Latest / PlanetGeo: The Geology Podcast / The Worst Year to Be Alive - 536 AD

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The Worst Year to Be Alive - 536 AD · PlanetGeo: The Geology Podcast

• 0:01
  SPEAKER_02: 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: What are you laughing at?
• 0:14
  SPEAKER_02: Because I'm laughing at you, man.
• 0:16
  SPEAKER_02: It's you got your technology figured out, at least, and now we're trying to figure out everything else.
• 0:20
  SPEAKER_02: I think I get the feeling that you, I'm looking at you right now.
• 0:24
  SPEAKER_02: I can see in your glasses the reflection of all of the screens you have in front of you.
• 0:29
  SPEAKER_01: I know it's really, I feel important.
• 0:32
  SPEAKER_01: I feel so important.
• 0:34
  SPEAKER_01: I have I have three huge monitors in front of me right now.
• 0:39
  SPEAKER_01: You are glowing.
• 0:40
  SPEAKER_01: My face is lit up.
• 0:42
  SPEAKER_02: You are lit up by that computer blue.
• 0:45
  SPEAKER_02: And to be honest, you look a little like flustered by it all.
• 0:50
  SPEAKER_01: I don't know where to look.
• 0:51
  SPEAKER_01: Okay.
• 0:52
  SPEAKER_01: I like I can't just avert my eyes to focusing on one screen.
• 0:56
  SPEAKER_01: I I have to like turn my whole head.
• 0:58
  SPEAKER_01: Yeah, you're cracking me up right now.
• 1:00
  SPEAKER_02: It looks to be honest, like you're you're looking at screens which are not the camera, and so it looks like you're kind of wandering off into space confused to look.
• 1:09
  SPEAKER_01: That same thing.
• 1:10
  SPEAKER_01: Like what?
• 1:10
  SPEAKER_01: Because I can see myself too.
• 1:13
  SPEAKER_01: And I'm like, you look like you're just drifting off la la land.
• 1:18
  SPEAKER_01: Oh man, it's killing me.
• 1:20
  SPEAKER_01: But I like this setup though.
• 1:22
  SPEAKER_02: I like it.
• 1:22
  SPEAKER_02: Yeah, I mean, it's professional, it's professional grade over there.
• 1:26
  SPEAKER_02: We're you're crushing it.
• 1:27
  SPEAKER_01: I need to say something.
• 1:28
  SPEAKER_01: So Jenny and I were listening to our podcast, okay?
• 1:32
  SPEAKER_01: And because we do that, and I was talking about Brandon and how I did not have a choice in the matter.
• 1:39
  SPEAKER_01: She, oh, did she get mad at me?
• 1:41
  SPEAKER_01: She's like, Jenny got mad at you.
• 1:43
  SPEAKER_01: Daughter listens.
• 1:44
  SPEAKER_01: Oh, yeah.
• 1:44
  SPEAKER_01: She said, You are implying that you don't like Brandon.
• 1:48
  SPEAKER_01: I'm like, that is not my implication at all.
• 1:50
  SPEAKER_01: What I'm saying, I love Brandon.
• 1:52
  SPEAKER_01: I'm saying that my daughter is very strong-willed.
• 1:56
  SPEAKER_01: And so I had no say in the matter at all.
• 1:59
  SPEAKER_01: And so I need to put a disclaimer out there that I do love my bonus son.
• 2:04
  SPEAKER_01: I call him my bonus son.
• 2:06
  SPEAKER_01: And I didn't mean anything derogatory when I said I had no choice in the matter.
• 2:10
  SPEAKER_01: That was more like a rip on my daughter than anything else.
• 2:13
  SPEAKER_02: So well, okay, if Jenny's listening, nobody took it that way.
• 2:16
  SPEAKER_02: I mean, uh Jenny, calm down.
• 2:18
  SPEAKER_02: Everybody understood that.
• 2:20
  SPEAKER_01: I understood it.
• 2:23
  SPEAKER_01: I think that's gonna go over really well.
• 2:24
  SPEAKER_01: You telling her to calm down, she's gonna love that too.
• 2:27
  SPEAKER_01: Calm down, Jenny.
• 2:28
  SPEAKER_01: Jenny, just calm down.
• 2:30
  SPEAKER_02: Well, today, Chris, we're talking about the worst year to be alive.
• 2:36
  SPEAKER_02: And shocker, spoiler, it's not 2020.
• 2:40
  SPEAKER_02: I mean, 2020 kind of sucked by most people's accounts, right?
• 2:43
  SPEAKER_02: I mean, COVID, lots of stuff going on in 2020.
• 2:46
  SPEAKER_02: That was not a banner year, at least in the US.
• 2:49
  SPEAKER_02: No, and but the thing is, it does not compare to 536 AD, which is the year we are gonna talk about here.
• 2:58
  SPEAKER_01: That's right.
• 2:59
  SPEAKER_01: This idea actually came from a listener question from Kathy about this mysterious fog or cloud that happened in 536 AD.
• 3:08
  SPEAKER_01: And I started looking into it and talked to you about it because it was really, really intriguing, and that's where this episode's coming from.
• 3:17
  SPEAKER_02: Yeah, absolutely.
• 3:18
  SPEAKER_02: And you know, the more you look into this, this is a very long story, and it could be a long episode, but we're gonna keep it kind of tight.
• 3:25
  SPEAKER_02: So, what we're gonna do here is we're just gonna give an overview of what happened in 536 AD and the years that followed.
• 3:33
  SPEAKER_02: Then we're gonna talk about what caused this, which shocker, it's geoscience related, it's a volcano.
• 3:39
  SPEAKER_02: Spoiler alert.
• 3:40
  SPEAKER_02: But then we're gonna talk about how volcanoes can drive sort of catastrophes of this scale, and then talk about what sort of data led scientists to that conclusion, how we measure this that far back in time.
