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What is a Tectonic Plate? · PlanetGeo: The Geology Podcast

0:05
SPEAKER_01: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
0:18
SPEAKER_01: All right, let's do some introductions, Chris.
0:21
SPEAKER_01: You are Chris Bullheis, high school science teacher extraordinaire in the great state of Michigan.
0:26
SPEAKER_01: I am Jesse Ramick, geoscience professor at Penn State, and your former student.
0:32
SPEAKER_01: And this is Planet Geo, a podcast where we talk about some amazing aspects of our planet and why they matter.
0:39
SPEAKER_00: All right.
0:40
SPEAKER_00: Hey Jesse, how are we doing today?
0:42
SPEAKER_00: Yeah, man.
0:42
SPEAKER_00: We're doing all right.
0:43
SPEAKER_00: We're doing all right.
0:44
SPEAKER_00: How about you, Chris?
0:45
SPEAKER_00: Doing all right.
0:46
SPEAKER_00: Hey, so uh let's go ahead and get this thing rolling.
0:48
SPEAKER_00: Today's topic is about plate tectonics.
0:51
SPEAKER_00: Oh, yeah.
0:51
SPEAKER_00: And uh wanted to ask you what's getting you fired up right now?
0:54
SPEAKER_01: Yeah, you know, um uh I've been pretty excited about uh future courses I'm gonna teach.
1:00
SPEAKER_01: A colleague suggested to me that I should offer a class on uh the early history of the earth and the early history of our solar system.
1:07
SPEAKER_01: So that's kind of what I've been thinking about uh quite a bit this week, and uh, I'm pretty excited about it.
1:11
SPEAKER_01: What about you?
1:11
SPEAKER_01: What's got you pumped up this week?
1:12
SPEAKER_00: Well, yeah, this week has been a big week with the the whole coronavirus thing going on.
1:16
SPEAKER_00: Um, I take 26 high school seniors out west on a three-week uh geology field course.
1:22
SPEAKER_00: So I'm trying to figure out how to get this to go right um yet within this, and I want to uh you know, we're trying to figure out how to do this smart and safe.
1:31
SPEAKER_00: Uh, but it's important.
1:32
SPEAKER_00: I don't want these students uh because if they miss this opportunity, then they miss the opportunity.
1:37
SPEAKER_00: It's it's gone.
1:38
SPEAKER_00: Yeah, and I don't want this to go by without having them, you know, have the opportunity for that exposure.
1:45
SPEAKER_01: Oh, that's great.
1:46
SPEAKER_01: That's such an amazing experience.
1:48
SPEAKER_01: Most people from Michigan have never seen the mountains until that point in time.
1:51
SPEAKER_01: Anyway, that this episode, we're we're dedicating this to to plate tectonics.
1:55
SPEAKER_01: Uh, we're gonna talk about what is a tectonic plate.
1:58
SPEAKER_00: And I think it's important though, you know, why are we doing this right away?
2:02
SPEAKER_00: Um, plate tectonics lays the foundation for uh really everything that happens in geology.
2:07
SPEAKER_00: And so, but before that, there was this idea of continent drift, and that that was you know about a roughly a hundred years ago, a hundred, you know, 1912-ish.
2:19
SPEAKER_00: So over a hundred years ago, this idea that was really groundbreaking of continental drift, the idea that the continents are moving about, um came into being from this this uh a guy that I have a lot of respect for, Alfred Wagoner.
2:36
SPEAKER_01: I uh I mean the the early the early geoscientists were they're just impressive people, just creative thinkers, you know, thinking outside the box.
2:44
SPEAKER_00: To me, the inter one of the interesting things about Wagoner is that this he was not a geologist.
2:49
SPEAKER_00: He was into you know climatology and and studying things like this.
2:54
SPEAKER_00: And so but one day he was staring at a map, and he looked at the map and and recognized right away that the I mean, if you look at the shape of the east coast of North America and South America, and then you look at the shape of the west coast of northern Europe and Africa, and you have this classic S shape.
3:14
SPEAKER_00: Yeah, Wagoner looked at that and said, Wow, they look like they fit together like a jigsaw puzzle.
3:22
SPEAKER_00: And that's how it kind of all began.
3:24
SPEAKER_01: Yeah.
3:24
SPEAKER_01: It's I mean, it's such a cool, like, first order observation.
3:28
SPEAKER_00: It started with that idea, but then if you put them together, he actually Wagner had a a team of people working for him.
3:36
SPEAKER_00: The evidence that they came up with is just amazing.
3:40
SPEAKER_01: Yeah, so let's let's go through a couple of those.
3:42
SPEAKER_01: Yeah, hit me with it.
3:43
SPEAKER_00: Yeah, so you know, you look at the eastern part of the United States, the the Appalachian Mountains.
3:49
SPEAKER_00: Okay, well, the Appalachian Mountains are are the same as the mountains that you see in northern Europe.
3:55
SPEAKER_00: They're the same rocks, the same fossils, the same structures, they're the same mountain range.
