July 13, 2020

Escape from Thera

Posted by Shane Hanlon

About 3,600 years ago, a colossal volcanic eruption blew apart the Greek island Thera, now the popular tourist destination known as Santorini. Falling volcanic rock and dust buried the Bronze Age settlement Akrotiri, on the south side of the island, preserving multi-story buildings, frescoes, tools, furniture and food, until archaeological excavations uncovered them in the last century, much like the eruption of Vesuvius in 79 CE famously buried Pompeii and Herculaneum. But unlike the Roman cities, Akrotiri has a notable lack of bodies.

Unlike Vesuvius, Thera’s volcano gave its inhabitants substantial warning. Minor eruptions sent a column of ash 40 kilometers into the sky and rained hot pumice on the island. University of Hawaii volcanologist Krista Evans says evidence of those precursory volcanic burps can be found within the archaeological site and in geological deposits around the island. The empty settlement implies the people left, but traces of their distinctive pottery and arts do not subsequently appear in the archaeological record on Crete or other nearby islands in their trading network. It’s as if they people just disappeared.

Evans explains how the people of Akrotiri likely fled south by boat toward Crete, 120 kilometers (75 miles) across the Mediterranean, and what eruption models suggest may have been their fate.

This episode was produced by Liza Lester and mixed by Kayla Surrey.

A fresco from an excavated room in the Bronze Age settlement Akriotiri on Santorini, Greece. The “Minoan” eruption of Santorini in 3,600 years ago buried the settlement in pumice and other volcanic rock. Credit: Wikimedia user smial.

Shane Hanlon (00:00):

Hi, Nanci.

Nanci Bompey (00:01):

Hi, Shane.

Shane Hanlon (00:02):

Hi, Liza.

Liza Lester (00:04):

Hi, Shane. Hi Nancy.

Nanci Bompey (00:06):

Hello everyone.

Liza Lester (00:07):

Hello through the little screen.

Nanci Bompey (00:08):

… from our home studios.

Shane Hanlon (00:10):

It’s so nice. Studio is a very generous phrase. Someday, I’m going to take a picture of the fluorescent pink closet that I’m currently sitting in just so folks realize the glamorousness of this.

Liza Lester (00:21):

I have a pillow fort.

Shane Hanlon (00:22):

Ooh, pillow fort’s nice.

Liza Lester (00:24):

Mm-hmm (affirmative).

Shane Hanlon (00:26):

I have a question, have either of you had to, I’m going to say, evacuate or just leave a situation that you just didn’t want to be in or maybe was dangerous, anything like that?

Liza Lester (00:37):

Ooh, so open-ended.

Shane Hanlon (00:38):

I know.

Liza Lester (00:39):

Let’s go with the straight disaster, I was in a house fire once.

Shane Hanlon (00:43):

Oh jeez.

Nanci Bompey (00:43):

Ooh.

Liza Lester (00:43):

It was while I was studying abroad in Austria. And so, it was this really old building from the 19th century. And so, they don’t really do fire alarms there, I guess. Right?

Liza Lester (00:52):

 We were just sitting there having breakfast, someone was in the shower and then someone opened the door and it was just floor to ceiling smoke. Right?

Shane Hanlon (01:00):

Oh my gosh.

Liza Lester (01:01):

You’re like, “Oh, ****. We should probably leave.”

Shane Hanlon (01:02):

Yeah.

Liza Lester (01:03):

So, we dragged the person out of the shower naked. You know? And we’re going down these stone stairs and we’re like, “We should crawl. Right? That’s what they taught us in grade school, get below the smoke.” So, we’re crawling out and we meet the feuerwehr coming up and they’re like, “What are you doing?”

Nanci Bompey (01:17):

What started the fire?

Liza Lester (01:18):

I’m not sure. I think it was a cigarette or something, it was the unit below us. And so, it was mostly contained there, I guess all that stone just kept it in. So, then they put it out no problem. I think it was practically out by the time we evacuated.

Nanci Bompey (01:30):

Wow.

Shane Hanlon (01:31):

Oh my gosh. And was everyone okay?

