PULLMAN - It's an explosive topic. The Chaitén Volcano erupting in Chile is causing chaos in the South American country, as villages are evacuated and a massive ash cloud billows out of the mountain.

WSU Geology Professor and volcano expert, Dr. John Wolff says the volcano has been blowing up since last Friday and there's no telling when it will stop. The 20-mile plume has sent ash into Buenos Aires, shutting down the airport. But if the plume changes formation, it could get even worse.

"Everybody’s seen or remembers the 9-11 footage, when the towers came down and the billowing clouds spreading out," said Wolff. "The type of activity I am referring to, which is called a pyroclastic flow, is like that except the cloud that is spreading out over the ground is several hundred degrees, it's very very hot."

Some have compared the situation to Pompeii, the Roman city destroyed by the eruption of Mount Vesuvius in AD 79.

Wolff said the activity is not unusual, but special in the fact that this type of eruption only happens about six times each century.

"At any one time, there might be 20 volcanoes erupting, the next week there might be only half a dozen, so it all evens out," he said.

Back in the US, Wolff said Yellowstone is a super volcano that will eventually blow.

"It would certainly devastate the surrounding area, the ash cloud could spread over most of the United States," be said.

Closer to home, he said, although Mount St. Helens has been getting more active since 2004, another Cascade Mountain is more dangerous.

"Rainer is an ice capped volcano and those are very dangerous, because as soon as any heat reaches the upper levels of the volcano, it doesn't even have to be a big eruption, the ice will melt and cause devastating mud flows," said Wolff.