Talk:Mantle (geology)

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etc[edit]

both the upper and lower mantle both deform by thermally activative diffusion and dislocation creep. both are solid but both deform. neither of them are "semi-molten" and both behave like fluids on long timescales. --195.96.247.34 09:23, 3 November 2005 (UTC)From Isak Avramov Avramov@ipc.bas.bg Avramov

TWO IMPORTANT QUESTIONS

I have the following two questions:

Why so much oxygen[edit]

1. The Mantle composition given in the table to the article is quite widespread. However there is a problem. One can see that the amount of oxygen atoms must exceed the overall number of all other atoms. What is the nuclear reaction that produces so much oxygen atoms. I can understand the enormous amount of H and He in the universe. The most stable atom is that of Fe, so there is also a lot of it. But why oxygen. It seems the assumed composition is wrong. The core though, is the size of the moon.

The extra iron is located in the core. Estimates of the total Earth composition are 35% Fe, 30% O, 15% Si, 13% Mg... It is thought that much of the iron sank to the center of the Earth in the "Iron Catastrophe" early in the history of the Earth. (see the book "Earth" pp.12-13 by F. Press and R. Siever, for example).
The question was why the amount of O exceeds the overall amount of all other elements (exept Fe) Avramov
It turns out that the Earth's composition is the same as that of the solar nebular less a lot of hydrogen and other very volitile stuff. Oxygen in the (hot cooling) nebula would have formed silicate minerals and so not have been removed to the outer solar system as much as hydrogen was. So why oxygen in the nebula? Oxygen is one of the major products of small-ish stars, not all the stars that produced the elements that formed the nebula were large enough to produce iron. Andreww 07:29, 14 November 2005 (UTC)

Need high temperature gradient if asthenosphere convects[edit]

2. The article states: “Due to the temperature difference between the Earth's crust and outer core there is a convective material circulation in the asthenosphere.” The appearance of convection depends on Rayleigh number. Can you imagine what must be the temperature gradient for convection appearance if viscosity is 10^22 Pa.s.

Ok, the article is wrong: the whole mantle is convecting not just the asthenosphere. You can estimate the Rayleigh number quite easily; the other numbers needed are the density (4000 kg.m^-3), thermal expansion (2*10^-5 /C), thermal diffusivity (10^-6 m^2.s^-1) and it turns out to be about 3000000 (see "Dynamic Earth" by Davies pg.218). The reason convection dominates is, of course, that rocks are really bad conductors of heat. Andreww 10:25, 3 November 2005 (UTC)

Is high temp due to conduction or radioactivity[edit]

Hello, I'm wondering whether the hot temperatures of the crust exist because of conduction from the mantle or from radioactive decay of naturally present isotopes? is there debate on this topic? I haven't found anything relevant on wikipedia nor can i get a conclusive answer from other sources... thanks for ur help. Alex

Francis Birch's group at Harvard was apparently the first to find that there is a simple relationship between local deep crust temperatures and radioactivity in the crust itself, though radioactivity does not account for all of the temperature difference. The simple equation they derived is commonly used to infer how much heat is input into the crust from underlying convection by removing the contribution from radioactivity. Basically, it is A+B, where A is due to radioactivity (which can be measured), and B is due to heat input from the mantle.

Note about temperature[edit]

Conduction questions aside, a note should be made about the uncertainty of the temperature throughout the mantle, specifically at the CMB.

exploration[edit]

should mention be made of the first attempt to drill to the mantle? See here: http://www.physorg.com/news9073.html

Done, please check/correct. Any idea on how they can claim to reach mantle rock at 'only' 7 km below seabed? --danh 16:30, 17 December 2005 (UTC)

Because they are aiming for the Moho and you can only detect that (so far) by seismic. It's thin ocean crust, not thick continenal crust. So you don't need to drill 70km, just 7. You may be missing the whole point, which is to investigate the moho, and what causes it, not to drill the mantle and discover "OMGZORZ there's ultramafic rocks and they're hot", because that's implied from 1) mantle xenoliths and xenoliths and 2) the fact that magma comes from the mantle. Rolinator 05:59, 27 December 2005 (UTC)

Stubbed this[edit]

The reasons I've stubbed this are;

  1. The article is poorly set-out
  2. There is little information on what evidence has been accumulated for the definition of the "mantle"; seismic, petrology, magmas, etc etc
  3. It hardly even does justice to the Moho, or Mohorovicic.
  4. The definitions are overly simplistic (even if a simplified summary is put up front for non-geologists and the layperson) and could do with a lot of work, cf, plastic flow and plate tectonics.
  5. The lithospghere being aboutl 1/2 of what geology is concerned with aside from pretty minerals and fossils, is an important thing to get right and do it justice. This is pretty embarassing when there's 50 pages on abiogenic oil...

