Latest / PlanetGeo: The Geology Podcast / The Spartans Last Stand: Geology of the Hot Gates

Transcript

The Spartans Last Stand: Geology of the Hot Gates · PlanetGeo: The Geology Podcast

• 0:02
  SPEAKER_01: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
• 0:12
  SPEAKER_01: Chris, how are we doing today?
• 0:15
  SPEAKER_01: I'm doing great.
• 0:16
  SPEAKER_01: How are you doing?
• 0:17
  SPEAKER_01: I'm doing great, man.
• 0:19
  SPEAKER_01: I'm I'm actually really good.
• 0:20
  SPEAKER_01: We've uh we saw each other recently in the flesh, actually.
• 0:24
  SPEAKER_00: We did.
• 0:25
  SPEAKER_00: And yeah, it was uh it's been a busy uh well, let's just say a busy couple weeks for you guys, right?
• 0:30
  SPEAKER_01: Yeah, that's right.
• 0:31
  SPEAKER_01: Well, we got married, Tess and I, and actually we got married at least in part by you.
• 0:35
  SPEAKER_01: So that was really fun, really cool.
• 0:38
  SPEAKER_01: You had some funny and some you know moderately wise things to say about it.
• 0:44
  SPEAKER_01: Moderately wise, yeah.
• 0:45
  SPEAKER_01: No, it was great.
• 0:46
  SPEAKER_01: It was really fun.
• 0:47
  SPEAKER_01: So that was that was really fun, really nice uh time in Denver, and uh we're happy to be back recording here, right?
• 0:53
  SPEAKER_00: Yeah, yeah, that was uh it was it was a fun time for us too.
• 0:56
  SPEAKER_00: Jenny and I went uh out to Denver.
• 0:59
  SPEAKER_00: Um I it was really I had to stop saying something.
• 1:02
  SPEAKER_00: I didn't realize what I was saying, you know.
• 1:03
  SPEAKER_00: People would be like, uh I where are you going?
• 1:05
  SPEAKER_00: I'm like, well, I have to go out to Denver.
• 1:07
  SPEAKER_00: Why?
• 1:07
  SPEAKER_00: Well, I'm marrying Jesse.
• 1:09
  SPEAKER_00: And then people would look at me like, what?
• 1:12
  SPEAKER_00: You've already got a wife.
• 1:13
  SPEAKER_00: What do you you know you can't do that?
• 1:14
  SPEAKER_00: And I'm like, no, no, no, no, no, no.
• 1:16
  SPEAKER_00: I'm officiating the wedding, you know?
• 1:17
  SPEAKER_01: Officiated, yes, that's right.
• 1:18
  SPEAKER_00: So you don't know how many times I said that.
• 1:21
  SPEAKER_00: Like, yeah, Marion Jesse.
• 1:23
  SPEAKER_01: I thought I would have thought you'd be proud to wear that badge, Chris, but I guess not.
• 1:28
  SPEAKER_01: You guys, yeah.
• 1:29
  SPEAKER_00: People were like, you took it to a whole nother level now.
• 1:32
  SPEAKER_01: Oh first, the podcast got real.
• 1:34
  SPEAKER_01: Yeah, that's right.
• 1:35
  SPEAKER_01: That's right.
• 1:36
  SPEAKER_01: Well, so anyway, so that was a that was a fun time.
• 1:39
  SPEAKER_01: But now we're back, you know, thinking about geoscience stuff.
• 1:42
  SPEAKER_01: I mean, we spent, I don't know, a week thinking about a wedding and then back to geology, right?
• 1:47
  SPEAKER_01: Straight back into it.
• 1:48
  SPEAKER_00: Yeah.
• 1:48
  SPEAKER_00: I think you probably thought a little bit more than a week about the wedding, but yes, that's true.
• 1:54
  SPEAKER_00: You were a funny guy.
• 1:55
  SPEAKER_00: You were uptight, you know that?
• 1:58
  SPEAKER_01: Oh, yeah.
• 1:58
  SPEAKER_01: I was I was uh I was a little bit nervous.
• 2:01
  SPEAKER_01: I don't I don't get uh worked up too much, but sometimes you don't, you pretty low-key, but that's no idea.
• 2:08
  SPEAKER_01: Okay, well, enough about that.
• 2:10
  SPEAKER_01: Um so what are we talking about today?
• 2:13
  SPEAKER_01: Well, first of all, first off, let's maybe do some introductions.
• 2:15
  SPEAKER_01: So you are Chris Bullheis, you are my former high school teacher.
• 2:19
  SPEAKER_01: You teach in Hudsonville, Michigan, southwest side of the state, and you're a nationally recognized earth science teacher.
• 2:26
  SPEAKER_01: You taught me geology and ninth grade earth science and a couple field courses, and you know, we've known each other since I was in high school, probably 15-ish years ago.
• 2:35
  SPEAKER_00: Yeah, going on 20, actually.
• 2:37
  SPEAKER_00: I had to think about that when I was putting the script together for the wedding.
• 2:40
  SPEAKER_00: So 20 years.
• 2:41
  SPEAKER_01: Yikes.
• 2:42
  SPEAKER_01: Okay, well, anyway, let's move on from that.
• 2:45
  SPEAKER_00: Yeah.
• 2:45
  SPEAKER_00: Your Dr.
• 2:46
  SPEAKER_00: Jesse Rymick, one of my former students, went on to get his PhD in geology and is now a professor of geoscience at Penn State University.
