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Science

Viewing Inside the Earth 133

Posted by Hemos from the one-big-MRI dept.
Roland Piquepaille writes "Last week, a study released by Princeton University said that geoscientists have captured images of the interior of the Earth by using techniques similar to body scanning by physicians. This study also revealed in-depth structures which might explain how our planet is changing -- and aging. They studied more than 86,000 earthquakes which occurred since 1964. And they found 32 "mantle plumes" which are believed to cause island chains, such as the Hawaiian Islands and Iceland. They have been conjectured thirty years ago, but this is the first visual evidence they exist. This overview contains more details and references, including a rendering of mantle plumes in action."
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Viewing Inside the Earth More

Viewing Inside the Earth

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  • This is awesome (Score:5, Funny)

    by ObviousGuy ( 578567 ) <ObviousGuy@hotmail.com> on Monday December 08, 2003 @08:07AM (#7658853) Homepage Journal
    It looks just like some scenes from The Core.

    I'm really amazed how Science Fiction is able to shape and mold our understanding of real science.
    • Dang... you bet me to it.

    • Re:This is awesome (Score:5, Informative)

      by understyled ( 714291 ) on Monday December 08, 2003 @09:45AM (#7659391) Homepage Journal
      The Core and Real Science should never ever appear within the same train of thought. Not only was it a horrendous movie, but the physics they used to explain it was complete garbage [intuitor.com].
      • You are aware that they set out to make a 60's style sci-fi movie right? You know, the kind where a difficult problem is discovered and some "smart" people solve it. It's a style of movie where the "truth" is irrelevent. The whole point is not whether you believe the science, but whether you feel the suspense. As a matter of fact, the genre counts on pseudo-scientific babbling only to drive the story forward. These types of movies are not intended to be "accurate".

        • Re:This is awesome (Score:2, Interesting)

          by ComaVN ( 325750 )
          No, it's the kind of crap movie where the producers know it's crap, so it's declared to be a homage or parody to a pulp genre, so the fact that it's crap is actually put forward as one of its good qualities. Compare with Godzilla.

          Suspension of disbelieve for me does not tolerate people drilling to the center of the earth, to do anything remotely noticable to the core.
    • [quote]And they found 32 "mantle plumes" which are believed to cause island chains, such as the Hawaiian Islands and Iceland.[/quote] 100000 is binary 32. So the computer that calculates the question to life the universe and everything operates at 6 bits. Anyone care to guess the frequency?

  • The Core (Score:2, Interesting)

    by CoboyNeal ( 730397 )
    Hey man, where are all the massive geode caves, as depicted in The Core [imdb.com]? Oh nevermind... (he could ask for anything and he asks for hot pockets and Zena *tapes*)

    In other news, with the recent Slashdotting, Princeton shows they're super-smart, for not posting the recent core scans online, at 2megs a pop.

    It is very cool to hear that a 30 year old theory can be turned into observation. Now if we could only do that with religion, there'd be fewer needless deaths in the world.
    • In other news, with the recent Slashdotting, Princeton shows they're super-smart, for not posting the recent core scans online, at 2megs a pop.

      Well, kinda except that a story about images of the center of the earth is now missing images. A torrent would have been nice.
    • Try the hot pockets, they're breathtaking.

    • Re:The Core (Score:1, Offtopic)

      by Lord_Slepnir ( 585350 )
      Now if we could only do that with religion, there'd be fewer needless deaths in the world.

      Right, because we all know that the only thing religion is good for is to convince people to go out and kill each other. I don't know if you're living under a rock, but religions do a lot of things that are good for people, like distributing food to the needy, and running countless charities that feed, clothe, and shelter people most of us wouldn't have the time of day for. Even for non-needy people, they run a lot

      • Consideration (Score:1, Offtopic)

        by dolo666 ( 195584 ) *
        I think you misunderstood my intention. Killing in any reason is wrong, imho. The fact that science allows us to prove in some facts, be them scientific or otherwise, is proof that science is the path of reason, while religious thinkings often are the flights of fantasy, based in greed or some other sin of the heart.

        I'm not knocking religious factions who set out only to do good. Just the ones who set out to do evil.
      • If only traditional religions were any good at explaining the world, people, or even the supernatural. There might be some truth about faith in there, but religion has become a straitjacket suitable only for lunatics. I believe in science: only one or two articles of faith, daily miracles, and lots more cooperation.

  • hollow earth (Score:5, Funny)

    by djdrew6k ( 526089 ) on Monday December 08, 2003 @08:11AM (#7658868)
    I wonder what this does to the hollow earth theory...