Liza Lester (01:34):

Everyone was fine. Yeah. We were like… it was just a weird thing that happened in a foreign city where you only sort of understand what’s going on. Right?

Shane Hanlon (01:44):

Oh, that’s amazing.

Nanci Bompey (01:46):

Yeah. Come to think of it, I had something similar in our old apartment when we had to leave for a week, there was a fire below us in the boiler room or something. And nothing happened but we had to get out. You know what I mean?

Liza Lester (01:56):

You’ve got to leave.

Nanci Bompey (01:57):

Nothing happened. Yeah, and we had to stay in a hotel for a week but it was a little like, “Uh, it’s a real fire.” You know? There’s so many false alarms and then you’re like, “Oh, this is real.”

Shane Hanlon (02:07):

Yeah, it is-

Liza Lester (02:07):

Your brain is like, “Is this really happening?”

Nanci Bompey (02:08):

Yeah, exactly.

Shane Hanlon (02:09):

I guess it is good to know though that that survival instinct does kick in. You think, “Oh, we were taught to stuff, we’re never going to need to use it.” But when that kicks in you’re like, “Oh, I remember something about this and maybe I should get the heck out of here.”

Liza Lester (02:21):

Yeah. Those drills actually, they stick with you.

Shane Hanlon (02:25):

Yeah.

Liza Lester (02:25):

There’s something to them.

Shane Hanlon (02:29):

Welcome to the American Geophysical Union’s podcast about the scientists and the methods behind the science. These are the stories you won’t read in the manuscript or hear in a lecture. I’m Shane Hanlon.

Nanci Bompey (02:37):

And I’m Nancy Bompey.

Shane Hanlon (02:39):

And this is Third Pod From The Sun.

Shane Hanlon (02:47):

So, there’s always a reason why I ask y’all silly questions, it’s not just how we catch up. Though, I guess this is how we’re catching up lately.

Nanci Bompey (02:59):

That’s true.

Shane Hanlon (02:59):

But yeah. So, asking about evacuation, about leaving a potentially dangerous situation. And actually, Liza, maybe you can shed some light on what we’re talking about today.

Liza Lester (03:08):

Yeah. Today, we’re talking about some people who had to get out of their island.

Nanci Bompey (03:10):

Of their island?

Liza Lester (03:12):

Of their island because their island was exploding.

Shane Hanlon (03:19):

Or, jeez.

Liza Lester (03:19):

Yeah, not great. Right? Kind of concerning when your island starts erupting. It was a volcanic island in The Greek Archipelagos. This was in the bronze age for Greece. This island is now called Santorini, it’s a resort island. Have you guys been there?

Shane Hanlon (03:34):

Okay, no.

Nanci Bompey (03:35):

No, but I’ve definitely heard of it, it’s definitely popular.

Liza Lester (03:37):

It’s a cruise ship destination. Yeah, yeah.

Nanci Bompey (03:39):

Yep, I think so. Okay.

Liza Lester (03:40):

It’s a really beautiful, sunken caldera that’s been flooded. Right?

Shane Hanlon (03:44):

Oh.

Liza Lester (03:44):

It’s this island. At the time, it was called Thera, this was 3,600 years ago, so 1600 BCE.

Shane Hanlon (03:51):

What’s that math? Okay.

Liza Lester (03:53):

Yeah, a pretty long time ago for us. But there were people living on the island then, the Therans or the [Akrotinis 00:04:01], as they’re sometimes called, they had a city there. And then, apparently they left.

Shane Hanlon (04:08):

What do you mean, apparently?

Liza Lester (04:09):

Well, there aren’t any bodies. It buried the city but it’s not like Pompeii, where there were bodies.

Shane Hanlon (04:16):

So-

Nanci Bompey (04:18):

You mean, they left because something happened?

Liza Lester (04:20):

Something happened — the volcano erupted.

Nanci Bompey (04:22):

Oh, wow. Okay.

Liza Lester (04:24):

And it buried-

Shane Hanlon (04:25):

But there’s literally not a single body.

Liza Lester (04:27):

But they don’t see any bodies caught in the eruption.