• 2:55
  SPEAKER_01: That's right.
• 2:55
  SPEAKER_01: We are.
• 2:56
  SPEAKER_01: And okay, this is Planet Geo.
• 2:58
  SPEAKER_01: We talk about all things geoscience, super fun stuff.
• 3:02
  SPEAKER_01: And today we have something really cool and the kind of lead-in to a series that we envision doing here.
• 3:08
  SPEAKER_01: That is how geoscience has influenced historical events, right?
• 3:12
  SPEAKER_00: Right.
• 3:13
  SPEAKER_00: Yeah, when you first uh hit me with this idea, I I had no idea what the heck you were talking about.
• 3:19
  SPEAKER_00: So uh here's what we're doing today.
• 3:21
  SPEAKER_00: We're gonna talk about the movie 300, uh, which I think was a 2007 movie.
• 3:27
  SPEAKER_00: Um and we're gonna talk about how geology played such a significant role in that famous historical event.
• 3:33
  SPEAKER_01: Yeah, that's right.
• 3:34
  SPEAKER_01: And so this is the Spartans, right?
• 3:36
  SPEAKER_01: This is the Spartans taking a stand against the Persians.
• 3:39
  SPEAKER_01: This is the movie 300, as you mentioned, you know, with I think it was Gerard Butler who was playing the main one and a whole bunch of other, you know, sort of uh alpha male actors.
• 3:49
  SPEAKER_00: Um this is like I'll tell you, I just watched the movie again, okay, this weekend.
• 3:53
  SPEAKER_00: Oh, you rewatched it.
• 3:54
  SPEAKER_00: Oh, awesome.
• 3:55
  SPEAKER_00: I rewatched it.
• 3:56
  SPEAKER_00: Okay, and I've never seen so many six-pack abs assembled in one location.
• 4:04
  SPEAKER_00: It was um not a really like uplifting, you know, feel good about yourself kind of thing to watch.
• 4:11
  SPEAKER_00: Oh, definitely.
• 4:12
  SPEAKER_01: I remember I think I had just started playing college basketball when this movie came out, and like the 300 workout, you know, was all over the internet.
• 4:19
  SPEAKER_01: Everybody was trying to do the 300 workout to get totally ripped.
• 4:22
  SPEAKER_01: Uh, but yeah, this movie they were.
• 4:24
  SPEAKER_01: This movie, I I loved this movie, you know, in part because it's like super fun and just like, you know, a rah-rah war movie a little bit, right?
• 4:32
  SPEAKER_01: But I also really liked it because it was made to look legendary, and there's this really amazing legend of like 300 Spartans taking a stand against, you know, 50,000 or even a million Persians.
• 4:44
  SPEAKER_01: Like who knows how many there were.
• 4:46
  SPEAKER_01: And so this is kind of what we're talking about.
• 4:47
  SPEAKER_01: And so in this episode, we're gonna cover, you know, basically why did the Spartans stand where they stood?
• 4:54
  SPEAKER_01: They stood at this place called the Hot Gates.
• 4:56
  SPEAKER_00: So here's what we're gonna do in this episode, Jesse.
• 4:58
  SPEAKER_00: Really, we're gonna hit four things, okay?
• 5:00
  SPEAKER_00: We're gonna begin with geoscience and how it impacts history in really dramatic ways.
• 5:05
  SPEAKER_00: Um, and we're gonna just start like hitting on these geological aspects and and how history kind of well was shaped by these.
• 5:13
  SPEAKER_01: Yeah, totally.
• 5:14
  SPEAKER_01: I mean, we're gonna have to get to Gettysburg eventually, and like, you know, why cities are established.
• 5:18
  SPEAKER_01: I mean, tons of cool stuff.
• 5:20
  SPEAKER_00: Yeah, so then we're gonna the second thing we're gonna do is talk about this.
• 5:23
  SPEAKER_00: It was a famous like phrase in the in the movie, the hot gates or thermopylae, which means hot gates.
• 5:28
  SPEAKER_00: We're gonna talk about what these are, what formed the gates, and so on.
• 5:33
  SPEAKER_00: And then thirdly, we're gonna talk about the hot part of the hot gates.
• 5:37
  SPEAKER_00: Really, we need to talk about you know, the hot gates, what the hot part of it, and then what the gates are, you know, because it's like it's such a cool story.
• 5:45
  SPEAKER_00: And then lastly, we're gonna talk about the hot gates.
• 5:49
  SPEAKER_00: The gate part of it doesn't really exist anymore, and what's changed then in the well, how long is it, Jesse?
• 5:56
  SPEAKER_00: Like 2,500 years ago.
• 5:58
  SPEAKER_01: Yeah.
• 5:59
  SPEAKER_01: So it's just the dramatic way the planet is kind of always changing, right?
• 6:03
  SPEAKER_01: It's such a I mean, this is such a cool story, and it's such cool geoscience uh in the region.
• 6:07
  SPEAKER_01: So let's get in, let's just give you a little bit of backstory.
• 6:10
  SPEAKER_01: I mean, you go watch the movie if you want to watch the movie.
• 6:13
  SPEAKER_01: If you like podcasts, you're listening to a podcast, but if you like podcasts and if you want to hear like 30 straight hours on Persia and the Spartans and kind of the the time period, go listen to Dan Carlin's King of Kings series.
