 35:29
  Speaker 2: sink and hot things rise. So now you get this
• 35:31
  Speaker 2: circular pattern cold things sinking on the edge of it
• 35:34
  Speaker 2: hot things rising in.
• 35:36
  Speaker 1: The middle, So then all of that energy that's moving
• 35:39
  Speaker 1: the continent comes from the energy kind of boiling under
• 35:43
  Speaker 1: the surface of the earth exactly.
• 35:44
  Speaker 2: And there's lots of really interesting questions there, Like for
• 35:46
  Speaker 2: a long time, people thought that the dominant force was
• 35:50
  Speaker 2: the seafloor spreading, that this bubbling up of the heat
• 35:53
  Speaker 2: was really driving it, and it was like pushing the
• 35:55
  Speaker 2: plates and it was crunching them together, and the subduction
• 35:58
  Speaker 2: was really just like the plates getting slammed together ultimately
• 36:01
  Speaker 2: from the seafloor spreading. That was like the dominant idea
• 36:04
  Speaker 2: for the first few decades after the whole concept of
• 36:07
  Speaker 2: plate technonics was accepted, But more recently people have been
• 36:10
  Speaker 2: convinced of the opposite, that it's the subduction that's actually dominant,
• 36:13
  Speaker 2: that it's the crunching of plates and pulling them underneath
• 36:16
  Speaker 2: that's really making it happen. That it's more of a
• 36:19
  Speaker 2: pull than a push.
• 36:21
  Speaker 1: Like people thought that what was driving the movement was
• 36:24
  Speaker 1: the new land being created pushing the plates outwards. But
• 36:27
  Speaker 1: you're saying it's more like maybe it's where they're dipping
• 36:31
  Speaker 1: underneath the surface that's actually pulling the whole continent away
• 36:35
  Speaker 1: and then where there's a crack left, then new ground
• 36:38
  Speaker 1: gets formed there.
• 36:39
  Speaker 2: Yeah, exactly, And that sort of makes more sense because
• 36:41
  Speaker 2: the surface is not that solid, so like what it's
• 36:43
  Speaker 2: easier to do to pull a carpet or to push
• 36:46
  Speaker 2: on a carpet, So pulling like at the edges of
• 36:48
  Speaker 2: the plates sort of makes a little bit more sense
• 36:50
  Speaker 2: to me. But it's really a question of like energy
• 36:52
  Speaker 2: dynamics and force balancing. Where is this really happening? And
• 36:56
  Speaker 2: you know, one of the deepest questions is like why
• 36:58
  Speaker 2: do you get these convicts the cells in the first place,
• 37:01
  Speaker 2: How do these cells get started? How many are there,
• 37:05
  Speaker 2: what is their structure. It's like we'd like to understand
• 37:08
  Speaker 2: the boiling tomato soup that's underneath the surface of the Earth.
• 37:11
  Speaker 1: And I think some of this boiling is also what
• 37:13
  Speaker 1: makes the Earth's magnetic field too, isn't it.
• 37:16
  Speaker 2: The Earth's magnetic field is definitely connected to the flow
• 37:19
  Speaker 2: of all this stuff inside the Earth. We don't understand
• 37:22
  Speaker 2: how much is connected to like the mantle or the
• 37:24
  Speaker 2: outer core, which is a little bit more metallic, but
• 37:26
  Speaker 2: definitely we need flow inside the Earth to generate the
• 37:29
  Speaker 2: magnetic field and It's an interesting connection, right, because the
• 37:32
  Speaker 2: magnetic field also flips, and that leaves a pattern on
• 37:36
  Speaker 2: the seafloor. So the whole thing is like a big, complicated,
• 37:38
  Speaker 2: beautiful dance.
• 37:40
  Speaker 1: Hmmm, the earth shuffle. But then I guess a question
• 37:43
  Speaker 1: that you can ask is like how long is that
• 37:45
  Speaker 1: going to keep going? Like is the Earth going to
• 37:47
  Speaker 1: run out of you know, inner boil? Is it going
• 37:49
  Speaker 1: to run out of energy inside? And then everything's going
• 37:51
  Speaker 1: to just stay still?
• 37:53
  Speaker 2: The Earth will eventually cool, right. This depends on the
• 37:55
  Speaker 2: Earth maintaining its temperature. And while the radioactive decay inside
• 37:59
  Speaker 2: the Earth is keeping us warm like a nice battery,
• 38:02
  Speaker 2: it's not enough. We are radiating more heat out into
• 38:05
  Speaker 2: space than it's being generated by those decays. So they think,
• 38:09
  Speaker 2: like in about a billion and a half years, the
• 38:11
  Speaker 2: temperature of the mantle won't be high enough anymore for
• 38:14
  Speaker 2: this kind of flow, and we think the place tectonics
• 38:17
  Speaker 2: will cease. So we got like another billion and a
• 38:19
  Speaker 2: half years.