    Hollow Earth Theory [v-j-enterprises.com]

  • ok... (Score:2)

    by pyr0 ( 120990 )
    Let me get this out of the way right now by saying that Iceland is not a mantle plume...it just happens to be sitting on a mid-ocean ridge!

    • Re:ok... (Score:5, Informative)

      by r4tf1nk ( 88905 ) on Monday December 08, 2003 @08:59AM (#7659106)
      Actually it is believed that Iceland _does_ sit on top of a mantle plume as well as being on a plate boundary - the evidence is that there is apparently just too much magma being produced there to be just explained by oceanic ridge magmatism. The online article on "VOLCANOES, MANTLE PLUMES, and HOT SPOTS" linked to in the weblog mentions that hotspots can occur on plate boundaries.

      • Re:ok... (Score:5, Informative)

        by Anonymous Coward on Monday December 08, 2003 @11:05AM (#7659920)
        There really is some debate over wether this is so. 3He/4He ratios are indeed high, and this is normally attributed to a lower mantle source (possibly as deep as the core mantle boundary). HOWEVER four recent (and independent) tomography experiments image a major, strong, low-wave-speed anomaly in the upper mantle beneath Iceland that does not continue down into the lower mantle. These studies strongly suggest that iceland is fed by an upwelling originating in (and confined to) the upper mantle.

        The suggested explanations for this are somewhat tenuous - that the plume gains strength in the upper mantle and is not imaged at depth runs counter to the improved tomographic resolution with depth, and besides, doesn't make much sense chemically.

        Speaking as a geochemist, the real interest lies in tieing in the 3He origin with tomographic images. The evidence is rapidly shrinking for a chemically seperate 'upper' and 'lower' mantle, but rather for a 'marble cake' type mantle with small regions of primitive material mixed in with more recent 'evolved' mantle material.

      • Re:ok... (Score:3, Interesting)

        by pyr0 ( 120990 )
        "The online article on "VOLCANOES, MANTLE PLUMES, and HOT SPOTS" linked to in the weblog mentions that hotspots can occur on plate boundaries."

        Sure they can. I have no problem with that, however I believe the AC that replied to you above me states is pretty nicely. I believe Iceland was discussed back when I took global plate tectonics, and I was given the impression that it was not a hotspot.

        The main fact that keeps me skeptical about the presence of a hotspot under Iceland is the fact that if there

        • Re:ok... (Score:3, Informative)

          by FroBugg ( 24957 )
          Well, the easiest answer for your question is that the mid-Atlantic ridge probably isn't moving. Material is produced there, the plates themselves slide away from it, and in other areas are subducted (or subduct). So it's perfectly reasonable for the ridge to have remained in one place for a long time.

          It's also possible that there's a relationship between the causes of hot spots and of the ridge itself, so that the two are moving, but move in concert.
          • That is true, material is produced there and spreads apart, and the ridge may seem to stay in the same fixed position relative to the coastline. This is an illusion, however. Think about it this way...if you locked the exact position of every mid-oceanic ridge in the world, then plate tectonics could not work. Mantle plumes, however, can be fixed because the plates move over them rather than with them. You can actually use the orientation of transform faults that accomodate differential spreading rates a
            • No, the ridge is not fixed relative to the coastline. The coastlines of Europe, Africa, and the Americas are all moving steadily away from the mid-Atlantic ridge.

              Now, I'm not saying that the ridges themselves don't move at all. But they are not moved by the same forces that move the plates themselves over hotspots. They are the cause for the plates moving. Also, in the case of the subduction around the Juan de Fuca plate (off the American Northwest), it's far more likely that the majority of the motion is
              • " No, the ridge is not fixed relative to the coastline. The coastlines of Europe, Africa, and the Americas are all moving steadily away from the mid-Atlantic ridge." Perhaps my statement didn't come across like I meant it to. What I was trying imply was that (especially in the case of the mid-Atlantic ridge), the ridge itself takes the shape of the coastlines it lies between, thus seeming like it is fixed in one spot.

  • Hype (Score:5, Insightful)

    by adlai ( 469308 ) on Monday December 08, 2003 @08:12AM (#7658879)
    I would argue that slashdot has just bought into hype surrounding one scientific paper. Seismic tomography work has been incrementally improving for many years.

