Geology of Natural Disasters, Volcanoes and Earthquakes
This week we shake up the world of science as Janet Sumner describes the dynamics of volcanic eruptions and the strutcure of the Earth, Tamsin Mather talks about how the gases from volcanoes affect our atmosphere and environment, Tiziana Rossetto discusses earthquakes, tsunamis and Pakistan, and Derek joins Herbert Huppert for an explosive experiment in Kitchen Science.
In this episode
Why Chocolate Is Good For You
Good news for all chocoholics out there - scientists have found yet more evidence that that our favourite foodstuff is a healthy one too. Chemicals called flavanols are found in foods like red wine, tea and chocolate, and have previously been linked to a healthy heart, and the chief culprit in chocolate is a molecule called epicatechin. Researchers from California studied a tribe called the Kuna Indians who live on the San Blas islands off the coast of Panama. The island-dwelling indians drink about three or four cups of hot chocolate every day, and hardly ever have high blood pressure or other cardiovascular problems. They also have high levels of a molecule called nitric oxide, which acts to relax the blood vessels and keep everything flowing smoothly. But when the indians move to Panama City, they drink only four cups of cocoa per week. The scientists found that the city types had higher blood pressure, and weren't so healthy. They also make less nitric oxide. Now, this may sound like it's the stressful effect of the city rather than the chocolate. But the team tried just giving pure epicatechin (the chocolate chemical) to human volunteers, and found that it had the same beneficial effects. Bet it didn't taste as good though! It should be pointed out that chocolate bars also pack a hefty dose of fat and sugar, and eating a high-fat diet and being overweight are major contributors to heart disease. To get the most cocoa (the bit that contains the good chemicals), go for a good quality dark chocolate with at least 70% cocoa - and eat it in moderation!
- The Science of Schadenfreude
The Science of Schadenfreude
with Now here's a story that'll bring tears to your eyes, and especially if you're a woman it seems. Tania Singer from University College London has been looking at the science of sympathy.
Tania - What we do is investigate empathy, so that's brain responses to the pain of other people. What we wanted to know was whether these rain responses to the pain of other people changed as a function of whether you like or dislike someone.
Chris - So how did you do it What was the actual paradigm you used?
Tania - We knew that using economic games is very potent to inducing liking and disliking in people. In these games, each subject engaged in monetary exchange games with two actors. The subject could send money to these actors. One actor would always reciprocate the trust of the subject by sending high amounts of money back, and so engaging in big amounts of co-operation. The other actor would always cheat by sending small amounts of money back and keeping most of the money the subject sent them to himself.
Chris - So very quickly, the subjects would have developed an intense dislike for the cheater.
Tania - Exactly, because humans really dislike to be cheated on but like, on the other hand, to engage in co - operation.
Chris - So once you'd nurtured these intense feelings of like or intense feelings of dislike in the volunteers, what did you do to see if the people's empathy could be changed?
Tania - The subject could now see either the fair player or the unfair player getting pain delivered through little electrodes attached to the hand of the actor. Now we could measure brain activity while the subject was perceiving the fair or the unfair player getting painful stimulation to the hand.
Chris - And what was the outcome? Were people generally less empathic to people who had cheated on them?
Tania - The surprising bit was that women showed empathy for fair and unfair players, but the men showed a total absence of these pain-related empathy responses to the unfair player. Instead, they showed an increase in activity in areas which process reward.
Chris - So the men were almost being satisfied by seeing the person get their just-desserts then.
Tania - Exactly. The men basically showed what we call schadenfreude, which is the satisfaction of seeing someone suffering who you dislike. That was also surprisingly correlated, so the more men expressed a desire for revenge, the higher the activity in these regions in men.
Chris - Why do you think it's just the men?
Tania - So that's a very good question. We had expected both men and women to show these responses. It might have been that the means of revenge is a physical means here, that is a painful stimulation. It might be that in evolutionary terms, men have favoured physical threat and women would perhaps take more of a psychological revenge. If we would have allowed the subjects to give punishment points, perhaps the women would have given the same amount of punishment points, but women don't actually like revenge in terms of physical threat.
- Analysing Stardust
with Prof. Donald Brownlee, Principle Investigator on the Stardust Mission, University of Washington
Chris - Tell us about the Stardust Mission. What's it all about?