Nanci Bompey (04:31):

Wow. So, it’s a mystery about, they knew people were there and then they weren’t there after the eruption. But what happened?

Liza Lester (04:36):

So, they think-

Nanci Bompey (04:37):

They show up up somewhere else, I guess.

Liza Lester (04:39):

Right. That was the thing, is like, it looks they left but where did they go? Is it like the lost city of Atlantis, they just sank beneath the waves and are magically living there. Probably not. Right?

Shane Hanlon (04:49):

Yeah. So, are you going to just leave us hanging here or are we going to find some answers to this?

Liza Lester (04:55):

Well, we talked to somebody that could maybe have an idea or a hypothesis about what maybe happened to these folks after they paddled away from their catastrophe.

Shane Hanlon (05:04):

All right.

Krista Evans (05:09):

I am Krista Evans and I am a master’s student at the University of Hawaii at Manila. And I study the precursory eruption of the late bronze age eruption at Santorini.

Liza Lester (05:21):

So, Santorini is still an active volcano.

Krista Evans (05:23):

Yes.

Liza Lester (05:24):

But what kind of volcano is it?

Krista Evans (05:29):

So-

Liza Lester (05:30):

Not the lava kind.

Krista Evans (05:31):

No, it is… it can be both. So, you do have effusive lava-type eruptions but you can also get very explosive eruptions. Which, the last one was about 3,600 years ago.

Liza Lester (05:50):

And it was a big one.

Krista Evans (05:51):

And it was a very big one, it’s considered one of the largest volcanic eruptions in the last 10,000 years, at this point.

Liza Lester (06:01):

Wow. How do we know that it was such a big eruption?

Krista Evans (06:05):

Well, we can see that in… we’re seeing ash and ice core records and just the volume that was a erupted at this time and the explosive index.

Liza Lester (06:21):

So, we can see in, if we make ice cores in the Arctic, you can see the evidence of this eruption.

Krista Evans (06:26):

Yes.

Liza Lester (06:27):

And they can see what it did to the island, I guess. What does Santorini look like today?

Krista Evans (06:43):

So, today Santorini consists of five islands. You have Thira, Thirassia and Aspronisi, which is remnants of one larger island. And then, you have two central islands in a flooded caldera ring that are more recent and have been building up from these effusive lava eruptions.

Liza Lester (07:09):

Okay. So, it’s coming back up from where it blew itself away 3,600 years ago.

Krista Evans (07:17):

Yes.

Liza Lester (07:17):

Yeah. Oh, wow. Okay. And this island, it’s in Greece, in the Mediterranean.

Krista Evans (07:24):

Yes.

Liza Lester (07:24):

How close is it to, I don’t know, Athens or something like that?

Krista Evans (07:28):

Kilometers-wise, I don’t know. But ferry-wise, it’s about an eight hour ferry ride.

Liza Lester (07:36):

3,600 years ago, who was living on this island? It’s Greece, so we know there were civilizations in this area.

Krista Evans (07:45):

Yes. So, at the time, 3,600 years ago, we had the Therans living on the island. Which is a culture in and of itself, separate from the Minoans who lived on Crete, about 120 kilometers to the South.

Liza Lester (08:03):

What makes them distinct when we look at their-

Krista Evans (08:08):

So, their boats were different, their art was different, the style of their art and the pottery.

Liza Lester (08:16):

Oh, what does the pottery look like? Have you seen it?

Krista Evans (08:18):

I’ve seen it in a museum but I could not describe it for you.

Liza Lester (08:23):

It’s something for the archeologist to tell you, “this is what’s specific about their particular art.”

Krista Evans (08:28):

Yes.

Liza Lester (08:28):

Okay. But it’s kind of like pottery can be a signifier. Right? Of a specific time period or a specific culture. And is this one way that we now identify the way culture flows or who people were through this kind of pottery?

Krista Evans (08:42):

Yes. And they were actually also using the pottery to, basically, trace trading routes.

Liza Lester (08:51):

Okay.

Krista Evans (08:52):

Because we’re also seeing Minoan pottery on Thera. So then, they must’ve been trading with the people on Crete.