Rolinator 06:05, 27 December 2005 (UTC)

Comments[edit]

This article needs serious work. The mantle is the most important part of Earth (the crust, atmosphere, core, and ultimately life are all derived from it, after all, and it essentially controls the dynamical evolution of the Earth, including plate tectonics), yet here is a wikipedia article discussing it in complete shambles, not even up to snuff for an introductory geology level. I feel impelled to instigate a complete re-write, while not jettisoning everything in it (rather incorporating as much as possible). However, it is appropriate to pose the question here first rather than simply going about and doing a major overhaul of the page. Any comments? Objections?

—Preceding unsigned comment added by 193.52.24.125 (talkcontribs) 23:03, 2 August 2006
Go for it. The article is definetly in need of some serious help. Vsmith 23:14, 2 August 2006 (UTC)
I fertilized it and tied it to a trellis. Grow! Grow! (SEWilco 05:17, 16 September 2006 (UTC))

Exploration[edit]

Where did you get the source "thousands of square miles"? Both sources quoted state "thousands of square kilometers" (kilometers are smaller than miles). This source states that it "is irregularly shaped, about 30 miles long and perhaps that distance or more at its widest". That gives it a maximum area of 900 square miles (if it were a perfect square), and it is probably much less than that.

PK9 23:19, 6 March 2007 (UTC)

Fixed. Vsmith 03:52, 7 March 2007 (UTC)

Asthenosphere?[edit]

Other articles refer to different ways of classifying layers within the mantle.

The Lithosphere/Asthenosphere system (necessarily) muddles the older distinction between crust and mantle, but this article doesn't make the situation any better to a lay person trying to develop a basic understanding.

Some attempt should be made to reconcile the different classification systems - and if this is not possible to at least acknowledge their difference while attempting to address the genesis of this disparity (these disparities????) Scientific disputes can be really interesting . . .

JP 00:06, 18 July 2008 (UTC)

So the distinction is that the crust and mantle are a compositional boundary, while the lithosphere and asthenosphere are mechanical boundaries. The Lithosphere contains the crust and mechanically-rigid upper mantle; together these form tectonic plates. The asthenosphere is the low-viscosity layer beneath the lithosphere, and is also part of the upper mantle. Hope this helps - I'll add this to the article when I get around to it; have had a little too much Wikipedia for the moment. Ping me if I take too long. Awickert (talk) 09:49, 24 March 2009 (UTC)
To complicate things further perhaps, the lithosphere-asthenosphere boundary (apparently known as the LAB, a new acronym for my collection) within the mantle occurs at about the 1600K (normally approximated to 1300 °C) isotherm beneath which the mantle is weak enough to convect. This occurs at constant temperature due to the flow-law for peridotite being virtually insensitive to pressure. Some workers in geodynamics refer to the lithosphere as being both a mechanical and thermal boundary layer, distinguising it from the crust which is a chemical boundary layer and only sometimes apparently a mechanical boundary layer (so yet another way of describing the layering of the mantle). I think that we may need sections describing the chemical boundaries separate from the thermo-mechanical ones. I will also give this some thought over the next few hours/days/weeks/..... Mikenorton (talk) 22:02, 24 March 2009 (UTC)

Undue Weight Being Used To Suppress Information and Violate NPOV[edit]

Collapsing long discussion on cold mantle. The reliable sources indicate that there are "cold spots" in the mantle, but they are only cold in relation to the hot spots, with the temperatures varying between 500 °C and 900 °C. Saying that the mantle is cold without qualifications misleads readers to think that it's at room temperature, which is not.Related RfC on the matter has been closed. --Enric Naval (talk) 09:33, 24 March 2009 (UTC)
The following discussion has been closed. Please do not modify it.

