A key part of the plot in a story I'm working on revolves around the main region being on top of volcano that is set to erupt. The trouble is that the region in question in my setting is roughly the size of Wyoming. It's on an Earth-like planet.
Clearly, the volcano needs to be a supervolcano. However, I'm having my doubts about it being so big. I also think that perhaps a volcano this big isn't necessary, because sizable volcanic activity can be had from much smaller volcanos (for an extreme dramatization, see Supervolcano.
How big can a volcano be?
Note: The setting doesn't take place on the sides of a volcano, but at the very top of it. I originally set it in a caldera, but it turns out that the volcano doesn't have to have erupted yet for the idea to be plausible. I'd also like answers rooted in hard-science.
- The planet is Earth-like, but plate tectonics don't have to be Earth-like.
- I care about width, especially at the top, but overall height isn't important.
- It seems like things are as I thought they might be - the idea is unrealistic. I might consider using smaller volcanic features, but they would all have to be tied together. The answers don't have to be edited to cover this; it's just my musings.
- No hand-waving, please! I can change the gravity of the world if necessary (in my story), but the gravity is still as I originally said - like that of Earth.
- The volcano doesn't have to exist on the Earth we live in, though if the biggest volcanic feature(s) on Earth is/are the limit, I'll be happy to hear about them.
All the answers so far are good - don't change them! I'd like some more sources (a la the hard-science tag) - not that I doubt them, but because I'd like to do a bit of reading afterwards about this topic. A volcanologist I am not.