Part of Earth's mantle shown to be conductive under high pressure and temperatures

Jan 20, 2012 by Bob Yirka report

(PhysOrg.com) -- Scientists studying the rotation of the Earth have long known that our planet doesn't have a perfect spin. Most believe this is due to the different types of materials that make up the core, mantle and crust, which all have different rates of spin causing inherent friction. Most models researchers have developed however agree that in order for the planet to wobble the way it does, the mantle would have to respond to the magnetic tug of the core. The problem with this though, is that the mantle is made mostly of rock, not metal, which means it’s not supposed to be conductive.

New research by a Kenji Ohta and his colleagues at Osaka University in Japan indicates they’ve found a possible explanation. As they describe in their paper published in Physical Review Letters, it appears that Wustite (FeO), believed to be one of the components that make up the Earth’s , can be made to conduct electricity at high and high temperatures.

This new work by the team builds on findings from the 1980’s that showed that FeO becomes more conductive when exposed to shock waves. To find out if other conditions might cause the same outcome, the team placed a sample of FeO in a diamond anvil and heated it using a laser. As the experiment proceeded, they also measured the conductivity of the FeO sample.

After heating the sample to 1600°C and applying 70 gigapascals of pressure, the team found the sample became as conductive as an average metal. They also noted it did so without any changes occurring to its structure.

To find out if the same conductive properties would occur under more harsh conditions, comparable to those found inside the Earth, the team turned up the temperature to 2200°C while ratcheting up the pressure to 1.4 million atmospheres and found the same results. Such measurements suggest, the team theorizes, that the same conductive properties would likely hold under even more extreme conditions such as those found near the boundary between the mantle and the core.

To better understand why FeO becomes conductive under and heat, the team did density and electrical conductivity tests as they relate to temperature and pressure and now believe that the metallization is related to spin crossover.

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More information: Experimental and Theoretical Evidence for Pressure-Induced Metallization in FeO with Rocksalt-Type Structure, Phys. Rev. Lett. 108, 026403 (2012) DOI:10.1103/PhysRevLett.108.026403

Abstract
Electrical conductivity of FeO was measured up to 141 GPa and 2480 K in a laser-heated diamond-anvil cell. The results show that rock-salt (B1) type structured FeO metallizes at around 70 GPa and 1900 K without any structural phase transition. We computed fully self-consistently the electronic structure and the electrical conductivity of B1 FeO as a function of pressure and temperature, and found that although insulating as expected at ambient condition, B1 FeO metallizes at high temperatures, consistent with experiments. The observed metallization is related to spin crossover.

via Physics Synopsis

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HannesAlfven
1.5 / 5 (8) Jan 20, 2012
Re: "The problem with this though, is that the mantle is made mostly of rock, not metal, which means its not supposed to be conductive."

The notion that the Earth cannot hold an electrical charge is actually an assumption which the existing gravitational scientific framework absolutely depends upon.

Most astrophysical textbooks agree that 99.999% of what we see with our telescopes is matter in the plasma state. Within the laboratory, plasma's charge-carrying capabilities are absolutely vital to the creation of plasma-based technologies. Yet, our cosmology appears to not have much use for electrical plasmas in space. The models reflect this.

Nevertheless, the charge density of the Earth's immediate environment is in constant flux. Is the claim being made that the Earth never absorbs this charge, simply because it is made of rock?

I truly hope that people direct their critical thinking skills at this assumption. There are, after all, these things called semiconductors ...
pauljpease
5 / 5 (5) Jan 20, 2012


Nevertheless, the charge density of the Earth's immediate environment is in constant flux. Is the claim being made that the Earth never absorbs this charge, simply because it is made of rock?

I truly hope that people direct their critical thinking skills at this assumption. There are, after all, these things called semiconductors ...


Here is me directing my critical thinking skills at your comment. First of all, yes, plasmas carry electric charges. So do atoms, neutral atoms. You see, they carry both positive and negative charges in equal abundance, so they have no net charge. Same with plasmas, they are electrically charged but carry no net charge. If too many like charges accumulate they would repel each other. If there was a large imbalance of positive and negative charges on Earth, the Earth would not be stable.
GSwift7
3 / 5 (4) Jan 20, 2012
yes Pauli,

Additionally, this is me using my critical reading skills on his post as well: He is obviously confusing conductivity (which the article is talking about) with static charge. As you might know, a plastic rod is perfectly capable of holding a static charge. The plastic rod is not conductive though. They are not talking about the Earth "holding a static charge", they are talking about the mantle being conductive.