Neutral point of view is a fundamental Wikimedia principle and a cornerstone of Wikipedia. All Wikipedia articles and other encyclopedic content must be written from a neutral point of view, representing fairly, and as far as possible without bias, all significant views that have been published by reliable sources. This is non-negotiable and expected of all articles, and of all article editors. For guidance on how to make an article conform to the neutral point of view, see the NPOV tutorial; for examples and explanations that illustrate key aspects of this policy, see Wikipedia:Neutral point of view/FAQ.

Information suppression

A common way of introducing bias is by one-sided selection of information. Information can be cited that supports one view while some important information that opposes it is omitted or even deleted. Such an article complies with Wikipedia:Verifiability but violates NPOV

However undue weight is being used to suppress information and observations published in peer-reviewed journals like Nature and Science that suggest the mantle is cold.Sophergeo (talk) 11:12, 20 March 2009 (UTC)

Rather tha wiki-lawyering and accusations of suppresion, why not present your links here for others to see and comment on. Vsmith (talk) 11:28, 20 March 2009 (UTC)
The cited sources do not support the claims that you trying to make. Ruslik (talk) 11:51, 20 March 2009 (UTC)
Here are the links that should receive due weight:

"The interior of the Earth is a problem at once fascinating and baffling, as one may easily judge by the vast literature and the few established facts concerning it." http://www.gps.caltech.edu/classes/ge164/ge164.files/Ge164_syllabus.pdf

"A Cold Suboceanic Mantle Belt at the Earth's Equator" http://www.sciencemag.org/cgi/content/abstract/sci;261/5119/315

"reflecting a weak magma supply from an unusually cold underlying mantle." http://www.nature.com/nature/journal/v394/n6694/abs/394637a0.html

"Cold Mantle Transition Zone Beneath the Baikal Rift" http://adsabs.harvard.edu/abs/2005AGUFMDI41A1266L

"Geophysical and geochemical evidence for cold upper mantle beneath the Equatorial Atlantic Ocean" http://www.scielo.br/scielo.php?pid=S0102-261X2008000100006&script=sci_arttext

"NASA Satellite Finds Interior of Mars Is Colder" http://www.nasa.gov/mission_pages/MRO/news/mro-20080515.html

"Mars Cold Goes Down Deep" http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2733

Sophergeo (talk) 12:02, 20 March 2009 (UTC)