• 38:20
  Speaker 1: A billion and a half years before the crust kind
• 38:23
  Speaker 1: of freezes in place. Right, Whatever we look like then
• 38:26
  Speaker 1: is how we're going to look like until the end
• 38:28
  Speaker 1: of time, or at least until the sun eats us up.
• 38:29
  Speaker 2: It's like another billion years of musical chairs and then
• 38:32
  Speaker 2: eventually the music just stops.
• 38:34
  Speaker 1: Now, is that heat from the center of the Earth significant, Like,
• 38:38
  Speaker 1: are we going to freeze or does? Right now? A
• 38:41
  Speaker 1: lot of our heat comes from the Sun.
• 38:43
  Speaker 2: The temperature of the surface of the Earth is not
• 38:45
  Speaker 2: too affected by what's going on inside the Earth. That's
• 38:48
  Speaker 2: more dominated by the Sun and the atmosphere and those
• 38:50
  Speaker 2: kind of effects. So even if the Earth's continents do
• 38:53
  Speaker 2: freeze in place, we can stay warm from the Sun.
• 38:55
  Speaker 2: That's not an issue.
• 38:56
  Speaker 1: Maybe a bigger issue by then will be that we
• 38:58
  Speaker 1: won't have a magnetic field.
• 39:01
  Speaker 2: Yeah, where the Sun is getting brighter and brighter, so
• 39:03
  Speaker 2: we're probably just going to overheat. In a billion years,
• 39:05
  Speaker 2: the Sun is going to be significantly brighter than it
• 39:07
  Speaker 2: is today.
• 39:08
  Speaker 1: And we've seen this kind of thing happen in other
• 39:10
  Speaker 1: planets too, right.
• 39:11
  Speaker 2: Well, Earth is the only planet in the Solar System
• 39:14
  Speaker 2: with active tectonic plates. We think there's evidence that the
• 39:17
  Speaker 2: Moon and Mars both once had tectonic activity, though they
• 39:21
  Speaker 2: are smaller than the Earth and they cool faster, and
• 39:23
  Speaker 2: so both of them are basically already frozen in place.
• 39:26
  Speaker 1: Well, there aren't that many rocky planets to begin with.
• 39:29
  Speaker 1: There's like three or four.
• 39:30
  Speaker 2: Right, Yeah, but they're also rocky moons, right, like Ganymede
• 39:34
  Speaker 2: and Io. These are planets, they're geologically active, but we
• 39:37
  Speaker 2: don't see tectonic plates on them either. You need like
• 39:40
  Speaker 2: just the right mix of temperature and also water. Like
• 39:44
  Speaker 2: water is really crucial to making this happen because it
• 39:46
  Speaker 2: weakens the crust. When the rocks are cooling, if there's
• 39:49
  Speaker 2: water around, it changes the chemical composition of it, which
• 39:53
  Speaker 2: makes the crust a little weaker, which allows for this
• 39:55
  Speaker 2: sort of like conveyor belt destruction and subduction. For example,
• 39:59
  Speaker 2: Venus is still internally hot. We think there's like oceans
• 40:02
  Speaker 2: of magma inside, but doesn't have tectonic plates the same
• 40:05
  Speaker 2: way Earth does, and we think that probably it's because
• 40:08
  Speaker 2: it lacks water. It doesn't have any surface oceans to
• 40:11
  Speaker 2: make this happen.
• 40:12
  Speaker 1: Yeah, it's just reaen about this. Water actually makes rock
• 40:14
  Speaker 1: melt at a lower temperature.
• 40:16
  Speaker 2: Right, yeah, So it encourages the flow, right. Essentially, it
• 40:18
  Speaker 2: weakens the rock and makes it more liquid. So the
• 40:21
  Speaker 2: fact that we have oceans and tectonic plates is not
• 40:24
  Speaker 2: a coincidence. You need really both of those things to happen.
• 40:27
  Speaker 2: Venus is a crazy planet anyway. They think like a
• 40:29
  Speaker 2: billion years ago there was a complete volcanic resurfacing, meaning
• 40:34
  Speaker 2: volcanoes completely created a new surface of the planet basically
• 40:38
  Speaker 2: just by spewing magma everywhere. But we don't think there
• 40:41
  Speaker 2: are plate tectonics on Venus.
• 40:43
  Speaker 1: Hmmm, weird. Interesting now, And you said this happens in
• 40:47
  Speaker 1: moons like our moon, but then also other moons in
• 40:50
  Speaker 1: other planets.