• 3:53
  SPEAKER_01: That's right.
• 3:54
  SPEAKER_01: You had an idea a long time ago for an episode, I think it was called the process of scientific discovery, something along that line.
• 4:02
  SPEAKER_01: And when you look into how they pieced all this together, the data that was used, it reminded me of that.
• 4:10
  SPEAKER_01: The process of scientific discovery in this story is so awesome.
• 4:15
  SPEAKER_02: Yeah, and I like it because it's yeah, it's right up your doctory alley.
• 4:19
  SPEAKER_02: Yeah.
• 4:20
  SPEAKER_02: Exactly.
• 4:20
  SPEAKER_02: And uh, it has a lot of technique development built into it.
• 4:23
  SPEAKER_02: So this is a cool story, but let's set the stage here, Chris.
• 4:26
  SPEAKER_02: So recently, Harvard professor Michael McCormick argued that 536 AD was literally the worst year to be alive in recent history.
• 4:36
  SPEAKER_02: And the reason is that Earth was cooled to the coldest it's been in a couple millennia, and it started this sort of century of economic ruin that had this plague, a plague of Justinian that hit uh Europe, Eastern Europe particularly, a bubonic plague in 541 AD.
• 4:54
  SPEAKER_02: And it kind of came about with this 18-month-long stretch of darkness that came across Europe, the Middle East, and parts of Asia.
• 5:04
  SPEAKER_01: Yeah, I want to interject something that 536 is just the beginning.
• 5:08
  SPEAKER_01: It was early in 536 AD.
• 5:10
  SPEAKER_01: Absolutely.
• 5:11
  SPEAKER_01: And then four years later, there was another volcanic eruption, a cataclysmic eruption that that affected the atmosphere.
• 5:19
  SPEAKER_01: A year after that, this plague took off, and then seven years in 547, there was another volcanic eruption.
• 5:26
  SPEAKER_01: So within 10 years, the world got just hit again and again and again.
• 5:32
  SPEAKER_01: It was unbelievable.
• 5:34
  SPEAKER_02: For instance, we're gonna read a couple quotes here because they're really, really awesome.
• 5:37
  SPEAKER_02: One of them, Michael Assyrian, wrote, The sun became dark, and its darkness lasted for one and a half years.
• 5:44
  SPEAKER_02: Each day it shone for about four hours, and still this light was only a feeble shadow.
• 5:49
  SPEAKER_02: Then I love this.
• 5:50
  SPEAKER_02: The fruits did not ripen, and the wine tasted like sour grapes.
• 5:54
  SPEAKER_02: End quote.
• 5:55
  SPEAKER_01: I mean That's the important part.
• 5:56
  SPEAKER_02: That's uh the wine didn't taste right.
• 5:59
  SPEAKER_02: Uh man, life sucks if the wine doesn't taste good.
• 6:02
  SPEAKER_02: I mean, come on.
• 6:03
  SPEAKER_01: Yeah, most of these quotes come from authors and politicians.
• 6:07
  SPEAKER_01: So that's how we know about what this was like.
• 6:10
  SPEAKER_01: There was another one that was written by an author, and it goes like this so we have had a winter without storms, spring without mildness, and summer without heat.
• 6:20
  SPEAKER_02: It's just and then it's crazy.
• 6:23
  SPEAKER_02: I mean, I can't imagine that.
• 6:24
  SPEAKER_02: And then the last one, a Roman politician, wrote, the sun had a bluish color, the moon lost its luster, and the seasons seem to be jumbled up together.
• 6:34
  SPEAKER_02: That's a great description.
• 6:36
  SPEAKER_02: I mean, it sounds catastrophic.
• 6:38
  SPEAKER_02: This is not a fun time to be alive, right?
• 6:40
  SPEAKER_02: And the reason that this is not a fun time to be alive, and what drove all this stuff is that summer temperatures fell during this time period.
• 6:47
  SPEAKER_01: Yeah, 536 was really just the beginning when this volcanic eruption happened, because four years later there was another cataclysmic eruption that happened, and then a year later is the bubonic plague that you just talked about, and then seven years later in 547 AD, another volcanic eruption.
• 7:05
  SPEAKER_01: So the planet got hit and smacked several times within a 10-year time span.
• 7:11
  SPEAKER_01: Just absolutely amazing.
• 7:12
  SPEAKER_02: So this was a really horrible time in the end.
• 7:17
  SPEAKER_02: I mean, this was a long period of time with cold, with very little light, poor growing seasons, plague, and worldwide hunger.
• 7:26
  SPEAKER_02: And as we said before, this kick started the coldest decade in the past 2300 years.
• 7:32
  SPEAKER_02: And the summer temperatures fell on average.
• 7:34
  SPEAKER_02: Now, this is a global average, but the temperatures fell by one and a half to two and a half degrees centigrade.
• 7:40
  SPEAKER_02: So that's you know, four or five degrees Fahrenheit.
• 7:42
  SPEAKER_02: And that doesn't sound like a lot, Chris, but in the global average, that's a ton.
• 7:48
  SPEAKER_01: Yeah, because we're only talking about an average, we're not talking about the extremes that could come along with something like this.
• 7:56
  SPEAKER_01: You know, I mean, there were reports of China getting snow in the summertime.
• 8:00
  SPEAKER_01: That's crazy.
• 8:01
  SPEAKER_02: So, Chris, we're gonna do this a little bit out of order, or it may seem a little bit out of order.
• 8:06
  SPEAKER_02: What we're gonna talk about next is how a volcano can actually cool the earth, like how the volcano influences Earth's climate on that scale or several volcanoes over the course of a decade or two.