4:04
SPEAKER_00: He looked at that and recognized that you know those mountains, they formed when Pangaea came together, when that supercontinent, you had this continent to continent collision, and it formed those mountains.
4:16
SPEAKER_00: When Pangaea broke apart, that's what we see today.
4:20
SPEAKER_00: And they're separated by thousands of miles of ocean right now.
4:22
SPEAKER_01: They broke the Atlantic Ocean, which formed the Atlantic Ocean, right?
4:25
SPEAKER_01: So so these things just match up.
4:27
SPEAKER_01: I mean, it's a jigsaw puzzle, they match up perfectly.
4:29
SPEAKER_00: Everything that they said was correct.
4:32
SPEAKER_00: The continents were moving, so things were moving.
4:34
SPEAKER_01: So it led right so it led to this idea of continental drift, which which is a nice idea, right?
4:39
SPEAKER_01: That these plates used to be together and it used to form since one big supercontinent.
4:43
SPEAKER_01: Okay, all looking back, it all fits, you know, beautifully, and we uh we we have a way to explain it now.
4:48
SPEAKER_01: But back then, this was not a well-accepted idea, right?
4:50
SPEAKER_01: This was there weren't many geoscientists back then, so you know maybe he pissed off like two or three people in the world, but but but it was not popular, right?
4:58
SPEAKER_01: Um, and so so now this was not accepted.
5:01
SPEAKER_01: And the reason was that he didn't have a process, there was no really good way to explain why did the continents move around, right?
5:08
SPEAKER_00: Yeah, that's exactly what happened.
5:09
SPEAKER_00: They're like, well, wait a minute.
5:10
SPEAKER_00: The so the if the continents moved, how did they move?
5:13
SPEAKER_00: Bottom line is it it came down to the crust plowing through the mantle, right?
5:18
SPEAKER_00: And it was quickly uh proved by physicists as being this is not possible, this didn't happen.
5:26
SPEAKER_00: And so the whole idea was rejected.
5:28
SPEAKER_01: There's also a couple other, you know, potentially uh a little bit more ridiculous ideas that that were used to explain this, like an expanding earth.
5:35
SPEAKER_01: You know, the earth used to be really tiny and then it just kind of started growing.
5:39
SPEAKER_01: And and if you know, you can imagine like blowing up a balloon, if you draw some face on a balloon and then you blow uh uh like a deflated balloon, then you blow up the balloon, the face gets big and ridiculous, right?
5:48
SPEAKER_01: The same could be said for Pangaea.
5:50
SPEAKER_01: You blow up the earth and Pangaea breaks apart into all these different continents.
5:53
SPEAKER_01: Uh looking back, it's a bit silly.
5:55
SPEAKER_01: This also led to the idea to the perception that continental drift was linked to some of the more ridiculous processes that it was uh assigned to, and then therefore continental drift was ridiculous, right?
6:06
SPEAKER_01: Which isn't the case.
6:08
SPEAKER_01: No.
6:08
SPEAKER_01: Um, so you gotta have a good process, you gotta have a good hook to to explain, you know, what you're observing um in the geosciences.
6:15
SPEAKER_00: Right, but but let's think let's look at that a second, Jess.
6:17
SPEAKER_00: Like he he didn't, you know, three-quarters of the earth is ocean.
6:21
SPEAKER_01: Right.
6:22
SPEAKER_00: And and he and Alfred Vay, we had no idea what the ocean was like.
6:26
SPEAKER_00: We thought the ocean was deep, which it is, we thought it was flat, we thought it was featureless.
6:31
SPEAKER_00: Um, and it's anything but that.
6:33
SPEAKER_00: And and so, you know, think about he came up with everything that he came up with, which was spot on, but without the knowledge of over three-quarters of the earth, which uh to me is just absolutely amazing.
6:46
SPEAKER_00: Here's what Vegader knew.
6:47
SPEAKER_00: Veganer knew that there was a difference between the crust and the mantle below us, which is a really a compositional difference.
6:54
SPEAKER_01: We're sitting on continental crust, there's oceanic crust, and it sits on top of the mantle, which is the this sort of you know, the bulk of the the earth is is this mantle.
7:04
SPEAKER_01: The crust is the skin of the athletic.
7:05
SPEAKER_01: Oh, totally.
7:06
SPEAKER_01: This is it's where all the action happens, in my opinion.
7:09
SPEAKER_01: But there, you know, there's a lot of people out there who who kind of love you know studying the mantle and all the details about the mantle.
7:14
SPEAKER_00: Yeah, I feel I feel kind of bad for for Alfred Wegener.
7:17
SPEAKER_00: He died uh in Greenland in I think 1930, and he died, I think, unhappy, you know, because this was his this was a lot of his work, and uh it was soundly rejected.
7:28
SPEAKER_00: Yeah.
7:29
SPEAKER_00: And it kind of went to bed.