Don - Stardust is a comet sample return mission. We went to a comet, grabbed a piece of it and brought it home.
Chris - And how does it actually work? What was the nature of the mission and what did you actually do?
Don - We flew for seven years in space and travelled almost three billion miles. Two years ago, we travelled close to a comet called Wild 2, which formed at the very edge of the solar system about where Pluto is. During the fly-by we took fabulous pictures of it and we exposed a collector composed of this amazing material called aerogel. We collected thousands of millions of particles that impacted into this collecter, folded it up and brought it home last week.
Chris - Why did you choose Wild 2? What was special about that comet?
Don - There are a lot of comets in the solar system but very few of them are inplaces we can get to. Most of them are very far away, and most of them are either very close to the sun or out beyond Neptune. This one was conveniently located and we could fly by it at a pretty low velocity for interplanetary speeds and get a sample. But this comet is also interesting because it's only been in its present orbit since 1974. It now travels between the orbit of Jupiter and Mars. Before 1974, it was in a much larger orbit.
Chris - Why has it moved?
Don - It moved because of planetary billiards! If comets get anywhere close to planets and they have gravitational encounters with them, their orbits change. They change all the time, and have very unstable orbits compared to the orbits of planets like the Earth, Mars and Venus.
Kat - So you've been flying this little capsule miles out in space. How do you actually control a space craft like that from such a distance?
Don - Well the space craft is controlled by a combination of the Jet Propulsion Lab in Pasadena, California and Lockheed Martin in Denver, Colorado. We track it using something called a deep space network, which is a series of antennae around the world. We send radio signals to it and we get radio signals back, and we track so that we know where it is. When we want to change its direction, we fire some of the sixteen little engines for a period of time and send it in a different direction.
Chris - Now why is a comet so interesting to you? What can it tell you about things that you couldn't learn from Earth?
Don - The most fundamental reason why we would want to go to a comet is to learn about the origin of the solar system. The sun and the planets formed four and a half billion years ago and they formed from a disk of gas and dust, which is called a solar nebula. The solar nebula was originally filled with things like comets and also asteroids. Yet almost all of those comets are now gone. They were either eaten by other planets, or they went into the sun, or they were thrown out into the galaxy.
Chris - And so this is almost like a time capsule really. You can look back at the four and a half billion years that have gone by since our planets were forming.
Don - Exactly. And at the very edge of the solar system, some of those bodies have survived from the very early beginnings. I look on it as a cosmic library. The records of our formation have been stored out there for the entirety of this phase of the solar system. We grabbed a piece of it and have it in our lab right now.
Kat - So really briefly, what kind of techniques will you be using to study these particles? Presumably they're absolutely tiny.
Don - The particles are very tiny but they are much larger than, say, DNA, and we know how much information is stored in one DNA molecule. These are not particles of DNA. They are particles of minerals, glass, sulphides, and all sorts of organic materials. There are people all over the world using a variety of instruments to studying the mineralogy, the isotope composition, and everything we can measure on the atomic scale. One of the ironies of this is that to study the very smallest samples, you use some of the largest instruments. In fact the largest instrument used is the Stanford Linear Accelerator, which is several kilometres long. This puts x-rays into small samples and works out their composition.
- How Volcanoes Work
How Volcanoes Work
with Dr Janet Sumner, The Open University
Chris - You work at the Open University and you're a volcanologist, but what does that actually involve?
Janet - I do field work, analytical work and monitoring work on active volcanoes. I started out life on volcanoes in the UK, which you'll be pleased to know aren't active anymore. I've now moved on to active volcanoes. What I do is look at volcanoes, but then come back and do stuff in the lab.
Chris - So do you go and get a sample of lava and then find out what's in it?
Janet - Yes, and I've brought along one of the things I collect to show you. Can you guess what it might be?
Chris - Well it actually looks like a coconut shell, as it's about the right size, but it's made of rock.
Janet - This is actually a volcanic bomb, and let me tell you how hard it is to get one of these on a plane nowadays, especially in your hand luggage!
Kat - It's like an enormous rock sherbet lemon and it's really heavy. I've got it here on my desk. But what is it?
