Talk:Geothermal gradient

Geothermgradients.jpg
The image: http://upload.wikimedia.org/wikipedia/en/thumb/f/fa/Geothermgradients.jpg/300px-Geothermgradients.jpg is currently in CMYK colorspace that many browsers (ie. Opera) are unable to display!

In addition the original image Geothermgradients.jpg is a BW line drawing. Would the creator of the original image please convert it to black-and-white paletted PNG image. See http://en.wikipedia.org/wiki/PNG#Comparison_with_JPEG for additional information.

Thanks. Keep up the good work!

Geologician changed image to B&W .png file as requested above on 11/13/2007 —Preceding unsigned comment added by Geologician (talk • contribs) 14:49, 13 November 2007 (UTC)

Does the data exist for the plot? Somehow the aspect ratio or something is drastically wrong. If I look at the plot, I see distance in the Y axis and Temperature in the X axis. Is this not right? Because that is how it is labeled. Consider the slope between the last two data points. (5150km,5000K) and (6370km, 7000K). The slope here is 2000K/1220km, or 1.6K/km, which is twice the slope between the previous two points. However, the line is flat temperature wise. Kaw in stl (talk) 13:58, 21 September 2016 (UTC)

Global average geothermal gradient
I am not a geologist (or natively English speaking), but...

The text says that the average geothermal gradient is 0.02º K/m. It would probably be good to mention that this number varies between 10º to 50º C/km (or 0.01º to 0.05º K/m).

Anomalies in the geothermal gradient is a way to chart deep structures of the crust.

(See fex: http://www.geo.wvu.edu/~jtoro/geol101/Outline-2.html http://www.targetexploration.com/tar8.htm )

I do not know what is the current truth. IMHO better average number would be 0.025º K/m, or 0.03º K/m. It is classically teached that temperature rises 1ºC per 33m (which is roughly equal to 0.03º K/m).

Second thing:

It would be good to mention the geopressure gradient that always accompanies the geothermal gradient.

See: http://www.glossary.oilfield.slb.com/Display.cfm?Term=geopressure%20gradient

Wikipedia has a pressure gradient page (http://en.wikipedia.org/wiki/Pressure_gradient) but currently it focuses on the atmospheric one. Little rearranging perhaps?

Adiabatic heat gradient in solids

Later down in the article is mentioned an adiabatic heat gradient in the mantle which is said to be solid. So why wouldn't such a gradient exist in the crust then? Gravitational and adiabatic heat gradient is the same thing. Since horizontal stress in the crust can be negative or positive it can explain the fact that some boreholes become cooler with increasing depth. Heat gradient theories based on conduction can not explain this. Davidjonsson (talk) 20:20, 16 June 2009 (UTC)

I have changed the "22.1C/Km" to "about 25C/Km". I suspect that the 22.1 came from a imperial-metric conversion with too many significant figures and as the value varies with position a 3 significant figure number is not helpful. Mtpaley (talk) 00:53, 26 August 2012 (UTC)

WikiProject class rating
This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 09:52, 10 November 2007 (UTC)

Temperatures at shallow depths
Should their be a subsection on this? —Preceding unsigned comment added by 173.51.113.96 (talk) 18:17, 30 June 2009 (UTC)

Yes, there should. Shallow surface zones only a few meters deep contain both diurnal and annual variations important to several technologies including agriculture, civil engineering, geothermal heat pumps, etc. In addition, zone from 5 to 15 kilometer becomes hot enough to affect petroleum, and other, drilling tools. Mydogtrouble (talk) 03:30, 27 March 2010 (UTC)

I came to this listing hoping to find a chart showing how temperature decreases to whatever depth, and then begins to increase. Also, wondering what the average (isocline, thermocline not sure the definition) depth at which temperature remains constant year around.Flight Risk (talk) 22:26, 11 December 2011 (UTC)

Geothermal is awesome
I agree, but how the hell did you do that man, I can't even find it in the source code. 85.167.119.115 (talk) 20:55, 14 October 2010 (UTC)


 * I have no idea, I just closed up the spare line at the top of the section and it disappeared. Mikenorton (talk) 21:14, 14 October 2010 (UTC)