7:30
SPEAKER_01: Now looking back, we understand he was, you know, his observation was spot on, and and we and we we have all these new ideas that that really led to the main revolution in the geosciences, which was understanding that continents do drift around, and the driving force is plate tectonics, which is the process that governs why you know the continents are why plates are moving around on Earth.
7:53
SPEAKER_01: So let's let's give a brief little, you know, what is a tectonic plate?
7:57
SPEAKER_01: How do we kind of define that, you know?
8:00
SPEAKER_00: Okay, we talked about the crust and the mantle.
8:03
SPEAKER_00: Vagener knew about this 110 years ago.
8:06
SPEAKER_00: The compositional difference and the thickness difference, you know, oceanic crust is much, much thinner, but it's denser, and that's a critical thing to plate tectonics.
8:14
SPEAKER_00: The continental crust is much thicker on the order of 70 kilometers thick, and but it's it's less dense, which is a crucial thing in terms of plate tectonics that we'll get into later, also.
8:25
SPEAKER_00: But the lithosphere is the cold and crunchy part of it's the crust and the upper mantle.
8:36
SPEAKER_00: The lithosphere is about a hundred kilometers thick.
8:40
SPEAKER_00: And and it's here's the way I think of it it's brittle, it's cold and it's crunchy.
8:46
SPEAKER_00: Okay, that's what a plate is.
8:49
SPEAKER_01: So when we talk about crust and mantle, we're talking about really a compositional difference.
8:54
SPEAKER_01: These are, you know, this is the the the eggshell on top of the egg.
8:58
SPEAKER_01: Um, but when we're talking about a tectonic plate, we're talking about a uh really a behavioral difference where the the lithosphere, what we're calling lithosphere, this is the crust and the upper part of the mantle, the stuff that is cool enough where it behaves rigidly.
9:13
SPEAKER_01: This stuff will break.
9:14
SPEAKER_01: If you bend it, it's gonna break, right?
9:16
SPEAKER_01: That's really kind of what we're talking about with with rigidity.
9:19
SPEAKER_00: Yeah, it's such a good point to bring up because the the um you know, the crust and the mantle, what what Wagner knew about, that was a compositional difference that brought that change about.
9:29
SPEAKER_00: Okay, the lithosphere spans that compositional difference.
9:32
SPEAKER_00: So we can throw that aside.
9:34
SPEAKER_00: We can get rid of crust and mantle right now, and we can just say, all right, the pot the part of the earth that behaves in a cold, crunchy way.
9:44
SPEAKER_01: That's what a plate is, and that's called a lithospheric.
9:47
SPEAKER_01: Cold and crunchy.
9:48
SPEAKER_01: I love it.
9:48
SPEAKER_01: I mean, it's you know, it's something that's it's a little bit cool.
9:51
SPEAKER_01: If it's like plastic, right?
9:52
SPEAKER_01: You cool it down, it's gonna break really easily.
9:54
SPEAKER_01: Like you, you if you live in a place where you get a little bit of winter, plastic, it gets cold, it breaks.
9:59
SPEAKER_01: If you're sitting in North America, you're moving in the same direction as the crust, which you're sitting on, which is like 60, 70 kilometers thick, something like that.
10:07
SPEAKER_01: Some places 30 kilometers.
10:08
SPEAKER_01: Okay, there's variability.
10:10
SPEAKER_01: And then you're sitting on top of another 50 kilometers or so of mantle, which is a different composition, but it is also behaving like this cold plastic.
10:18
SPEAKER_01: If you bend it, it will break.
10:20
SPEAKER_01: That is your tectonic plate.
10:21
SPEAKER_01: And what you're sitting on top of is mantle, same composition, but it's a little bit hotter.
10:26
SPEAKER_01: So this stuff is like when you heat up plastic, it'll flow.
10:30
SPEAKER_01: It's not gonna, if you bend it, it will not break.
10:32
SPEAKER_01: If you bend it, it will just kind of flow and deform.
10:35
SPEAKER_00: So the asthenosphere, uh, which by the way is my favorite layer of the earth.
10:40
SPEAKER_01: I didn't know we were I didn't know we had favorite layers.
10:42
SPEAKER_00: I this sounds like a stupid question.
10:43
SPEAKER_00: Like, hey, Mr.
10:44
SPEAKER_00: Bullheist, what's the favorite layer of the earth?
10:46
SPEAKER_00: Well, you know what?
10:47
SPEAKER_01: I And also that's like the most boring answer possible.
10:50
SPEAKER_01: Like, I mean, come on, the your most favorite layer of the earth is the asthenosphere.
10:53
SPEAKER_01: Okay, just because what?
10:54
SPEAKER_01: It's the biggest or something.
10:55
SPEAKER_01: Come on.
10:56
SPEAKER_00: Why is it?
10:57
SPEAKER_00: Because you know what?
10:57
SPEAKER_00: The asthenosphere makes plate tectonics happen.
11:00
SPEAKER_00: And if we didn't have the asthenosphere, we wouldn't have plate tectonics.