• 6:29
  SPEAKER_01: It's I love Dan Carlin and I think it's amazing, but he talks about all this stuff.
• 6:33
  SPEAKER_01: Here's a a short version of it.
• 6:34
  SPEAKER_01: Basically, the Persian Empire was massive and was really interested in conquering Greece.
• 6:40
  SPEAKER_01: It had conquered you know most of the rest of the mapped world at that stage, and it was really interested in in conquering Greece.
• 6:47
  SPEAKER_01: There were several major battles uh in during this sort of several year period when this happened, but we're focusing on one particular battle, which is where so the legend goes, and I think there seems to be some good historical evidence to back this up, that there was about 300 Spartan warriors plus some of their friends from neighboring Greek cities that stood their ground against at least 50,000 and maybe up to a million.
• 7:13
  SPEAKER_01: I mean, history is a very important thing.
• 7:14
  SPEAKER_00: Yeah, the numbers here are wildly uh depends on what you read.
• 7:18
  SPEAKER_00: Um, it goes from 50,000 Persians up to almost a million Persians.
• 7:22
  SPEAKER_01: So yeah, so it's a it's a part of history that's a little it's a little bit sketchy uh to figure out the numbers.
• 7:29
  SPEAKER_01: But so that they, you know, these 300 Spartans they managed to hold their ground for a few days, which is incredible.
• 7:35
  SPEAKER_01: They ended up being defeated, but it's an incredible phenomenon, and they use geology, the local geology, really to their advantage.
• 7:43
  SPEAKER_01: So they took a stand in this area called the Hot Gates, which is a series of three narrow passes between a cliff face and a gulf of Aegean Sea.
• 7:52
  SPEAKER_01: And in the movie, you can kind of visualize this, right, Chris?
• 7:55
  SPEAKER_01: Like you just watched it recently, right?
• 7:57
  SPEAKER_00: So I did.
• 7:58
  SPEAKER_00: So yeah, basically, the way it was portrayed in the movie most of the time, not all the time, but most of the time, is the gates part of it was this narrow stretch of land with steep cliffs on one side, on the usually it was on the left side in the in the scenes in the movie, and then an ocean on the right with just this narrow stretch of land that went in between.
• 8:19
  SPEAKER_01: Right.
• 8:20
  SPEAKER_01: So basically, you know, they went there because the Persians weren't great at traveling by sea, and so they had to cross this narrow strip of land, which is the gate part, right?
• 8:29
  SPEAKER_01: So we got to get to like why are those cliffs there, and why is this like sort of straight drop-off to the sea there, right?
• 8:35
  SPEAKER_01: That that's kind of the key part to the gates part of the hot gates.
• 8:39
  SPEAKER_00: Yeah, and it is a really, really steep drop-off, first of all.
• 8:43
  SPEAKER_00: You can Google image this uh and just you get a feel for how steep this really is.
• 8:47
  SPEAKER_00: These are very steep mountains.
• 8:49
  SPEAKER_01: So let me just interject let me just interject here and say that you know we're referring to hot gates.
• 8:53
  SPEAKER_01: In the Greek it's called thermopylae, and so we'll kind of use those interchangeably because thermopylae is hot gates, or I forget what the other thermal means heat, and uh I don't know.
• 9:03
  SPEAKER_00: I don't know.
• 9:04
  SPEAKER_00: I kind of love but I don't know what opaly means.
• 9:07
  SPEAKER_01: Yeah, something something along those lines.
• 9:09
  SPEAKER_01: There's another term for it.
• 9:10
  SPEAKER_01: I can't remember what.
• 9:11
  SPEAKER_01: Oh, gates of fire, that's the other one.
• 9:13
  SPEAKER_01: So hot gates are gates of fire, so kind of interchangeably, but that's thermopylae, and there's now a city of thermopylae uh in the region where there used to be the hot gates, anyway.
• 9:22
  SPEAKER_00: Right.
• 9:22
  SPEAKER_00: So, yeah, let's talk about why the you have such a steep cliff there, okay?
• 9:28
  SPEAKER_00: And this is something that we've already actually hit on in earlier episodes when we talked about the Tetons.
• 9:34
  SPEAKER_00: It's very similar to the Tetons.
• 9:36
  SPEAKER_01: And if you recall, yeah, we talked about this with the Tetons, and so go back and listen to our Grand Teton National Park episode because we talk about the specific type of fault here, and and so go back and listen to that if you're interested, or if you're traveling to the Tetons this summer.
• 9:49
  SPEAKER_00: Yeah, which by the way, go.
• 9:50
  SPEAKER_00: So basically, mountains like this, where you have really steep, grand, tall, big mountains and no foothills, it's just it goes into broad, flat plain, you know, it's very abrupt.
• 10:03
  SPEAKER_00: And that you get this in geology due to a force that we call tension.
• 10:06
  SPEAKER_00: So, Jesse, what's tension?
• 10:08
  SPEAKER_00: What's that mean?
• 10:08
  SPEAKER_01: Tension is stretching.
• 10:10
  SPEAKER_01: Think of it as like tension between your friendship.
• 10:13
  SPEAKER_01: If you have a tense friendship, you know, you're feeling some like sort of spreading apart.
• 10:17
  SPEAKER_01: You're feeling some sort of distance between you.
• 10:19
  SPEAKER_01: That's tension, is spreading apart.
• 10:21
  SPEAKER_01: So the area underneath this is being.
