I live a few hundred miles south of the Yellowstone supervolcano. So I have two plans for how to deal with an eruption… plans that are based on the strength of the eruption and the wind patterns at the time:
1) Gather up my valuables and my critters, getting in the car and beating feet towards the west.
2) Sit there and wait to die. Won’t be long.
As you can see, there is a wide range of possible outcomes from an eruption, and my location is such that the details make a big difference in whether the event is escapable or not. It’s always possible that a surprise eruption could occur, say, just after sundown. In this hypothetical, the Big News aspect of it crashes the cell phone network. I’m busy, say, reading or writing, so I don’t see the news on TV or the internet. With no cell phone, no warning calls come in. And a few hours later, not seeing the dark ash cloud against the dark night sky, I go to bed. And I only waked up to the sound of the house collapsing under the weight of the meter or so of ash. This, obviously, is not a survivable scenario.
That said, the Yellowstone supervolcano is not the only volcano in the world. Hawaii and Guatemala have recently demonstrated smaller scale eruptions… incredibly survivable if you just have the wherewithal and wisdom to get the hell out of Dodge. Witness: