You know how in the chapter 36 commentary I asked for anyone who knows volcanoes to please e-mail me about exactly how nonsensical Crater Town is? Well, I didn't expect anyone to take me up on this in detail, but someone did! Here is an explanation from Ang Vaiana
for anyone else who is curious, published with permission:
Hi, Butterfree. My name is Ang and I'm currently in my second year of college studying geology. I saw in your commentary for TQFTL ch. 36 (I'm a little behind on reading them) that you wanted to learn more about how realistic Crater Town was, so I thought I could try to help out a little. If someone else has already responded that's fine and you certainly don't need to read this whole thing.
But first, I just wanted to say when I read this for the first time in high school, I thought Crater Town was to coolest thing (and I still think it's awesome). I love volcanoes, and what got me into them was actually a TV program I watched on volcanoes you have in Iceland, like Eyjafjallajökull and Laki. But now that I've actually learned about them in class, I know the sad truth.
Crater Town indeed makes no sense.
Mount Fever sounds like it's a stratovolcano (example: Eyja), given its size and that it's solid rock, which is a cone that has built up from the eruption of felsic (high SiO2 and therefore very high viscosity) magma. Stratovolcanoes have explosive eruptions because the magma has such high viscosity that gases can't escape easily, so the pressure just builds up until it blows. This all happens in an underground magma chamber. If the lava is exposed, the gases are able to escape, so there's no buildup and therefore no cause for eruption. The exposed lava would also cool and harden into rock relatively quickly.
So Crater Town would either not be over a pit of lava as it would have cooled or if it hadn't for some reason the gases released would make the crater uninhabitable. Another issue is that you state that the volcano is dormant, but have any lava from the magma chamber on the surface means that the volcano is currently erupting. For example, Kilauea in Hawaii is currently erupting because lava is coming out of it, even though it's not the explosive eruption that felsic volcanoes have. On a very minor note, I feel as though building the floor of the town out of wood isn't the smartest idea as a speck of lava that flew too high could easily burn the whole town (though I wasn't able to find a place where you mentioned how high up the town was I'm sorry if you did mention it).
When the volcano erupts, there would be a pyroclastic flow of hot gas, ash, and rock fragments that would cover a pretty large area of both the sky and ground, moving at 100-700 km/hr. Pretty much anything caught up in it would die, even fire Pokémon as ash is essentially small pieces of glass that would tear up their lungs. There would also be globs of lava and pieces of the mountainside flying through the air. Overall, not a great place for a battle (but cool as heck).
The other kind of volcano Crater Town could possibly be is a cinder cone (example: Cerro Negro). These are closer to hills than mountains in height, and are composed of loose rock fragments, usually scoria (dark, lightweight rock full of air holes). I don't think the crater of that kind of volcano would have either a large enough size or solid enough walls to support a town, though. But their eruptions are a bit more tame, producing smaller ash clouds and the gas they expel is way less concentrated since it can escape the magma easier. Lava will shoot vertically out of the crater and even seep out the sides and base of the cone as it's only made of loose rock. Bits of lava will still fly through the air and it's still pretty dangerous, but it's not quite as bad.
An alternative could be that Crater Town is over a shield volcano (example: Kilauea). The lava they erupt is mafic (lower SiO2 and lower viscosity). Their eruptions aren't as violent and there's no dangerous ash and the gas isn't as concentrated either. It's really just lava shooting out of the vent and then flowing away. The only problem is that they don't really form any sort of mountain or hill at all since the lava flows much faster than the felsic lava of stratovolcanoes. But maybe the town could be around the crater? Or if you're committed to what you have now that's completely understandable as it's a really neat concept.
I'm sorry this ended up being so long (I don't get to talk about volcanoes too often). Thank you for taking the time to read though!
Huge thanks to them! I have not decided exactly what I will be doing with Crater Town in the next revision, but it really helps to know what I'm working with. :D