• 10:24
  SPEAKER_01: I I've been feeling a lot of tension with you recently, by the way, after I'm really I I think you didn't, you know, you were kind of being a little bit of a dick.
• 10:30
  SPEAKER_01: So, you know, I'm feeling a little bit tension with you.
• 10:33
  SPEAKER_00: You know, like it's I don't even know what to say to that.
• 10:37
  SPEAKER_00: I I have I don't even know how to come back to that.
• 10:39
  SPEAKER_00: It's not often where I don't have something to say back to you, but it's that is so outside of the realm of even reality that I don't like You just don't even detect it.
• 10:48
  SPEAKER_01: You're never paying attention to my emotions, you're never listening to me.
• 10:51
  SPEAKER_01: Unbelievable.
• 10:52
  SPEAKER_01: Wow.
• 10:52
  SPEAKER_00: I take back all of the good things that I said about you.
• 10:56
  SPEAKER_00: I I leave them in place for tests, but you take it all back.
• 11:00
  SPEAKER_01: All right, so we'll get over our attention.
• 11:03
  SPEAKER_00: Yeah, here's what we got going on, though.
• 11:05
  SPEAKER_00: The the rocks underneath are being pulled, and but it doesn't just stretch like taffy, so it pulls, pulls, pulls, pulls, and then you have these seismic disasters.
• 11:14
  SPEAKER_00: And those are those earthquakes, that's what those are.
• 11:18
  SPEAKER_00: Um, what happens then is the mountains are thrust up and the flat prairie is dropped down.
• 11:26
  SPEAKER_00: That's exactly why you know in the Grand Tetons, you have the Tetons themselves, and you have what's called Jackson Hole.
• 11:32
  SPEAKER_00: Jackson Hole is that flat land that sinks every time there's a seismic disaster.
• 11:37
  SPEAKER_00: And that's what's going on here.
• 11:39
  SPEAKER_00: It's just being pulled, and every few hundred years, uh you know, even thousands of years, you'll have this massive earthquake where you know displacement happens very fast and very violently.
• 11:52
  SPEAKER_01: And so that displacement, I mean, you're you're referring to so basically, you know, in the regards to the hot gates here, in the movie, we're imagining these swinging doors, right?
• 12:01
  SPEAKER_01: Where the left side, the mountains are being pushed up, and on the right side where the the ocean is, that's basically the prairies compared to the Tetons.
• 12:10
  SPEAKER_01: That's the ocean is there because that block of land is being swung downward into the earth a little bit.
• 12:15
  SPEAKER_00: They're like oppositely hinged saloon doors.
• 12:18
  SPEAKER_00: Ah, good analogy.
• 12:20
  SPEAKER_00: You push one side open and the other side it it swings the other way, and that's what happens.
• 12:25
  SPEAKER_00: So the mountains swing up and the ground swings down the other direction.
• 12:31
  SPEAKER_00: It's really beautiful, actually.
• 12:33
  SPEAKER_00: If you like look at thermopylae and you Google image this, it's there's I love mountains like this because there isn't any introduction.
• 12:41
  SPEAKER_00: There's no foothills, it's just massive mountains that appear to come out of nowhere.
• 12:46
  SPEAKER_01: Yeah.
• 12:46
  SPEAKER_01: And in this case, they're filled with uh with water in the valleys, which is even more beautiful.
• 12:51
  SPEAKER_01: All right, so we've got these normal faults.
• 12:54
  SPEAKER_01: I mean, you described it as these saloon doors, this really perfect analogy.
• 12:58
  SPEAKER_01: And these are, again, caused by extension.
• 13:00
  SPEAKER_01: So the region is stretching apart, but this is kind of weird here.
• 13:04
  SPEAKER_01: I mean, if you've thought about this region or you pay attention to the news a little bit, you know that Italy and Greece, they have a lot of volcanoes, and these are subduction zone volcanoes, which subduction zones are when two plates come together and one of them thrusts beneath it and subducts.
• 13:19
  SPEAKER_01: So these are like kind of collisional or compressional environments, yet there's this tensional stress over.
• 13:26
  SPEAKER_00: It seems really counterintuitive.
• 13:28
  SPEAKER_00: We have two things going on at the same time in very similar geographic areas, right?
• 13:34
  SPEAKER_00: We have compression, which causes subduction zones and the volcanic activity and the earthquakes that you get associated with that, and we also have nearby tension.
• 13:42
  SPEAKER_00: So, how how in the world can you get them both going on at the same time in the same region?
• 13:50
  SPEAKER_00: That's right.
• 13:50
  SPEAKER_01: And this is a little bit complicated, and we're gonna try and get there.
• 13:53
  SPEAKER_01: It's hard to visualize, right?
• 13:54
  SPEAKER_01: But we're gonna get there, right, Chris?
• 13:56
  SPEAKER_01: All right, so why don't you lead us off?
• 13:57
  SPEAKER_01: What do we got going on?
• 13:58
  SPEAKER_00: So it's something that is it's called back arc spreading.
• 14:02
  SPEAKER_01: Yeah, so there's a good analogy here.
• 14:03
  SPEAKER_01: That is think of uh, you know, you're hanging out in a pool, it's you know, we're approaching summer, so let's say you're sitting on your pool listening to Planet Geo.
• 14:11
  SPEAKER_01: You got one of those silly plastic floating mattresses, right?