Liza Lester (09:00):

Okay. So, we know they were probably going back and forth and they knew these other people but they’re living here on this island and it has this massive eruption. So, did they have warning that this was going to happen? What was it leading up to this huge eruption?

Krista Evans (09:15):

That is a really good question, that’s what I work on.

Krista Evans (09:17):

So, we think that they had no idea that they were living on a volcano. They probably knew what volcanoes were but when this started to erupt and ash was falling from the sky, they were probably like, “What is going on? Let’s let’s get out of here.” Because that’s what they did, they left.

Liza Lester (09:48):

So, maybe made the right choice.

Krista Evans (09:51):

Probably.

Liza Lester (09:52):

Maybe we need to step back for a minute. What kinds of warnings might volcanoes give us or not?

Krista Evans (09:59):

So, they can give us several different types of warnings. So, you have earthquakes, you can have minor volcanic eruptions, ground deformation, changes in geothermal systems. So, hot springs could get hotter. A significant gas emission increase, those are the major ones.

Liza Lester (10:27):

So, you might see the land coming up, poofing up or sinking.

Krista Evans (10:33):

Yes.

Liza Lester (10:33):

And if you see that happening, you’re kind of like “What’s happening? The ground is changing.” Or definitely, if something’s falling out of the sky, that’s going to be probably pretty alarming. Rumbling.

Krista Evans (10:43):

Yes.

Liza Lester (10:44):

Yeah, okay. So…

Liza Lester (10:45):

And you think that this is something that Therans were experiencing?

Krista Evans (10:49):

Yes.

Liza Lester (10:50):

How do we know that they left?

Krista Evans (10:53):

So, we can see that at the archeological site of Akrotiri, which is located on the southern peninsula of Thera.

Liza Lester (11:02):

And this is a bronze age settlement.

Krista Evans (11:04):

Yes.

Liza Lester (11:05):

What are the characteristics of that? What kind of buildings did they have? What kind of artifacts?

Krista Evans (11:09):

So, they have three to four story buildings, they are stunning, they’re significant. I remember walking into that archeological site for the first time, two years ago, and going… my mind was just blown.

Liza Lester (11:28):

It’s like, there was a city there. Was it buried?

Krista Evans (11:32):

Yes. So, it was buried under several meters of tephra and ash.

Liza Lester (11:37):

And tephra is?

Krista Evans (11:39):

Pumice.

Liza Lester (11:40):

Okay. And there were these buildings but, you said, notably not bodies.

Krista Evans (11:45):

Yes.

Liza Lester (11:46):

So, not like Pompeii where we see people perished in their homes or in the streets.

Krista Evans (11:53):

Correct.

Liza Lester (11:53):

Okay. Kind of, in contrast to that.

Krista Evans (11:55):

Just, very in contrast. So, they must’ve gotten out of there. Originally, when it was first starting to be excavated, archeologists had associated with… all of this with earthquake activity and that being more of the precursory for the eruption. And that’s why they left. But we’re now arguing that they had to be very familiar with earthquakes.

Liza Lester (12:25):

Oh, because you think there were earthquakes in the region?

Krista Evans (12:28):

Yes. Because between the middle bronze age and the late bronze age, which was about several centuries prior to the eruption, there was what we call a seismic destruction level found both on Santorini and on Crete that marks that cultural transition.

Liza Lester (12:51):

Oh. So, you see it… you see a change in the culture at the same time as you see evidence that there had been earthquakes or there’s damage to their buildings or to the surrounding environment.

Krista Evans (13:02):

Yes.

Liza Lester (13:03):

Wow. That’s so interesting that you can still see that 3,600 years later.

Krista Evans (13:08):

Yeah. Well, it’s actually preserved in the archeological record. So, all their buildings were completely destroyed and instead of cleaning everything up, they just rebuilt on top of the rubble.

Liza Lester (13:21):

So, where did the people go?

Krista Evans (13:23):

That’s a good question. We’re not exactly sure because we don’t see an influx of people coming in at the time of the eruption on Crete nor do we see their art or their craft.

Liza Lester (13:36):

Like we were saying about the pottery, it’s not showing up.