11:03
SPEAKER_00: If we didn't have plate tectonics, we wouldn't have the mountains and we wouldn't have the valleys and everything in between.
11:08
SPEAKER_00: So because we have plate tectonics, we have the awesome planet we have flat out.
11:13
SPEAKER_00: So the asthenosphere is my favorite layer of the earth.
11:16
SPEAKER_00: And to me, Jess, you gotta give me credit.
11:18
SPEAKER_00: That makes sense.
11:19
SPEAKER_01: I mean, all right, I'll give I'll I'll throw you a little bit of a bone.
11:22
SPEAKER_01: I mean, I I I like it for the most part.
11:24
SPEAKER_01: I think there's some more interesting, uh, interesting layers of the earth.
11:27
SPEAKER_01: But important does not equal favorite for me.
11:30
SPEAKER_01: But I I see I see your point.
11:32
SPEAKER_00: Oh my gosh.
11:33
SPEAKER_00: Plate tectonics was the unifying theory.
11:35
SPEAKER_00: Um, it really didn't come about until the 1960s.
11:40
SPEAKER_00: And um, it's interesting how war um kind of brings on new technology.
11:46
SPEAKER_00: Absolutely.
11:47
SPEAKER_00: And and so during World War II, um, we had developed, I don't know, prior to World War II, obviously, but uh it was used widely though as sonar.
11:58
SPEAKER_00: And so during World War II, there you know, Harry Hess, he was in command of a ship as he was you know steering his ship from one destination to another, he would turn his sonar down because he was a geologist, he was a curious guy, and and so he started making maps of the ocean floor, and we found out that you know the abyssal plane, that's what the ocean floor is called.
12:21
SPEAKER_00: Abyss is deep and plain is flat, right?
12:24
SPEAKER_00: Well, we found out that it's yeah, it's deep, but the the ocean floor is not flat and featureless.
12:29
SPEAKER_00: Bagner had no idea of that.
12:31
SPEAKER_00: That led to the discovery of the of these mid-ocean ridges and so on.
12:34
SPEAKER_00: And you know, I talked about earlier when we first began the S shape of the East Coast of the US and the S shape of the west coast of the US.
12:41
SPEAKER_00: Well, you know what we found is we found an S-shape ridge in the middle of the Atlantic Ocean.
12:47
SPEAKER_00: Oh man, that's crazy.
12:48
SPEAKER_00: It's crazy.
12:48
SPEAKER_01: But it takes generations, right?
12:50
SPEAKER_01: I mean, it takes technological development, it takes exploration, it takes that kind of stuff, and it takes a long time to really piece together the the fundamental ways that the earth operates.
13:01
SPEAKER_01: But you know, like you said, we find these mid-ocean ridges, and then as we started to be able to detect, you know, this magnetism in rocks can let's get into that just a little bit.
13:09
SPEAKER_00: It's the smoking gun of plate tectonics.
13:11
SPEAKER_00: Right.
13:12
SPEAKER_00: Paleo is ancient, old.
13:14
SPEAKER_00: Magnetism is the magnetic record in in iron-bearing minerals.
13:19
SPEAKER_00: Okay, well, here's what happens when when lava, which comes out on the ocean floor, in geology, we call it mafic, which means it's loaded with iron and magnesium.
13:28
SPEAKER_00: And so these iron and magnesium rich minerals, uh, these minerals begin to grow and they're in this soup of magma, right?
13:35
SPEAKER_00: So that means they're free to align, like a compass needle.
13:38
SPEAKER_00: A compass needle, in order for it to work, it has to be free to move, right?
13:42
SPEAKER_00: Well, because these iron-rich minerals are in this soup, they're free to move.
13:47
SPEAKER_00: They're in a liquid.
13:48
SPEAKER_00: They they point like compass needles, because every compass is a north and a south pole.
13:54
SPEAKER_00: They point like compass needles uh to according to where the north and the south poles are at that point, the magnetic north and south pole.
14:02
SPEAKER_00: But Earth's magnetic field reverses, it flips where our magnetic north pole becomes the magnetic south south pole, and and vice versa.
14:11
SPEAKER_00: So, what do we see when we go to a mid-ocean ridge and drive perpendicular to uh away from it?
14:20
SPEAKER_00: We see these magnetic reversals.
14:23
SPEAKER_00: And then so then when you go to back to that mid-ocean ridge and and drive the other way, perpendicular to it, right?
14:32
SPEAKER_00: Uh, you see the exact same pattern.
14:34
SPEAKER_00: They're mirror images on either side of it because the magnetic record is preserved when that lava erupts out and become cools below the curry point.
14:45
SPEAKER_00: That's right, and then gets magnetized and locked in time because now it's cemented in rock, right?
14:51
SPEAKER_00: And that, but as that's going on, it's getting shoved aside by this this this plate tectonic movement, this convection below the lithospheric plate.
15:01
SPEAKER_00: And and so then if a magnetic reversal happens, now the all of the north poles are uh are pointing the other direction.
