[outofsalt]

The Icelandic volcanoes are remote but also capable of global impacts. I can’t imagine evacuating Mexico City and what tragedy that would evoke. There are so many densely populated areas that could be destroyed by volcanoes worldwide.

[rlmorel]

I have heard that one of the potentially most catastrophe-prone areas in the USA is Mount Rainier...it has not had a major eruption in over a thousand years, and there are huge swaths of populated areas directly in the path of where lahars have flowed from its past eruptions.

[RayChuang88]

The fear is that Popocatépetl could have a MAJOR eruption, which could threaten millions of people in the cities of Mexico City and Puebla. And a major eruption will cause global cooling, as we remember from the Eyjafjallajökull eruption in 2010, which caused unusually high rainfall in California in the winter of 2010-2011.