The Associated Press reports that Mt. Merapi on the island of Java is pouring tons of hot ash, dust and smoke into the air in a massive eruption today. The volcano, one of world's most active, is located in the Ring of Fire, an area high in volcanic and seismic activity due to the extreme forces of plate tectonics that occur around the Pacific Ocean basin.

Merapi began erupting last week and has forced tens of thousands of villagers to evacuate the area. So far, the eruptions have killed nearly 40 people and burned several others, causing authorities to expand the danger zone from a 6-mile to 9-mile radius. Several flights in and out of local airports have been canceled due to the ash cloud. The recent eruption is the largest so far, and scientists think things could get worse.

To give you an idea of what's involved, here's a video showing a pyroclastic flow from an eruption last year on Mt. Merapi. From the looks of it, it's not something you want to try to outrun.