15:10
SPEAKER_01: I mean, and and it it's such a cool thing because these, you know, the the the time when the magnetic field flips, it can vary, and et cetera, and the and the eruption rate can vary at all these different mid-ocean ridges.
15:20
SPEAKER_01: But what you so you what you get is this kind of variable thickness of these little stripes, right?
15:24
SPEAKER_01: And it creates this basically barcode of Earth history.
15:27
SPEAKER_01: So so that's like you know, the the smoking gun of of plate tectonics, which in the 1960s really became the paradigm that governs the geosciences, is that we have these tectonic plates that are moving around on Earth's surface.
15:41
SPEAKER_01: And the point is that if you're sitting there at home listening to us on your continent, you're sitting on a continent, you're moving right now.
15:49
SPEAKER_01: You're moving at a at a very slow rate.
15:51
SPEAKER_00: I mean, we're talking like centimeters per year, so you can't comparable to the rate that your fingernail grows.
15:58
SPEAKER_00: That's the common analogy out there.
16:01
SPEAKER_01: That's I mean, super slow, right?
16:02
SPEAKER_01: You won't notice it.
16:03
SPEAKER_01: But if you're sitting, you know, somewhere in North America, anywhere in North America, you're for the most part moving in the same direction as everybody else in North America at relatively the same rate, but we're moving in a different way than people sitting in Europe, or people sitting in Hawaii, or people sitting, you know, in Australia.
16:20
SPEAKER_01: We're moving away from each other and closer to each other.
16:23
SPEAKER_01: So let's kind of like summarize this.
16:24
SPEAKER_01: I mean, the take home points of of plate tectonics, you know, a tectonic plate is this cold part, it's the crust and the upper part of the mantle beneath us.
16:34
SPEAKER_01: That's the the stuff that if you bend it, it will break.
16:37
SPEAKER_01: It's behaving like a rigid thing, it's behaving like cold plastic.
16:40
SPEAKER_01: That's a tectonic plate.
16:42
SPEAKER_01: And because it's behaving, if you because if you bend it, it will break.
16:46
SPEAKER_01: If you kind of stress this stuff enough, it's gonna break and it's gonna break along the edges.
16:50
SPEAKER_01: So we have these little blocks, these plates that are moving around.
16:56
SPEAKER_01: What are they moving on?
16:57
SPEAKER_01: They're moving above this asthenosphere, which is the plastic part or the hot plastic part, where if you bend it, it will flow.
17:05
SPEAKER_01: So it's moving, it's kind of sliding around on top of stuff.
17:08
SPEAKER_01: They're interacting in really interesting ways.
17:10
SPEAKER_01: In some ways, convection or the this sort of plastic flow is driving the plates to move in different directions.
17:17
SPEAKER_01: In some places, if you get a plate diving down into the mantle, it'll pull other stuff along with it.
17:22
SPEAKER_01: So you kind of get these different driving forces that are that are moving the plates around at different points in time.
17:28
SPEAKER_01: And that's a really complicated question that we don't really understand.
17:31
SPEAKER_01: It is if you pick any single tectonic plate boundary, you know, the San Andreas Fault, that's a tectonic plate boundary.
17:38
SPEAKER_01: The subduction zone, you know, uh that's creating the Andes, that's a tectonic plate boundary.
17:43
SPEAKER_01: We kind of know, we know that it's there.
17:44
SPEAKER_01: We know which direction things are moving in.
17:47
SPEAKER_01: We still don't really have a great understanding of what the processes are that are driving those behaviors.
17:53
SPEAKER_01: We don't really understand how a tectonic plate can break.
17:57
SPEAKER_01: You have to break a rock from zero kilometers from at the surface all the way down to like 200 kilometers deep, and you have to break it all in one spot.
18:05
SPEAKER_01: We don't, we can't model that.
18:06
SPEAKER_01: No, you can't really, we don't really understand how that happens.
18:10
SPEAKER_01: So it's an astonishing thing, right?
18:11
SPEAKER_01: But it happens all over the place.
18:13
SPEAKER_01: We can see the the repercussions, we can see it actively happening.
18:17
SPEAKER_01: But that's what a tectonic plate is, right?
18:18
SPEAKER_01: Is we have, I don't know how many.
18:20
SPEAKER_01: There's probably what I don't know the number, dozens, I'm guessing 30 or something tectonic plates.
18:24
SPEAKER_00: It depends on where you divide the line.
18:26
SPEAKER_00: I mean, we have look, we have like you know, nine or ten major plates and then several smaller plates.
18:31
SPEAKER_00: You know, don't forget about Wanda Fuca.
18:33
SPEAKER_00: I love Wanda Fuca.
18:34
SPEAKER_01: The last little the little bit that's just hanging out still there.
18:36
SPEAKER_01: It's it's about to go down.
18:37
SPEAKER_00: But but I I do want to jump on something real quick, Jess.