Janet - It's a piece of molten rock that got thrown out of a volcano when it exploded. As it travels through the air, it gets shaped into an aerodynamic form, and hence it looks likes a sherbet lemon sweet. It's got a very chilled rind on the outside and then the inside would have been filled with what was once molten rock. I can't use that stuff in the lab because it's about 2000 degrees centigrade and much too hot, so I use something called an analogue. I've also bought my analogue in to show you, and Kat's got it in her hand.
Kat - It's a Cadbury's Cream Egg!
Janet - I hope it's still complete because it has to be complete for my experiments! It's basically the same kind of thing as a bomb, because it has a chilled, brittle outer rind and a viscous, runny interior. What happens is that when these things come falling out of the sky, they land on the ground and burst open. The runny molten rock comes out, runs together and forms lava flows. I'm working with cream eggs and golden syrup to work out how far these lava flows can go.
Chris - OK, well tell us a bit about what a volcano is, because everyone's seen the pictures and seen eruptions, but what's actually going on? If you were writing a geology textbook, what would you say was happening?
Janet - Well it's linked into plate tectonics. Most volcanoes occur where you either have spreading plate boundaries or one plate is being forced down under another. What happens is either hot molten material from the mantle or nearer to the Earth's core is rising up to the surface. This is because it becomes very buoyant when it's warm, or cold heavy material is being squashed down and forced under another tectonic plate. That then goes down and melts. So it's like a constant recycling motion. You can think of it as a pot of custard that you've allowed a skin to form on. If you then heat that up on the stove, the runny custard underneath will start to convect and boil. It will eventually split open the surface skin and then new runny custard will boil out onto the skin surface.
Chris - Why do we have plate tectonics? If you look at Venus, it doesn't have any plates.
Janet - Well it doesn't really have plate tectonics, but it does experience the same kind of over-turning that the Earth experiences. It's just that Venus over-turning happens on a global scale within a few tens to hundreds of thousands of years, or at least this is what we think happens. Rather than individual plates jostling around, what happens with Venus is that the whole surface resurfaces itself within a short space of time. This gives Venus a new planetary surface. Earth resurfaces itself on a slower scale than Venus.
Kat - Other things you've brought in here are a pumice stone that looks a bit like it's been used on someone's feet, and also a big chunk of black glass. What have these got to do with volcanoes?
Janet - I brought along the pumice stone because I thought it was the one bit of a volcano that most people will have in their bathroom and might actually have touched. I brought in the glass because it was also formed by a volcano. It's incredibly sharp and used to be shaped and used as cutting blades. It's basically a form of silica, and because it cools so incredibly quickly, it forms glass. So these are just a few examples of what a volcano can produce. It's tremendously varied.
Kat - It's a beautiful colour. Is this obsidian?
Janet - It is obsidian.
Kat - It's absolutely jet black. A fantastic colour.
Chris - When you look in a text book, you will often see this beautiful picture of planet Earth with layers peeled away almost like an onion, and they'll say that this is the crust, and then we're into the mantle, the outer core and the core. How do we actually know what's in there and what that structure is? It's obviously not practical to drill a hole down to the centre of the Earth.
Janet - Well no, but I think some people have tried and gone some considerable distance, but we're never going to get that far. It's a probably a question that my colleague sitting next to me could answer, because a lot of it has been done through seismic studies. People have fired seismic waves through the Earth and basically worked out whether it's molten or solid rock from the delay times.
- Earthquakes, Tsunamis And Pakistan
Earthquakes, Tsunamis And Pakistan
with Dr Tiziana Rossetto, University College London
Chris - So Tiziana, can scientists use other people's misfortune when having an earthquake in order to learn more about what's happening inside the Earth and the structure of the Earth?
Tiziana - Strangely enough, it's already been done. There are two main types of wave that are generated when you have an earthquake. They're called primarya nd secondary waves, mainly because primary waves arrive first and secondary waves arrive second. Through the monitoring these waves around the globe, we can basically see how long they've taken to reach various locations around the Earth. They travel different speeds through different chemicals. We also found that part of the core is liquid because S-waves, which are compression waves a bit like sound waves, can't travel through liquids, and therefore aren't visible on the other side of the planet.
Chris - So that's how we know what bits are liquid and which bits are solid.