    Moreover, I suspect this paper will be very controversial -- the inversion of tomographic data is necessarily model-dependent, and many scientists are going to be skeptical of the claim that the have settled the source claim of plumes once and for all. [It's much easier to understand why plumes would originate at the thermal boundary at the core; what causes a plume to begin if it starts somewhere in the middle of the mantle?]

    • Re:Hype (Score:5, Informative)

      by herwin ( 169154 ) <herwin AT theworld DOT com> on Monday December 08, 2003 @08:24AM (#7658946) Homepage Journal
      Yes, the inversion problem is potentially ambiguous. I haven't my copy of the article yet, but I will be interested in seeing how they address these criticisms. Plumes originating above the thermal boundary may have originally originated at the boundary and are no longer being fed. The base of the column continues to rise due to its lower density. Yellowstone may be in this category, given its age. The issues appear similar to those in atmospheric and hydrospheric modeling that involve chaotic dynamics.
    • While in graduate school we had a professor who considered the existence of mantle plumes to be the product of "mass hysteria". I must admit their research is intriguing, but I would be curious as to the dimensions and geometry of these plumes and the minimum size of such plumes that can be resolved. In other words does the Yellowstone hot spot not show up because the plume is below the resolution of detection? Or is it that all hotspots != mantle plumes.
    • Yes, seismic tomography has been around for at least 30 years. Around that time I remember seeing pictures of the Pacific Ocean plate being subducted under California. For an interesting article that places the current article in context, see Plumes From the Core Lost and Found [mantleplumes.org].

  • seismic survey (Score:4, Interesting)

    by eyenot ( 102141 ) <eyenot@hotmail.com> on Monday December 08, 2003 @08:14AM (#7658888) Homepage
    another ramp up in seismic survey was reported in this article [sfgate.com] in the san francisco chronicle.

    • Re:seismic survey (Score:5, Interesting)

      by eyenot ( 102141 ) <eyenot@hotmail.com> on Monday December 08, 2003 @08:42AM (#7659015) Homepage
      this new research grant seems to follow pretty closely on the heels of new activity occuring at yellowstone national park, described here [bozemandai...onicle.com], here [sltrib.com], and here [slashdot.org] (where you can also buy your own survey equipment.)

      apparently, yellowstone park is right on top of a vent or something that has exploded catastrophically and according to some is overdue to do the same soon.

      i'm willing to bet that the funding discussed in the article i linked to above [sfgate.com]:

      Grants totaling $319 million from the National Science Foundation have been awarded to cover the first five years of the major new project, called EarthScope. Work has already begun on its array of instruments and facilities, which will provide the tools for decades of future detailed studies.

      ... has eveything to do with attempting to determine just how soon and how badly North America is going to be covered with ash and oochi-hot burning lava. Cool, or what?

      • somehow i messed up the third link. it is supposed to point to http://terrasearch.net
      • ... has eveything to do with attempting to determine just how soon and how badly North America is going to be covered with ash and oochi-hot burning lava. Cool, or what?
        Yeah, if the caldera lets loose like it did before, the ash will cause a major cooling, all over the place.

        Of course, very few people west of the Appalachians will be around to know about it, but Eurasians and North Africans will be able to stop worrying about global warming for a few centuries.

        • living in Michigan, not very far from slashdot itself, i somehow feel safe and cozy. mainly, knowing that

          when the skies turn dark for days on end and for my very victuals i will must fend,

          only nerds will oppose my wrathful blade, i'll cut them all down and take their vittles away.

          (cut them all down, and take their vittles away!)

      • Re:seismic survey (Score:3, Insightful)

        by GeoGreg ( 631708 )
        While understanding Yellowstone is certainly an interesting and significant problem, EarthScope will probably be of more immediate social benefit in helping us understand what's going on at the San Andreas fault system and the Cascadian subduction zone. The impacts of earthquakes in California and volcanic eruptions in the Cascades are much more immediate than the potential of a catastrophic caldera-forming eruption at Yellowstone. The more likely threat at Yellowstone is from localized hydrothermal (stea

  • Pictures? (Score:1, Interesting)

    by Zardoz44 ( 687730 )
    Where are they? We were told what it looked like years ago.

    • Re:Pictures? (Score:2, Informative)

      by understyled ( 714291 )
      RTFA [montana.edu]

      • Re:Pictures? (Score:2, Informative)

        by Zardoz44 ( 687730 )
        I did. Did you? Here's the text that preceeds the illustration you liked to:

        Here is an illustration of how these mantle plumes are *moving* under ourselves (Credit: Jamie Painter, Visualization Scientist, Copyright The Regents of the University of California, Link).

