GeologyRocksThickness of continental crust ?
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Jon
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You want to look up Pratt
Sun, 07/01/2012 - 20:50You want to look up Pratt isostacy and Airy isostacy.
The reason you've been given all those data is that you compare two columns: one with ocean, oceanic crust, and mantle; and the other continental crust and mantle. You then "balance" these two columns and can hence work out the thickness of the continental crust.
See this worksheet: http://www.geology.siu.edu/people/pinter/pdf/IsostasyExercise.pdf
It might be helpful.
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Thickness of continental crust ?
Submitted by Kajsa1990 on Sun, 07/01/2012 - 19:11.I'm taking an introductory geology class and am having big trouble with the math questions, as it's been many many years since I last took math classes.
I am to use Archimedes Principle to calculate the thickness of continental crust beneath a certain coastal geographical point (at sea level and not accounting for post glacial rebound effects).
Data given:
Water depth to the abyssal plain: 5000m
Thickness of abyssal oceanic crust: 10000m
Density of continental crust: 2800 kg/m3
Density of oceanic crust: 3000 kg/m3
Density of mantle: 3300 kg/m3
Density of water: 1000 kg/m3
Our course material does not include any formula for Archimedes Principle, just a brief description of how it works. So, I've googled to find a formula, but really am having a hard time understanding what it is I'm looking at. I have the basic formula, but I'm not seeing how I should use it to get what I need: Apparent immersed weight=weight-weight of displaced fluid.
I understand that the fluid here is the mantle, with density given for it, and of course the cont. crust density appears relevant, but that's about as far as I can get with this! And I don't understand why there is data for oceanic crust, water depth and density of water....
I'm assuming there are some other formulas involved in this calculation. I know thickness can be calculated from Volume=height*length*width. But nothing in the data seems to hint at length or width....?? aaah, this is so confusing, I don't know where to begin even. Any hints or tips will be greatly appreciated.