• 8:17
  SPEAKER_02: And then we're gonna talk about the type of volcano and where it erupted, and then we're gonna come back to the evidence.
• 8:23
  SPEAKER_02: So we're gonna end with the evidence.
• 8:24
  SPEAKER_02: Don't worry, we're gonna get there.
• 8:26
  SPEAKER_02: But we need to start out with how a volcano can cool the earth.
• 8:30
  SPEAKER_02: And you gotta picture a big volcanic eruption.
• 8:33
  SPEAKER_02: We've all seen images of these, some of them videos, Mount St.
• 8:36
  SPEAKER_02: Helens, Pinatubo, all of these ones that have erupted while we had video cameras and cameras around.
• 8:42
  SPEAKER_02: You know, it sends this huge plume of ash up into the sky, way up into the upper atmosphere.
• 8:50
  SPEAKER_02: And that is importantly both dust, rock dust, and gas, volcanic gases.
• 8:56
  SPEAKER_02: And those two things get sent really high up into the atmosphere, and that's kind of what does it.
• 9:00
  SPEAKER_01: So the volcanic dust is microscopic volcanic glass, essentially, that is spit up high into the atmosphere, it'll circle the globe, but that stuff is gonna come out relatively fast.
• 9:12
  SPEAKER_01: It's not gonna stay there long because even though it's microscopic, it still has enough mass where it's gonna settle out rather quickly.
• 9:20
  SPEAKER_02: And that's exactly right.
• 9:21
  SPEAKER_02: And we're gonna come back to that.
• 9:22
  SPEAKER_02: So remember that dust comes out.
• 9:25
  SPEAKER_02: We're gonna come back to that.
• 9:26
  SPEAKER_02: Now, what about the gases?
• 9:27
  SPEAKER_01: Yeah, the gases, there are a lot of gases that are spewed by a volcano.
• 9:31
  SPEAKER_01: The gas that we're mostly concerned with is it's sulfur dioxide that forms these sulfates.
• 9:38
  SPEAKER_01: And the thing about these gases is that they get higher up into the atmosphere.
• 9:43
  SPEAKER_01: So we live in a layer of the atmosphere that's about 20 miles-ish thick, that's called the troposphere.
• 9:48
  SPEAKER_01: The next layer up is called the stratosphere.
• 9:51
  SPEAKER_01: That's about 20 to 50 miles above the surface.
• 9:54
  SPEAKER_01: That's the layer that's super important because it's also the layer that contains ozone.
• 9:58
  SPEAKER_01: And these sulfates get up into the stratosphere and they're gonna stay there for quite a long time.
• 10:04
  SPEAKER_01: Why they're important though, is because they have what's called a really high albedo.
• 10:09
  SPEAKER_01: And that means that it's just really reflective.
• 10:12
  SPEAKER_01: So the incoming solar radiation hits that layer, that kind of blanket that's up there, and then a lot of the radiation is reflected back out into space.
• 10:22
  SPEAKER_01: And so it's not allowed to do what it normally would do, which is heat the surface of the earth.
• 10:26
  SPEAKER_02: Yeah, it's exactly right.
• 10:27
  SPEAKER_02: And and this is a really important molecule in the end.
• 10:30
  SPEAKER_02: SO2, sulfur dioxide, bonds with water, produces sulfuric acid, and those things have exactly as you said, Chris, this reflective thing.
• 10:37
  SPEAKER_02: And so it creates this cooling.
• 10:38
  SPEAKER_02: Like that's that's what it is.
• 10:40
  SPEAKER_02: It's preventing sunlight and sun energy from making it into Earth, which therefore cools the earth.
• 10:46
  SPEAKER_02: If you don't have as much energy from the sun making it to the surface, then you just don't have as much energy to heat the surface of the earth, right?
• 10:54
  SPEAKER_02: Like that's actually a lot of heat energy that's coming in through radiation and sunlight, and that is being trapped in the atmosphere normally.
• 11:02
  SPEAKER_02: But if you kind of put a layer, a blocking layer in the upper atmosphere, it doesn't make its way in, and therefore it cools the planet.
• 11:09
  SPEAKER_01: The volcanic rocks, this dust, these microscopic grains that are spit up higher up into the troposphere.
• 11:15
  SPEAKER_01: To me, that's a lot like a big forest fire.
• 11:18
  SPEAKER_01: You know, this haze that you get and things like that, it's really affected by the wind, the direction of the wind and so on, but it will settle down quickly.
• 11:27
  SPEAKER_01: This other stuff is not affected by the wind because the atmosphere is so thin up there anyway, and it's really just a reflectivity issue that's going on.
• 11:36
  SPEAKER_01: So it's a very different, it's really kind of this this two-pronged punch, if you will.
• 11:41
  SPEAKER_01: You got the volcanic dust, doesn't really last long.
• 11:44
  SPEAKER_01: And then these aerosols that they last much longer, they stay up in the air.
• 11:48
  SPEAKER_02: That's exactly right.
• 11:48
  SPEAKER_02: And so those dust particles are the key to identifying where the volcano erupted that caused this in 536, in 540, I think it was the other eruption, 540, yep.
• 12:02
  SPEAKER_02: And then uh 47 again.
• 12:05
  SPEAKER_02: Is that right?
• 12:05
  SPEAKER_02: Yeah, 47.
• 12:06
  SPEAKER_02: So we can pinpoint, we can fingerprint where those volcanoes come from.
• 12:12
  SPEAKER_02: And again, spoiler alert, they come from Iceland, or they came from Iceland at this time.
• 12:16
  SPEAKER_02: And so we'll get to how we know that, but it's it's fingerprinting these little dust particles that rain out after they get chucked up into the stratosphere.
• 12:24
  SPEAKER_02: They rain out, and we can use those to fingerprint where the volcanic eruption came from.