        This is not the "images" captured by geoscientists mentioned earlier on that page.

  • Background (Score:5, Informative)

    by Anonymous Coward on Monday December 08, 2003 @08:22AM (#7658934)
    How do we know how hot the core of the Earth
    is?

    We derive our primary estimate of the temperature of the deep earth from the melting behavior of iron at ultrahigh pressures. We know that the earth's core depths from 2,886 kilometers to the center at 6,371 kilometers (1,794 to 3,960 miles), is predominantly iron, with some contaminants. How? The speed of sound through the core (as measured from the velocity at which seismic waves travel across it) and the density of the core are quite similar to those seen in of iron at high pressures and temperatures, as measured in the laboratory. Iron is the only element that closely matches the seismic properties of the earth's core and is also sufficiently abundant present in sufficient abundance in the universe to make up the approximately 35 percent of the mass of the planet present in the core.

    The earth's core is divided into two separate regions: the liquid outer core and the solid inner core, with the transition between the two lying at a depth of 5,156 kilometers (3,204 miles). Therefore, If we can measure the melting temperature of iron at the extreme pressure of the boundary between the inner and outer cores, then this lab temperature should reasonably closely approximate the real temperature at this liquid-solid interface. Scientists in mineral physics laboratories use lasers and high-pressure devices called diamond-anvil cells to re-create these hellish pressures and temperatures as closely as possible.
    • "sufficiently abundant present in sufficient abundance"

    • Resolution? (Score:3, Interesting)

      by jmichaelg ( 148257 )
      To assert categorically that the core is iron strikes me as foolish. It's hard for me to believe that the density of Uranium wouldn't almost guarantee that it forms the central core of the earth. At 19,000 kg/m^3, it's almost 3 times as dense as iron. Although iron is around 30,000 times as abundant as uranium on the surface and assuming the abundance ratio didn't change much as you went down towards the core, you're still talking about a fair amount of Uranium.

      It wouldn't take a lot of uranium settling to

      • Re:Resolution? (Score:3, Interesting)

        by jandrese ( 485 ) *
        If this were true, wouldn't volcanos be far more radioactive than they are today? I woudn't think the uranium would make a 100% pure seperation in the core.

        Besides, doesn't uranium refract sound waves differently than iron? That seems like something we could test somehow. Perhaps reading the article will be enlightening...

        • Re:Resolution? (Score:4, Interesting)

          by jmichaelg ( 148257 ) on Monday December 08, 2003 @12:17PM (#7660478) Journal
          If this were true, wouldn't volcanos be far more radioactive than they are today?

          Not necessarily. I can think of two ways the radioactivity wouldn't be expressed.

          1. If a uranium core is small, then a few miles of surrounding material would serve to contain the radioactivity. The heat, however, would conduct outwards and drive the lighter basalts upward.
          2. The other possibility is that the transit time from the core to the surface is sufficiently long that the fission debris have completely decayed.
          Lord Kelvin's estimate of the age of the earth was 100 million years based on his understanding of heat radiation and conduction. He started with a molten sphere at 7000 Kelvin and figured out how long it would take to cool to what we see today. His math was right but his estimate was wrong by a factor 45 because he didn't know about radioactive heat sources. Point being that radioactivity is already implicated in explaining why the earth is as hot as it is. The question is are the fissionable elements concentrated at the center or dispersed throughout the mantle or both? The best argument that they're dispersed is that uranium is chemically reactive and readily forms oxides which are lighter than iron. On the other hand, there isn't a lot of lab chemistry being done at the intense pressures and heat found just a few miles below our feet, let alone several thousand miles down so we don't really know how uranium chemically behaves under those conditions.

          As to your refraction question - it goes back to the resolution of the tool being used and the size of a uranium core as to whether it would show up or not.

          • Uranium is not a particularly abundant element cosmically, being only produced in small quantities by supernovae. The meteorites we recover are not particularly uranium-enriched. I don't believe that significant quantities of uranium have ever been observed spectrographically in the solar system. The seismic velocity of the core is well known (it doesn't require tomography to determine). The moment of inertia of the earth constrains the density profile. The solid inner core does show some seismic aniso
            • I'm not saying the core is all uranium - iron is 30,000 times more abundant than uranium is. However, uranium, while scarce in meteorites, is not uncommon on earth. Even at a 30,000 to 1 ratio, earth has more than enough uranium for some of it to have trickled down to the the center, even accounting for the various losses to oxidation and the silicates. Uranium oxide, a common compound of uranium, is lighter than molten iron as are the uranium bearing silicates. On the other hand, some forms, such as urani
          • IANAVulcanologist, but how would one handle a "molten sphere" under terrestrial conditions such as gravity? Perhaps a molten amorphous entity sitting in a container, like a hollowed out sphere, but then the container would act like an insulating buffer, which might skew the results.

