I got an idea last night for my Sci-Fi x High Fantasy(?) world, where a continent South of the equator on a world not too much unlike Earth is permanently dark (edgy I know, but I could do with more edge in my story ). The concept is essentially a volcano that is constantly* emitting ashy fumes over the continent. An ancient civilization called the Gigas built a floating wall in the stratosphere** that prevents the fumes from spreading past the continent. What would this entail in terms of effects on the continent itself? *Unsure of whether a volcano constantly, and I mean indefinitely, emitting fumes is believable. **If they built a floating wall there (ignore the questions that come with a floating wall, my science magic covers that part), what would the fumes do? Would the leak over the wall and continue through to the rest of the world anyways? Would it have to be a dome? As you can see, I'm not that knowledgeable when it comes to anything past Wikipedia, so I figured I'd come here for some possible insight.