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The Pacific Ring of Fire wraps around the Pacific Ocean, including countries like Japan, Canada, New Zealand and Chile. And the inhabitants within those countries are prone to… oh… killer earthquakes, volcanoes and tsunamis. Let’s chat about the history of this region and the kinds of risks they face.
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This episode is sponsored by: 8th Light, Swinburne Astronomy Online
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Transcript: Pacific Ring of Fire
Fraser: Astronomy Cast episode 307 for Monday, May 20, 2013 – Pacific Ring of Fire
Welcome to Astronomy Cast, our weekly facts based journey through the cosmos. Where we help you understand not only what we know, but how we know what we know.
My name is Fraser Cain, I’m the publisher of Universe Today. With me is Dr. Pamela Gay, a professor at Southern Illinois University Edwardsville, and the director of CosmoQuest.
Fraser: Hi Pamela, how are you doing?
Pamela: I’m doing well, how are you doing Fraser?
Fraser: Doing well. So this is our last reminder to people… well by the time they get this it will already be too late.
Pamela: They can go back and watch it all on YouTube.
Fraser: Yeah, go back and look at all of the mad 24 hour CosmoQuest-a-thon. What’s the official name of this?
Pamela: Hangout-a-thon.
Fraser: Hangout-a-thon, yes. I guess at this point we did more than 24 hours of space hanging out… well not “we”, mostly you and Nicole.
Pamela: Noisy astronomer, Nicole Gugliucci.
Fraser: I only jumped in on occasional moments after being well rested and helped to entertain.
Pamela: That’s okay, you have children, you are never well rested.
Fraser: That’s true too. So that goes from June 15th to the 16th. What time does that start?
Pamela: We are starting at noon Eastern, 9am Pacific US time zones and going through until 8pm Eastern, 5pm Pacific on Sunday. We’re going from Saturday morning until Sunday evening. We’re going to a Virtual Star Party on Saturday, we have Scott Sigler to talk with Seth Shostak about the trope of aliens existing everyone on human habitable worlds. We have Amy Roth coming on to talk about making space jewelry, we have the band The Jungle Fire which does secular soul music and I just love that concept. So many others that are too numerous to name here. All of this is going on the YouTube Astrospherevids channel so go check it out.
Fraser: Check out the CosmoQuest page, I’m sure there will be more information on there. Okay so let’s go.
Fraser: The Pacific Ring of Fire wraps around the Pacific Ocean, including countries like Japan, Canada, New Zealand and Chile. And the inhabitants within those countries are prone to… oh… killer earthquakes, volcanoes and tsunamis. Let’s chat about the history of this region and the kinds of risks they face. Pamela we always talk about how you live in the danger zone for tornadoes, adorable and horrible tornadoes that as we’ve seen recently there has been terrible tragedy in Oklahoma.
Pamela: Oklahoma was horrible.
Fraser: These are absolutely a big risk to humanity for the people that are living there but on the same side folks like me, living on the west coast of Canada, live in the Pacific ring of fire. That’s where I’ve got volcanoes, I’ve got earthquakes, I’ve got Tsunamis and as we’ve seen recently, the folks in New Zealand, the folks in Chile and with the folks in Indonesia there is a lot of dangerous stuff going on there.
Pamela: Yeah, we have the rare extreme earthquake here because we have the San Madre fault which no one understands because it’s in the middle of a plate being confused. The folks along the coast of North and South America on the western side and then the folks all along the bands of island nations so Indonesia, the Philippines all the way through Japan across the Elysian Islands, off of Siberia and Alaska depending on which end you start, all of these people have the misfortune of being on the edge of the Pacific plate. This is a plate that is moving in unfortunate directions. It is pulling away from the Nazca line which is a plate that is rubbing up against South America and as it pulls away from the Nazca plate, it is bashing itself wholeheartedly into the plate that Japan and Australia rest on. At these points of collision the plates are colliding and you are ending up with welling up of magma so you end up with a lot of volcanoes. In Japan Mt Fuji is perhaps the most notorious example although it doesn’t do too much damage nowadays. There are lots of active volcanoes there and there are also lots of active volcanoes throughout the Indonesian islands and the Philippines; Krakatoa is a famous example. This is again from the upwelling of magma and as the plates collide, it’s one of those things where it’s like trying to move something along asphalt. It will move and then it will get stuck with friction on the asphalt and you have to give it a good solid push to overcome that getting stuck, that friction. When a giant continental plate becomes unstuck it can have traumatic consequences as we saw in Japan two years ago.