You seems not to understand that cold in this context does not mean room temperature. 150 K is actually a very small difference as compared to the upper mantle temperature of about 1200 K. Some parts of the upper mantle are cooler than others, but nowhere these sources say that the mantle is cold (meaning a temperature of about 300 K as you implied in your edits). The last two sources are irrelevant—this article is about Earth, not Mars. Ruslik (talk) 12:13, 20 March 2009 (UTC)
No justification to suppress links and information. Wikipedia is an encyclopedia and NPOV is a fundamental Wikimedia principle and a cornerstone of Wikipedia. All Wikipedia articles and other encyclopedic content must be written from a neutral point of view, representing fairly, and as far as possible without bias, all significant views that have been published by reliable sources. This is non-negotiable and expected of all articles, and of all article editors.Sophergeo (talk) 12:45, 20 March 2009 (UTC)
(ec)Having checked through all the links provided concerning the earth (and I don't have access to all the full text articles), they are all talking about areas of relatively cold mantle in a similar way to the areas of relatively hot mantle found at hotspots. The temperature of the upper mantle varies around the globe so there will be both relatively cold and hot areas. None of this is sufficient reason to change the article IMO. Mikenorton (talk) 12:15, 20 March 2009 (UTC)
Neutral point of view is a fundamental Wikimedia principle and a cornerstone of Wikipedia. All Wikipedia articles and other encyclopedic content must be written from a neutral point of view, representing fairly, and as far as possible without bias, all significant views that have been published by reliable sources. This is non-negotiable and expected of all articles, and of all article editors.Sophergeo (talk) 12:42, 20 March 2009 (UTC)
A neutral point of view that is supported by evidence. The claim that the entire mantle is cold and there is no convection is factually wrong and the articles that were cited in support of this claim did not make any such statement. Present the evidence found in those papers for what is it -regions of the mantle have been found to have a lower temperature than other regions, thus indicating the mantle is a complex thermal system. Making wild, unsupported claims and then demanding they are retained despite there being no supporting evidence what-so-ever is any BUT neutral.Yorrike (talk) 01:00, 21 March 2009 (UTC)
Yorrike, Let us then add the following sentence with the verifiable reliable sources "regions of the mantle have been found to have a cold temperature, thus indicating the mantle is a complex thermal system." Every single verifiable and reliable reference from peer-reviewed scientific sources uses the word "cold" to describe the mantle. Your claim that Science and Nature are "making wild and unsupportable claims" is unverifiable and unsourced and does not justify suppression of information.Sophergeo (talk) 03:55, 21 March 2009 (UTC)
Sophergeo the current text of the Temperature section states "In the mantle, temperatures range between 500 °C to 900 °C (932 °F–1,652 °F) at the upper boundary with the crust" showing that there is a large variation in temperature in the uppermost part of mantle. I fail to see the need to add text that says that some parts are hotter and others are colder as that is already implied. Also Yorrike is clearly saying that you are "making wild, unsupported claims" not the sources you refer to. Mikenorton (talk) 11:33, 21 March 2009 (UTC)
All of the sources I refer to use the word "cold" to describe the mantle. So if what you're saying is true then that is a personal attack and action should be taken.Sophergeo (talk) 11:55, 21 March 2009 (UTC)
All of the sources that I have been able to check use the term 'cold' to mean 'colder than normal' rather than cold per se. When you use the term what exactly do you mean by it? I would support the expansion of the current temperature section to include a discussion of variations away from the normal range (both hot and cold). As to Yorrike's comments, I should leave him/her to confirm my interpretation. However, I agree that your claims (that the article does not meet the NPOV guidelines) are unsupported, no matter how many times you repeat part of them. NPOV also states "Neutrality requires that the article should fairly represent all significant viewpoints that have been published by a reliable source, and should do so in proportion to the prominence of each. Now an important qualification: In general, articles should not give minority views as much or as detailed a description as more popular views, and will generally not include tiny-minority views at all" and "Wikipedia should not present a dispute as if a view held by a small minority deserved as much attention overall as a majority view. Views that are held by a tiny minority should not be represented except in articles devoted to those views. To give undue weight to a significant-minority view, or to include a tiny-minority view, might be misleading as to the shape of the dispute. Wikipedia aims to present competing views in proportion to their representation in reliable sources on the subject." Note particularly the "in proportion to their representation in reliable sources" part. You may find a few articles in reliable sources that support a 'cold mantle' viewpoint, but they would vastly be outweighed by articles in reliable sources representing the viewpoint expressed in the current version of this article. Mikenorton (talk) 13:42, 21 March 2009 (UTC)
Sophergeo, if you have, in fact, read and understood the sources you're referring to, then please give the temperature they define as "cold." Temperatures of "500 °C to 900 °C (932 °F–1,652 °F)" are cold, in comparison to the temperature at the centre of the Sun, but are very hot indeed compared to the temperature of interstellar space. The word itself is meaningless without a contextual comparison. What ranges of values are you claiming justify claiming that the mantle is "cold"? I posture that you are simply using the appearance of particular words in reliable sources to promote a minority, unsupported view. Have you read the cited papers, or is the summation of your evidence seeing the word "cold" in the aforementioned sources? Yorrike (talk) 17:16, 21 March 2009 (UTC)
The definition of cold is "the opposite of hot." I have referenced multiple verifiable and reliable peer-reviewed sources from mainstream scientific publications such as Nature and Science which use the word "cold" to describe the mantle. However there is an obvious attempt to suppress any use of the word "cold" in mantle discussions. This is an obvious and blatant violation of NPOV. No matter what the temperature of the outer core is, and most likely it is quite high, the mantle is cold, and its rigidity increases with depth, because otherwise seismic wave velocity cannot increase with depth, for example for P waves from 6-7 km/sec in the surface layers to about 14 km/sec at the mantle-core boundary.Sophergeo (talk) 18:12, 21 March 2009 (UTC)
Your first statement is true, but doesn't reference "cold" as with respect to what temperatures, which is important. I could define hot up to infinity and cold to absolute zero. Numbers are important. Your second statement is wrong: please learn about seismic waves, the Lamé parameters, and the bulk modulus and shear modulus. Even a hot mantle is mechanically rigid over time-scales of seismic wave propigation. Awickert (talk) 18:17, 21 March 2009 (UTC)
We've strayed right off of topic here. The cited papers use the word cold when referring to regions of the mantle where the temperature is below "normal." If you'd read and understood them, you'd know this. However, no matter how the word "cold" was used in the cited articles, they do not imply in any way what-so-ever that the mantle does not convect. End of story. If you find peer-reviewed papers that do make a case for a non-convecting mantle, it may justify a mention if the case is strong enough. In the mean time, the scientific consensus is that the mantle is between 500 and 900 °C and that convection is occurring. Yorrike (talk) 20:58, 21 March 2009 (UTC)