Ocotober 26, 2011 WSJ resource, focus Indonesia
97.87.29.188 (talk) 23:41, 26 October 2011 (UTC)
 * http://online.wsj.com/article/SB10001424052970203791904576608384138650542.html A Power Struggle Boils in Indonesia; Foreign Investment in Geothermal Sector Gets Bogged Down; A Nod to the Gods. by ERIC BELLMAN
 * http://online.wsj.com/video/indonesias-underground-power-supply/B2685D0E-D9BF-49DF-A8E7-09D46E294218.html (video) Indonesia's Underground Power Supply; Throughout its jungle-capped mountains, Indonesia is literally bursting with clean, geothermal energy. But many problems are stalling investment. 10/25/2011 5:20:51 PM by Eric Bellman reports from Jakarta.
 * This might be better in Geothermal energy, or some place else. 99.190.85.15 (talk) 03:26, 27 October 2011 (UTC)

Discovery of Geothermal Gradient
Is the claim in the article on Robert Were Fox correct? Should his discovery of Geothermal Gradient be noted in this article? Vernon White '''. . . Talk''' 10:26, 1 March 2012 (UTC)

Article is too Earth-centric
All terrestrial planets and terrestrial-like natural satellites have geothermal gradients, yet the definition used here apparently applies only to Earth. Mars, Mercury, Venus, Vesta, Titan, Ganymede, the Moon etc are all thought to have geothermal gradients under standard models although Earth has the only proven gradient. Therefore I have tagged the article so that information from these other planets can be included. --EvenGreenerFish (talk) 03:38, 30 April 2012 (UTC)
 * Perhaps it's because of the geo, which indicates earth. I'd suggest you start an article on planetary thermal gradients or some such, which could be linked to where appropriate here. Vsmith (talk) 09:30, 30 April 2012 (UTC)
 * Or simply add a section to the article re: planetary ... thermal gradients based on WP:RSs. Vsmith (talk) 09:37, 30 April 2012 (UTC)


 * I understand what geo means, but all the same, geology which uses the prefix has a general application, given that Planetary geology retains it (I mean without the geo, you're left simply with "ology" which doens't mean anything in this context). Attribution of the nomenclature is natural given that its only recently that other planets have been studied we don't have any new words for them, that does not mean however that they don't fall under the same definition.  It makes sense to add another article but it also needs to be explained in the opening paragraph that the concept applies to almost all terrestrial planets (the prefix terra also paradoxically relates to Earth). --EvenGreenerFish (talk) 23:29, 30 April 2012 (UTC)
 * The terminology planetary geology always has bugged me -- I'd rather use planetology, but that's just a redirect. And I'll agree the planetary science folks have chosen to appropriate geo- to non-geo stuff despite logic and my objections :) (the moon landing happened in the middle of my undergrad geology studies). A separate article (with a link and blurb somewhere here) would be best in my view. I'm assuming there's plenty of sourced material to use. And it wouldn't have to be restricted to rocky bodies as I'm sure there exist thermal gradients w/in the gassy ones also. Vsmith (talk) 01:29, 1 May 2012 (UTC)

Weasel Words
There are several statements in this article that feel like weasel words.

"Because much of the heat is provided by radioactive decay, scientists believe that early in Earth history, before isotopes with short half-lives had been depleted, Earth's heat production would have been much higher"

Is the ", scientists believe that early in Earth history, " part informative?

"Highly viscous or partially molten rock at temperatures between 650 to 1,200 °C (1,200 to 2,200 °F) is postulated to exist everywhere beneath the Earth's surface at depths of 80 to 100 kilometres"

"is postulated" implies that this is mere speculation.

Comments? Mtpaley (talk) 21:50, 4 December 2012 (UTC)

Geothermal v's groundsource.
Hi, This article states that ... Because heat is flowing through every square meter of land, it can be used for a source of energy for heating, air conditioning (HVAC) and ventilating systems using ground source heat pumps. In areas where modest heat flow is present, geothermal energy can be used for industrial applications that presently rely on fossil fuels.[10]

Which contradicts statements in articles about ground-source heat pump technology where it is observed that the heat energy used by such systems is in fact of solar origin.