Fraser: Yeah, so lets go into that. So when you say that these plates can get stuck, what does that mean exactly?
Pamela: You have three different processes going on when you have a collision taking place. You can have subduction where one plate goes under as the other plate goes over. Just like if you’re trying to slide one piece of paper underneath another piece of paper you might end up with the one plate buckling instead of just politely sliding underneath due to frictional forces.
Fraser: A quick note for the audio listeners: Pamela is making some really awesome hand gestures to show this so if you ever want, we record these live on Google+ and if you want to see Pamela’s thrilling hand gestures, I highly recommend you watch it every Monday at noon Pacific or 3pm Eastern so you can watch Pamela make hand gestures to go along with astronomy. Please continue.
Pamela: (Laughing) Yeah, okay, anyways, speaking non-actual sign language at the camera… so as the one tries to go under friction might cause it to get stuck and it buckles up at the edge. That buckling up is one thing but as it gets stuck eventually all of that force building up behind it is going to give way to that plate moving and it can sometimes move a few meters at a time. When you are talking about a continent moving a few meters in a few minutes, that is a whole lot of energy that is getting released. It gets released in the form of sound waves, kinetic energy and you can get everything from sharp jolting motions to slow rolling and rumbling motion but either way it’s motion of things that have building, people or water on top of it.
Fraser: I remember in the case of Japan there was an earthquake and it was very bad but the even worse part was the terrible tsunami that followed moments after.
Pamela: The release of energy into the water is what caused this terrific standing wave to start radiating away from the epicenter of this earthquake. The earthquake appears to have occurred off the coast a ways off from Japan. People are working to understand how to predict which seafloor earthquakes are going to generate tsunamis and which aren’t and what they are finding is that they can look at the energy that is being released in the form of sound and measure that using horns dropped into the water to listen. Ones that produce tsunamis release vast amounts of sound wave energy and that can be used to predict just how tall the tsunami that is heading toward land might be. You have all of the potential energy basically the spring energy of the two plates trying to collide getting released. During the release of essentially spring energy, some of the energy gets converted into sound energy and some of that sound energy predicts just how big the standing wave that is carrying the water with all of the energy trapped in towards land might be. One of the problems in Japan was their predictions for how tall the tsunami would be. It was predicted to be much shorter than what it actually was so people didn’t seek high enough ground.
Fraser: I think people kind of imagine this tsunami as a great big breaking wave that comes and crashes in. What it was though was an up swell The water just got deeper and deeper then overflowed the banks. Material from the ocean was being pushed inland and cars and buildings were being inundated. It was just this fast relentless rise of water and it was quite terrifying. You can see how once you realize that you are in the middle of this and you wouldn’t see the wave off in the distance then you would seek higher ground. It just a rise of water all around you; it’s really scary.
Pamela: The best demonstration you can do to try and wrap your head around what’s going on with the tsunami is the next time you change your sheets and you go to put the flat sheet on (I’m assuming you’re not using a duvet being a westerner here), grab the edge of that flat top sheet and just fluff it up with just one quick jerk on the edge. You’ll have a wave that propagates through the sheet. When it does this the other side of the sheet has to come toward you to have that wave get formed out of something. In this case with the tsunami, instead of having someone’s hands yank the edge of the sheet to put in the wave, it’s the energy of the earthquake that initial point for the formation of the wave. The water that goes into the tsunami has to draw from somewhere so all the water goes out from the shore and suddenly you end up with significantly more beach than you would even during the lowest of low tides. That’s one of the early warning signs.