• 12:29
  SPEAKER_02: But let's have a short little interlude here, Chris, about why volcanoes are on Iceland.
• 12:34
  SPEAKER_02: Just a real brief thing.
• 12:35
  SPEAKER_02: It's super complicated, but I think we can distill it down, don't you think?
• 12:39
  SPEAKER_01: Well, yeah, I think we're gonna have to.
• 12:41
  SPEAKER_01: The volcanism on Iceland is unbelievably complicated.
• 12:46
  SPEAKER_01: So we can't do that justice in this episode at all.
• 12:49
  SPEAKER_01: But here's our go at it.
• 12:51
  SPEAKER_01: Here's our run at what what's going on with Iceland.
• 12:54
  SPEAKER_01: You have the mid-Atlantic Ridge, which is the longest divergent boundary that's on our planet right now.
• 13:01
  SPEAKER_01: It's it looks like a big zipper that goes all the way from the South Pole to the North Pole-ish, right?
• 13:07
  SPEAKER_01: And so divergent boundaries is where two plates are pulling apart, hot mantle rises up through that crack, then leading to the surface of the earth.
• 13:16
  SPEAKER_01: And so the magma that comes out at mid-ocean ridges is what forms the ocean floor.
• 13:21
  SPEAKER_01: And that's where Iceland sits, right on top of the mid-Atlantic ridge.
• 13:27
  SPEAKER_01: But it's odd, right?
• 13:29
  SPEAKER_01: Because Iceland is the only spot along the mid-Atlantic Ridge where it's actually elevated to an island, it's above sea level.
• 13:37
  SPEAKER_01: So, what's going on in addition to just this mid-ocean ridge, Jess?
• 13:43
  SPEAKER_01: What's going on?
• 13:44
  SPEAKER_02: Well, it's a really interesting place.
• 13:46
  SPEAKER_02: And Iceland is unique on the modern earth for having this process.
• 13:49
  SPEAKER_02: It has a mantle plume sitting underneath of it as well.
• 13:51
  SPEAKER_02: So there's a mantle plume that's bringing heat and magma up to the surface of the earth.
• 13:56
  SPEAKER_02: There's a mantle plume under Hawaii, there's a mantle plume under Yellowstone, there's a mantle plume under a bunch of different places.
• 14:03
  SPEAKER_01: Another word for a mantle plume is a hot spot.
• 14:05
  SPEAKER_01: I know you like mantle plumes, and that's like the doctory word for it, but uh just for our listeners, a mantle plume is on a hot spot, they're synonymous.
• 14:13
  SPEAKER_01: They mean the same thing.
• 14:14
  SPEAKER_01: So that's right.
• 14:15
  SPEAKER_02: Go ahead.
• 14:15
  SPEAKER_02: Yeah, so there's a hot spot right underneath of Iceland as well.
• 14:19
  SPEAKER_02: So you have, as you described, this mid-ocean ridge system, which is producing a lot of magma.
• 14:24
  SPEAKER_02: It's melting the mantle.
• 14:25
  SPEAKER_02: There's a lot of heat being added there, but also you have a mantle plume.
• 14:28
  SPEAKER_02: So you have two sources of heat and two sources of magma, which basically doubles the volume of magma that's produced.
• 14:35
  SPEAKER_02: When you combine those two things together, you actually have the ability to melt the oceanic crust that you were talking about, Chris.
• 14:42
  SPEAKER_02: So you talked about this first step, you melt the mantle to form the oceanic crust.
• 14:46
  SPEAKER_02: In Iceland, you're remelting that oceanic crust.
• 14:49
  SPEAKER_02: So that's why Iceland is sitting above sea level, is because it's a little bit thicker, it's a little bit less dense, it erupts felsic rocks as well as mafic rocks, so the light-colored ones, the continental crust-like ones, as well as the mafic, the dark ones, the oceanic crustal kind of ones.
• 15:05
  SPEAKER_01: Hold on, hold on.
• 15:06
  SPEAKER_01: I'm gonna stop you right there.
• 15:08
  SPEAKER_01: You're getting really wordy, but I want you to get a little bit more wordy.
• 15:10
  SPEAKER_01: Oh no, you're sending me into the weeds.
• 15:13
  SPEAKER_01: I am, I am.
• 15:15
  SPEAKER_01: Why would we have if the source of the magma is a mantle plume and divergence, why does Iceland have this diversity then of extrusive volcanism?
• 15:27
  SPEAKER_01: Why is that going on?
• 15:29
  SPEAKER_01: Because one third of the volcanism on our planet, one third of the lava that comes is Iceland related.
• 15:36
  SPEAKER_01: So it's a big deal.
• 15:38
  SPEAKER_02: Yeah, good question.
• 15:39
  SPEAKER_02: It's a huge amount.
• 15:40
  SPEAKER_02: And the reason that you get so much is because you have two sources of heat, two sources of magma, the mid-ocean ridge system and the mantle plume or the hot spot, which produces loads of basaltic volcanism, loads of mafic primary melting of the mantle produces the dark colored rocks that you see in the photos of Iceland.
• 15:58
  SPEAKER_02: But you have so much volume of that that it stacks up on top of each other and it eventually buries those basalt flows.
• 16:05
  SPEAKER_02: So basalt flows that erupted 20 million years ago, five million years ago on Iceland are buried deeper because there's more on top of them.
• 16:13
  SPEAKER_02: And when they get buried deeper, they get heated up and they start to melt.
• 16:16
  SPEAKER_02: And that produces the felsic rocks, which can produce the big eruptions.
• 16:22
  SPEAKER_01: So you have a wide So partial melting of the basalt produces then, and the reason this is important, it produces a more felsic um magma.
• 16:32
  SPEAKER_01: The reason this is important is because felsic magma is stickier, it's more viscous, and therefore it tends to be more violent and explosive.