18:40
SPEAKER_00: Like I think, I think what you said is is true that I I this has got to be the next major thing coming out of geology, is a firmer understanding of the interior of the earth.
18:54
SPEAKER_00: Right.
18:54
SPEAKER_00: You know, we we know a lot, and and we really learned a lot in the 19 late 1950s and 1960s with the testing of nuclear bomb.
19:04
SPEAKER_00: So we were able to strategically place seismographs and and we're able to measure you know the way that seismic waves are traveling through the earth because we knew exactly when, we knew exactly where these detonations were going to take place.
19:16
SPEAKER_00: So we really honed in on the interior structure of the earth.
19:19
SPEAKER_00: But before I retire, there's gonna be just this explosion of knowledge coming out about the way that convection happens in the asthenosphere.
19:31
SPEAKER_00: And I I just think it's the next big thing.
19:34
SPEAKER_00: So why does this matter?
19:35
SPEAKER_01: Why like why are we leading?
19:37
SPEAKER_01: Why why are we you know talking about this in like the second episode?
19:40
SPEAKER_00: That's easy for me.
19:41
SPEAKER_01: Okay.
19:42
SPEAKER_00: Uh this is the easiest question on the planet for me.
19:44
SPEAKER_00: I had a professor who was so gifted, and he would, but he was one of those rare treats you get in college where this guy he could just flat out teach.
19:53
SPEAKER_01: Yeah.
19:54
SPEAKER_00: And he he began uh his intro into plate tectonics talking about an earthquake that he had been in Alaska in 1964, and this was a major, it's a famous earthquake, and he was in it, he was studying glaciers, and his description of the violence of what happened and the horror of it all.
20:18
SPEAKER_00: My reaction was are you kidding me?
20:23
SPEAKER_00: Like um, that's that is so cool.
20:28
SPEAKER_00: I know you were scared, but man, do I want to feel that, right?
20:33
SPEAKER_00: Like, what kind of power is that?
20:35
SPEAKER_00: That's what I was thinking.
20:37
SPEAKER_01: I mean, it's so cool.
20:38
SPEAKER_01: Like, what you know, what a what a powerful thing to to have a you know a teacher uh who can who can hook you in that way um and really define your life in that sense.
20:46
SPEAKER_01: But uh I mean it's it's also about the the subject matter, right?
20:49
SPEAKER_01: It's also about this is important, and and it, you know, plate tectonics and and why why should your everyday person care about what the hell a tectonic plate is?
20:59
SPEAKER_01: Well, it's because it defines how our earth operates, right?
21:03
SPEAKER_01: It defines where volcanoes occur, where earthquakes occur.
21:06
SPEAKER_01: All these really important phenomena that matter for a lot of people's everyday lives um are fundamentally fair because plate tectonics operates on earth.
21:16
SPEAKER_01: Um, so I mean it's a beautiful story.
21:18
SPEAKER_01: Have you ever been in an earthquake?
21:21
SPEAKER_00: Uh yeah, it was um I'm embarrassed though.
21:24
SPEAKER_00: Uh I was in an earthquake.
21:26
SPEAKER_01: I mean, you should be more embarrassed than you are, but I'm embarrassed often, but that's okay.
21:30
SPEAKER_00: I gave I gave up on pride a long time ago.
21:33
SPEAKER_00: Uh um, but I was in a a smaller earthquake.
21:38
SPEAKER_00: I was in California and it was maybe a the five.
21:41
SPEAKER_00: Um uh I you know, to be honest with you, I thought it was the rumbling of a truck passing by.
21:47
SPEAKER_00: And uh then I ru I found out later that it was an earthquake.
21:51
SPEAKER_00: And can you imagine my disappointment?
21:52
SPEAKER_00: I'm like, what kind of geologist are you?
21:55
SPEAKER_00: You are pathetic.
21:56
SPEAKER_00: You are the worst.
21:57
SPEAKER_00: All right.
21:58
SPEAKER_00: So that yeah, you just
22:00
SPEAKER_01: You couldn't even experience it in the moment, right?
22:01
SPEAKER_01: You couldn't you couldn't be like, no, wow, that was an earthquake.
22:04
SPEAKER_01: How cool, right?
22:04
SPEAKER_01: You were like, ah, some stupid truck driving by.
22:07
SPEAKER_00: So you know my wife, right?
22:08
SPEAKER_00: And you know that that was relentless shit after that for what kind of geologist I am for not even reading.
22:14
SPEAKER_01: It's amazing that you can make a living being a geoscientist if you can't even identify an earthquake.
22:19
SPEAKER_00: Yeah, it is.
22:20
SPEAKER_00: It really is.
22:20
SPEAKER_00: The other thing is, too, is that you know, plate tectonics makes sense of everything that I love about this planet.
22:27
SPEAKER_01: Yeah.
22:27
SPEAKER_00: You know, you know, because this planet, without plate tectonics, what would it look like eventually?
22:32
SPEAKER_00: Give it time, right?
22:33
SPEAKER_00: Without tectonics, you have no force that lifts things up.
