Slashdot Mirror
Viewing Inside the Earth
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."
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.
I have been pwned because my
Hey man, where are all the massive geode caves, as depicted in The Core? 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.
I wonder what this does to the hollow earth theory...
Hollow Earth Theory
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!
Project Steve
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?]
I'm assuming here that it's kinda dark inside the earth, at least it was the last time I went down a cave. They must have used a rather large flashgun.
Ed
The more corrupt the state, the more numerous the laws. - Tacitus, 56-120 A.D.
another ramp up in seismic survey was reported in this article in the san francisco chronicle.
"Stratigraphically the origin of agriculture and thermonuclear destruction will appear essentially simultaneous" -- Lee
Dang... you bet me to it.
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.
...about the Earth's Core (fantasy):
At The Earth's Core, by by Edgar Rice Burroughs.
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/)
- Dr. Evil
Free your ecomony and enact the FairTax
"sufficiently abundant present in sufficient abundance"
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!)
These sigs are more interesting tha
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.
"Stumble before you crawl"
It wouldn't take a lot of uranium settling to the core to form a natural nuclear reactor. I can imagine the reactor pulsing as it heats up, poisoning itself like Hanford did when they first fired it up, shutting down and cooling which allows it to shrink. Since the core is molten, the lighter fission products would convect away allowing pure uranium to accrete once again and repeating the cycle.
At the imaging resolution we're currently getting from seismographs, it's not clear to me the reactor would show up in these images. It wouldn't take a lot of "contaminates" to form a small nugget of uranium at the center of the putative iron core.
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."
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 to the UK Geological Society.
Remember, an open mind is a terrible thing to waste.
The Apollo missions deployed seismometers on the moon and recorded over 12000 "events" from 1969-1977. There's some info in this abstract, 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.
I hold it, that a little rebellion, now and then, is a good thing. -- Thomas Jefferson
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.
...no images. Where's the goat guy when you need him.
I assume this is what you meant?
Ydco co
At the same time, some expected plumes, such as one believed to be under Yellowstone National Park, did not show up.
Whew!
who are those slashdot people? they swept over like Mongol-Tartars.
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."
Proud member of the Weirdo-American community.
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.
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.
boom boom boom
A few random comments on this subject.
/. 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.
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
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.
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.
It'll not only form oxides which are lighter than iorn but it'll also form hydrides that are heavier and would therefore sink.
If the people on the inside surface were much more evolved than us, then surely they would know calculus. Therefore, they would figure out that anywhere inside the sphere, they would actually be weightless.
-CausticPuppy "Of all the people I know, you're certainly one of them." -Somebody I don't know
Since they would be weightless based on the hollow sphere's mass alone, that means they would all die horrible, fiery deaths when they fell into the inner sun. Oh well.
-CausticPuppy "Of all the people I know, you're certainly one of them." -Somebody I don't know
COME ON! show us the reptoids. we know they exist. you can't hide them from us forever.
sig - .
And here I was expecting the answer to life, the universe and everything!
It somewhat suprises me that the fac that the plumes come from the upper mantle as well is a surprise. I just finished reading the Self Made Tapestry by Philip Ball. (I'd highly recommend this book if you're interested in self-organized behavior or chaos theory. It's getting a bit old but still a very good introduciton to the topic)
In one chapter, he discusses fluid convection dynamics and the tendancy for self-organized structures to form in diferentially heated fluids. He then goes on to mention a simulation done by Paul Tackley in *1993* which predicted the formation of two layers of convection cells. (the layers are seperated at the 660 km discontinuity in the mantle) Furthermore, these two layers are incompletely seperated and plumes originating from both the 660 km discontinuity and the core-mantle boundary reach the surface. There's a picture of the simulation results and they look strikingly similar to the the ones in the article.
What suprised me the most was that the Yellowstone plume was absent. I thought that what was supposed to be why the great plains are about a mile higher than they whould be. Did the yellowstone plume poop out recently or something?
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.
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.
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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 though, you can read about them here:
http://www.telegraph.co.uk/news/main.jhtml
The other thing is you don't need an awful lot of it to form a critical mass. If just 1/10% of the earth's uranium made its way to the core, you'd have around 2 cubic miles of uranium. That's a sphere with a 1 mile diameter - pretty hard to pick out tomographically.
With regard to the magnetic field, the iron core is still there. The uranium would only occupy a small fraction of the core. The interesting thing is that if the very nucleus of the earth turned out to be uranium and it did undergo periodic poisoning or fuel starvation and shut down, that may be a mechanism that drives the pole reversals. The idea would be that the field is driven by the charge flux associated with fission. The surrounding iron not only emphasizes the field but provides a positive feedback mechanism that drives the orientation of the flux. When the center shut down due to poisoning or a temporary insufficiency in uranium, the source of the charge flux goes away with it. The poisoning decay products get cleared out via convection or more uranium trickles in and the reactor starts back up. But by this time, the magnetic field is provided by the sun as the earth's field has dissipated. So whichever way the sun's field happens to be at the moment, that's the way the reactor fires up. As long as the reactor keeps operating, future solar field reversals are insufficient to overcome the field provided by the uranium/iron core.
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 and how he thinks the interior of the earth is inhabited by lizard people. :) :)
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 three paths - it can shrug the neutron off, it can, as you say, "gobble" the neutron and begin transmuting to plutonium or it can fission. Two of the three events lead to heat. Fission generates immediate heat and plutonium generates heat sometime within its relatively short half life.
Although u238 has a long half life, it is still a source of neutrons so you wouldn't need u235 to keep the reactor going. The reason is that you have a reactor that dwarfs any we've made so when a u238 atom fissions, two things are likely to happen - the 2 neutrons will eventually collide with enough hydrogen atoms supplied by the hydride to slow them down and they'll impact another u238 nucleus. In a man-made reactor, a u238 atom fissions and the neutrons have another option - they can escape the reactor before they slow down. Because our reactors have a relatively large surface area to volume ratio, you need u235 to improve the fissioning odds and supply more neutrons. In a reactor a mile in diameter, u238 would supply more than enough neutrons because the surface area/volume ratio is considerably smaller so the neutrons from the u238 can't as readily escape before they encounter another u238 atom.