• 16:41
  SPEAKER_01: It's less frequent, but it's more explosive.
• 16:44
  SPEAKER_01: And so that's how you get this diversity of magma that comes out of a place where the source shouldn't be that.
• 16:52
  SPEAKER_01: The source should be more mafic, and that's important because mafic magma is more runny, less viscosity, and it tends to be then less violent when it does erupt.
• 17:03
  SPEAKER_01: It tends to produce more just lava flows, kind of like what you get in the water.
• 17:08
  SPEAKER_02: That's exactly right.
• 17:09
  SPEAKER_02: Absolutely, Chris.
• 17:10
  SPEAKER_02: And Iceland, I people probably remember from a couple years ago when there was a big volcanic eruption that was disrupting air travel between Europe and North America.
• 17:18
  SPEAKER_02: And I'm not gonna try, I'm not gonna embarrass myself by trying to pronounce the name of it, but Iceland is a key place where there's a lot of volcanism and there's some pretty violent volcanism that can throw stuff up into the upper atmosphere.
• 17:30
  SPEAKER_02: This is not like stuff oozing out to the surface and running around.
• 17:34
  SPEAKER_02: That happens in Iceland too, but you also get the big ones, the big boys are there too.
• 17:38
  SPEAKER_01: Yeah, I'm not gonna try to pronounce it either, but there's a volcano that is has recently come to life again and gotten very active.
• 17:46
  SPEAKER_01: And they think that this might be the beginning then of decades-long volcanism from this particular volcano.
• 17:53
  SPEAKER_01: So it this is these aren't singular events, and same thing with the 536 thing that started this whole thing.
• 18:00
  SPEAKER_01: That was not one singular eruption.
• 18:02
  SPEAKER_01: This went on for a period of time.
• 18:04
  SPEAKER_01: It went on during the course of that year.
• 18:07
  SPEAKER_02: That leads us nicely into how do we measure this stuff?
• 18:10
  SPEAKER_02: How do we know that the story we've just told you?
• 18:12
  SPEAKER_02: How do we know this, right?
• 18:13
  SPEAKER_02: Let's get to the data.
• 18:14
  SPEAKER_02: And it really comes down to ice core records.
• 18:17
  SPEAKER_02: And this is a good lead-in because next week we're gonna have a conversation with Dr.
• 18:22
  SPEAKER_02: Richard Alley, who's at Penn State and works a lot on ice core data and has done a lot for the modern climate perspective, um, and and sort of looking at this type of data.
• 18:33
  SPEAKER_02: So stay tuned to that for next week.
• 18:34
  SPEAKER_02: But what is an uh ice core?
• 18:36
  SPEAKER_02: I mean, people don't know what an ice core is, Chris.
• 18:38
  SPEAKER_02: Can you describe what's going on here?
• 18:39
  SPEAKER_01: Think of an apple corer, if you will.
• 18:41
  SPEAKER_01: You know, these things that you put on top of an apple and you clunk it down and it slices the apple into nice and neat little things, but it leaves this cylindrical core of an apple left behind.
• 18:52
  SPEAKER_01: That's what an ice core looks like.
• 18:53
  SPEAKER_01: So if you take a hollow drill and you drill down through the ice and you remove the casing, and the casing still has the ice in it, you get this perfectly cylindrical, uh, you know, what are they, Jesse?
• 19:04
  SPEAKER_01: A couple of inches in diameter, uh-huh, two to four inches in diameter, probably.
• 19:08
  SPEAKER_02: Yeah, that's exactly right.
• 19:09
  SPEAKER_01: They use these cores to study what was locked up in the ice at the time that it was formed, right?
• 19:19
  SPEAKER_01: Because I think of these ice sheets, these glaciers, they're time machines.
• 19:24
  SPEAKER_01: If you think about it, the Greenland ice sheet is really a two-mile thick time machine because if you can drill down all the way through that, locked up in the ice can be all kinds of things, little tiny bubbles of air.
• 19:37
  SPEAKER_01: But those bubbles of air represent atmospheric composition at the time that that fell as snow.
• 19:43
  SPEAKER_01: And so we're going back in time, and man, we can learn a ton.
• 19:49
  SPEAKER_01: This is really, really cool stuff.
• 19:51
  SPEAKER_01: This gets me excited.
• 19:52
  SPEAKER_02: Let me interrupt there, Chris, and say that we got to picture this a little bit more because we think of a glacier as you know, we see these pictures of glaciers coming down the mountainside, and we see the end of the glacier where the glacier is actually melting out.
• 20:04
  SPEAKER_02: But up where the glacier's forming, up where the ice is forming, that is actually adding ice to the system.
• 20:09
  SPEAKER_02: And these style glaciers, the ones in Greenland and Antarctica, are huge.
• 20:14
  SPEAKER_02: And you have a zone where the glacier is actually forming ice, where as you described, snow is falling, snow is interacting with the air, there's air stuff there.
• 20:24
  SPEAKER_02: If there's dust around, hint, hint, hint, if there's dust around, it'll fall on top of the snow.
• 20:30
  SPEAKER_02: Then next season or you know, the next month, there'll be more snow, which buries it.
• 20:34
  SPEAKER_02: And as you bury it, you form ice.
• 20:37
  SPEAKER_02: As it gets deeper and deeper and deeper, it forms ice.
• 20:40
  SPEAKER_02: So those little dust particles and the gas particles from the atmosphere are trapped in the ice.
• 20:44
  SPEAKER_02: And so think of it as like you're just layering more ice on top of each other.
• 20:48
  SPEAKER_02: It's like a tree ring growing except turned on its side.
• 20:51
  SPEAKER_02: That's how ice is forming.
• 20:52
  SPEAKER_02: And so we just drill down into it and we get this nice record, this sort of we can see the bands in the record.