Krista Evans (13:40):

Yes. It’s just not showing up on Crete or any other nearby islands. So, the question of where did they go still remains. However, we have a slight theory behind where they may have gone.

Liza Lester (13:57):

Okay, I want to hear about this theory then.

Nanci Bompey (14:01):

Yeah, I want to know about this theory. Where did these people go?

Shane Hanlon (14:03):

Yeah. Seriously, where did they go?

Krista Evans (14:06):

So, after this precursory eruption, a small group of people came back and started to clean up. We see this because at the site there was a pile of rubble that had building debris and layers, one through three, of the precursory. So, there’s four pulses of the precursory.

Liza Lester (14:31):

So, it’s like the volcano is spitting out this pumice and things and you can see distinct layers of that?

Krista Evans (14:39):

Yes.

Liza Lester (14:39):

Okay.

Krista Evans (14:40):

Yeah. So, all of this is swept up in a corner and then we have the fourth pulse of the precursory that blankets this pile of debris and rubble. And so, they got out of there again.

Liza Lester (14:58):

They’re like, “Oh, it’s not over.”

Krista Evans (14:59):

“It’s not over.”

Liza Lester (15:00):

“This maybe looks worse.”

Krista Evans (15:01):

Like, “Uh-oh.” And pulse four then, quickly transitions into the first phase of the main, Plinian eruption. So, now we have a nice sustained Plinian column.

Liza Lester (15:19):

And a Plinian column is what? Tell me about that.

Krista Evans (15:21):

So, a Plinian column is a column of ash and gas that is just going straight up into the air and it eventually reaches what we called buoyancy. And wind will blow this plume in the direction of the wind, basically, obviously. And you have the tephra and ash falling out of this plume. So, being an island, you have pumice rafts forming because pumice is very light so it floats on water.

Liza Lester (16:09):

Oh, it’s this rock that almost looks styrofoam.

Krista Evans (16:11):

Yes. So-

Liza Lester (16:12):

And it’s full of holes.

Krista Evans (16:14):

So, it’s full of holes, very bubbly.

Liza Lester (16:16):

So, it actually floats styrofoam.

Krista Evans (16:18):

So, it floats.

Liza Lester (16:20):

That must be interesting to see and maybe scary if it’s right where you are.

Krista Evans (16:25):

Yeah.

Liza Lester (16:26):

So, big masses of this stuff just floating on the ocean.

Krista Evans (16:29):

Yes. So, here we have the pumice rafts and these people have to get away in boats.

Liza Lester (16:37):

What kind of boats do they have? Are these sailboats or are they more like canoes?

Krista Evans (16:42):

So, they’re not quite… probably similar to canoes, they’re paddling. So, they’ve got-

Liza Lester (16:49):

Okay. Human power, then.

Krista Evans (16:50):

Yeah. So, it’s all human power. You don’t have the technology for engines and things like that, so it’s all of them paddling away.

Liza Lester (17:00):

And how far is Crete from Santorini?

Krista Evans (17:03):

It is 120 kilometers south.

Liza Lester (17:06):

That’s a long ways to paddle.

Krista Evans (17:07):

Yes.

Liza Lester (17:08):

So, you can’t see it on the horizon. It’s like you’re heading out into the ocean.

Krista Evans (17:12):

Well, you can actually see it on the horizon on a nice, clear, pristine winter day from what I’ve been told. I’ve never been able to see it but I’ve never been there in the winter either.

Liza Lester (17:28):

But they’d been trading, so they knew that Crete was out there, they could escape somewhere.

Krista Evans (17:32):

Yes.

Liza Lester (17:33):

And you think they did this by boat.

Krista Evans (17:34):

Yes. There are other nearby islands that you can also see from the island but they would have had to go around the eruption in order to get there since they’re on the southern coast. So, the obvious way to go is south.

Liza Lester (17:52):

Okay. So, they get in their boats, they’re paddling away, this terrifying cloud is coming up behind them as they try to leave.

Krista Evans (18:01):

Yes. And there’s actually a book out there by [inaudible 00:18:06], who estimated that they can only paddle out about 1.7 to 2.3 kilometers per hour, and that’s with pristine conditions.