Tiziana - Yes, it's surprising.
Kat - So earthquakes only travel around the surface. If there was an earthquake in Australia now, we wouldn't feel it because we're on the other side of the planet.
Tiziana - Well another type of wave released when you have an earthquake is a P-wave. When the P-waves and S - waves hit the Earth's surface, they set up vibrations. This is what we feel as the strong ground motion. It's also what causes the most damage to buildings and causes panic among populations. They attenuate quite rapidly with distance from where the earthquake has happened.
Chris - Are we any closer to predicting when an earthquake is going to happen?
Tiziana - Unfortunately not. I think the greatest progress that has been made so far is to monitor the relative strains along faults.
Chris - Why is it so difficult to do an earthquake forecast, just like we have weather forecasts? What are the difficulties that scientists encounter?
Tiziana - An earthquake will generally occur along a fault and we don't always know where the faults are. We only have about 10 years worth of instrumental data on which to base our predictions. People have made studies of historical data by looking at old news cuttings and historical records to try and find out where earthquakes have occurred and assigning sizes to those earthquakes, but essentially we don't have enough data. We don't understand the Earth as well as we might and we can't predict what amount of time will lapse between one earthquake and the next. That's our main problem.
Chris - Now tell us a bit about what you've been up to in Pakistan. You work as a structural engineer, and as the old saying goes, it's not earthquakes that kill people, it's the buildings.
Tiziana - It is. If an earthquake happens in the middle of the desert, no-one will get killed. Even if a person is standing there they won't fall into the rupture even though people think that they would after seeing films. What happens in cities is that buildings that aren't built to resist the earthquake loads, which is the majority of buildings, will collapse and be damaged. This causes life loss and economic loss to the city or the country. I was in Pakistan after the Kashmir earthquake that occurred in October last year. I looked at the different types of building there and the different materials being used, and tried to work out why different buildings collapsed.
Kat - So what can you do to make a building earthquake-safe?
Tiziana - If you're building a new building, you can apply seismic codes, which will tell you what kind of structural forms will resist the lateral loads imposed by buildings. But if you have an existing structure, you have to see how strong it is, what size earthquake it can resist, and whether or not someone should intervene with a strengthening of that structure.
Kat - Can you make springy buildings? Aren't there some that have big springs up the inside?
Tiziana - Yes, these are called base isolation systems. They look like gum drops except they have steel plates between them. What they do is isolate the building above from the ground motion, so that when the ground shakes, these gum drops absorb all the energy and the structure above will stay relatively still.
Chris - Roughly how many earthquakes are going on around the world today?
Tiziana - Oh gosh, hundreds probably. Some are too small to be detected by humans, and some occur under the oceans or elsewhere.
Chris - Why is it that we can have an earthquake in Dundee or Dudley, as happened recently in this country, but we're not near any plate boundaries. How does that happen?
Tiziana - Well there are deformation stresses that build up within plates themselves and we don't fully understand how these events happen. You do sometimes have small earthquakes happening in places that have never experienced earthquakes before, or at least we don't think they have.
- How Volcanoes Affect The Atmosphere
How Volcanoes Affect The Atmosphere
with Dr Tamsin Mather, University of Cambridge
Chris - Now Janet works on the nuts and bolts of volcanoes, but you're interested in what comes out of them. Tell us about your work.
Tamsin - I started off looking at atmospheres, and now I'm looking at the effect volcanoes have on our atmosphere. Like Janet, I go out into the field and take measurements of volcanoes.
Chris - So you have to wander around on erupting volcanoes?
Tamsin - Not erupting in the sense that most people think of with a big erupting lava column, but erupting with gas coming out of them.
Chris - Have you never been caught with your pants down so to speak. You've never been really close?
Tamsin - No, I've had ash falling on my head but never had anything bigger, which is fortunate really. I try to avoid that.
Kat - What kinds of gases come out of volcanoes and are they very smelly?
Tamsin - There's often fire and brimstone. You can see the fire in the crater below you. The brimstone, which is actually sulphur, creates a lot of sulphurous gases. This is the egg smell that some people think of when they think of volcanoes. This is hydrogen sulphide. Sulphur dioxide is a more major component of the volcanoes I work on. You also get acid gases such as hydrogen chloride and hydrogen fluoride.