RFC notification[edit]

Resolved: 3 contributors banned as master and socks. RFC closed. Awickert (talk) 20:43, 23 March 2009 (UTC)

I have initiated a request for comment on the Expanding Earth hypothesis at Talk:Expanding Earth#Request for Comment: Expanding Earth and Plate Tectonics. Please leave a comment there, or a statement if you were involved in the debate. Thank you, Awickert (talk) 05:08, 22 March 2009 (UTC)

Measurements[edit]

The measurements in the article are not realitive to the measurements in the other articles. "These layers (and their depths) are the following: the upper mantle (33–410 km) (20 to 254 miles), the transition zone (410–660 km), the lower mantle (660–2891 km), and in the bottom of the latter region there is the anomalous D" layer with a variable thickness (on average ~200 km thick)[2][3][4][5]." Wikipedia, Mantle (geology) and "The oceanic crust is 5 km (3 mi) to 10 km (6 mi) thick[1] and is composed primarily of basalt, diabase, and gabbro. The continental crust is typically from '30 km (20 mi) to 50 km (30 mi) thick, and it is mostly composed of less dense rocks than is the oceanic crust." Wikipedia, Crust (geology). The measurements are the continential plates extend from 30 km to 50 km in one artice and another article says the upper mantle extends from 33 km to 410 km. Please note the italics. —Preceding unsigned comment added by LouisSS13 (talkcontribs) 19:07, 5 July 2009 (UTC)

Also, how is the mantle about 2,870 km thick when the mantle only stretches to 2891 km deep? —Preceding unsigned comment added by LouisSS13 (talkcontribs) 19:22, 5 July 2009 (UTC)

Image[edit]

I think the "to scale" and "not to scale" labels on the top image need to be moved around. As I understand it, the full hemi-sphere image is to scale, whereas the segment is not, but the positions of the two labels do not make this clear. Kernow (talk) 13:45, 18 June 2010 (UTC)

Higher Elevation over Hotspots due to Buoyancy?[edit]

There is a sentence that mentions that areas of the Earth's surface located over hotspots are predicted to have higher elevation due to the increased buoyancy imparted by the hotter, lower-density mantle beneath. However, this prediction does not match current observations. While known hotspots often exhibit higher surface elevation, the causes are not known to be due to mantle buoyancy. For example, the Hawaiian hotspot's current surface manifestation (Mauna Kea) exhibits high elevation due to volcanic accumulation. In fact, the crust is actually DEPRESSED nearly four miles here due to the weight of accumulated material, quite contrary to what is claimed in the section I am disputing. While there is evidence that mantle plumes can explain large-scale elevation anomalies such as the African superswell, this hypothesis has not yet been proved and much of the evidence used to support it is conjectural. I propose that this sentence be removed or at least acknowledged to be a controversial claim, but I would appreciate the input of editors with more technical knowledge of the subject before making the change. 63.115.56.33 (talk) —Preceding undated comment added 19:17, 25 January 2012 (UTC).