• 14:15
  SPEAKER_01: So take one of those and push it up against another one.
• 14:18
  SPEAKER_01: And one of them's really thick, one of them is a little bit thinner.
• 14:20
  SPEAKER_01: The thinner one's gonna kind of slide under the thicker one, right?
• 14:24
  SPEAKER_01: Chris, you with me so far?
• 14:26
  SPEAKER_00: I thought you said you were doing a good analogy here.
• 14:28
  SPEAKER_00: Okay, well, well, let's let's see where it goes.
• 14:31
  SPEAKER_01: Let's see where it goes.
• 14:32
  SPEAKER_01: You know, we're kind of winging it.
• 14:33
  SPEAKER_01: Let's see where it goes.
• 14:33
  SPEAKER_00: Alright, take me there.
• 14:34
  SPEAKER_00: Let's go.
• 14:35
  SPEAKER_00: Don't ask me for help though.
• 14:36
  SPEAKER_00: I don't even know where you're going with this.
• 14:38
  SPEAKER_01: Okay, all right.
• 14:38
  SPEAKER_01: Well, I'll get there.
• 14:39
  SPEAKER_01: So we're gonna take the two matches, we're gonna the floating plastic mattresses, air mattresses, we're gonna shove them together.
• 14:46
  SPEAKER_01: The thicker one is gonna like float above the other one.
• 14:50
  SPEAKER_01: This the thinner one's gonna sort of subduct underneath of it.
• 14:53
  SPEAKER_01: But let's say you like pop the thinner one.
• 14:55
  SPEAKER_01: That thinner one now is just deflated and it's just plastic.
• 14:58
  SPEAKER_01: That plastic will start to sink.
• 15:00
  SPEAKER_01: Well, let's say it's dense plastic, so it starts to sink.
• 15:03
  SPEAKER_01: This is where my random off-the-guff analogy is breaking apart.
• 15:06
  SPEAKER_01: But let me finish.
• 15:07
  SPEAKER_01: Let me finish.
• 15:07
  SPEAKER_00: Is that oh, this is where it's breaking apart?
• 15:09
  SPEAKER_00: Yeah, yeah.
• 15:10
  SPEAKER_00: It wasn't breaking apart earlier, but thanks for clearing up.
• 15:13
  SPEAKER_01: Hang with me.
• 15:14
  SPEAKER_01: Hang with me.
• 15:15
  SPEAKER_01: So the this plastic starts to sink.
• 15:17
  SPEAKER_01: And where you started pushing the mattresses together, that one's gonna sink and it's gonna pull down the whole rest of that thin mattress.
• 15:25
  SPEAKER_01: And so that whole mattress kind of gets pulled down, which means that it generates space between the thick mattress and the thin mattress, which is what we call this sort of rollback.
• 15:36
  SPEAKER_01: And the thick mattress is going to extend.
• 15:39
  SPEAKER_01: It was compressed together, and now it's gonna relax a little bit, and that's the tension right there.
• 15:45
  SPEAKER_01: That's the relaxation as this dense deflated mattress starts to sink and pull the part of pull it down.
• 15:53
  SPEAKER_01: Can can I interject here, like well, I've I can tell you've been waiting to for the last minute and a half.
• 15:59
  SPEAKER_01: So please go ahead.
• 16:00
  SPEAKER_01: Minute and a half.
• 16:02
  SPEAKER_01: Quit making faces at me and interject.
• 16:04
  SPEAKER_00: Oh wow.
• 16:05
  SPEAKER_00: So look, I'm gonna stick with what you were laying down.
• 16:09
  SPEAKER_00: All right.
• 16:09
  SPEAKER_00: The mattresses.
• 16:10
  SPEAKER_00: So we have two mattresses.
• 16:12
  SPEAKER_00: One of them is thin, and the key is that it's also dense.
• 16:15
  SPEAKER_00: The other one is much thicker, but it's fluffier.
• 16:17
  SPEAKER_00: It's not as dense.
• 16:19
  SPEAKER_00: Okay.
• 16:19
  SPEAKER_00: So if you push the thick, fluffy one and I push the thin, denser one against each other, the thin, dense one is gonna slide underneath the thick, fluffy one.
• 16:31
  SPEAKER_00: Okay, and that's gonna start what we call in in geology, we call that subduction, just plate tectonics 101.
• 16:38
  SPEAKER_00: Okay.
• 16:38
  SPEAKER_00: Now, in reality, that plate is gonna dive at an angle.
• 16:42
  SPEAKER_00: It's gonna dive down at, let's say, oh, a 45 degree angle or whatever angle you want to put to it, right?
• 16:48
  SPEAKER_00: But what happens is that subducting thin, dense plate or mattress, the faster it subducts, the more it's gonna pull and kind of curl that overriding mattress down with it.
• 17:05
  SPEAKER_00: And that's gonna move the deep sea trench.
• 17:08
  SPEAKER_00: And it's gonna move it, what they call that rollback, and that's gonna move it towards the overriding plate.
• 17:14
  SPEAKER_00: So we have this, you know, we have these, these are the deepest areas on the planet, Jesse, like the Tonga trench, the Mariana trench.
• 17:20
  SPEAKER_00: You could take the Himalayas and slice them off and fit them upside down in these trenches.
• 17:25
  SPEAKER_00: I mean, so the deepest places on the planet are deeper than the tallest places are tall.
