Question: How long before a volcano do u need to evacuate people?

David Pyle answered on 18 Mar 2011:

Good question – and one which is hard to answer! The ideal would be ‘just in time’ – and I’ll just give some examples of why this might be hard to achieve.

In order to evacuate successfully you need somewhere for the people to go to, ideally with their livestock and some possessions. You also need a way to get the people there – vehicles, roads, and so on. And you need a way to call for an evacuation – which is getting easier, with mobile and wifi technology. The evacuation can’t happen too soon – in case an eruption doesn’t happen, people return and then ignore the next evacuation call. It also can’t happen too late – you don’t want everyone in a city to be sitting in traffic jams when the eruption happens. Other factors that we need to take into account include things like: does the volcano have any particular local religious significance which might affect when (or if) people evacuate? Is the place where people will be evacuated to a place where they might wish to live (there could be geographical, political or cultural reasons why not). We also need to be careful not to have false alarms; to have a well-known and widely-accepted call for evacuation (to avoid confusion); and to have a clear chain of command – in terms of who makes the evacuation call. The final set of complications include: what the typical eruption behaviour is (short but violent eruption? or one that goes on for a long while?); how to deal with crises on, for example, small islands – or even on small island nations (where would you evacuate a whole country?). This is all an active area of research!