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Calderas, how do they work?

RyuRed

Acolyte
Watching a documentary on Yellowstone and I was curious on whether an entire medieval fantasy city could be built in one and what would be the benefits and/or disadvantages of them.
 

CupofJoe

Myth Weaver
Of course, it could. We can write what we want. As long as you don't go the full Mount Doom with rivers of flowing lava, a reader could buy in to it.
Volcanic ground is often very fertile [after a few years] and the volcanic activity could warm the ground. So there could be warmed fertile ground to produce multiple harvests of different crops year after year. The wall of the Caldera might act as a defensive structure for a city [and so would rivers of lava admittedly].
On the flip side, unless the place was dormant/extinct, there would almost certainly be toxic gasses, earthquakes and the like. The water might not be too wholesome either, full of impurities and minerals.
The big disadvantage is that at some point things are likely to go very very wrong and probably without much warning. I'd do a bit of web-fu to look at how Pompei and other volcano adjacent civilisations worked.
 

RyuRed

Acolyte
The documentary talked about how Yellowstone gets about 3000 earthquakes a year which may be an issue with permanent buildings. I wasn't aware of the toxic gas but that makes sense. So would that means castles are out of the question? And the erupting bit I'm ok with, I was thinking it would be moderately dormant, perhaps magic keeping it that way atleast temporarily. I'm also fairly curious on how geothermal fissures could be used for heating, I think Winterfell stays warm from a large fissure in the first novel.
 

TheKillerBs

Maester
I don't think it could work. If it was an active volcano, you'd have a hard time living there due to the problems CupOfJoe mentioned. On the other side, if it was a dormant or extinct volcano like they suggested... well, I don't know any calderas of dormant or extinct volcanos that haven't become flooded and become lakes.
 

skip.knox

toujours gai, archie
Moderator
Sure it'd work. The city would be built of a magical, yellow stone that absorbed the poisonous gases and either neutralized them or turned them into something nifty. The heat provides power, of course. The constant earthquakes--most are never felt--could make for some fun architectural decisions. Maybe only the denizens of Yellow Stone know how to build and live there, which makes for a natural defense against enemies.

All it takes is some imagination.
 

RyuRed

Acolyte
What if the caldera was rather large. Would the gases come out in more predictable places?
 

CupofJoe

Myth Weaver
What if the caldera was rather large. Would the gases come out in more predictable places?
I imagine that any residents would just avoid the bad areas... probably the lowest areas [I seem to remember that the trouble of the gasses was at the lowest point of the claderas].
Lake Nyos - may be of interest.
You might be able to drill relief holes to get the gasses out in places you want. They do something like that in Landfill [but I think they have a lot of underground structures to help achieve that].
Depending on how exotic you want to get, you could make huge fans, cooling towers and chimney stacks to blow the gasses higher into the air. They do that with pollution.
There are lots of places and people living with volcanoes and earthquakes so looking at how they build and deal with things might prove interesting.
 
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