Fraser: Don’t go out and pick oysters, run. Right?
Pamela: Yeah. So when you see the water go down, go up, go up, go up, go up. Unfortunately although they did get very early warning that a tsunami was coming, they didn’t yet understand the roll that measuring sound had in predicting the height. They underestimated the height and because of this drowning was the leading cause of death and it was just because people didn’t get high enough.
Fraser: But even so that is a well organized country, a well organized response to the tsunami. It could have been so much worse and we’ve seen so much worse recently. We saw what happened in Indonesia and Haiti. I live on the Pacific ring of fire; I live on Vancouver Island. As you are well aware of and made aware of are the risks of tornadoes where you live, we’ve got something very similar for earthquakes and tsunamis where I live. For example, our buildings are all done in a very special kind of code. All of our houses have to be done in a special wood frame and if they are larger than that they have to be done with steel.
Pamela: Floating levels
Fraser: Yeah exactly. In Vancouver there is a great building that actually has a pillar in the middle and the whole building actually floats on these cables that hang from this pillar so the whole building can rock back and forth in an earthquake. The children are trained and go through earthquake and tsunami drills.
Pamela: I remember that. I grew up in southern California and they had those as well.
Fraser: Just like your kids will do fire drills, ours will do earthquake drills.
Pamela: We do tornado drills.
Fraser: When you’re out on the west coast they mark out every spot which is at tsunami risk. You’ll be driving along and then a sign will say “You’re now entering a tsunami zone” and there are sirens on all of the poles and trees in the area. There are also defined routes to get to higher ground in every one of these tsunami zones. In fact if you drive down the west coast of the United States it’s the same thing, it’s like “now I’m in a tsunami zone… now I’m out”. How does the ring of fire manifest itself in different ways? You mentioned that the plates are coming together over in Japan but here I know they’re going sideways right?
Pamela: It depends on which plate is involved. Along the Elysian islands and along the coast of Japan you have plates that are mushing together then you have the Philippine plate and they are still trying to figure out which direction it’s going. That one has been harder to tell. We’re colliding with the Australian plate; there is a rogue plate, the Naska plate, that is between South America and the Pacific plate. It’s another one where it’s colliding with the South American plate, that’s part of what’s creating the Andes Mountains. Along the coast of where you are there is again this extra floating plate, the San de Fuca plate, and it’s one that is kind of caught in the middle with the North American plate and the Pacific plate. Those two plates are moving in different directions which is where California runs into all of its problems when those two collide. There are points of weakness so the San Andreas fault can be viewed as a point of weakness where these two plates are rubbing against each other and the land is fracturing underneath.
Fraser: Yeah and I know that for us it runs a couple hundred kilometers off the coast of Vancouver island which I guess is a good thing and a bad thing.
Pamela: Yeah that’s actually the San de Fuca plate there.
Fraser: Yeah, I think it’s San de Fuca (Few-kah). So we actually did have a very strong earthquake just south of an area called Haida Gwaii, sort of the Queen Charlotte islands, and it was very powerful but if was far enough away that I didn’t feel it. It was like a magnitude 8? Yeah so quite enormous. So what causes this plate and what causes this whole region to have this? You talk about this plate, but why do we have one big plate like this? Why isn’t it smaller? Why isn’t it bigger?