Thanks for listening

Jonathan — Preceding unsigned comment added by Jonnyhugs (talk • contribs) 15:26, 6 January 2013 (UTC)


 * I deleted both sentences from the article. The first has to be wrong (based on the 65mW/m^2 figure earlier in the article). The second speculates on an issue which has already effectively been covered in the sentence(s) immediately above it. I wouldn't usually be so bold as to delete something without checking its reference (which I can't access online), but I think that's better than leaving something visible with the potential to mislead (people trust Wikipedia). An alternative would be to explain that the paragraph only applies in areas of "exceptionally high geothermal activity" or some other weasely description, which isn't very relevant to an article about the geothermal gradient in general. Another approach would be to show that most ground source heat pumps can only gain an insignificant portion of their heat from the geothermal source. Adx (talk) 09:37, 1 November 2018 (UTC)

== I had the impression that geothermal power plants for heating and etc will cool the rock down and get all finished. Isn't that how it works?Patriot1423 (talk) 11:13, 28 January 2019 (UTC)

Consistency needed in using temperature units
In one sentence, a temperature is given in Fahrenheit and Celsius units but not Kelvin. In the very next sentence, a temperature is given in Kelvin and nothing else. This makes it hard to do an eyeball comparison of temperature when they are different units. Plus, it makes the article look sloppy when it switches units. The article should pick one unit and stick with it 129.63.129.196 (talk) 16:06, 4 October 2013 (UTC)

Science errors there are
Some of the speculative content comes from ref 8 the rest are not publicly accessible "Heat released as abundant heavy metals (iron, nickel, copper) descended to the Earth's core." that article makes several obviously incorrect statements "gravitalional heat" might make an iota of sense if metal density is 8 and rock is 4 but Iron et al do not exist as metal but as minerals of rock density. The statement in that article that "most of the earth's heat is in the mantle" is contradicted by him stating the core's temperature and density (temp X density = heat content). "The mantle is mostly made up of high density minerals with high contents of atoms that have relatively small atomic radii such as magnesium (Mg), titanium (Ti), and calcium (Ca)." Again Magnesium and Iron(II) Silicates (Olivine) is the current beleived to be the primary Mantle forming mineral. Both are larger diameter atomic radii ions. Calcium and Potassium are even larger diameter atomic radii ions. Calcium (+2) and Thorium (+4) are interchangeable in rocks that they occur in e.g. Flouride, Phosphate rock, Granite to name a few. Ditto Uranium.

These only a few of the faulty and questionable references (not meeting Wiki guidelines) that permeate this article. See Abundance of the chemical elements(Solar System abundance and Earth's Crust abundance) and Wikipedia metal properties of individual elements. Shjacks45 (talk) 07:25, 11 October 2013 (UTC)
 * Article fails to note that only the Earth and Jupiter emit more radiation (heat etc.) than they absorb from the Sun. This would improve perspective as other planets do not have this internal heating, migration of metals to the non-existent core, et al. The article implies a certain divine intervention in that it does not mention that Venus, Mercury, and Mars are exceptions to these theories?
 * Article fails to note that distribution of elements in the Earth's crust and the Solar system as a whole is significantly different. The elements lacking in the crust (Nickel, Chromium, Platinum, Thorium, etc. and including Carbon and Sulfur)are Ferrophilic or "Carbide forming" elements (used to alloy with Iron in various steels). The metals that are common on Crust/Lithosphere versus Solar System abundance are Ferrophobic metals (rejected by the core) like Calcium and Magnesium. The assumption of an Iron-Nickel core is partly based on Nickel and Iron depletion in the crust.
 * The above information noted in article on Late Heavy Bombardment in http://www.sciencedaily.com/releases/2011/09/110907132044.htm (notes all metals migrate to core, including radioactive ones, but crust enriched in heavy elements by meteorites.)
 * Caveats that composition of Mantle and Core are proposed and not verifiable.
 * And the release of huge quantities of Water Vapor, Carbon Dioxide, and Sulfur Dioxide during vulcanism, c.f. Deccan traps, would tend to lower Earth's internal heat. Current Mantle theories don't account for these gases origin (core-mantle interaction?). Kimberlite article notes origin in upper mantle?