Chris - Pretty nasty.
Tamsin - It is. A colleague went up wearing a pair of spectacles and his glasses got etched by the hydrogen fluoride, so this shows you how corrosive these gases are.
Chris - I was lucky enough to be in Japan around Christmas of 2001 and I went to Mount Fuji. If you climb up adjacent to Mount Fuji, you can see hot springs there. They absolutely stink of bad eggs! There's also a big sign which says, although it's very loosely translated from the Japanese, if you stop noticing the smell of hydrogen sulphide, that's a bad sign. This is presumably because once it reaches a certain level, it just abolishes your sense of smell.
Tamsin - Basically yes. There's a window in which we are sensitive to the smell of hydrogen sulphide. Once it gets above that window, that's when it starts to become quite toxic.
Chris - But why is analysing some of these gases useful to science. What can it tell us about science and how volcanoes actually work?
Tamsin - It can tell us all sorts of things. I think the interesting thing is the different length scales on which volcanoes influence the environment. The local effects in places in the South Pacific include residents showing signs of fluorosis, such as discolouring of their teeth. The fluorine levels in the water that they drink are about ten times the World Health Organisation recommendations. There are also global effects. For example, after the Pinatubo eruption it shot up sulphur dioxide into the upper atmosphere, such as the stratosphere and ozone layer. This created an aerosol vale that went all around the planet and reduced the temperatures.
Chris - By reflecting sunlight back into space.
Tamsin - Yes exactly.
Chris - Because we also had some wonderful sunsets. I remember in 1991, when Mount Pinatubo erupted in the Philippines, these beautiful orange sunsets every night for the whole year.
Tamsin - Even the moon looked yellow because of all the small particles up in the stratosphere. After a bigger eruption such as the Tambora eruption in 1815, people painted some beautiful paintings. It has some beautiful aesthetic effects as well as negative effects.
- Is Santa Barbara at high risk from a tsunami?
Is Santa Barbara at high risk from a tsunami?
Tsunamis occur after earthquakes when one tectonic plate subducts or goes below a continental plate. This is generally between an oceanic plate and a continental plate. The deformation that accumulates between the two surfaces causes the tsunami. If you have two pieces of sandpaper and push them against each other, you'll see that at a certain point they'll move apart. That's essentially what happens between two tectonic plates. In the case of a tsunami, it needs a vertical movement of the ground to initiate a disturbance to the surface of the water. There is a plate in that region and it is a subduction zone, so it's possible that there will be a tsunami. However, you can get movements of one plate relative to another without large earthquakes happening and without vertical displacements of the ground below.
- Does extracting oil and gas affect the way the world spins?
Does extracting oil and gas affect the way the world spins?
I think the problem is that it sounds like an incredible amount, but if you actually weigh that amount up with the weight of the entire globe, then it's an incredibly small amount. You're looking at something that's the size of a pin head compared to the entire volume of the Earth. So I think the answer is no, it's much less than you might think.
- I think I'm right in saying that diamonds are produced by some volcanoes. Why?
I think I'm right in saying that diamonds are produced by some volcanoes. Why?
They are certainly produced due to volcanic action. Diamonds are formed in diatreme pipes, which are a kind of very steep sided vent down into the Earth. This provides the very high pressure and temperature that diamonds need to form. So it's more of a drilling downwards effect than a coming up and exploding out of a volcano effect. You need the high temperatures, but principally you need the high pressures as well.
How does the Richter Scale work?
The Richter Scale, contrary to popular perception, is actually just derived for California. It's a measurement based on the displacement measured on a seismograph. This measures the displacement of the Earth due to ground motion. It's an empirical measure, and also logarithmic. If you take a magnitude 5 and a magnitude 6 earthquake, the magnitude 6 will be bigger in terms of energy release than a magnitude 5. But a magnitude 7 will be roughly 1000 times bigger than a magnitude 5.
- Why are there two or three waves in a tsunami instead of one?
Why are there two or three waves in a tsunami instead of one?
It's essentially the same principle as if you get a cube of sugar and drop it in your cup of tea. It sets up a disturbance in the water surface and it doesn't reach equilibrium again immediately, so you get a lot of oscillations instead of just one. This gives you more than just one wave. They all add together.