Pamela: Some of these things we can’t easily answer. The best way to try and understand this is if you’ve ever tried to cook something that convects instead of boils. So oil convects where you get cells of hot oil rise and the cells of cold oil sink but you don’t end up with the bursting bubbles and you don’t have gas manifesting itself in oil, you just end up with this churning. If you get your cherry filling just right it will convect. Now if you have a semi-solid floating on top of this convective surface, that motion and churning underneath can lead to a fracturing of the semi-solid surface. In this case we have a planet that is molten and convective in the layer beneath the crust and our crust is just like that semi-solid surface on top of your convecting food. It ends up fragmenting and those fragments get moved around by the, in this case, it’s that everything is rotating and you end up with a certain amount of differential rotation. It’s not a big deal with the earth but it does act to add to the motion. One of the things that I’ve seen questions raised about is part of the reason that Venus doesn’t have plate tectonics the way we do simply because it’s not rotating sufficiently fast. Does that play a roll? No one knows yet. We’re still figuring these things out. When we look at the biggest plates, there are actually arguments as to whether we are dividing the plates up enough, can we divide them down further, what really defines a plate etc… because we do have fault lines, like I said, near the San Madre fault line. I live right in the middle of the North American plate but does that mean that the North American plate is several smaller plates or does it mean that the plate I’m on is cracked and some of the pieces move a little bit more readily than other pieces? This starts to get into fine grained arguments of taxonomy but overall you have these large plates that the continents rest on that are moving apart. For instance right through the center of Iceland which has a stripe of fire, you might say, that’s where the two plates are pulling apart. Iceland is gradually getting larger and larger as the plates pull apart and there are volcanoes all over Iceland The ring of fire is almost entirely where plates are colliding together. You have a mid-ocean trench with the Naska plate and the Pacific plate and as they collide together you end up around the entire pacific rim with volcanoes and earthquakes. The one confusing point is Hawaii. Hawaii is just this random set of hot spots and people are still trying to figure out how it sits smack in the middle of a plate so Hawaii isn’t a part of the ring of fire.
Fraser: Right it’s a hot spot that could appear almost anywhere.
Pamela: Yeah
Fraser: Although it has been right in the middle of the ring of fire. Coincidence?
Pamela: I can’t speak to that. There is everything from people thinking that the Hawaiian islands are actually where something broke through the crust, left a weak point and as the surface crust moves there is a weakened hot sp… there are all sorts of things that don’t entirely make sense that get put together to try and explain Hawaii. What we know for certain is that as the plate moves, it’s exposing new parts of crust to the hot spot underneath so you end up with a chain of islands as the crustal plate moves exposing more to the hot spot.
Fraser: Back to the United States, have you ever driven on I5 from Canada down to California.
Pamela: I’ve done LA to San Francisco which is far less exciting.
Fraser: Right. There is constantly, pretty much, a volcano in sight for huge chunks of that drive. As you drive south there is Mt Baker, Mt Rainier, Mt Hoot, Mt Adams and Mt Shasta which is gigantic and you see for hours and hours. You can really see that you’ve got these volcanoes up and down the coast. There is some stuff in Canada but not a lot but when you get down to places like Costa Rica there are some amazing volcanoes Why do we get volcanoes, in Costa Rica for example, that are in constant state of eruption and are blobbing out lava nonstop? In the United States though you get places like Mt. St. Helens which build up for a long time then detonate. Why do you get that difference although it’s all the same plate?
Pamela: It’s different chemistries in different kinds of volcanoes is one part. It’s different geometries to the different volcanoes as a different roll. The rate of magma production plays a roll into this so if you have one that is more active in creating the magma or rather there is a larger channel that allows the magma in, it’s going to grow much more quickly. There was a case in Mexico in the 50’s I believe that got a hot spot that a few years later was a huge volcano and then it pretty much stopped.
Fraser: Yeah I remember that story. We had that as like a kids book.
Pamela: Yeah, we talked about that. I always wanted the farmers field behind our house to grow a volcano.
Fraser: Me too!
Pamela: I was a stupid small child, it would have ruined our house.
Fraser: But it would have been awesome.
Pamela: Yeah it would have been awesome. So all around the ring of fire it’s a matter of how the plates are colliding. What’s kind of neat is you don’t always, when you have the plates colliding, end up with a ring of volcanoes Where you look at the India plate hitting the Asia plate you have the Himalayan mountains and Mt. Everest is not a volcano. It’s just a giant (insert expletives) mountain because in this case you have two plates coming together and ridging upwards. It’s where they come together and ridge upwards that you don’t get the same volcanism but you do get giant mountains. Kudos to the giant mountains.