• 20:59
  SPEAKER_01: Yeah.
• 20:59
  SPEAKER_01: Hey, I just had a thought.
• 21:00
  SPEAKER_01: This is right up your alley.
• 21:02
  SPEAKER_01: Can you really fast, you know, don't be too wordy this time, okay?
• 21:06
  SPEAKER_01: But can you tell us how we're able to analyze composition of little gas bubbles?
• 21:13
  SPEAKER_01: How are we able to measure the chemical composition of a gas?
• 21:16
  SPEAKER_02: Yeah, this is really cool.
• 21:18
  SPEAKER_02: And it's using the same techniques that I use in my lab.
• 21:22
  SPEAKER_02: If we made a just a slight modification, we could do these types of measurements.
• 21:25
  SPEAKER_02: But basically, in this case, you take that core, you kind of cut it in half, and so you're looking at all of these layers.
• 21:32
  SPEAKER_02: You got the layers and you got this long core with tons of layers in them.
• 21:35
  SPEAKER_02: All you really need to do is blast that ice with a laser.
• 21:39
  SPEAKER_02: And most of that material is water.
• 21:42
  SPEAKER_02: Great.
• 21:42
  SPEAKER_02: That's just gonna go into your machine and not really do anything.
• 21:46
  SPEAKER_02: But the stuff trapped in the gas will give you spikes in composition.
• 21:51
  SPEAKER_02: So we can measure things like lead, we can measure things like calcium, we can measure things like carbon and CO2, and so you can get this trajectory through this.
• 22:00
  SPEAKER_02: Where you're measuring the chemical composition of the stuff all the way down the core back in time.
• 22:06
  SPEAKER_02: And you can do just a straight line so you get a continuous record all the way across.
• 22:10
  SPEAKER_02: Now you can do more complicated things.
• 22:12
  SPEAKER_02: You can drill out little parts of the ice if you want to make more precise measurements.
• 22:16
  SPEAKER_02: That's a, in some ways, a better way to do it for certain types of analyses.
• 22:20
  SPEAKER_02: The point is you put little drills or you use a laser and you just get a nice clean chemical line down it.
• 22:25
  SPEAKER_01: Cool.
• 22:26
  SPEAKER_01: That was that was a decent explanation, Jesse.
• 22:28
  SPEAKER_01: Well done.
• 22:28
  SPEAKER_01: Thank you.
• 22:28
  SPEAKER_01: My young sage.
• 22:29
  SPEAKER_01: Nice job.
• 22:30
  SPEAKER_01: Not too long.
• 22:31
  SPEAKER_01: Here's how it went, though.
• 22:32
  SPEAKER_01: In 2015, researchers had a core uh from Greenland and Antarctic, so ice cores from both ice sheets.
• 22:40
  SPEAKER_01: Okay.
• 22:40
  SPEAKER_01: And what they found is very high levels of sulfate.
• 22:43
  SPEAKER_01: And that's that reflective aerosol that got very high into the atmosphere.
• 22:47
  SPEAKER_01: And they combined those findings with tree ring analysis to find that over the last 2,500 years, every single cold summer was tied to a volcanic eruption.
• 23:00
  SPEAKER_01: So cool.
• 23:01
  SPEAKER_01: That's amazing.
• 23:02
  SPEAKER_01: So cool.
• 23:03
  SPEAKER_01: Geology.
• 23:03
  SPEAKER_02: Can't get away from it.
• 23:05
  SPEAKER_02: Because we can get temperature out of the ice core.
• 23:07
  SPEAKER_02: And we're going to come back to that next week with Richard Alley, kind of more detail about how we get temperature out of it.
• 23:11
  SPEAKER_01: And they can get temperature out of tree rings too, because the of the slow growth because of the colder summers.
• 23:18
  SPEAKER_02: So now we have this story where we've got ice core data, we've got tree ring data, we can get globally average temperatures, and we can link those with chemical records.
• 23:27
  SPEAKER_02: Now it comes back to how did we fingerprint this stuff, and it's the dust particles because you can find little shards of glass, that's the volcanic dust, that is preserved in the ice core.
• 23:39
  SPEAKER_02: So that dust came out of volcano, moved around the atmosphere, fell down on ice cores in the Alps.
• 23:44
  SPEAKER_02: Um Yeah, let me can I jump in here?
• 23:46
  SPEAKER_01: I'm gonna interrupt you.
• 23:48
  SPEAKER_01: Well, in 2013, researchers they took a 72-meter long core of a glacier in the Swiss Alps.
• 23:56
  SPEAKER_01: That 72 meters spans back the last 2,000 years.
• 24:01
  SPEAKER_01: They found fallout from this volcano, little microscopic volcanic glass beads.
• 24:08
  SPEAKER_01: And you know what else they found in certain layers of this 2,000-year-old time machine?
• 24:13
  SPEAKER_01: They found Sahara dust storms, they found lead pollution from human activities like the mining of silver.
• 24:20
  SPEAKER_01: They so they found spikes of these chemicals that really tell such a cool story.
• 24:26
  SPEAKER_01: That all happened in this research that involved the glacier in the Swiss Alps.
• 24:31
  SPEAKER_02: It's exactly right.
• 24:31
  SPEAKER_02: And we can put that chemical record.
• 24:34
  SPEAKER_02: So you take the little tiny dust fragments, you know that that's probably a volcanic eruption.
• 24:38
  SPEAKER_02: And so you can look at the chemistry of that dust particle and link it to volcanic eruptions that we know from the record, or know, oh, that volcano has a kind of a chemical fingerprint to it.
• 24:49
  SPEAKER_02: And so it's probably that volcano that produced that ash that ended up in the Swiss Alps in the ice, locked in this time machine in the Swiss Alps, and then link it with all these other chemical tracer.
