View Full Version : Gas from earth's core seeping out?
Aug 14th, 2005, 9:18 AM
Engine at the centre of the Earth
Monday, 30 April 2001
Found an artical of interest in the earths core:
The Earth houses a "four-piston heat engine" that is responsible for earthquakes, volcanoes, the movement of continents and even climate change, according to a new model developed by Canadian researchers.
The comprehensive model, reported by Alessandro Forte of the University of Western Ontario and Jerry Mitrovica of the University of Toronto in the current issue of Nature, drew from many disciplines in the earth sciences.
"In effect we found that the solid Earth is being churned by a four-piston heat engine with two immense sinking cold slabs and two equally large rising hot plumes," says Forte.
According to Professor Sue O'Reilly of Macquarie University's Key Centre for Geochemical Evolution and Metallogeny of Continents, the work is another step in the "really exciting discovery" of how the deep Earth circulates.
Below the relatively cool and brittle crust of the Earth, lies a 2,800 kilometre thick mantle which continually circulates and mixes due to the heat of the planet's molten core. Professor O'Reilly said a "big breakthrough" in understanding mantle convection came in 1999 when researchers suggested that circulating within the mantle were blobs of primitive Earth material.
"Like a lava lamp, these blobs within a viscous liquid rise as they heat up, expand and become less dense. As they cool, they fall to the bottom again," she told ABC Science Online.
Professor O'Reilly says that Forte and Mitrovica have added a lot of weight to and refined this earlier idea by showing that these are blobs with a different composition to the rest of the mantle.
The Canadian model is "extremely important", according to Professor O'Reilly, because it combines both geophysics and geochemistry. The research also uses seismic tomography - a process similar to medical CAT-scans but using seismic waves from earthquake zones.
"They show a snapshot of the Earth's convection today which takes a lot of notice of the composition of deep Earth," she said. "It is not just physical modeling without dealing with the geological realities."
"This internal heat engine determines everything that happens on the surface of Earth," she adds. "Without it we'd have no uplifting, no mountains, no erosion, no volcanoes and no earthquakes. The planet would be flat and covered in water."
Are these the same blobs of gasses found in california recently?
And if it is, how did it get out?
Aug 14th, 2005, 11:47 AM
Where did you get the idea that the blobs were gas?
Sounds to me like they are talking about mantle material.
Aug 14th, 2005, 3:52 PM
There was a post here (but I couldn't find it) a few months ago about blobs
found. I thought they were talking about gases. interesting, so this material
is more like a rock not a viscious liquid?
Aug 14th, 2005, 9:52 PM
Not exactly rock, but very viscous rock-like material (otherwise it wouldn't flow). It takes thousands to hundreds of thousands of years for this material to flow from the innermost mantle to the crust- and along the way it has to pass through at least two discontinuities. There is some evidence that the lower mantle material does not pass through the lower-upper mantle discontinuity, but this has not been proven.
Just below the crust is a thin layer called the asthenosphere, which is more ductile, lower density and flows easier than the mantle. It is believed that the tectonic plates move on the asthenosphere.
Geologists have suspected the existence of mantle plumes since the late 70's, and new techniques like seismic tomography supports their view. At present, there is quite a debate about the depth of these plumes- some think they start at the core-mantle boundary and other believe they are much shallower. Plumes are postulated to be underneath Yellowstone, Hawaii, Iceland and other hot-spots, and probably caused the breakup of Pangea.
Aug 14th, 2005, 10:57 PM
so, let me see if I got this right, the Earth's core is a roughly spherical zone within which four (or so) blobs are doing the lava-lamp shuffle (in 3-D no less) and they're made out of a material dissimilar to the rest of the hot, dense soup they're floating in.
however, is it accurate to suggest these blobs 'cool down' as they drop into the core? from what I know of thermodynamics and stuff another explanation seems to be more probable. rather than being temperature dependent the blobs are orbiting around the theoretical center point down there and their orbits are not perfectly circular. as they 'rise' they expand and their increased 'area volume' (the size of the displacement they produce moving through the molten sludge) creates a larger 'wake zone' behind them.
we are looking at conditions of ultra-high pressure, where even stuff like hydrogen can verge on becoming metallic (or is the Earth's core too small? I forget...). in terms of temperature literally everything is really hot down there and the further down you go the higher the temperature gets. so the 'lava lamp' analogy falls short there.
as well the relatively compact nature of the core would insure that the blobs would affect each other in their trajectories, thus they wouldn't have a 'stable' pattern.
all brain farts, forgive if I'm not seeing something obvious. but I like the fact that these blobs provide a neat piece to 'how things work' file. namely, turbulence in the mantle created by the slow passage of these blobs is the most reasonable explanation for the magma 'spikes' and the patterns of the ring of fire. if these things were responsible for the breakup of Pangea then perhaps the plate boundaries are crustal records of the 'harmonic' which tore things apart. stuff for the realm of pure speculation. oooh, my brain hurts...