22:37
SPEAKER_00: You only have the force that wears things down.
22:39
SPEAKER_00: Right.
22:40
SPEAKER_00: And so, given enough time, this planet would be really flat and featureless.
22:48
SPEAKER_00: Uh, because then you just have weather and erosion and gravity.
22:51
SPEAKER_00: Yeah.
22:52
SPEAKER_00: And uh, I don't care to live here on that planet.
22:55
SPEAKER_01: It'd be it'd be it'd be a tough life.
22:56
SPEAKER_01: That's not my thing.
22:57
SPEAKER_01: It'd be tough life if there was no plate tectonics here.
22:59
SPEAKER_01: That's right.
23:00
SPEAKER_00: Yeah, yeah.
23:01
SPEAKER_01: That's right.
23:02
SPEAKER_01: That's right.
23:02
SPEAKER_00: So let me ask you.
23:03
SPEAKER_00: Yeah.
23:03
SPEAKER_00: Okay.
23:04
SPEAKER_00: What does plate tectonics mean to you?
23:06
SPEAKER_01: I think for me, you were that teacher who kind of conveyed this this sort of really beautiful picture of of the value of the earth sciences um any interesting aspects.
23:15
SPEAKER_01: But another added part of it was when what drives me a lot today in my research is that plate tectonics, it operates today.
23:23
SPEAKER_01: We can observe it, we can we can watch these plates move.
23:26
SPEAKER_01: You know, we can put GPS instruments on them and watch them move at a couple centimeters per year.
23:30
SPEAKER_01: We really do not understand when plate tectonics began on Earth.
23:34
SPEAKER_01: Um, so you can have many different what are called tectonic modes or or ways that a planet operates um in a tectonic sense.
23:43
SPEAKER_01: And and Earth operates with this plate tectonics.
23:46
SPEAKER_01: There are plates that move around and interact with each other.
23:48
SPEAKER_01: We don't know when that started.
23:49
SPEAKER_01: Uh, there's people, you know, very, very good, very high quality scientists out there, geoscientists who will argue that you know it only began about you know 800 million years ago or so.
24:00
SPEAKER_01: Um, there are people who would argue that as soon as the earth was formed, 4.5 something billion years ago, plate tectonics started.
24:08
SPEAKER_01: The fact of the matter is that we do not understand when plate tectonics began on Earth history.
24:13
SPEAKER_01: Was Earth a teenager when plate tectonics began?
24:15
SPEAKER_01: Was it a young adult?
24:17
SPEAKER_01: I mean, was it an 80-year-old?
24:19
SPEAKER_01: You know, we don't really know uh when plate tectonics began on Earth.
24:23
SPEAKER_01: And plate tectonics governs so yeah.
24:26
SPEAKER_01: This is the problem you're trying to solve with your research, correct?
24:31
SPEAKER_01: It's it's absolutely the probably the driving force because it matters for the history of our planet, it matters for how we perceive other planets in our solar system and in other solar systems as we begin to discover more and more of them.
24:44
SPEAKER_01: It also matters for the history of our planet, it matters for um recycling of water back into the mantle.
24:50
SPEAKER_01: It could be the reason why we have oceans on Earth.
24:53
SPEAKER_01: Um all the resources that we have to all the resources, it drives gold deposits, you know.
24:59
SPEAKER_01: Plate tectonics is fundamental.
25:01
SPEAKER_01: And it is why the earth looks the way it is, um, and why earth is unique and why actually there's life on earth.
25:09
SPEAKER_01: So I think you know, a good exercise that we should we should go through here is is why you know what would what would Earth look like without plate tectonics?
25:17
SPEAKER_01: And I think we have some pretty good examples of that when we look around the solar system.
25:20
SPEAKER_00: You know, I teach astronomy, high school astronomy.
25:25
SPEAKER_00: And you know, the biggest known volcano in the solar system is not on Earth.
25:32
SPEAKER_00: And you you'd think, oh well, that doesn't make sense.
25:36
SPEAKER_00: You know, we have this this active tectonic you know, planet.
25:40
SPEAKER_00: Why would why would uh Earth not have volcanoes?
25:44
SPEAKER_01: Plate tectonics creates mountains on Earth.
25:45
SPEAKER_01: So like you expect it does, it's what it does.
25:47
SPEAKER_01: It would create yeah, it wouldn't create mountains if you didn't have plate tectonics, right?
25:51
SPEAKER_01: But that's not the case, right?
25:53
SPEAKER_00: But Mars has a an enormous, like it do Mars has several volcanoes that dwarf anything on Earth, but the biggest one that we know of is Olympia is called Olympus Monds.
26:04
SPEAKER_00: It's 22 kilometers tall.
26:06
SPEAKER_01: Now this dwarfs anything on a on an Earth scale.
26:09
SPEAKER_01: That's from like the bottom of the mountain to the top of of the mountain.
26:13
SPEAKER_00: Yeah, it's 22 kilometers, which is 13.6 miles tall.