Liza Lester (18:18):

Yeah. It probably depends a little on like, is the tide in your favor?

Krista Evans (18:22):

And then, there’s that. And now… but now you’re also paddling through these pumice rafts.

Liza Lester (18:27):

Right.

Krista Evans (18:28):

That’s going to make it a lot harder to paddle through. Even in the 1883 eruption of Krakatau, we can see that ships that are motor powered are struggling to sail through these-

Liza Lester (18:47):

Floating rocks.

Krista Evans (18:47):

Yes.

Liza Lester (18:48):

Yeah, okay. Wow.

Krista Evans (18:51):

Yeah. So, paddling through pumice rafts…

Krista Evans (18:57):

And then, we use the higher end…

Krista Evans (19:02):

So, about eight hours later, this eruption is transitioning into phase two. So, in phase two, we get destabilization of this nice, Plinian column and it collapses, creating a whole series of pyroclastic density currents.

Liza Lester (19:23):

And describe a pyroclastic density current. What does that look like?

Krista Evans (19:27):

So, think Mount St. Helens. It’s this big cloud of ash and gas flowing at a very high speed. And it’s hot, it’s not a cool temperature like a landslide but it’s similar to a landslide. But you got hot ash moving at a very high speed, typically follows topography but it can jump river valleys if it’s moving fast enough.

Liza Lester (20:02):

And these things are going hundreds of miles per hour.

Krista Evans (20:05):

Yes.

Liza Lester (20:06):

You can’t outrun it.

Krista Evans (20:08):

No.

Liza Lester (20:08):

You can’t even get away in a car, probably.

Krista Evans (20:12):

No.

Liza Lester (20:13):

Yeah. You just need to not be in front of on of these things.

Krista Evans (20:15):

Exactly, you don’t want to be anywhere near it.

Liza Lester (20:19):

And that was what happened at Mount St. Helens really dramatically. Right?

Krista Evans (20:22):

Yes.

Liza Lester (20:22):

That it blew out the side and then these pyroclastic density flows came over the sides of the next ridge.

Krista Evans (20:29):

Yes. And you also have debris flows that occurred with Mount St. Helens. Yeah.

Liza Lester (20:34):

But how big was this Santorini eruption compared to something Mount St. Helens it was much bigger. So, I’m not sure what Mount St. Helens was, off the top of my head, but Santorini has of volcanic explosivity index of about 7.2.

Shane Hanlon (20:53):

7.2 sounds big to me but that’s actually pretty big. Right? Like, scientifically.

Liza Lester (21:02):

Yes. So, she’s talking about this volcanic explosivity index which was a way that people devised to try to compare different volcanic eruptions, their relative strength and power and how much…

Liza Lester (21:14):

So, they base it on how much stuff comes out of the volcano and how high it goes into the stratosphere, how long it goes on for, to try to give an idea of how big it was. Right? And the biggest ones that they have measured are eight.

Shane Hanlon (21:31):

Oh, okay.

Liza Lester (21:31):

So, seven is big. Right?

Nanci Bompey (21:34):

Yeah.

Liza Lester (21:35):

Oh, and this is a logarithmic scale too. So, seven is 10 times bigger than six and a hundred times bigger than five.

Nanci Bompey (21:43):

Like how they measure earthquakes.

Liza Lester (21:45):

Yeah, like the Richter scale.

Shane Hanlon (21:47):

Oh, okay.

Liza Lester (21:47):

Yeah, yeah. So, Mount St. Helens was a five.

Shane Hanlon (21:51):

Oh.

Liza Lester (21:52):

Yeah. And the 1883 eruption of Krakatau, that was a six.

Nanci Bompey (21:56):

Oh, wow. So, this is huge. Yeah.

Liza Lester (21:58):

So, it’s big. And the ones that were eights were the Yellowstone supervolcano, hundreds of thousands of years ago. Right? Not within experience of our lifetimes or anyone that we know. And so, seven is big, I think we can establish that. Super-colossal.

Shane Hanlon (22:15):

That’s impressive. Super-colossal, I like that.

Nanci Bompey (22:19):

That’s a technical term. Right?

