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where did all the ash come from?


king of nowhere

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I can't believe I never thought about this before!

See, the ashmmounts were spewing ash, and a LOT of it. The final empire was continent-sized, and covering it is an incredible task. Assuming a surface of 15 million square kilometers (the size of antartica, which seems appropriate as it is a continent covering a polar region) to cover the whole empire with one meter of ash one would need 15000 cubic kilometers of ash, which means a cube of over 20 km in side.

A shard is certainly capable of generating that amount of matter, but a big plot point of the story is that ruin could do nothing because it was trapped, and preservation could do nothing because it had no mind and was using everything it had to keep ruin trapped. The lord ruler made the ashmounts, but then he had no shardic power left. So the ashmounts kept spewing ash for a full millennia, and it was a natural phenomenon, as no shard could fix it.

And there is just no way this would have been possible. volcanoes spew mostly lava; some of that get nebulized into very fine dust and goes up in the atmosphere, so volcanoes produce some ash, but not nearly enough for our purposes. If the ash was produced this way, then also lava would have been produced, in much greater amounts, and it would have covered the whole final empire in kilometers of rock.

It also does not work to assume that the ashmounts had ash inside; subjected to the pressure and temperature of the planet's mantle, the ash would get melted and compacted and become regular rock. There's no way it could remain fluffy over a thousand years. Not to mention that ash doesn't offer much support for the weight of the above strata of rock, and a reservoir that big would probably cause the above crust to collapse.

So, is there a way to make this work?

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Well, I mean the Lord Ruler creates them for the specific purpose of spewing ash, so if there were a way to optimizing that, I’m sure he did it. And the ash isn’t typically a meter deep. That was only after Ruin had been freed to influence the world. Before that there was some, but not too much. They were raking it away from the crops but it wasn’t burying the entire surface like it does in HoA.

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2 hours ago, Windrunner said:

Well, I mean the Lord Ruler creates them for the specific purpose of spewing ash, so if there were a way to optimizing that, I’m sure he did it. And the ash isn’t typically a meter deep. That was only after Ruin had been freed to influence the world. Before that there was some, but not too much. They were raking it away from the crops but it wasn’t burying the entire surface like it does in HoA.

but it went on for a whole thousand years. I am sure the total ash that was spewed in that time was much greater than the equivalent of one meter over the whole continent.

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38 minutes ago, king of nowhere said:

but it went on for a whole thousand years. I am sure the total ash that was spewed in that time was much greater than the equivalent of one meter over the whole continent.

Sazed mentions this in the HoA Epigraphs:

Quote

The ash.

I don't think the people really understood how fortunate they were. During the thousand years before the Collapse, they pushed the ash into rivers, piled it up outside of cities, and generally just let it be. They never understood that without the microbes and plants Rashek had developed to break down the ash particles, the land would quickly have been buried.

Though, of course, that did eventually happen anyway.


4 hours ago, king of nowhere said:

The final empire was continent-sized, and covering it is an incredible task. Assuming a surface of 15 million square kilometers (the size of antartica, which seems appropriate as it is a continent covering a polar region)

 From the Annotations:

Quote

One side effect of this is that all compasses point toward Luthadel. Since it’s been that way for a thousand years, no one finds it odd–in fact, it’s used as evidence of the Lord Ruler’s divinity. It also makes it mathematically very easy to pinpoint one’s exact location in the Final Empire using a combination of the compass reading and noon observations. Not that it’s easy to get lost in the Final Empire in the first place—the geographical area of the planet’s surface that the Final Empire covers is actually quite small.

Would you consider Antarctica to be a "geographically small area of the planet's surface?" [This is an opinion question. I feel that TFE would be smaller than that, but the Map has no scale on it]

4 hours ago, king of nowhere said:

volcanoes spew mostly lava; some of that get nebulized into very fine dust and goes up in the atmosphere, so volcanoes produce some ash, but not nearly enough for our purposes.

Depends on the type of eruption. Bigger eruptions put out more(duh), but according to the Volcanic Explosivity Index(VEI), even a VEI 1 eruption puts out at least 10⁴ m³ of tephra(ash, lapilli, and volcanic blocks). 10 to the 4th power is 10,000. Assuming that the Ashmounts are all VEI 0 Eruptions so they aren't as dangerous to those nearby, they just have to put out less than 10,000 cubic meters of tephra per eruption. When you consider that there are 7 nearby Ashmounts on the map of the Final Empire, I think even those small numbers can start to add up.

With the exception of Tyrian(which is rather close to Luthadel), the other 6 Ashmounts form a circle around the Central Dominance. This puts them in a prime position to spread throughout the other Dominances, while Tyrian(which also appears to be bigger than the others) can likely tackle the Central Dominance by himself.