• 24:59
  SPEAKER_02: And those dust particles, lo and behold, are about at the 536 AD mark, which led to this year and a half of darkness and then sort of decline of civilization in the decade after that, with plagues, and you know, you can imagine a scenario where if there's no food, if your wine is bad and there's no food, then you know, life gets pretty hard, and actually plagues can come out, and you know, it's terrible, right?
• 25:25
  SPEAKER_02: It's led to sort of a decline of the Eastern Roman Empire.
• 25:29
  SPEAKER_01: And so I I just want to jump back because I I would think that you would find this to be really interesting, how they did this with the glacier, that 72-meter long ice core from the Swiss Alps.
• 25:40
  SPEAKER_01: They carved 120 micron slivers of ice.
• 25:44
  SPEAKER_01: So a micron is a millionth of a meter, and so they were using 120 micron little tiny slivers, and each of those microns, Jesse, represented just a few days and sometimes weeks of snowfall along the length of the entire core.
• 26:04
  SPEAKER_01: So each meter of this core had 50,000 different samples, 50,000 different little tiny slices from each meter.
• 26:14
  SPEAKER_01: That is painstaking research.
• 26:16
  SPEAKER_01: And what they did is they ran these cores, they analyzed them for about 12 key elements.
• 26:23
  SPEAKER_01: And they used this to pinpoint all this other stuff that was going on, like the sandstorms, volcanoes, and other chemicals that would have been put into the atmosphere from human activities, like the mining of silver.
• 26:34
  SPEAKER_02: That's a great description, Chris.
• 26:36
  SPEAKER_02: Very well done.
• 26:37
  SPEAKER_02: And you can find these glass shards.
• 26:38
  SPEAKER_02: It's a field called Tephrochronology.
• 26:41
  SPEAKER_02: Tephra is what the little glass shards are, but you can find these shards all over the place, and you find them in bogs, in lakes.
• 26:48
  SPEAKER_02: People do this all up and uh down the Canadian Arctic.
• 26:51
  SPEAKER_02: You can find shards from Iceland eruptions, shards from ancient volcanoes all over the earth that kind of make it everywhere.
• 26:59
  SPEAKER_02: So this dust getting blasted all over the place is actually a really powerful tool for reconstructing the chemical history and the volcanic eruption history of the planet, really.
• 27:10
  SPEAKER_01: Jesse, they found in the Swiss Alps, they found some glass shards that are embedded in the snow that fell out.
• 27:16
  SPEAKER_01: Okay.
• 27:17
  SPEAKER_01: Where else did they find this stuff then?
• 27:18
  SPEAKER_01: How like how did this lead to Iceland?
• 27:21
  SPEAKER_02: Well, this led to Iceland because you can match the chemistry of volcanic shards in the ice core to volcanic shards that you found elsewhere.
• 27:30
  SPEAKER_02: So things like lakes and peat bogs in Europe or Greenland ice cores.
• 27:34
  SPEAKER_02: And you can look at the chemical fingerprint of a particular eruption and match it to volcanoes in Iceland.
• 27:41
  SPEAKER_02: Volcanoes on Iceland produce magma and ash of a very different chemical composition to the Andes or to the Cascades or to volcanoes basically anywhere else on the earth.
• 27:53
  SPEAKER_02: It's pretty diagnostic.
• 27:54
  SPEAKER_02: It's a pretty unique place that produces magma and ash that's pretty unique from a chemical standpoint.
• 28:00
  SPEAKER_02: So you can kind of do this fingerprinting by matching the Tephra, the dust particles in the ice core in the Swiss Alps to other locations and really pin down where and when that volcano erupted.
• 28:11
  SPEAKER_01: That's amazing that they found the same chemical fingerprint in you said peat bogs in Europe and lakes in Europe, the same fingerprint as the shards that were in a Swiss Alps glacier, the shards that were in Greenland and Antarctic ice sheets.
• 28:28
  SPEAKER_01: That's unbelievably cool.
• 28:31
  SPEAKER_01: I mean, that had to be really exciting to do that.
• 28:34
  SPEAKER_01: Now, what's next, right, is to find the volcano, right?
• 28:39
  SPEAKER_01: That's got to be the next progression in this research.
• 28:41
  SPEAKER_01: I mean, they're not done.
• 28:42
  SPEAKER_02: Right.
• 28:43
  SPEAKER_02: No, for sure.
• 28:43
  SPEAKER_02: We could kind of say, oh, it looks like Iceland, but we need to find exactly which volcano.
• 28:47
  SPEAKER_01: So well, they haven't found the exact volcano yet.
• 28:50
  SPEAKER_01: They don't know.
• 28:51
  SPEAKER_01: Okay.
• 28:52
  SPEAKER_01: And then so now they have to go back to Iceland, find more of these shards that are preserved in whether that be lakes or what I don't know where they're gonna look.
• 29:03
  SPEAKER_01: But from what I read, that's what's next, is they want to actually find the exact volcano that this came from, because then they can study that and why it was so devastating.
• 29:13
  SPEAKER_02: And this leads really nicely into how the story kind of wraps up because around 605 AD, so 536 was the first eruption in this dark period, this 18 months of darkness, 540 and 547 AD had more volcanic eruptions.
• 29:31
  SPEAKER_02: And around 605, so uh you know, 70 years later, there starts to be a kick up in you said it before, Chris, the lead signal.
• 29:41
  SPEAKER_02: So atmospheric lead that is again kind of raining down on the glaciers.
• 29:46
  SPEAKER_02: We can measure a kick up in lead in the ice core, which the inference is that this is civilization rebuilding itself, and this is lead produced during silver mining.
• 29:57
  SPEAKER_02: So society and civilization started to mine silver and other metals which can produce lead and put lead into the atmosphere.