Fraser: So now living here in the ring of fire, I think we don’t get the same kind of constant, in your face, fear of it. I think that you do for example with tornadoes You experience a certain amount of tornado fear and rightly so with what happened a couple of weeks ago with you having a tornado pass right through. We get occasional earthquakes. How dangerous is this for me to live here?
Pamela: It’s one of those types of statistics that is hard for a human to wrap their brain around. For instance when you look at 1 in however many thousand will die in an airplane that doesn’t mean that each individual has that kind of probability. You need to instead look at how many 747s fall out of the sky and the probability comes from the fact that the 747 carries a shed load of people on it. One tornado generally won’t kill a lot of people but one earthquake will kill a lot of people. What you need to consider isn’t what the probability of an individual getting killed by an earthquake but what is the probability that I am getting violently shaken by an earthquake. Places where you are look like it’s probably every hundred years to every couple hundred years there is a devastating earthquake. We’re still trying to understand those things better. Some plates are moving more than others that’s why China keeps having so many issues.
Fraser: I know that there are some examples of some pretty bad… as archeologists look back in time and look at these different sites, we had a situation a couple of hundred years ago where we had pyroclastic flows which wiped out villages of the Niska tribe in my area.
Pamela: In our area we did see the city of St Louis as if was first getting founded, got completely flattened by an earthquake that actually changed the flow of the Mississippi river. When you consider that the largest river in the United States had it’s path changed, moved and temporarily reverse direction because of an earthquake, it can give you a sense of how much power they can have.
Fraser: Big chunks of Seattle are built on the pyroclastic flows from Mt Rainier.
Pamela: When you start thinking that Mt Rainier isn’t dormant, it’s simply paused and we don’t know when it will un-pause. There is a huge population around it and that’s a little bit unsettling to say the least. If you ever want to have a very fast, comparatively, view of vast numbers of volcanoes and you have lots of money to burn, the flight from Beijing to Seattle goes up and over the Elysian islands and back down along the coast of Canada. I remember waking up at one point on that flight and couldn’t stop looking out the window because it was snow capped volcano after snow capped volcano. You can occasionally see some of the Alaskan ones smoking out in the distance and it’s just amazing.
Fraser: You’ve got all those ones up the coast of Russia and then all the ones along the Elysian islands. It would just be amazing.
Pamela: That’s one way to get a great view of them is to take that morning flight out of Beijing and land in the afternoon in Seattle.
Fraser: What impact did the large movement of the continents have on the ring of fire? Hundreds of millions of years ago we had Pangea and I guess in the far future we’re going to have a different situation. Is this making the ring of fire larger or smaller?
Pamela: One of the things we are still trying to get a handle on is how it is that the plates rotate the way they do. We know that a new plate is basically going to come into existence Plate may be too strong of a word. We know that a new continent is going to slowly grow into existence where Iceland is, baby, tiny, but growing.
Fraser: In Pangea time you had South America crunched into Africa so that whole area, that whole ocean is brand new right?
Pamela: The Saudi Arabian peninsula is breaking off of the Arabian plate, off of Africa and so this is all just part of all the continents being in constant motion. There are predictions about what the different configurations would be. We know that there is a sea that is going to open up between Saudi Arabia and Africa and it’s just kind of amazing to think of Ethiopia growing an ocean kind of like the Mediterranean inside of it. That’s the future that we’re looking at. Everything is in motion we just need to wait the billion years or so to see where it all goes.
Fraser: Right so based on this conversation I will probably be killed by any manner of terrible catastrophe.
Pamela: I would not say that.
Fraser: The universe is trying to kill me specifically.
Pamela: The universe is trying to kill you but I think genetics and old age are are much more of a fear. I think if you’re going to walk away with anything it’s colliding plates that are subducting like debris-ed volcanoes, they are pretty but stay away from them. If you happen to live in that zone know how to go up quickly. If you want the Himalayas just crash two plates in and let their ends fork up together.
Fraser: Well cool. Thank you very much Pamela.
Pamela: Thank you.
This transcript is not an exact match to the audio file. It has been edited for clarity.
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