Earlier this year CBS's programme 60 Minutes aired Volcanoes, nature's ticking time bombs. Volcanoes are found all over the world and many could spew lava and mass destruction, although we just don't know when.
This is the way reporter Scott Pelley introduced the programme.
"If you think we're living in an unstable world, well, just listen to this: only one percent of our Earth is solid rock. Most of the other 99 percent is an oozing, mass, churning beneath our feet like road tar at temperatures between 2,000 and 10,000 degrees. The Earth's crust is only 20 miles thick. When that cracks, one of the greatest forces in nature erupts. There are 1,500 active volcanoes. And, earlier this year, we first told you about three; one that caused the most recent mass disruption, another that's the biggest threat to a major city and a third, in the United States, that could wreak havoc all around the world."
You can read the transcript here.