Additionally, the ash is ferromagnetic, which makes this even easier. From the same annotations link as above:

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He worried that the new location of Luthadel would be too hot due to the latitude, but it turned out that moving the Well created an unexpected effect. The planet’s magnetic pole followed the Well as he relocated it—and the ash from the ashmounts was slightly ferromagnetic. (Ferromagnetic volcanic ash has some precedent in our world.) So the interaction of the ash with the planet’s magnetic field’s new alignment meant that its protective cloak over the area of the Final Empire caused it to be cooler than the now unprotected geographic north pole.

Ash can spread across the globe, but I think having the magnetic pole so close would hem in that spread a little.

I'd agree with Windrunner that the volcanoes are probably specialized to produce more than the usual quantity of ash, largely because TLR created these volcanoes from scratch. He'd have more creative freedom that way compared to altering existing ones, and whatever he did definitely worked.

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54 minutes ago, The One Who Connects said:

Would you consider Antarctica to be a "geographically small area of the planet's surface?" [This is an opinion question. I feel that TFE would be smaller than that, but the Map has no scale on it]

antarctica is 1/7th of the total land area of the planet, and 1/30th of the total surface. we have no scale for the map, but seems an appropriate size for "big, but still a small part of the planet". We also can make an estimation according to kelsier's travel in secret history: he takes a few  months to reach the edge, and he doesn't tire (much) and never needs to sleep. walking at 4 km/h he would be able to cover 100 km/day, a bit less because he did stop sometimes. we could give him 2000 km in a month? a circle of 2000 km radius would have a surface of about 12 million square kilometers. And kelsier takes more than a month, so it is likely bigger.

Quote

Depends on the type of eruption. Bigger eruptions put out more(duh), but according to the Volcanic Explosivity Index(VEI), even a VEI 1 eruption puts out at least 10⁴ m³ of tephra(ash, lapilli, and volcanic blocks). 10 to the 4th power is 10,000. Assuming that the Ashmounts are all VEI 0 Eruptions so they aren't as dangerous to those nearby, they just have to put out less than 10,000 cubic meters of tephra per eruption. When you consider that there are 7 nearby Ashmounts on the map of the Final Empire, I think even those small numbers can start to add up.

don't forget that a cubic kilometer is one billion cubic meters.

to get even one single centimeter of accumulation on the continent (which seems reasonable for a normal ashfall) we need 10^12 cubic meters, and 10^4 cubic meters is a pittance. not enough to add up. in luthadel it rained ash once per week, in the ouside dominances oonce per month, and even if we assume that an ashfall is only one millimeter (which is the minimum to be reasonably called ashfall) it still takes a lot more ash than my knowledge of vulcanology can account for.

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3 hours ago, king of nowhere said:

antarctica is 1/7th of the total land area of the planet, and 1/30th of the total surface. we have no scale for the map, but seems an appropriate size for "big, but still a small part of the planet".

Maybe I'm subconsciously thinking Antarctica is bigger than it is because of that "1/7th land area," rather than remembering that 1/30 total area. Your logic makes sense, even if I feel it should be a little smaller than Antarctica. (In the end, close-ish is good enough for me)

3 hours ago, king of nowhere said:

don't forget that a cubic kilometer is one billion cubic meters.

Yea, my powers of 10 were off there.

Um.. well, if we bump up the primary 6 Ashmounts to a VEI 2, they'd produce 10^6 each. I've stated that Tyrian appears bigger on the map, so a low VEI 3 (10^7). 10^7 + 6(10^6) = 16,000,000 cubic meters. Given the 16 in that number, I'm almost convinced that's right. :)

If we bumped up all the Ashmounts one VEI level, that 16 would (conveniently) still be there, but with another zero at the end. I'm hesitant to do that though, because stronger eruptions are more dangerous, and they happen less often. I suppose you could split the difference by having the outer 6 go off at different times, but still...

Doing the math, we'd need bigger numbers, or a larger timeframe. Imagine if it took six months or so to cover the continent normally, that's let us get away with smaller individual ashfalls(albeit not much smaller). Ruin was free for nearly a year, and he hadn't entirely covered the continent by then, even with him making more eruptions. I'd say we reconsider how long it'd take to cover the continent and work backwards from there. We need to produce 10^12 over X amount of time, and go from there.

3 hours ago, king of nowhere said:

in Luthadel it rained ash once per week, in the Outer Dominances once per month

Wasn't aware we had that info. Good to know. I'm having trouble reconciling the timing issues though, as the larger ashmount(Tyrian, by Luthadel) should theoretically go off less often, even though Luthadel gets ashfalls more often. Could be a strong magnetic pole pulling in some of the ash from the outer 6 ashmounts, which could also account for them getting them less often further out. Does that sound reasonable?

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