• 17:31
  SPEAKER_00: That trench is gonna move.
• 17:33
  SPEAKER_00: And so that overriding fluffy mattress is being pulled.
• 17:39
  SPEAKER_00: And so the rest of the plate behind it that's being pulled and stretched just to keep up.
• 17:47
  SPEAKER_01: Okay, well, I think that's kind of basically what I said, but you maybe you said it in a little bit better of a way.
• 17:53
  SPEAKER_01: I'll give you that.
• 17:53
  SPEAKER_01: I'll give you that.
• 17:54
  SPEAKER_00: I I don't know.
• 17:55
  SPEAKER_01: It is a complicated So here's so here's the thing: it's governed by these mineral reactions that occur in this subducting plate in this thinner, more dense mattress.
• 18:07
  SPEAKER_01: Once that mattress gets to a certain depth, there's a series of reactions that occur that make that thing really dense.
• 18:13
  SPEAKER_01: It's like a weight on the end of your fishing line.
• 18:15
  SPEAKER_01: If you cast your fishing line out, that weight hits and it immediately sinks down.
• 18:19
  SPEAKER_01: And what does it do?
• 18:20
  SPEAKER_01: It pulls that line that is floating, it pulls it down.
• 18:24
  SPEAKER_01: So that's what's going on.
• 18:25
  SPEAKER_01: It's a it's a reaction that occurs at depth and it pulls this thing down, which pulls your line down into the water, which means that anything that was pushing against that now has this relaxing of forces in this tension.
• 18:37
  SPEAKER_01: It gets pulled apart.
• 18:38
  SPEAKER_01: So this is kind of what's going on.
• 18:40
  SPEAKER_01: It's a difficult thing to visualize, but this is how you get compression and tension in the same region, relatively nearby one another.
• 18:49
  SPEAKER_01: For instance, on the west side of Greece and Albania, where we have a subduction zone and subduction volcanism compared to the east side of Greece, where the hot gates exist because of this tensional normal faulting.
• 19:00
  SPEAKER_00: Right.
• 19:00
  SPEAKER_00: So this is in geology, this is called the back arc spreading.
• 19:04
  SPEAKER_00: Okay.
• 19:05
  SPEAKER_00: The arc itself is the volcanic arc that is created by the subduction zone.
• 19:12
  SPEAKER_00: Okay.
• 19:12
  SPEAKER_00: The back arc spreading is further away from the subduction zone, uh, from that plate that's being pulled to keep up with the subducting slab.
• 19:23
  SPEAKER_00: So the faster it subducts and the deeper it subducts, the more this back arc spreading becomes prominent.
• 19:29
  SPEAKER_00: So it may seem counterintuitive, but it's still a pretty common phenomenon.
• 19:35
  SPEAKER_01: Yes, it occurs very frequently.
• 19:38
  SPEAKER_01: And I think before we move on, uh we need to highlight that there are other ways and other mechanisms to create tensional forces in a region, and and some of them have been suggested for this particular region of the hot gates, but they are complicated and perhaps less um serious of competitors for the prevailing model.
• 19:58
  SPEAKER_00: So well, and every every region is a little bit different, and so some of these other mechanisms might apply to very specific tectonic localities.
• 20:07
  SPEAKER_01: That's right, that's right.
• 20:08
  SPEAKER_01: But in general, back arc basins, these are pretty common features on Earth, and it might be applied here as well.
• 20:13
  SPEAKER_00: So can we just real quick summarize this up, right?
• 20:17
  SPEAKER_00: We have we have subduction going on there in that in that region.
• 20:21
  SPEAKER_00: Um, but the the mountains and the hot gates, they weren't formed directly by the subduction, they were formed more as a result of this back arc spreading, where the subduction further away was happening quite fast, causing the overriding continental plate to kind of be pulled and tugged.
• 20:41
  SPEAKER_00: And that's where the spreading takes place that formed the mountains that formed the gate part.
• 20:47
  SPEAKER_00: And that's what these 300 Spartans used.
• 20:50
  SPEAKER_00: They used geology to hold off a lot of Persians for a long time.
• 20:54
  SPEAKER_01: Yeah, great summary, Chris.
• 20:55
  SPEAKER_01: That was great.
• 20:56
  SPEAKER_01: I mean, uh, you know, your analogy was better than mine.
• 20:58
  SPEAKER_01: That was a really good summary.
• 21:00
  SPEAKER_01: Okay, fine.
• 21:01
  SPEAKER_01: You're doing really well so far today.
• 21:02
  SPEAKER_01: I'll give you a little bit of credit.
• 21:04
  SPEAKER_00: Hey, thanks for saying I did well.
• 21:07
  SPEAKER_00: That's that's awesome.
• 21:08
  SPEAKER_00: Yeah, it warms my heart right there.
• 21:10
  SPEAKER_00: Yeah, for sure.
• 21:12
  SPEAKER_00: That's right, that's right.
• 21:13
  SPEAKER_01: You could you could go home happy.
• 21:14
  SPEAKER_00: Feeling all warm and fuzzy inside.
• 21:16
  SPEAKER_00: All right, Jesse.
• 21:17
  SPEAKER_00: So we've covered the gates.
• 21:19
  SPEAKER_00: All right, you know what formed the gates.
• 21:22
  SPEAKER_00: Now, what about the hot part?