            Also, how would Lord Kelvin have accounted for the temperature differential of a "molten sphere" in a laboratory vs. a molten earth in the vacuum and extreme coldness of space? What about the effect of gravity to pull heavier

      • Re:Resolution? (Score:5, Interesting)

        by The Fun Guy ( 21791 ) on Monday December 08, 2003 @10:32AM (#7659721) Homepage Journal
        Uranium is rarely, if ever, found in the pure metallic form. Uranium has a valence of 6, forms uranium oxides very readily, and doesn't lose the oxygen without a lot of chemical coaxing. These oxides would rarely break down under natural conditions to free up the pure metal. Uranium is indeed denser than iron, and would be expected to sink, but uranium oxides are lighter, and float up to the mantle.
        • What if you took nuclear waste and subjected it to the extreme temperatures of volcano lava? Would it oxidize, mix in, or what? Would that be an effective way to convert it back to its original form and dilute it?
          • <disclaimer>IANAG</disclaimer>

            Volcano lava is mantle material on its way out to the earth's surface. Depositing our waste there is not the safest approach for us surface inhabitants. A more plausible approach might be to bury the waste near subduction zones. But most of these zones are under water and subject to volcanism themselves. It would be rather expensive to do and there is no telling what percentage will come back at us.

            • Volcano lava is mantle material on its way out to the earth's surface. Depositing our waste there is not the safest approach for us surface inhabitants. A more plausible approach might be to bury the waste near subduction zones. But most of these zones are under water and subject to volcanism themselves. It would be rather expensive to do and there is no telling what percentage will come back at us.

              Nope. You run into the same problem.

              If you look around all major subduction zones on earth, you will notice
            • Doh... I'm a genius. In my relative haste to feel geeky and answer a question, I didn't read that you had already considered volcanism. :-X

              Watch out folks. Many may not read the articles, but I don't read the comments!
          • The tmperatures by themselves probably wouldn't do it. You'd have to have something to accept the oxygen, and to keep it away from the freed uranium to let it form macroscopic amounts of the metallic form. Even then, if it sank, you'd end up with a molten uranium/nickle/iron mixture. I don't recall what the neutron capture profile of nickle or iron is, but most of the uranium in the mix would be U-238 anyway, not U-235, so I don't really think that a fission reaction could get going. The only heat contribut
        • It'll not only form oxides which are lighter than iorn but it'll also form hydrides that are heavier and would therefore sink.

      • Re:Resolution? (Score:4, Informative)

        by Anonymous Coward on Monday December 08, 2003 @11:18AM (#7660032)
        geologically, uranium doesn't 'like' to be in the metallic form, but rather exists on earth mainly as a sulfide or oxide. Given the redox state of the earth (and ignoring the hydrosphere - the wet bit at the top), it is very hard to get *any* uranium to mix in with the iron phase. Since we know approximately how much U we should have in the earth from solar condensation type experiments, meteorites and cosmic abundances, we still have more (by many orders of magnitude) Fe than U. So, given that uranium likes to be with the rock (its a strongly lithophile - 'rock loving' element ), it is very unlikely that there is a extant reactor in the core. The ONLY possible way i can get ANY U into the metallic phase is by making the core predominantly iron sulfide, but that messes with the density profiles given by seismic waves....

        the best heat sources for the core appears to be latent heat of crystallisation, continued gravitational settling and the decay of radioactive potassium dissolved in the metal.

      • Re:Resolution? (Score:4, Interesting)

        by mikerich ( 120257 ) on Monday December 08, 2003 @12:30PM (#7660592)
        To assert categorically that the core is iron strikes me as foolish.

        Actually its not, we have plenty of iron meteorites in our museums which are essentially an iron-nickel alloy. The crystallisation patterns (known as Widmanstatten patterns show that the metal cooled extremely slowly (ie. it was well insulated ie. it was at depth ie. it formed the core of a planetoid).

        Uranium settling to the core would not form a reactor since natural uranium cannot sustain a chain reaction (the U238 gobbles up the neutrons) without a moderator. Even if there had been one long ago fuelled by relatively abundant U235, natural decay would have killed it by now. The 'reactor' in West Africa was moderated by ground water, which there isn't a lot of in the middle of the Earth.

