Could this happen today?

Just because Pompeii was destroyed centuries ago doesn't mean it is an unlikely event these days. Many cities live in the shadow of a volcano or two - large cities - like Seattle, Washington, for one.

Seattle is near a volcano called Mt. Rainier. It is one of the loveliest mountain peaks in North America - much the same as Mount St. Helens was, which erupted in 1980. Both of these mountains are part of the Cascades Mountain range.

According to the USGS (United States Geological Service), Mt. Rainier (pictured here) is one of the most hazardous volcanoes in the United States, due not only to its regular activity, but also to its proximity to a populated area.

There is a geological observatory in Vancouver that monitors the seismic activity (underground earthquakes and movement) of mountains in this range.

Lahars (which are volcanic mud flows) are the biggest and most frequent danger to cities near Mt. Rainier these days. The USGS has a fantastic information page on Learning to Live with Volcanic Risk.