CrustalTrudger t1_iv1b7kc wrote on November 4, 2022 at 3:19 PM

Reply to comment by ZoneEnder666 in If the inner core is the hottest part of the Earth, hotter than the liquid outer core, then why is it a solid? by Paradigm7657

Gravitational acceleration decreases with depth as you move from the outer core inward (e.g., this estimate using PREM), but overburden (i.e., the mass above a given point) is still increasing, especially given the large density increase from the mantle to the core, so pressure is definitely still increasing, especially considering the inner core boundary.

EDIT: If you want to directly see estimates of pressure with depth, you can look at table 2 starting on page 312 of the original PREM paper by Dziewonski & Anderson, 1981. Looking at this, you can see that pressure broadly is predicted to increase with depth despite the decline of gravitational acceleration as you approach the center of the planet.

Coomb t1_iv3iamt wrote on November 5, 2022 at 12:23 AM

I don't even think it would be possible for pressure to decrease with increasing depth. Pressure must be continuous unless something like a shock exists, and every additional shell adds some amount of gravitational pressure which is greater than or equal to 0. If somehow a situation existed where pressure were higher in outer layers than in inner layers, the pressure would drive movement and compression of the material in between such that the stress developed was adequate to support the pressure.

mfb- t1_iv3quf8 wrote on November 5, 2022 at 1:32 AM

A decreasing pressure is physically possible on a small scale (imagine a vacuum chamber placed in the center of an asteroid), but I don't see that happening on a planetary scale.