• 21:24
  SPEAKER_01: Yeah, so the hot is really very intimately related to the gates part because anytime you have the crust breaking apart because of these tensional forces, you have a lot of water and fluids circulating down into the earth because there's these big fractures in the earth.
• 21:40
  SPEAKER_01: So there's a always a lot of like hydro what we call hydrothermal or hot water features because groundwater is seeping into the ground and it's getting heated up and then it's become coming back up to the surface.
• 21:52
  SPEAKER_00: So, I mean, when you have a subduction zone, you have magma rising up closer to the surface of the earth, shallow into in the crust.
• 22:00
  SPEAKER_00: That magma then is providing the heat for this circulating water that gets down there from the cracks created by all these faults that you're talking about.
• 22:09
  SPEAKER_01: And so all this heat, all this water, you know, comes out in hot springs, it comes out in hydrothermal vents.
• 22:16
  SPEAKER_01: I mean, again, very similar to Yellowstone.
• 22:18
  SPEAKER_01: We have an episode on Yellowstone as well, where there's a lot of magma at shallow levels, which heats up the water and generates all these amazing hydrothermal features.
• 22:26
  SPEAKER_01: This is adding the hot into the hot gates part of this name.
• 22:29
  SPEAKER_01: And interestingly enough, in the movie, you know, the King Leonidas, the Spartan King, has to go like see this oracle, this Oracle of Delphi, which is somebody who probably actually existed, or a series of people who had this position.
• 22:42
  SPEAKER_00: Um, and there was a movie, it was a horrifying oracle, by the way.
• 22:46
  SPEAKER_01: Yes, very, very horrifying that you know took advantage of young women and all this kind of stuff.
• 22:51
  SPEAKER_01: Not very, yes.
• 22:52
  SPEAKER_01: Yeah, yeah, not great.
• 22:53
  SPEAKER_01: But basically, they the thought here is that you know, Leonidas needs to go get approval for his war with Xerxes, which he does not get, which is why he only took 300 dudes to go defend the hot gates with him.
• 23:05
  SPEAKER_01: But basically the idea is that this oracle might have been hallucinating on CO2, methane, or even ethylene that was escaping from the hydrothermal waters in the region of Delphi, which is very similar to the hot gates.
• 23:18
  SPEAKER_01: So this is one, you know, sort of theory.
• 23:20
  SPEAKER_01: Who knows if it's true, but it's kind of a good theory.
• 23:23
  SPEAKER_01: It's one of those theories that's fun to think about.
• 23:26
  SPEAKER_00: It is.
• 23:26
  SPEAKER_00: So, question though, and I don't know the answer to this.
• 23:29
  SPEAKER_00: Were the hot springs the kind that you could soak in, or were these like too hot and too acidic?
• 23:35
  SPEAKER_00: Do you think?
• 23:35
  SPEAKER_01: It's a good question.
• 23:36
  SPEAKER_01: I don't really know.
• 23:37
  SPEAKER_01: I don't know in that region if there are you know really hot springs that were used for like health purposes in that way, or if they were a bit more dangerous.
• 23:44
  SPEAKER_01: I don't really know.
• 23:45
  SPEAKER_01: It's a good question.
• 23:46
  SPEAKER_01: We'll have to look that one up.
• 23:47
  SPEAKER_00: Well, hey, let's finish this off because we have to talk about then you know, the the hot part of it is still there.
• 23:53
  SPEAKER_00: There are still hot springs at the base of the mountains there, but the gates don't exist anymore.
• 23:58
  SPEAKER_00: And the gate is just simply this really narrow passageway that they had to funnel all these Persians through, and so they couldn't take advantage of their numbers, right?
• 24:08
  SPEAKER_00: That's what the the 300 Spartans were capitalizing on.
• 24:11
  SPEAKER_01: That's right.
• 24:12
  SPEAKER_00: So, what happened to the gates?
• 24:13
  SPEAKER_00: Why are the gates not there?
• 24:15
  SPEAKER_01: Yeah, so the mountains are still there, as you said, but the ocean has retreated, or the ocean hasn't really retreated, but the ocean has retreated away from the mountains at least.
• 24:25
  SPEAKER_00: The shoreline has regressed, yeah.
• 24:27
  SPEAKER_01: The shoreline has regressed, that's right.
• 24:29
  SPEAKER_01: Because it's not actually ocean level dropping, that's not what's happening on our planet at the moment, but it's dropping in this region relative to where it used to be, and that's actually because the ground has been lifted up.
• 24:44
  SPEAKER_01: So in this region, in the Gulf of Malia, this is fed by a river called the I'm probably gonna pronounce this wrong.
• 24:51
  SPEAKER_01: So if you're Greek, forgive me.
• 24:52
  SPEAKER_00: You want me to go ahead and jump on it?
• 24:53
  SPEAKER_00: I think it's called the Spercius.
• 24:55
  SPEAKER_01: Okay, the Sperquius River.
• 24:56
  SPEAKER_01: All right, well, that saves me from mispronouncing it.
• 24:58
  SPEAKER_01: So the Sperquius River feeds into the Gulf here, and with this river comes sediment, comes sand and gravel and everything else that a river carries.
• 25:08
  SPEAKER_01: In that river, over the last 2,500 years since the the Spartans stood in the hot gates, that river has been bringing sediment into this region, and it's filled up that gulf such that it's pushed sea level back from the hot gates in Thermopylae.
• 25:26
  SPEAKER_00: This is actually kind of a well a common phenomenon, right?