Everyone knows that the Earth has lots of charged particles. The ionosphere is loaded with them. Everyone knows that massive plasma clouds are also made up of various charged particles. The solar wind is made of charged particles too. When Hannes says
Yet, our cosmology appears to not have much use for electrical plasmas in space. The models reflect this
I have no idea what he is talking about. That doesn't make any sense at all.
GDM
not rated yet Jan 20, 2012
I'm no physicist, nor a planetary geologist, but isnt the Earths wobble due to being smacked by a Mars-size planetoid early in the formation of the Earth? It seems reasonable to me that the collision imparted a 23 degree tilt, the 25,000 year precession, and perhaps even increased the planets rotation. The material displaced from the collision (in the Pacific?) could have formed the supercontinent Columbia/Nuna/Hudsonland on Earth and the mountainous far-side of the Moon. Ive always wondered about the presence of the hot spot that is the Hawaiian Islands, at 19 degrees north, and practically dead center in the Pacific. Is this possible? When I was much younger, tectonics was ridiculed and the shapes of the continents were just a coincidence.
GSwift7
3 / 5 (4) Jan 23, 2012
but isnt the Earths wobble due to being smacked by a Mars-size planetoid early in the formation of the Earth?


Yes and no. Yes, the theory is that some of our orbital characteristics are due to a large impact. But, there are other irregularities in our orbit that are not explained by that. The irregularities you are talking about remain constant, since we don't get hit again every year. The wobbles they are talking about above are currently taking place, and changing over time. The only way that could happen is if there's some sort of active mechanism that's causing it. An impact billions of years ago wouldn't still be causing changes.

When you take the overall motion and subtract the impact wobble, the tectonic wobbles, tidal wobbles, etc, there's still some extra wobbles left over that could be explained by a magnetic/conductive mantle. It's kinda like planetary forensics. Eliminate all the suspects until you only have one.
Shelgeyr
1.8 / 5 (4) Jan 23, 2012
@GSwift7 said, regarding HannesAlfven's comment:
I have no idea what he is talking about. That doesn't make any sense at all.

Careful with swinging that axe around... You say that you don't have any idea what he is talking about. But then you say that it doesn't make any sense, after having just disqualified yourself from having a valid opinion.

To those who do know what he's talking about, he either makes sense, or he doesn't and they can point out why.

I do know what he's talking about (and no, I'm not a sock puppet), and for what it's worth he makes sense to me. If you're still curious, I suggest you Google "the earth is a leaky capacitor" or words to that effect.
GSwift7
2.8 / 5 (4) Jan 23, 2012
I suggest you Google "the earth is a leaky capacitor" or words to that effect


I specifically quoted the part of his comment about cosmological models. You are talking about the other part of his comment, which I didn't have a problem with, except that he missed the difference between charge and conductivity. You and he are both talking about something that is a different topic than the article above.

When I said that I have no idea what he's talking about, that's a figure of speach. It doesn't mean that I don't know what I'm talking about. It means that I think he doesn't know what he's talking about. Then I expanded on that though by saying that he didn't make any sense. I gave numerous examples of how magnetism and electricity are included in current cosmological models. So, I have no idea what he means when he says that the current models don't take them into account. They do.
GSwift7
2 / 5 (3) Jan 23, 2012
The topic of the article is whether the Earth's mantle is a conductor or not. That has nothing to do with whether it has a charge or carries a current. The question the researchers were trying to answer, is whether the materials in the mantle, which are normally an insulator, will become a conductor under mantle pressure and temperature. Since they have found that the answer is probably "yes", now they can look into whether there is current and/or charge.

But I do have a question. Isn't just about anything a conductor when you have enough voltage? Air, wood, rock, all become conductors when the voltage is high enough.
Shelgeyr
3 / 5 (2) Jan 23, 2012
@GSwift7 said:
When I said that I have no idea what he's talking about, that's a figure of speech.


Sorry, I didn't realize that. And since I apparently completely misunderstood YOU, I think that makes a logic circle of some sort - a linear argument twisted möbius-like in my head, no doubt.

Anyways, after admitting that, I'm going to skirt dangerously close to hypocrisy and suggest that when he says the current models don't take them into account, and you say they do, that you are still talking to cross purposes and/or about different things. Of course, I can't speak for him, so take that with a grain of salt, at best.

The topic of the article is whether the Earth's mantle is a conductor...

True. That's my read as well.

...has nothing to do with whether it has a charge or carries a current.

I see that as tangential, but let's skip that...

Isn't just about anything a conductor when you have enough voltage?

