Talk:Geothermal gradient
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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)
[edit] 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?
To AMR You changed back the heat gradient to 20 K/km from 10 K/km but you didn't do that further down in the article. Now the article is inconsistent. Note that the air has an adiabatic heat gradient of 9.8 K/km. Measuring temperature in air filled mines or bore holes must thus remove this gradient leaving it again at 10 K/km. I don't see a reason to change before we have determined what the situation is.
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? I admit that it should be much smaller than what I said initially. Gravitational and adiabatic heat gradient is the same thing. If the adiabatic gradient is of the same order as in the mantle, 0.3 K/km, then the strong horizontal stress gradient around a bore hole would cause a thermal gradient of the same nature as the adiabatic heat gradient. 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) 11:30, 17 May 2008 (UTC)
[edit] 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)