        And I'm sure a geochemist in the house will be able to tell me for sure. Isn't uranium partial to binding with silica - so the outer layers of the Earth are relatively enriched in uranium - it gets scarcer as you go down.

        Best wishes,
        Mike.

        • I don't think water was the crucial moderator in the African event. I believe it was the hydrogen in the water that served as the moderator, not the oxygen. Presumably, the hydrogen attached to uranium hydride would suffice as a moderator.

          If I recall correctly, u235 is more radioactive because it fissions in the presence of both fast and slow neutrons whereas u238 only fissions in the presence of slow neutrons. As I understand it, and I may be wrong, when u238 is hit by a slow neutron it can take one of

      • Might this hypothesis be tested by using the KamLAND [tohoku.ac.jp] anti-neutrino oscilation detector to see the antineutrinos emitted by the beta decays from the fission products produced by the core(just like it sees them [physicsweb.org] from our fission reactors)? I wonder if anyone has thought of doing this yet.

  • ...about the Earth's Core (fantasy):

    At The Earth's Core [gutenberg.org], by by Edgar Rice Burroughs.

  • Offtopic sidenote... (Score:5, Interesting)

    by _Pinky_ ( 75643 ) on Monday December 08, 2003 @08:33AM (#7658974)
    While predicition of seismic and volcanic events is still, well, progressing... Detection and tracking of such an event is very much doable...

    A tsunami resulting from a seismic event can be devistating, however the landing times can be predicted... The WestCoast/Alaska Tsunami Warning Center (US specific, though I'm sure there are others..) has a page (http://wcatwc.arh.noaa.gov), that include papers, faqs, and also nice charts showing if an eartquake hit how long would it take the wave to hit (http://wcatwc.arh.noaa.gov/ttt/ttt.htm)

    Volcanic eruptions also are interesting in that they tend to throw up ash detectable via satellites... On the NOAA polar orbitals, channel 4 (10.3-11.3 microns) minus channel 5 (11.5-12.5 microns) shows most plumes... A good website for more information is NESDIS's volcano page (http://www.ssd.noaa.gov/VAAC/)

  • They've discovered my Evil Plan (Score:5, Funny)

    by thepuma ( 721283 ) * on Monday December 08, 2003 @08:36AM (#7658989) Homepage
    This has been a very bad day for me. Today, Slashdot discovered my fricken "laser" [slashdot.org], and now they've also discovered my plan to drown the earth in motlen, hot "magma"!

    - Dr. Evil

  • Shame it requires earthquakes (Score:5, Interesting)

    by CaptainAlbert ( 162776 ) on Monday December 08, 2003 @08:44AM (#7659023) Homepage
    I read the headline and immediately thought, wouldn't it be great if we could map the interior of other planets, or the moon? The knowledge we have about what lies beneath the surface of Mercury, Venus and Mars seems to be mostly speculation, with no easy way of investigating. But on a body without active plate tectonics, I guess this technique wouldn't be usable at all. I suppose there are other sources of disturbance such as significant meteorite impacts, but they're much rarer than earthquakes (on Earth, anyway).

    Also, does this method rely on the liquid nature of the mantle? Would these acoustic waves propagate as effectively through solid rock (I guess not)? So, even if we could create the effect of an earthquake on, say, the moon, would it even help?

    (should get back down to Earth, really!) :)

    • Re:Shame it requires earthquakes (Score:4, Informative)

      by MrMr ( 219533 ) on Monday December 08, 2003 @09:10AM (#7659174)
      Dropping a few thousand nukes in a nice pattern will also work.
      And no, solid rock is fine for wave propagation (even better as it will transmit both P and S waves).
    • Anything can cause "earthquakes" The interior of the moon was mapped when astronauts placed seismic detectors at the various apollo landing sites. But the moon has no known natural earthquakes, so the engineers shipped along a "scientific grenade launcher" that was activated after the astronauts had left, producing artificial earthquakes that the other sensors picked up, revealing the core structure. Additionally used Saturn booster stages were intentionally crashed into the moon along with the dicarded
      • Can't you use high-power lasers to detect remote vibrations? Fire the beams at the edge of craters to maximize luminance delta, place them on a super-stable air platform (or just drop it in space), and "listen".

        We do the same w/ IR lasers and glass windows, so it's not unimaginable (glass window = drum to our speech).

        --Dan
      • But the moon has no known natural earthquakes,

        It has tidal quakes caused by the stresses and strains of orbiting the Earth, but their energy is minute.