Liza Lester (22:19):

A technical term.

Shane Hanlon (22:20):

Yeah.

Nanci Bompey (22:21):

Super-colossal. All right.

Shane Hanlon (22:22):

That sounds legit.

Nanci Bompey (22:23):

Yeah.

Liza Lester (22:25):

Okay. So, it’s these… these pyroclastic density currents are now flowing down the side of the mountain.

Krista Evans (22:30):

Yes, and-

Liza Lester (22:33):

But they’ve left the mountain, they’re paddling away.

Krista Evans (22:36):

Yeah, they left the island so, as of now, they’re fine. But we know from the 1883 eruption of Krakatau… and we just actually, recently saw this at Stromboli, back in July or August, where pyroclastic density currents can travel across water. We get this from…

Krista Evans (23:01):

We know this from eyewitness accounts at Krakatau and we have video of it at Stromboli.

Liza Lester (23:10):

Because, though look they’re moving like water, they’re actually ash and gas and super-heated gases. That’s terrifying.

Krista Evans (23:18):

Yes, and moving at a very high speed. But we also have the pumice rafts that help this pyroclastic density current stay above the water and travel at a very high speed. This is something that I want to look into a little bit more. Is, how do you pyroclastic density currents interact with ocean water? And then, how does pumice rafts affect this interaction? And does the thickness of those pumice rafts inhibit or enhance the movement of these things?

Liza Lester (23:58):

So, are people from [Akrotini 00:24:04], they’re not safe then. They’re paddling away-

Krista Evans (24:02):

No, they’re paddling away and now they have this pyroclastic density current coming after them.

Liza Lester (24:09):

That’s terrifying. Okay. So, you were saying they were going, what, one to two kilometers per hour, maybe.

Krista Evans (24:16):

Yes.

Liza Lester (24:16):

How…

Liza Lester (24:17):

And they’ve had eight hours, they’ve only made it maybe eight to 10 kilometers away. How far did they get?

Krista Evans (24:22):

Not very far, I think. If I remember off the top of my head from my research, it’s only about 13, 14 kilometers.

Liza Lester (24:31):

So, they made this valiant effort probably, they probably were moving along but this is as far as they could get under their own paddle power.

Krista Evans (24:39):

Yeah. And we’re assuming…

Krista Evans (24:40):

Again, we’re assuming that they are paddling in pristine conditions. So, they’re probably not even that far yet.

Liza Lester (24:49):

And the pyroclastic density flows are coming across the water at them. Do you think that it reached them?

Krista Evans (24:57):

Yes, within minutes. Because using information from [inaudible 00:25:06] that calculated using ship records and using when the ships heard the sound from the eruption and from when hurricane forced winds hit them, they calculated the velocity of the pyroclastic density currents of the 1883 Krakatau eruption.

Krista Evans (25:29):

So, I went ahead and used that information and it’s about 260 kilometers per hour. So, these things are moving real fast and probably caught up to the Therans within five minutes.

Liza Lester (25:47):

So, you think they were just overwhelmed by these and that’s the answer to the mystery.

Krista Evans (25:52):

Yes.

Liza Lester (25:53):

They may be at the bottom of the ocean.

Krista Evans (25:55):

Yes.

Liza Lester (25:57):

It’s a little bit of a sad ending but very dramatic.

Krista Evans (26:00):

It is very dramatic.

Liza Lester (26:03):

Do you see evidence of these pyroclastic density flows having come across the water from that eruption? Is there evidence on the other islands? How far did they go?

Krista Evans (26:12):

So, that is a very good question and that is something else that I want to look at in the future.

Liza Lester (26:20):

Yeah. So, how do you do go about that? Do you have to do dives or do you go look at the other islands and look in geologic record for it?

Krista Evans (26:27):

So, I will probably, mainly, do… look for deposits on other islands. I know we have not published this yet but we’re going to be looking at it, but we have some first phase pumice on a nearby island that we think may have come from the pumice rafts. So, that also shows that pumice rafts existed and were formed.