• 25:30
  SPEAKER_00: Um basically what we have going on is the river is dumping sediment off too fast, the ground can't sink, or we call in geology we call that subside.
• 25:40
  SPEAKER_00: It can't sink fast enough to keep up with the deposition from the Spercheus River.
• 25:46
  SPEAKER_00: And so that's a it's a phenomenon in geology that's called progradation, which is not important, but that's what's going on.
• 25:53
  SPEAKER_00: And so this buildup of sediment, the essentially the delta of this river is happening very fast, which then caused the land to build up, which pushed the shoreline back toward the sea.
• 26:05
  SPEAKER_01: It's just filling in this basin, basically.
• 26:07
  SPEAKER_01: It's filling in the gulf, it's pushing the ocean back because it's filled up.
• 26:11
  SPEAKER_01: And actually, this is a sign of a healthy river delta, is that this is occurring.
• 26:15
  SPEAKER_01: We'll talk in our next episode coming up about dams, in that when you starve the dams of sediment, you know, the river deltas don't really get filled up and it's not a healthy system.
• 26:24
  SPEAKER_01: This is a sign of a healthy system, and it's just the earth naturally changing over the last 2,500 years, which is kind of an incredible amount of time to think about that us as humans have seen this change uh happen.
• 26:35
  SPEAKER_01: It's it's really cool.
• 26:36
  SPEAKER_01: So, right now, as you said, Chris, the hot part is still there.
• 26:39
  SPEAKER_01: There's still hydrothermal vents and springs, but the gate is now instead of a hundred feet wide, it's now five kilometers between the mouth of the river and the Gulf of Malia, uh, which is a significant amount of progradation.
• 26:53
  SPEAKER_01: A lot of sediment has been deposited in there, in part because there's mountains so close by.
• 26:58
  SPEAKER_00: Yeah, that is absolutely amazing.
• 27:00
  SPEAKER_00: Cool stuff.
• 27:02
  SPEAKER_01: Yeah.
• 27:02
  SPEAKER_00: Well, hey, Jesse, I think that's a wrap, right?
• 27:05
  SPEAKER_01: Yeah, I think we're to babble on.
• 27:07
  SPEAKER_01: You you think you're done?
• 27:08
  SPEAKER_01: I can always babble a little bit more, but I think this really wraps it up.
• 27:12
  SPEAKER_01: Uh this is a really cool story.
• 27:14
  SPEAKER_01: Uh, I love, I mean, Chris, I know you're a great fan of history, as am I.
• 27:18
  SPEAKER_01: We have our particular time periods that we love in history, but this was just a super fun thing.
• 27:23
  SPEAKER_01: And geology and geoscience has impacted history in extremely dramatic ways.
• 27:27
  SPEAKER_01: And we're gonna be highlighting these in the future as well.
• 27:30
  SPEAKER_00: Yeah, we were just talking about this a couple days ago, weren't we?
• 27:33
  SPEAKER_00: Uh you know, we got some more ideas, like maybe we'll get into the Battle of Gettysburg and how geology played a role in that and and how that all came out.
• 27:41
  SPEAKER_00: I don't know.
• 27:41
  SPEAKER_01: Super cool.
• 27:42
  SPEAKER_01: There'll be more episodes on the role of geoscience in historical events coming your way through Planet Geo in the near future.
• 27:48
  SPEAKER_00: See, everybody just thinks geology is just all you learn about rocks and it's geology, you know.
• 27:52
  SPEAKER_00: But actually, geology shapes history in a way that is uh super cool.
• 27:59
  SPEAKER_01: Oh, I mean, it shapes biology, it shapes history, it shapes human development.
• 28:03
  SPEAKER_01: I mean it really is the center of the universe, isn't it?
• 28:05
  SPEAKER_01: It really is.
• 28:06
  SPEAKER_01: It shapes society.
• 28:07
  SPEAKER_01: Uh-uh.
• 28:07
  SPEAKER_01: I mean, geology is massively important, and that's partly sarcasm, partly a shot across the bow of my biology-focused family.
• 28:16
  SPEAKER_00: But well, all the biology does is cover up our geology.
• 28:19
  SPEAKER_01: It's all that lichen and moss and all that garbage.
• 28:22
  SPEAKER_01: Who cares about that?
• 28:23
  SPEAKER_01: Anyway, that's a wrap on the hot gates and why the Spartans stood where they stood.
• 28:27
  SPEAKER_01: If you like this episode, if you got something from it, we'd ask you to do one or two things for us.
• 28:33
  SPEAKER_01: Either share it with somebody who you know who you think might like this kind of stuff, who likes history, who likes their planet.
• 28:39
  SPEAKER_01: I mean, who doesn't really like that.
• 28:40
  SPEAKER_01: So share it with someone you know.
• 28:42
  SPEAKER_01: Also, give us a five-star review, tap that subscribe button on your podcast service.
• 28:47
  SPEAKER_01: Those really help us uh and go a long way into promoting the geosciences in general.
• 28:53
  SPEAKER_01: So, so give us a like, a subscribe, give it, leave a comment or a review if you're willing, and uh stay tuned to Planet Geo in the future.
• 29:01
  SPEAKER_01: We'll talk to you soon.
• 29:02
  SPEAKER_01: You bet.
• 29:02
  SPEAKER_01: See you next week.
• 29:03
  SPEAKER_01: Alright, peace.