You don’t need to have a mountain to have a volcano. All you need is a hotspot where light, hot, molten rock from the mantle rises toward the surface. It’s under a lot, a LOT of pressure. If it blows out hard enough, the upsurging material that would otherwise make the “mountain” gets scattered over a wide area. Like, 15 states.
If it goes boom not to worry as you will soon die. No food, no water, no power, no SUNLIGHT. All that will be left will be lawyers and cockroaches.