KEY_ABRADE

@ErikHall The metallic hydrogen stops being metallic if all the mass above it gets ablated away by the planet's host star, and then I would imagine it get blasted away itself. Think of the rocky core as a "sponge" whose gaps are filled with metallic hydrogen; once there's not enough pressure the metallic hydrogen turns into normal-phase hydrogen and the "sponge's" gaps collapse under gravity, turning it into a ball of rock.

@ErikHall I think the idea is that it's the rocky core of a super-Jupiter gas giant whose gas got ablated off by the force of its star's solar winds but kept spinning at the same rate. Without the continual downwards force of all that gas the centripetal force at its equator could bulge it outwards.

@SurpriseDog Unless the question was retroactively edited after you commented, it says 10 AU.

WH40k Orks, basically

Let us continue this discussion in chat.

@JBH Basically, think of it as a shield volcano, except, instead of the magma coming out of the peak, it's formed on the sides, by crust constantly being pushed into the relatively hot diamond and then melted back down the flanks.

@JBH "A magma chamber without pressure" like what you said is what I want; it allows for relatively high surface heat fluxes, allowing things like hot springs, geothermal power, melted or at least shallower permafrost, etc.). The diamond isn't as dense as the mantle, albeit close (~3.5 g/cm^3 diamond, 3.6 g/cm^3 mantle); this isn't Earth, the mantle is different. If the crust constantly melted off the diamond, wouldn't the constant lava flows build the crust up thick enough that it wouldn't melt for long enough to creep over the diamond?

@BobaFit This is not Earth. The crust is 3.15 g/cm^3, because it's made of other stuff than Earth's crust. Maybe the diamond is 3.5 g/cm^3, if that's the only density diamond can be at, but it's still not as dense as the mantle.

@BobaFit It has sunk to some extent, but it isn't as dense as the mantle, so it "floats" in the mantle like an iceberg. Some of it protrudes upwards into the crust. A portion of what protrudes into the crust protrudes above sea level. The force of the diamond's weight and the weight of the crust above the diamond are enough to "sink" the diamond to some extent, but not enough to make it irrelevant to the question. Also, it's not "roughly 50% more dense than ordinary crust rock"; the crust is 3150 kg/m^3 and the diamond is 3300 kg/m^3.

@John I doubt its thermal conductivity approaches the crust's, even at the temperatures here; I'm assuming at least 100 W/m/K even at 1400 K. Also, the atmosphere isn't relevant to this; as in the drawing, there's a multi-km-deep sheet of poorly-conducting earth/rock atop the diamond that heat must penetrate to reach the atmosphere. I chose diamond specifically because it's good at forming monolithic structures which don't collapse under their own weight; if granite can survive mountain formation, why would diamond "fracture" under the same conditions?

@AlexP Although I understand diamond>crust heat transfer cannot surpass mantle>diamond heat transfer, wouldn't convection currents cause cooled-off mantle to "drop off" the bottom of the diamond while hotter rock rises and comes into contact with it? There wouldn't be a "layer of mantle rock" next to the diamond, because the rock next to it would constantly cool and sink. If nothing else, I think the convection currents caused by this constant "radiator" effect would have notable consequences on the surface.

@TheDemonLord I think is one of those questions that's on the borderline of needing that tag but could be answered without it. An answer showing its math would be helpful but isn't necessary, IMO.

It's not 4000K, it's 1400K. Much less.

Thanks.

Aye. There seem to be too many problems with this, as it currently is, for it to work.

Something more akin to this, then?

You said my idea would only work if the mountain was an upright cylinder; I presume that's based off of how shield volcanos work (i.e. central point in a circular mound, constantly spews lava down the sides)?

There's no crust over it in this case, just air.

The top's poking above sea level into the atmosphere. Green is crust, red is magma/lava/mantle.

The plates getting pushed into the magma area around the diamond, then melted before they have time to ride up the sides?

Gotcha. You're envisioning something like this, then?

It's the same way Olympus Mons got so high: not by being tall and thin, which means you run into issues with the compressive strength of the rock, but by having so much stuff to the sides of it that it essentially builds a giant layer cake of molten crust with each eruption. It's just that, in this case, it's not an eruption, it's a tectonic plate trying to creep over the diamond (which is maybe something I should've made clearer in the original question).

I suppose a better analogy would be taking a quadrilateral pyramid and pouring a bucket of sand on it from directly above its apex. Initially, the sand piles up at its base , but, over time, enough builds up to bury it, as more-recently poured sand builds up on the sand poured previously. And this won't encounter the issues normal mountains do, where too much rock slides down the sides; here, the crust encounters something it can't pass, so it just sort of peels back and pile on top of itself.