        The Apollo sensors also picked up a number of minor impacts, one of them estimated as being about 10 tonnes smashing into the far side.

        Best wishes,
        Mike.

    • Moonquakes do occur (Score:5, Informative)

      by teridon ( 139550 ) on Monday December 08, 2003 @09:36AM (#7659338) Homepage
      The Apollo missions deployed seismometers on the moon and recorded over 12000 "events" from 1969-1977. There's some info in this abstract [cosis.net], which I found using, you guessed it, google (search term "moonquakes study interior"). Apparently most of these events are moonquakes caused by tidal forces, as opposed to plate tectonics on Earth.

    • Re:Shame it requires earthquakes (Score:1, Interesting)

      by Anonymous Coward
      Seismic detection equipment is very sensitive, able to detect waves beyond the ability of humans. An earthquake needs to be at least a 3 on the richter scale for people to feel it. I also believe geologists used explosives to generate seismic waves to study the earth,(search for oil).

      I remember reading an article in the 80's in either Science Digest or Scientific American about how underground testing of nuclear weapons sent waves all over the planet and how some geologists were taking advantage of it to
    • Also, does this method rely on the liquid nature of the mantle?

      Not really, no, because the mantle isn't liquid. Technically it's a plastic solid - it's a solid for all practical intents and purpouses, but over long enough time scales, and under the sort of pressures and temperatures you get in the mantle, it can exhibit liquid-like properties, like flowing and convection and so on.

      Would these acoustic waves propagate as effectively through solid rock (I guess not)?

      Solid rock is much better for the pr
    • The P and S waves from an earthquake can both travel through solid material. The speed varies depending on the nature of the material.

      In fact, the S (or Secondary) waves from an earthquake cannot propogate though a liquid, because they are shear waves, and require the material with cohesion between molecules to propogate. The fact that S waves don't pass through liquid is how we determined the upper core is liquid.

  • So... (Score:1, Funny)

    by Anonymous Coward
    The inside of the Earth is simply a giant Lava(tm) lamp?
  • Man, I was really optimistic that there'd be some sort of inner-earth, i.e. a civilization living on the inside of the earth's crust, looking inward toward the core...

    Ah well, I guess when its been decades since your theory has been debunked, sometimes you've just got to give it up.

  • The Core (Score:1, Redundant)

    by Anonymous Coward
    For all the cool answers just watch the movie The Core. Movies are always true and projects like that one really do exist. Especially their new element "Unobtanium."

  • Plumes not universally accepted (Score:5, Interesting)

    by pongo000 ( 97357 ) on Monday December 08, 2003 @09:28AM (#7659287)
    There is a growing movement in the geosciences that claims there is no evidence pointing to "mantle plumes." Everyone knows /. readers are well-balanced and open to new ideas, so in that spirit I offer up this link [geolsoc.org.uk] to the UK Geological Society.

    Remember, an open mind is a terrible thing to waste.
    • Yeah, one of the louder critics of the plume hypothesis has his office in the basement of the building I'm in. I'm not a geodynamicist, so I am not sure what to think about that. However, the critics are all respectable earth scientists, so they are worth listening to. I wouldn't be surprised if some proposed plumes turn out not to be. There's already significant evidence that there is no plume at Yellowstone, even before this paper. That doesn't mean there aren't plumes elsewhere, though.

  • New Evidence (Score:5, Funny)

    by Sigl ( 691196 ) on Monday December 08, 2003 @09:45AM (#7659392)
    ["mantle plumes"] have been conjectured thirty years ago, but this is the first visual evidence they exist.
    I dunno, The tons of molten lava spewing into the air seemed like good visual evidence to me.
    • I dunno, The tons of molten lava spewing into the air seemed like good visual evidence to me.

      Who are you going to believe? Him or your lying eyes? Go! And never darken my pyroclastic clouds again!
  • What would it take to port this guy's dataset to Quake so you could view the data from any perspective you wanted? I think it would be cool to see the continents rendered on the sphere's surface and be able to spin the sphere, dive in and look around at the plume structures.

  • Darn (Score:1, Offtopic)

    by djupedal ( 584558 )
    ...no images. Where's the goat guy when you need him.
  • At the same time, some expected plumes, such as one believed to be under Yellowstone National Park, did not show up.

    Whew!

  • No surprise, really (Score:4, Funny)

    by Angst Badger ( 8636 ) on Monday December 08, 2003 @11:47AM (#7660243)
    I suppose this shouldn't surprise me, but the first thing I thought when I looked at the rendering was, "Gee, the interior of the earth looks like a lava lamp."