Aug 15th, 2005, 10:28 AM
I wouldnt say those blobs cool down as it drops into the core. I'd say more like a magnatized nuclear gas explosion /expansion concept w/ super hot temps alway. Anyhow, I loved both of your thought processes on this, both of your minds are HOT and a total turn on! Anyhoo,
I was told months ago in the forum that "the earth won't crack apart" and I know that the plate tectonics are doing just that in places. so, i wanted to re-iterate what the core er: earth engine really is and
is it possible that,like the sun,(shoots photons out into the atmosphere)earth
material could shoot out of the earth at a possible weak point or tectonic joint that is weakened? or/ would it be ejected through volcanic activity?
I'm interested because I live near a very old fault fracture zone.
Aug 15th, 2005, 11:18 AM
Mezurashi- These "blobs" are in the mantle- not the core. There is a very distinct boundary between the outer core (liquid nickel-iron) and the lower mantle. For some reason (and we really are clueless as to why) the mantle seems to heat up in spots at this boundary. Once heated, like you said, volume increases, density decreases and it slowly migrates upward. When the "blob" hits the top of mantle, it spreads out (since it can't go up anymore), cools, becomes more dense and slowly flows downward. Subducting plates may provide additional cooling.
A basic convection current. As you suggested, it may not be entirely tempurature dependent.
Protostar- Ancient fracture zones do provide plumbing systems for fluids and gas. Volcanoes typically erupt along fracture zones, and the rocks along fracture zones are commonly altered (changed) by fluids moving through them. These fluids are, most often, hot; but they still originate in the relatively thin crust- not the mantle or core. As to gases, helium concentrations are frequently elevated in these old fracture zones, as is radon. Again, they concentrate because the fractures provide a plumbing system that allows the gas to move more freely (the gas is present everywhere in the crust but is locked up by the surrounding rock), not because the gas is being ejected from the inner earth.
Just the musings of an old rock-hound.
Aug 15th, 2005, 5:42 PM
bass, dont you find it interesting that the sun spews out a photon or deep sun material (after climbing its way from the inner sun appx 94,000 years) or so
it was thought it took that long but anyway, dont you find it a coincidence that
the earth makes the same movement kind of? I'm just starting to understand
the mechanics of the earth so whatever you can tell me is Appreciated.
Aug 15th, 2005, 8:16 PM
I will take your word for the boundaries of the core, bass, but how do we know this for certain? what method of determining this has been utilized? I ask because so much of our info on the processes down there are theoretical or inferred from the reactions of the stuff on top. Though I am not 'current' on stuff like this it would seem odd that we could make such absolute statements about deep structure and yet be uncertain about stuff going on in the midrange.
at least, to my muddled thinking it seems that way. but I have also had a really bad day (in short, I 'threw away' about two hundred bucks due to mis-measurement and a moment's inattention).
I so want to blame my circumstances on these blobs, but I can't. I just can't... :alcoholic
Aug 15th, 2005, 11:06 PM
The boundaries have been determined by different geophysical methods and the core's makeup by both geophysics and meteorite composition. Scientist can figure the mass of the earth by its movements in relation to the Sun and Moon. The average densities of silicate rocks are not enough for the earth's mass, so there must be denser material at the core. Meteorites are thought to be the remains of planetary bodies- the two major types of meteorites are iron meteorites and stony meteorites. Iron meterorites come from the interior of planets and stony meteorites (made up of mostly silicate minerals) are probably equivilent to our mantle/crust.
The fact that the earth has a large magnetic field argues for the presence of high concentrations of iron- some of which much be molten.
Seismic (earthquake) waves are deflected when density of the rocks change- they also speed up in denser, cooler rock and slow down in hotter, less dense rock. Certain types of seismic waves (s-waves) don't travel through fluids (or molten material). Seismic studies show the distinct boundaries of the inner earth- and the s-waves stop at the lower mantle-upper core interface- suggesting that the outer core is molten.
The blobs were detected by seismic waves using a relatively new technique called seismic tomography.
Also, these blobs should affect gravity. Gravity changes can be measured and are correlated to the density of underlying rocks. So on those days when you feel the weight of the world is on your shoulders- perhaps you are standing over a cool blob and gravity really is more powerful! Blame the blobs- I do!
Aug 16th, 2005, 7:27 AM
other than seismic topography, have we any other methods of 'seeing' the proceseses down below?
also, the core stuff was determined by Inference, am I correct?
(need clarity, brain slow today)
Aug 16th, 2005, 3:01 PM
You are correct that it is inference- nobody has yet figured a method to get direct results. But, the inference is pretty strong- including research in several lines- astrophysics, mass studies, seismic, gravity, magnetic, geochemical, meteorites. All these lines of inference point to the same solution. My above post just scratched the surface of research available.
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