=Yes and thank you there are science errors in the article but if maybe the earth emits more radiation (heat etc.) then it absorbs from the sun (as you claim) then geothermal power could hardly account for any large part of it. Instead the consensus seems to be that the geothermal power of the earth is about 30 TW or 3⋅12 watts and everyone knows that the solar radiation (heat etc.) is about 1300 or 1400 watts per meter2 around here, though it may be that some large part of it is reflected as by ices and etc.. However that may be at least the solar radiation (heat etc.) that is incident on the earth and its atmosphere must have several thousand times the power of any heat that comes up from the depths of the earth.

=For example if you estimate the cross section of the earth from an ellipse that fits the WGS 84 (a=6378.1370 km and b=6356.7523 km)you get about 1.273⋅108 square kilometers or 1.273⋅14 square meters and etc. and if we get 1300 watts per meter2 then it seems to add up to about (1300⋅1.273⋅1014) or 165,490 TW.

=Your complaint on this particular point seems to be misinformed (the earth could not possibly emit much more radiation (heat etc) than it absorbs from the sun).Patriot1423 (talk) 09:08, 12 January 2019 (UTC)

==Oh on second thoughts it occurs to me that if you interpret it the other way then of course you are very probably right on that and if the earth had no geothermal power then it should presumably make thermal radiation at whatever power it does have (from the incident solar radiation). I don't see how that would add anything to the article since it would be roughly equivalent to just saying that the earth has some geothermal power.Patriot1423 (talk) 12:14, 12 January 2019 (UTC)

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Lithosphere gradient
An interesting detail here that I think gets asked by a lot of science newbies but is rarely explained is the high temperature gradient of the lithosphere. That is, many newbies wonder how it is that the entire interior of the earth from the mantle down sits at temperatures of thousands of degrees and yet the crust is mostly solid rock. The gradient between the surface and the mantle is dramatically higher than anywhere else in the earth. For most beginners the reason for this is not obvious (the answer being, of course, that the lithosphere sits at the boundary between frigid outer space and the hellish inferno underneath). Seems worthwhile to explain this little detail explicitly in the article, obvious though it may be to any real student of science.

-- MC — Preceding unsigned comment added by 141.131.2.3 (talk) 18:21, 1 August 2017 (UTC)


 * Thanks for raising this point. I have added a sentence to the "Heat sources" section of the article. GeoWriter (talk) 15:41, 2 August 2017 (UTC)


 * @ an interesting detail: As far as I can tell your reasoning would make as much sense if you expected such very unequal gradients like that inside a warm bowling ball in a cold room but I would have thought that the radioactivity of the continental crust would come closer to explaining it and it STILL doesn't seem to add up so good.  Does heat get around faster in the mantle?  Didn't they say something about convection way down in there?  THAT would help to explain it, if there were mantle materials moving around at very high speeds like rivers of fire but if it is only solid materials and they move at the slow rates like a few centimeters per year like the continents then I don't see how they are going to move heat much faster than thermal conduction by itself and the very low gradient in the mantle does not seem to be explained enough YET.Patriot1423 (talk) 20:11, 8 February 2019 (UTC)

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Graph at top
I removed a description from the graph at top because it seemed to apply to a different picture. Lollipop (talk) 03:49, 17 May 2018 (UTC)

Sorry, but I find the top schematic figure (https://en.wikipedia.org/wiki/File:Temperature_schematic_of_inner_Earth.jpg) very confusing. What is on the horizontal axis ? There is no scale, no label other than "Temperature". — Preceding unsigned comment added by 2001:1458:202:55:0:0:101:EBB1 (talk) 14:28, 2 March 2022 (UTC)

Conversion of geothermal gradient range from °C per km to °F per mi
In the first paragraph of this article, the geothermal gradient is given as "about 25–30 °C/km (72-87 °F/mi)".