• 40:51
  Speaker 2: Yeah, so the our moon probably had plate tectonics in
• 40:53
  Speaker 2: the past, but now it's cooled. Io, which is one
• 40:57
  Speaker 2: of the moons of Jupiter, and it's about the same
• 40:59
  Speaker 2: size as our our moon is still actively volcanic, Like
• 41:02
  Speaker 2: the voyager saw several volcanic plumes rising like hundreds of
• 41:06
  Speaker 2: kilometers above the surface. So there's definitely stuff going on
• 41:10
  Speaker 2: inside there, and it's probably mostly due to like thermal
• 41:13
  Speaker 2: energy from tidal forces from Jupiter, which produces like convection
• 41:17
  Speaker 2: in the interior of Io. It's like getting squeezed by
• 41:19
  Speaker 2: Jupiter's gravity. But we haven't actually seen plate tectonics on
• 41:23
  Speaker 2: Io as well, though, you know, Io has not been
• 41:26
  Speaker 2: studied in great depth yet.
• 41:28
  Speaker 1: So it seems like, it's kind of rare to have
• 41:30
  Speaker 1: plate tectonics or is it just that the other planets
• 41:33
  Speaker 1: had it but then they stop?
• 41:34
  Speaker 2: It might be both. It might not be an automatic
• 41:36
  Speaker 2: thing for every planet to have it. You need the
• 41:38
  Speaker 2: right combination of temperature and convection underneath the surface and
• 41:42
  Speaker 2: water on the surface to weaken the crust. So it
• 41:44
  Speaker 2: doesn't happen all the time. But you know, if it
• 41:47
  Speaker 2: happened on the Moon and on Mars and on Earth,
• 41:50
  Speaker 2: that means it's not super duper rare. Another question is like, well,
• 41:53
  Speaker 2: how important is it? Does it really matter if you
• 41:55
  Speaker 2: have plate tectonics. It's kind of fascinating on Earth that
• 41:58
  Speaker 2: the continent's drifting apart changes the evolution of animals because
• 42:02
  Speaker 2: if like a community gets split in half, now you
• 42:04
  Speaker 2: have two of them isolated and they can evolve in
• 42:07
  Speaker 2: separate directions. We don't know what would have been the
• 42:09
  Speaker 2: history of life on Earth if we didn't have plate tectonics.
• 42:13
  Speaker 2: It might be very very different. Hmm.
• 42:16
  Speaker 1: We wouldn't have kangaroos.
• 42:18
  Speaker 2: For example. Right, Sometimes it's important to have an isolated
• 42:22
  Speaker 2: community so they have times develop some new capacity before
• 42:25
  Speaker 2: they have to compete with the mainland. This is called
• 42:28
  Speaker 2: like biogeographic islands and communities. It's a whole field of
• 42:31
  Speaker 2: study and it's actually replicated and really interestingly in artificial intelligence,
• 42:36
  Speaker 2: sometimes when you're training neural networks and you give them
• 42:39
  Speaker 2: a hard new task, you create like a subpool of
• 42:41
  Speaker 2: these neural networks, so they train on this hard new
• 42:44
  Speaker 2: task in isolation before they have to come back and
• 42:46
  Speaker 2: compete with the other neural networks on the mainland. So
• 42:49
  Speaker 2: you know, having islands and having divisions between these things
• 42:52
  Speaker 2: can be really helpful for creating diversity and weirdness in
• 42:56
  Speaker 2: life on Earth.
• 42:58
  Speaker 1: I guess it can affect life. Is it necessary to life?
• 43:02
  Speaker 2: Fascinating question I wish we knew the answer to. The
• 43:04
  Speaker 2: only way to really figure that out is to see
• 43:06
  Speaker 2: a bunch of other planets. So we're not there yet,
• 43:09
  Speaker 2: but people are hoping that eventually we'll be able to
• 43:11
  Speaker 2: study the surface of exo planets planets in other solar systems,
• 43:16
  Speaker 2: so we get more data and we could see like, oh, look,
• 43:18
  Speaker 2: there happens to be life only on planets that once
• 43:20
  Speaker 2: had plate tectonics. Maybe there's a connection there. We don't know,
• 43:24
  Speaker 2: but it's something we might figure out in the future
• 43:26
  Speaker 2: if we can see and study other planets.
• 43:29
  Speaker 1: M But I guess there's no mechanism for how it
• 43:32
  Speaker 1: might help life that we know about. Or maybe being
• 43:34
  Speaker 1: in a super continent helps or I don't know. Do
• 43:37
  Speaker 1: we have any ideas how that might affect the formation
• 43:39
  Speaker 1: of life, the.
