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
I wonder what this does to the hollow earth theory...
Hollow Earth Theory
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?]
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.
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
this new research grant seems to follow pretty closely on the heels of new activity occuring at yellowstone national park, described here, here, and here (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:
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?
"Stratigraphically the origin of agriculture and thermonuclear destruction will appear essentially simultaneous" -- Lee
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.
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.