Question about Volcanoes.?

To add to the other answer: It's not a question of activity that makes it a threat. Mt. Saint Helen's had been dormant for 400 years before 1980's eruption. It was not considered a huge threat but when it blew it surely was a natural disaster. Obviously volcanoes that show a lot of little activity are watched more closely but sometimes the quiet ones are ignored and big, bad things happen.