Liza Lester (26:57):

All right. So, what does this tell us about the way we relate to volcanoes over time? Is it just…

Liza Lester (27:05):

Are we the same as the Therans, we see this hazard that we live with and are like, “I’m kind of used to it but…” I don’t know. I don’t know what I’m asking here. When you think about comparing their reaction, I guess, to, say, the way the people in Pompeii and Herculaneum reacted to Vesuvius 1500 years later.

Krista Evans (27:24):

Yeah, that’s a good question. That’s a very interesting topic for me because, granted the Pompeians didn’t really have the warning like they did at Santorini, but yet they were still ignoring some of the signals like earthquakes and they had obvious ground deformation. And we see that in their aqueduct system because it kept breaking.

Liza Lester (27:50):

Because water has got to flow downhill in the aqueduct. Right?

Krista Evans (27:54):

Yeah, so-

Liza Lester (27:54):

So, if it’s lifting up or dropping then it doesn’t… it’s not flat anymore.

Krista Evans (27:58):

Exactly. So, the system keeps breaking but they keep rebuilding it not thinking, “Why does this keep breaking? Maybe we should look into this a little bit.” But instead are building their pipes deeper underground instead, thinking, “Maybe this’ll fix the problem.” But they didn’t have the venting like we see at Santorini so there wasn’t a precursory eruption. And so, putting all of that together, they just didn’t know how to respond.

Liza Lester (28:39):

It’s hard to leave your home.

Krista Evans (28:42):

Yeah.

Liza Lester (28:43):

I mean, we even see that now when there’s eruptions. Right? You have to persuade people that it’s really something that they have to leave for. And you can’t be sure exactly when it’s going to happen. There’s this threat out there, it could erupt, we’re not exactly sure when or how but you might be in the path of it.

Krista Evans (28:59):

Yes.

Liza Lester (28:59):

Yeah. So, next you’re going to be looking at more of the pyroclastic density flows and where they went, looking for evidence of those.

Krista Evans (29:07):

Yes, that is my goal.

Liza Lester (29:12):

Do you want to see a volcano erupt?

Krista Evans (29:15):

Yes. As an explosive physical volcanologist, yes I do.

Shane Hanlon (29:25):

I can’t imagine being on a raft or a boat or whatever it is and seeing a pyroclastic flow coming towards me. Or I guess, at least what the current hypothesis is now. Right?

Liza Lester (29:40):

Yeah, it’s like horror movie level.

Shane Hanlon (29:42):

Oh my gosh, it is.

Liza Lester (29:44):

And they almost… they made the right choice. You know? They left, they almost made it.

Shane Hanlon (29:50):

Yeah. But I guess it…

Shane Hanlon (29:51):

I mean, this is 3,600 years ago. They’re still… they ultimately made the right choice. Right? But hemmed and hawed and…

Shane Hanlon (29:58):

But that’s like, this far… this much later, I don’t know if I can blame them. You know what the right action is but we still wrestle with this. Right?

Liza Lester (30:08):

When to leave your home?

Shane Hanlon (30:09):

When to leave your home, the only thing you’ve ever known. What is right?

Liza Lester (30:14):

Yeah. This is still a question with volcanic eruptions today.

Shane Hanlon (30:19):

And we just… we literally just talked about this a couple episodes ago in the Mount St. Helens episode, when there were people going in, the morning of the big eruption, because they wanted to go to their cabin, they wanted to go to their houses. And so…

Liza Lester (30:32):

Nothing was happening.

Shane Hanlon (30:33):

Right. Right. Everything can change in a moment.

Liza Lester (30:37):

Right? You know, sometimes it’s a super-colossal eruption coming and sometimes it’s just a burp.

Shane Hanlon (30:43):

All right, folks. Well, that’s all from Third Pod From The Sun.

Nanci Bompey (30:47):

Thanks so much to Liza for bringing us this story and to Krista for sharing her work with us.

Shane Hanlon (30:52):

This episode was produced by Liza and mixed by Kayla Suri.

Nanci Bompey (30:56):

And you can check us out wherever you get your podcasts, please rate and review us on Apple Podcasts. And you can always find us as thirdpodfromthesun.com.

Shane Hanlon (31:07):

Thanks all, and we’ll see you next time.