Why does the pressure increase only by 0,3-0,4bar per km in stone but 1bar per 10m in water while stone has the higher density?
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$\begingroup$ It's been a long time since I was involved with this, but look at co-efficient of earth pressure & how a proportion of vertical stresses dissipates into horizontal stresses. As I recall it has something to do with how grains of minerals with the rocks (& soil) transfer stresses. $\endgroup$– FredJun 10, 2020 at 4:52
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$\begingroup$ @Fred tell me more! $\endgroup$– uhohJun 11, 2020 at 11:13
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1$\begingroup$ Because the numbers are piffle (should cite a source, possibly confused units, or m and km ?) and things are bit more complicated. Overall, pressure gradient is not linear, as isn't density and gravity with depth. For the crust this can be simplified. Pls. tell us where you've searched, and maybe you can limit your question to the earth's crust. Pressure gradient in the crust ~330bar/km (but people use GPa), which rougly corresponds to the density difference to water (100bar/km). $\endgroup$– user20217Jun 11, 2020 at 19:34
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Why does the pressure increase only by 0,3-0,4bar per km in stone but 1bar per 10m in water while stone has the higher density?
Because it doesn't!
Plots in this Physics SE answer and here and here show about 0.4 or 0.5 $\times 10^6$ bar at 1000 km depth, which is 0.4 or 0.5 bar per meter compared to your 0.1 bar per meter for water. If rock is 4 to 5 times denser than water, then all is well.
