6 volcanoes that could shut down the world

Excerpt: Iceland's Eyjafjallajokull wreaked havoc on European air travel, but it could have been worse. Much, much, much worse

The eruption of Iceland's Eyjafjallajokull caused billions of dollars in economic damage, and left millions of travelers stranded. But on the Volcanic Explosivity Index — volcanologists' tool for rating the severity of an eruption — the event rated only a two out of a possible eight. More severe eruptions cause "death and destruction" on a planetary basis, points out Simon Winchester in The Guardian. "They can darken skies and cause devastating changes in the weather. They can and do bring about the abrupt end to the existence of entire populations of animals and people" — not to mention economic damages that could run into the trillions. Here are six volcanoes worth fearing: Read about the 6 and their potential here.