The Template:Convert seems to be unable to cope with simultaneous conversion (1) from a °C range to a °F range and (2) from km to mi. Therefore, the calculation has been done manually. Here is the calculation: 25-30 °C per km. Convert °C per km range from km to mi by dividing °C per km range by 0.6214 (the km to mi conversion factor); so 25 to 30 °C per km divided by 0.6214 equals 40.2 to 48.3 °C per mi. Multiplying both of the °C per mi values by 1.8 (the °C range to °F range conversion factor) gives 72.4 to 86.9 °F per mi. Rounding up or down to whole numbers gives 72 to 87 °F per mi. GeoWriter (talk) 12:37, 14 March 2020 (UTC)

Another way to calculate the conversion is "°C per metre x 54.86 = °F per 100 feet". (See source reference: Lovering, TS and Goode, HD (1963) "Measuring Geothermal Gradients in Drill Holes Less Than 60 Feet Deep East Tintic District, Utah", United States Geological Survey Bulletin 1172, page 2 at https://pubs.usgs.gov/bul/1172/report.pdf ). Thus: 25 °C per km = 0.025 °C per m. Multiply by 54.86 = 1.3715 °F per 100 ft. 52.80 x 100 ft = 1 mile. 1.3715 x 52.8 = 72.4 °F/mi. 30 °C per km = 0.030 °C per m. Multiply by 54.86 = 1.6458 °F per 100 ft. 52.80 x 100 ft = 1 mile. 1.6458 x 52.8 = 86.9 °F/mi. Rounding up or down to whole numbers gives 72 to 87 °F per mi.

The geothermal gradient is a temperature change per unit distance; adding or subtracting 32 is not applicable to calculations of temperature changes. (Conversion of individual specific temperatures, however, does add or subtract 32). GeoWriter (talk) 22:51, 10 June 2023 (UTC)

Earth - planet name - inconsistency
This article refers to our planet as "Earth"', "the Earth" and "the earth". This inconsistency seems unencyclopedic to me. I suggest that a single variant should be used throughout for consistency. Any preferences or comments? GeoWriter (talk) 18:11, 8 August 2021 (UTC)
 * I changed all occurrences (except "earth tides") to "Earth" on 2 March 2022. —GeoWriter (talk) 00:30, 17 November 2022 (UTC)

Depths in the first Graph are wrong
Hey all, I don't know how to change it myself but the depths on the first image are completely wrong (https://commons.wikimedia.org/wiki/File:Temperature_schematic_of_inner_Earth.jpg?uselang=de) The lithosphere is not 410 km thick, at 410 km there is a phase transition which marks the boundary between upper and lower mantle (see, e.g. here https://en.wikipedia.org/wiki/Upper_mantle_(Earth)). — Preceding unsigned comment added by Linesbijan (talk • contribs) 13:04, 7 November 2022 (UTC)
 * Agreed. The graph itself seems okay; the 410 label looks wrong, and should be replaced with a more reasonable value for the base of the lithosphere (say, 280 km, the maximum continental thickness). I suggest copying this criticism to the Commons page for the graph, as its originator is in the best position to correct the graoh. Kent G. Budge (talk) 14:42, 7 November 2022 (UTC)
 * I have added some text to the image caption in the article: "410 refers to the top of a "transition zone" in the upper mantle. The lithosphere is less than 300 km thick.". I hope this clarifies the graph, at least until the actual image can be improved. GeoWriter (talk) 20:55, 11 November 2022 (UTC)

Need a better source for the Geothermal Gradient
The article lead currently quotes an IPCC document on " "The possible role and contribution of geothermal energy to the mitigation of climate change" as its source for a 25–30°C/km gradient. The focus on geothermal energy generation limits the scope of that document to accessible continental crust.

"The magnitude of the geothermal gradient depends on the rate of heat production at depth, the dynamics of the system, and the conductivity of rocks. The highest gradients, 40–80 K km−1, are measured at oceanic spreading centers (mid-ocean ridges) or at island arcs where magma is close to the surface. The lowest gradients occur at subduction zones where cold lithosphere descends into the mantle. The gradient in old stable continental crust is ~30 K km−1 and is somewhat lower in cratons."

The source quoted above may be too detailed for the article lead and does not directly address the much higher average thermal gradient in oceanic crust which is typically thinner, covers more than half of the Earth's surface and is where most of the heat flow occurs.

It seems strange that an entry titled "Geothermal gradient" provides more information about Heat Flow while the only numerical information about the thermal gradient is partial and misleading. Annette Maon (talk) 23:38, 29 February 2024 (UTC)