26:18
SPEAKER_01: Yeah, it's amazing.
26:19
SPEAKER_00: Now, for scale, Mount Everest is just under six miles above sea level to the top of it.
26:25
SPEAKER_00: Yeah, okay.
26:26
SPEAKER_00: Now that's not necessarily the height of the mountain itself, but that's the tallest point on Earth, right?
26:30
SPEAKER_00: Six miles.
26:31
SPEAKER_00: This volcano is 13.6 miles tall.
26:34
SPEAKER_00: Now you think, all right, well, why?
26:36
SPEAKER_00: Mars doesn't have plate tectonics, and which means the lithospheric plates don't move right on Mars.
26:44
SPEAKER_01: There's just one plate.
26:45
SPEAKER_00: And so if they have a hot spot, which we'll talk about later on, but this this this source of magma coming up, right?
26:53
SPEAKER_00: Imagine this.
26:53
SPEAKER_00: You have this source of magma coming up, but the plates don't move.
26:56
SPEAKER_00: So what you get then is just this center of volcanism, but the plate never moves, so the volcano just gets bigger and bigger and bigger and bigger over time, right?
27:06
SPEAKER_00: That's right.
27:07
SPEAKER_00: On Earth, does it that doesn't happen.
27:09
SPEAKER_00: You know, you think of Hawaii, Hawaii's a hotspot.
27:12
SPEAKER_00: Almost everybody knows Hawaii is a hot spot.
27:14
SPEAKER_00: But as that source of magma comes up, and and you get these eruptive centers, like for right now, the eruptive center is on the big island of Hawaii, Kilauea, you know, the the most active volcano on the planet.
27:27
SPEAKER_00: Uh, but the plate continues to move over top of this hot spot, of this source of magma.
27:34
SPEAKER_00: And so the volcanoes get to a certain height, and then they have moved past the hot spot, and then a new eruptive center shows up.
27:42
SPEAKER_01: Right.
27:42
SPEAKER_01: I mean, it's it's really one of the coolest things.
27:44
SPEAKER_01: I mean, Google Earth is so cool, right?
27:46
SPEAKER_01: To just play around with.
27:48
SPEAKER_01: If you are if you're listening to this and you're like having trouble picturing this, go to Google Earth, look at Hawaii, and look at like the Hawaii Emperor Seamount chain.
27:56
SPEAKER_01: I mean, and this is what we're talking about.
27:58
SPEAKER_01: It's it's basically a single point eruption that creates this chain of islands, which are now under, you know, we used to be islands which are now have been eroded down to just below sea level, but it's this volcanic eruption that because the plate has been moving over it, all that magma has been carried away, all that lava has been carried away from the source.
28:19
SPEAKER_01: And so on Mars, we don't get that.
28:22
SPEAKER_01: On Mars, all that magma is just piled up on top of each other.
28:25
SPEAKER_01: So it creates this Olympus Mons volcano, which is massive.
28:28
SPEAKER_01: I mean, it's it's just a giant.
28:30
SPEAKER_01: So the only reason that Hawaii is not, you know, five times the size of Everest, or whatever, whatever it is, three times the size of Everest is because of plate tectonics.
28:39
SPEAKER_01: I mean, it's so cool.
28:40
SPEAKER_01: What a cool comparison.
28:41
SPEAKER_01: It's amazing, right?
28:42
SPEAKER_01: Yeah.
28:44
SPEAKER_00: So I want to say this.
28:46
SPEAKER_00: I want to say this that you know, in geology, we can simplify things down to you know, we we can make it really simple, right?
28:55
SPEAKER_00: There are two forces in geology forces that lift things up and forces that wear things down.
29:01
SPEAKER_00: The force that lifts things up is called plate tectonics.
29:05
SPEAKER_00: The force that wears things down is called weather and erosion.
29:09
SPEAKER_00: Plate tectonics makes this planet awesome.
29:11
SPEAKER_00: Yeah.
29:11
SPEAKER_00: Flat out.
29:12
SPEAKER_00: There's no there's no denying.
29:14
SPEAKER_01: So, I mean, we were talking about hotspots, and and this is a really nice lead-in to what we're gonna talk about next, which is uh one of our, I would say, well one of mine certainly, and I think one of yours favorite hotspot locations to go visit, um, which is Yellowstone National Park.
29:40
SPEAKER_01: So that's all for this week.
29:42
SPEAKER_01: As usual, thank you for joining us, and stay tuned for our next episode coming up in two weeks, where we'll talk about Yellowstone National Park.
29:49
SPEAKER_01: Uh, again, we are really excited about this project, and as always, we're looking for your feedback and input.
29:55
SPEAKER_01: So please leave us any questions, topic ideas, or comments uh on any of our social medias.
30:00
SPEAKER_01: We are at Planet Geocast, and our email account is planetgeocast at gmail.com.
30:06
SPEAKER_01: Again, we'd love it if you'd like to subscribe to this podcast, and we'll chat with you soon.