• 43:40
  Speaker 2: Formation of life, the actual genesis of life from non
• 43:43
  Speaker 2: living materials. No, I don't think the continants can really
• 43:46
  Speaker 2: play a role. But it might help develop more complex life.
• 43:50
  Speaker 2: It might give life an opportunity to develop in weird
• 43:53
  Speaker 2: new directions. Maybe it's crucial for civilization and intelligence. Who knows.
• 43:58
  Speaker 2: We're really just speculating.
• 44:00
  Speaker 1: I see, just arguing about what counts as a continent
• 44:04
  Speaker 1: or not. You're saying might have the driven evolution for
• 44:07
  Speaker 1: us to be better arguers.
• 44:09
  Speaker 2: Probably started a bunch of wars. You know, wars have
• 44:11
  Speaker 2: definitely been fought over dumber stuff than that.
• 44:13
  Speaker 1: Wars and podcast episodes.
• 44:16
  Speaker 2: Wars on podcast episodes.
• 44:18
  Speaker 1: Crucial on the way to enlightenment.
• 44:20
  Speaker 2: As a speak, well, you know, the culmination of all
• 44:22
  Speaker 2: of evolution of life on Earth? Is this podcast? So yes?
• 44:25
  Speaker 1: Absolutely, yeah, of course we're here to explain the universe.
• 44:27
  Speaker 1: I mean, how much more evolved?
• 44:30
  Speaker 2: Can it get Before we explain the universe, we got
• 44:32
  Speaker 2: to explain the Earth. You know, it's fastened into me.
• 44:35
  Speaker 2: How much we still don't understand and how recent any
• 44:38
  Speaker 2: of this understanding is. As of just one hundred years ago,
• 44:42
  Speaker 2: nobody believed this continental drift theory, and now it's an
• 44:45
  Speaker 2: essential part of modern geology and geography and biology. It's
• 44:50
  Speaker 2: like the theory of evolution. You know, once you see it,
• 44:52
  Speaker 2: you can't unsee it. It's just so obvious. But it
• 44:55
  Speaker 2: takes a while to absorb these crazy new ideas. But
• 44:58
  Speaker 2: those are the best moments in science, right when we
• 45:00
  Speaker 2: have to pivot to something totally bonkers and new, because
• 45:03
  Speaker 2: that's just the way the data is.
• 45:05
  Speaker 1: Yeah, and it sounds like there are still a lot
• 45:07
  Speaker 1: of mysteries left to answer about how the Earth moves
• 45:10
  Speaker 1: around and what it's doing under the surface, which means
• 45:12
  Speaker 1: that we may be wrong right now, right and who
• 45:15
  Speaker 1: knows what we're going to discover about the future.
• 45:17
  Speaker 2: Exactly, not just the future, but also the past. They've
• 45:20
  Speaker 2: done these reconstructions of these super continents from two billion
• 45:23
  Speaker 2: years ago, one of them is called Nuna, and another
• 45:26
  Speaker 2: super continent from a billion years ago called Rhodinia, but
• 45:29
  Speaker 2: that whole history could also be wrong. We may need
• 45:32
  Speaker 2: to rewrite the entire history of life and continents on Earth.
• 45:37
  Speaker 2: It's going to be fascinating to see what people figure out.
• 45:39
  Speaker 1: Yeah, maybe the continents just looked like a giant smiley
• 45:42
  Speaker 1: face before and the Earth was hoping that it would
• 45:45
  Speaker 1: freeze out with smiling. But then you know, the universe
• 45:50
  Speaker 1: took too long to take.
• 45:51
  Speaker 2: The picture like a giant continent until selfie.
• 45:53
  Speaker 1: All right, Well again, an interesting dive into our own planet,
• 45:57
  Speaker 1: this thing we're all standing on, and how it's moving
• 46:00
  Speaker 1: underneath our feet, and how there are still deep mysteries
• 46:03
  Speaker 1: as deep as the center of the Earth going on
• 46:06
  Speaker 1: right under.
• 46:06
  Speaker 2: Us, and how long it can take to figure out
• 46:08
  Speaker 2: the story of our very own planet.
• 46:10
  Speaker 1: We hope you enjoyed that. Thanks for joining us, See
• 46:13
  Speaker 1: you next night.
• 46:22
  Speaker 2: Thanks for listening, and remember that Daniel and Jorge Explain
• 46:25
  Speaker 2: the Universe is a production of iHeartRadio. For more podcasts
• 46:29
  Speaker 2: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever
• 46:33
  Speaker 2: you listen to your favorite shows.