Yes, you're right about that
GSwift7
1 / 5 (1) Jan 24, 2012
Anyways, after admitting that, I'm going to skirt dangerously close to hypocrisy and suggest that when he says the current models don't take them into account, and you say they do, that you are still talking to cross purposes and/or about different things. Of course, I can't speak for him, so take that with a grain of salt, at best.


Yes, he is trying to push a fringe theory that he likely read in some magazing. I've heard it before, but it isn't mainstream. He's exagerating when he claims that the mainstream cosmology doesn't account for plasma because he's cynically trying to discredit it. Furthermore, he knows that he is exagerating and that the plasma theory isn't consistent with mainstream cosmology. He's trolling to try to get people to argue against a straw man that he can't possibly care about, and has nothing to do with the actual topic of the above article. He does this on purpose, in many threads. It's some kind of sad attention seeking behaviour. An illness.
Shelgeyr
1 / 5 (1) Jan 24, 2012
@GSwift7 said:
It's some kind of sad attention seeking behaviour. An illness.


I can't join you in that opinion. I have to say that there's "fringe", and then there's "FRINGE" and a person's own point of view, background, and educational history have a huge impact on what one considers "fringe".

For what it is worth, I'm generally on HannesAlfven's side in the sense that we're both apparently firmly within the EU camp (you probably guessed that).

When you say "He's exagerating when he claims that the mainstream cosmology doesn't account for plasma because he's cynically trying to discredit it", you're going past your own observations and making an assumption as to his motive. Again, although I don't know him, allow me to disagree because I think you two would define the phrase "mainstream cosmology doesn't account for plasma" to mean wildly different things.

Sure mainstream cosmology acknowledges the existence of plasma, (to be continued...)
Shelgeyr
1 / 5 (1) Jan 24, 2012
(continued...)
...mainstream cosmology acknowledges the existence of plasma, but since the mainstream doesn't "buy into" space plasmas being able to do what laboratory experimentation has led a lot of EU proponents to believe it can do, our saying the mainstream "doesn't account for plasma" is not totally inaccurate (albeit needing clarification).

Reverse example: I don't believe there is any such thing as "dark matter", so if you said my cosmology "doesn't account for dark matter", you'd be correct. But pretend that I did believe in it, but just didn't grant that it had all the effects commonly attributed to it. You could still make a HannesAlfven-ish claim against me that my cosmology didn't account for it, wherein I'd be in your/mainstream's shoes saying "yes it does - see, I account for it right here". And you'd know I'd missed the mark because my understanding of dark matter didn't line up with yours.

That was probably clear as mud, but I hope it helped..
Shelgeyr
1 / 5 (1) Jan 24, 2012
To haul things back onto the actual topic of "Part of Earth's mantle shown to be conductive...", I hope you understand that from an EU point of view, this may be excellent corroborating evidence, since actual telluric currents (and thus the mantle's ability to carry them) are deemed an integral part of our planet's formative history. Therefore, I have a different issue with HannesAlfven saying:
The notion that the Earth cannot hold an electrical charge is actually an assumption which...


My issue isn't one of disagreement, but one of transition or timing. Hannes, old man, you need to signal before you make such an abrupt turn!

Just because some of us can make the leap doesn't mean that most people won't see this as a complete change of topic.

I think this type of transition is best illustrated by commedian Brian Regan in this brief clip on the Mortgage Crisis, beginning 20 seconds in:
http://www.youtub...9amLsiq4
Kevin Mead
1 / 5 (2) Jan 25, 2012
In respect to the oil we are taking out of the earth.

If we dont replace the hole we are taking the oil out of with something liquid. We are creating a problem with the rotation of the earth.
The oil is heavy. Air is light. The size of the hole we are taking the oil out of is huge. Thus causing a change in the rotation of the earth. If you take a sphere and fill it with water in pockets. Then cause it to rotate.
Then deplete the pockets of the water, one at a time or even simultaneously, the rotation is thrown off causing a wobble and consequently a vibrating effect.
If we deplete these oil pockets of the liquid in the earth, The pockets become dry and if the liquid is gone, the absorption of the vibrations is gone. The pockets will vibrate, thus earth quake occur. The pocket collapses and we have huge disasters. Tsunamis, Atmosphere disasters such as Hurricanes Tornados Etc.
Cracks in the earth crust.
So I believe we should Replace the oil with a Liquid so as not to throw the ear
Shelgeyr
2.5 / 5 (2) Jan 25, 2012
@Kevin Mead spake:
We are creating a problem with the rotation of the earth.

Uh, no we're not.

It seems that your understanding of the end-state of petroleum extraction is incorrect, and furthermore that the consequences you describe as the result are not only wrong, but will still be wrong even if you had a firm grasp of the situation, which I must politely suggest you do not.