• 30:05
  SPEAKER_01: This is something I don't know, so I'm gonna put you on the spot because you're the smartest guy in the room right now.
• 30:10
  SPEAKER_01: Um the room's pretty small.
• 30:13
  SPEAKER_01: It is a small room, yeah.
• 30:15
  SPEAKER_01: But I don't know this.
• 30:17
  SPEAKER_01: Why is the mining of silver responsible for putting lead into the atmosphere?
• 30:22
  SPEAKER_01: Do you know how that works?
• 30:24
  SPEAKER_01: I don't I don't get it.
• 30:25
  SPEAKER_01: I don't understand.
• 30:26
  SPEAKER_02: Lead is it's kind of the silver ores that you have.
• 30:29
  SPEAKER_02: Like you rarely find pure silver.
• 30:32
  SPEAKER_02: Silver is often encased in another metal, sometimes it's in galena, lead sulfide.
• 30:38
  SPEAKER_02: We have collected galena together, Chris.
• 30:40
  SPEAKER_02: I think you know the big people have probably seen this.
• 30:43
  SPEAKER_02: Like it's the big, beautiful, blocky silver metal, uh silver crystals.
• 30:48
  SPEAKER_02: They grow in perfect cubes.
• 30:49
  SPEAKER_02: And when you break them, they break in perfect cubes.
• 30:52
  SPEAKER_02: And it's very shiny, and that's a good silver ore.
• 30:54
  SPEAKER_02: There's trace amounts of silver in that.
• 30:56
  SPEAKER_02: So as soon as you start to crush that up to get silver out, lead is an element that is extremely what we call volatile.
• 31:03
  SPEAKER_02: It can be a gas pretty quickly, so it can get pulled into the atmosphere.
• 31:07
  SPEAKER_02: If you crush anything with lead in it, it can get in the atmosphere.
• 31:10
  SPEAKER_02: And so that's how this kind of works.
• 31:12
  SPEAKER_01: Okay, interesting.
• 31:14
  SPEAKER_01: So lead is a common marker then for studying what's going on in human civilization.
• 31:20
  SPEAKER_02: That's right, that's right.
• 31:21
  SPEAKER_02: And there can be, you know, changes if if people were originally sort of mining copper and then they start mining silver, there can be an increase in lead.
• 31:28
  SPEAKER_02: So it's sort of a civilization shift.
• 31:31
  SPEAKER_02: And for instance, there's a huge lead spike and then a big lead decline in modern civilization record because we started to use leaded gasoline.
• 31:40
  SPEAKER_02: We put lead into gasoline in like the 1930s to prevent engine knocking, and so there's lead all over the place in the record.
• 31:47
  SPEAKER_02: But then we we went to unleaded gasoline in like the 70s, and so there's been a drop-off in that.
• 31:52
  SPEAKER_01: Do you remember that or not?
• 31:54
  SPEAKER_01: You are you too young?
• 31:55
  SPEAKER_01: Did you ever go to a gas station and get asked, do you want leaded or unleaded?
• 31:59
  SPEAKER_01: Is that something that ever happened to you?
• 32:01
  SPEAKER_01: Not that I remember, no.
• 32:03
  SPEAKER_01: But us old people, we remember that.
• 32:05
  SPEAKER_01: I I remember, I think I was probably with my parents.
• 32:07
  SPEAKER_01: I don't think that was still around when I started driving, but I remember, yeah, leaded or unleaded, that was a common thing that you got at full serve gas stations.
• 32:15
  SPEAKER_02: So yeah.
• 32:16
  SPEAKER_02: So there's some complexities in the lead uh record, especially in the modern earth, but it's this great indicator of civilization recovering at 605 AD in the ice record.
• 32:26
  SPEAKER_02: So that kind of wraps up the story here.
• 32:28
  SPEAKER_02: And it's just a really cool example of how geoscience, volcanoes, can dramatically influence civilization and affect civilization in various ways, and in this case, a fairly negative way.
• 32:40
  SPEAKER_01: This is just more proof that geology, you just can't get away from it.
• 32:44
  SPEAKER_01: There's no escaping it.
• 32:46
  SPEAKER_02: I mean, it's just the best.
• 32:47
  SPEAKER_02: Like, I don't know why we don't all know this.
• 32:49
  SPEAKER_02: This should be like this is basic.
• 32:51
  SPEAKER_02: Geology is the best.
• 32:52
  SPEAKER_02: Like, end of story.
• 32:53
  SPEAKER_02: We don't really need to worry about anything else.
• 32:54
  SPEAKER_01: That's why we do this podcast.
• 32:56
  SPEAKER_01: That's right.
• 32:57
  SPEAKER_01: To enlighten everybody, to bring them around.
• 32:59
  SPEAKER_01: Geology is where it's at.
• 33:01
  SPEAKER_01: It's just so fun.
• 33:02
  SPEAKER_02: So, hey, if you like Planet Geo, this kind of ends our wrap-up.
• 33:04
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• 33:08
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• 33:09
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• 33:14
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• 33:15
  SPEAKER_01: This episode came from listener question.
• 33:17
  SPEAKER_01: Kathy, thank you again.
• 33:19
  SPEAKER_02: Absolutely.
• 33:19
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• 33:20
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• 33:21
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• 33:26
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• 33:57
  SPEAKER_01: Can I jump in here?
• 34:02
  SPEAKER_01: In 2013, researchers did they took a seventy-two meter long core of a of a glacier in the Swiss Alps.
• 34:12
  SPEAKER_01: That seventy-two meters spans back the last two thousand years.
• 34:16
  SPEAKER_01: What they found, they found fallout from this volcano, little microscopic volcanic glass beads.
• 34:24
  SPEAKER_01: And you know what else they found in these in