    The second thing I thought, of course, was, "Well, duh."
  • So this was done using seismic data. Why not do it the same way you do body scans of the body, where you shoot xrays through in all directions, and do some math magic to deduce the internal structures?

    It's a big thing to scan, but with a few airplanes it could easily be done in a few years.

    My best guess is that there is no radiation that works well for it. you need something that is strong enough to pass through the planet, but is weak enough to be partially stopped by features you're interested in.

    • Re:Why not real body scanning techniques? (Score:4, Insightful)

      by mikerich ( 120257 ) on Monday December 08, 2003 @12:43PM (#7660688)
      My best guess is that there is no radiation that works well for it. you need something that is strong enough to pass through the planet, but is weak enough to be partially stopped by features you're interested in.

      Bingo! Earthquake waves are the only things we know about that go through the planet. Even radio waves don't make it.

      Best wishes,
      Mike.

      • If you want to get technical, quark strangelets also pass through the earth (and actually at faster velocities than sound). Basically, they are extremely small, dense bundles of quarks travelling at a nearly 0.2% of the speed of light that can pass clear through the planet. Actually, they also cause seismic events when they enter and leave the planet.

        I have no idea how you'd use these to map the earths core (asides from their seismic signatures), and they happen pretty infrequently. If you're interested th
    • To elaborate on mikerich's reply, EM waves (e.g. x-rays) attenuate rapidly in the earth. Ground penetrating radar, for instance, can penetrate about 10 meters in good areas. Experiments have been done with extremely high-powered GPR systems, but they tend to turn the ground surface into glass (not good from an airplane). Very low frequency electric currents generated by the interaction of the earth's magnetic field with the solar wind are used in the method known as magnetotellurics. You can see down ma
      • Thanx. That's good info.

        What I had in the back of my mind was probably neutrinos and similar cosmic radioation particles. Their problem is the opposite, in that they pass through earth much easier than xrays through paper, so you would need very sensitive instruments, or very long measurment times.

        I'm not up on the latest in elementary particles, so I don't know if there is some exotic little species of them that could be more practical.
  • I want to know where the "unexpected plumes" were found. I'd like to stay away from those regions ;)
  • I was under the impression (from my university geo course), that to map the inside of the earth using seismic waves, you need to know the exact time and location that a seismic event began at. This would mean only nuclear weapon tests would be useful for seismic studies.

    Does anyone know how they've got around this? A link describing the exact provedure for doing this would be sweet too.
    • I was under the impression (from my university geo course), that to map the inside of the earth using seismic waves, you need to know the exact time and location that a seismic event began at. This would mean only nuclear weapon tests would be useful for seismic studies.

      In part you're right, but nuclear weapons tests aren't the only things you can get precise times for. Using seismographs to record earthquakes, scientists can determine exactly when an earthquakes happened by looking at the record from t

  • Random thoughts (Score:4, Informative)

    by craw ( 6958 ) on Monday December 08, 2003 @12:33PM (#7660609) Homepage
    A few random comments on this subject.

    So-called hot spots (fixed volcanic positions) was first proposed by the great Canadian geophysist J. Tuzo Wilson almost 40 years ago.

    The mantle plume origin of these hot spots was proposed by W. Jason Morgan (as mentioned in the Princeton link). Morgan also the put forth the first model for global plate tectonics on a sphere (spring AGU meeting, 1967). This extended the work of Wilson that looked only at transform faults.

    I've known Jason for 25 years and can truly say that he is one of the nicest guy you could ever meet. He is also an incredible smart scientist.

    Ironically, this /. story is posted on the first day of the fall AGU (American Geophysical Union) meeting. I'm quite sure that there will be discussions and debate about this.

    Seismic tomography has been around for over two decades. Global body-wave seismic tomography has been performed primarily since the 1990's. I did seismic tomography work about twenty years ago albeit using surface waves covering only a portion of the Earth.

    I hope that they publish a resolution map of their inversion model. An error map would also be good. Many times only the final model is presented.
  • no reptoids? [reptoids.com]

    COME ON! show us the reptoids. we know they exist. you can't hide them from us forever.

  • And here I was expecting the answer to life, the universe and everything!
  • I saw the Story and spit my Dr. Pepper all over the screen -- I figured it was about time \. started making fun of David Icke [davidicke.com] and how he thinks the interior of the earth is inhabited by lizard people. :) :)

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