@JBH Right, but where does sloughed-off crust go? As I understand it, the sloughed-off, molten crust will, on geological timescales, form a layer thick enough to cool, allowing solid crust to creep over it to reach parts of the diamond that are still exposed. The crust reaches those, melts, and adds more to the solid slopes around the diamond, allowing more crust to climb further still.

@JBH Basically, think of it as a shield volcano, except, instead of the magma coming out of the peak, it's formed on the sides, by crust constantly being pushed into the relatively hot diamond and then melted back down the flanks.

@JBH "A magma chamber without pressure" like what you said is what I want; it allows for relatively high surface heat fluxes, allowing things like hot springs, geothermal power, melted or at least shallower permafrost, etc.). The diamond isn't as dense as the mantle, albeit close (~3.5 g/cm^3 diamond, 3.6 g/cm^3 mantle); this isn't Earth, the mantle is different. If the crust constantly melted off the diamond, wouldn't the constant lava flows build the crust up thick enough that it wouldn't melt for long enough to creep over the diamond?

@BobaFit This is not Earth. The crust is 3.15 g/cm^3, because it's made of other stuff than Earth's crust. Maybe the diamond is 3.5 g/cm^3, if that's the only density diamond can be at, but it's still not as dense as the mantle.

@BobaFit It has sunk to some extent, but it isn't as dense as the mantle, so it "floats" in the mantle like an iceberg. Some of it protrudes upwards into the crust. A portion of what protrudes into the crust protrudes above sea level. The force of the diamond's weight and the weight of the crust above the diamond are enough to "sink" the diamond to some extent, but not enough to make it irrelevant to the question. Also, it's not "roughly 50% more dense than ordinary crust rock"; the crust is 3150 kg/m^3 and the diamond is 3300 kg/m^3.

@John I doubt its thermal conductivity approaches the crust's, even at the temperatures here; I'm assuming at least 100 W/m/K even at 1400 K. Also, the atmosphere isn't relevant to this; as in the drawing, there's a multi-km-deep sheet of poorly-conducting earth/rock atop the diamond that heat must penetrate to reach the atmosphere. I chose diamond specifically because it's good at forming monolithic structures which don't collapse under their own weight; if granite can survive mountain formation, why would diamond "fracture" under the same conditions?

@AlexP Although I understand diamond>crust heat transfer cannot surpass mantle>diamond heat transfer, wouldn't convection currents cause cooled-off mantle to "drop off" the bottom of the diamond while hotter rock rises and comes into contact with it? There wouldn't be a "layer of mantle rock" next to the diamond, because the rock next to it would constantly cool and sink. If nothing else, I think the convection currents caused by this constant "radiator" effect would have notable consequences on the surface.

@TheDemonLord I think is one of those questions that's on the borderline of needing that tag but could be answered without it. An answer showing its math would be helpful but isn't necessary, IMO.

Try polonium-210 instead of tetrodotoxin. It's much more lethal; Po-210's median lethal dose is ~50 nanograms.

@ARogueAnt. No - I'm trying to figure out what a one-time event that could cause this would be. It's not supposed to be a regular occurrence.

@JoinJBHonCodidact "It's NOT supposed to be a regular but exceptionally long winter that's a part of a recurring cycle of seasons"

@JoinJBHonCodidact Not quite; it's supposed to be a one-time kind of thing, hence the asteroid impact or volcanic eruption as a possible cause. It's not "all the seasons vary wildly in length"; it's "we have normal seasons...and then this one REALLY nasty winter".

@sphennings I don't think so. I'm asking for a specific meterological or physical phenomonon that could cause such a thing.

@Falco Spies don't come with super-fast-firing guns and magical communications devices. Nor do they have fifty stars on their version of the American flag. Nor do they include black people. Nor can they predict historical events unrelated to the war.

@laolux That was the 1600s, not the 1800s.

@StevenGann They're referring to Union soldiers being taught modern tactics.

@Cadence I think that when they show off their automatic weapons and radios, people are going to pay attention rather quickly.

It still depends on the creature. Animals eat what their biology is optimized for. Humans drink what's technically poison - alcohol - not because our biology is optimized for it, but because we like it (and it's addictive). The factors depend on the creature.

You're going to have to tell us what the characteristics of this species are.

@Pelinore It worked for me.

@Pelinore I'm the one who decided that it was a duplicate.

@Pelinore They tried that. It went badly. That's why they need a bunch of disposable population - that country secretly had a pact with a much stronger one, and the war is going poorly.

@Pelinore I'll add that, but the point is that they've already done all the stuff that wouldn't make people revolt en masse if they found out.

In that case, I suppose it's a race between aircraft and these tanks to see what the most resource-efficient method of putting high-explosives into zombies is. I'm willing to bet it's the aircraft.

Also, I'm pretty sure that artillery is the king of the battlefield, and infantry the queen. And we all know what the king does to the queen...