Furthermore, upon investigating the source cited to support this claim, I found that it is a book chronicling the controversy surrounding claims such as this one, going so far as to acknowledge in the description of the book that the hypothesis has undergone numerous alterations over the past 30 years to account for observations that do not match its predictions, ultimately becoming what amounts to an unfalsifiable hypothesis. As Wolfgang Pauli once said, "Not only is it not right, it's not even wrong!"63.115.56.32 (talk) —Preceding undated comment added 19:38, 25 January 2012 (UTC).

Asthenosphere/ Plastic Rock[edit]

This fails to mention that "Plastic Rock", or the asthenosphere is merely a theory. Could someone more knowledgeable in this subject could correct this. — Preceding unsigned comment added by 24.18.170.209 (talk) 04:35, 16 November 2012 (UTC)

Dead link reference for mantle viscosity[edit]

Reference 20 (http://www.igw.uni-jena.de/geodyn/poster2.html) which is supporting the claim of mantle viscosity of 1019–1024 Pa·s. Furthermore, the content of a poster is not usually peer-reviewed and isn't the best citation for a number such as this.

Myfriendebin (talk) 04:00, 8 February 2013 (UTC)

I've looked for other sources for this particular range and found none, but I have found a lot of variation. An overall viscosity of 1021 (as calculated by Haskell in in 1935) is still considered a good estimate for the whole mantle, but various numbers in the range 1019 (for the upper mantle) to almost 1023 (for parts of the lower mantle) are mentioned. I'm still thinking about how to discuss this variability and uncertainty in the article. Mikenorton (talk) 23:38, 10 February 2013 (UTC)

Link needed for seismic velocity[edit]

A link to the the article on seismic velocity would be useful. It is not necessarily obvious to a lay person precisely what this is. Itsmeitis (talk) 13:29, 1 May 2015 (UTC)

There isn't an article specifically about seismic velocity, so I linked it to S-wave, as it's the decrease in shear wave velocity that defines the low velocity zone. I think that a separate article on seismic velocity would be a good idea, though. Mikenorton (talk) 19:41, 1 May 2015 (UTC)

Semi-protected edit request on 16 February 2016[edit]

On 16 February 2016 Russia Beyond the Headlines reported that an international group of scientists has discovered a previously unknown layer in Earth’s mantle, and they estimate that it contains about eight to ten times more oxygen than Earth’s atmosphere. “This discovery came as a big surprise to us and so far we don’t know what is happening to these ‘rivers of oxygen’ in the depths of our planet,” said Dr. Elena Bykova, a member of the group of scientists who made the discovery.[1] Phys.org, also, reported on 11 February 2016 that Dr. Elena Bykova from the University of Bayreuth reported these results in the peer-reviewed open access scientific journal Nature Communications.[2]

References

Picomtn (talk) 16:45, 16 February 2016 (UTC)

The Nature Communications paper is a little more nuanced than that. In the discussion it says "Seismic tomography reveals pronounced complex heterogeneities in the lower mantle at depths of 1,500–2,000 km associated with subducted slabs and the presence of oxidized material may be a reason for these observations" and goes on "our study suggests the presence of an oxygen-rich fluid in the deep earth’s interior that can significantly affect geochemical processes by changing oxidation states and mobilizing trace elements". So, certainly interesting, but I think a bit too early to add it to the article - better to wait for reaction from other people that work in that area. Mikenorton (talk) 17:29, 16 February 2016 (UTC)

Semi-protected edit request on 14 September 2016[edit]

I love food!

2601:204:100:5834:3149:49D0:8CFE:1883 (talk) 03:26, 14 September 2016 (UTC)

Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format. EvergreenFir (talk) 04:57, 14 September 2016 (UTC)

Average thickness[edit]

The average thickness I've encountered in sismology is 5 KM and not ~2 as mentioned in the article. Which is correct? ÞunoresWrǣþþe (talk) 13:58, 3 February 2017 (UTC)

Add temp schematic[edit]

I think this would be suitaible, no? 193.167.228.180 (talk) 08:57, 29 March 2017 (UTC)

I'm all for something that demonstrates the change in temperature with depth, but this one is not clear. The graph shows constant temperature within the inner core, but gives values of 5000 to 7000 K from top to bottom, so that doesn't make any sense. I can't find a graphic that matches the current understanding of temperature changes with depth. Mikenorton (talk) 08:28, 31 March 2017 (UTC)