There are, currently, about 500 active volcanoes in the world. If that sounds like a lot, don’t worry. Only 50 of them are in the United States, and most of those are probably in Hawaii. A bit more worrying is the fact that there are about 1,500 potentially active volcanoes around the globe. That’s 2,000 volcanoes that could, at any time, go boom.

What constitutes active and potentially active? That is a very good question. It’s one I probably should have asked myself before moving to the Ring of Fire. Now, faced with a volcano to the east that has erupted almost every day for a week and a volcano to the west that erupted 251 times while I was sleeping on Sunday night, I find myself—for the first time ever—interested in geology. And so, the Googling began in earnest.

According to one science blog I found, to be classified as active, a volcano has to be presently erupting or making noise coupled with seismic and thermal activity. The second category is dormant. Dormant volcanoes aren’t active now, but they could be in the future. Extinct volcanoes are inactive and unlikely to erupt again. But the link above points out that it’s not that easy to classify a volcano because there’s no prior notice or approval needed. When a volcano decides it wants to join the active class, it does. And volcano years are kind of like dog years multiplied by…uh, multiplied by a lot. Turns out that they age slowly, being part of the actual Earth and all. So, any volcanoes that have erupted during the past 10,000 years are, by some definitions, still active.

Now, if you’re wondering whether there is a self-interested component to my geological research, well, you bet your ass there is. Prior to moving to the Pacific Rim, the closest I’d ever been geographically to a potentially hazardous volcano was the distance between St. Paul, Minnesota and Mount St. Helen’s. That’s about 1,800 miles.

As I write this, I am 350 miles to the west of Mt. Merapi. The closest big city to the volcano is Yogyakarta and it’s about 45 miles away. While people on the slopes of the volcano have been impacted—in some cases devastatingly, the city of Yogya seems almost unaffected, save temporary airport and school closings. And Anak Krakatau (Krakatoa’s Son), 100 miles to my west, erupts all the time. It’s so perpetually hot, you can only hike half way up. After that, your shoes start to melt. It’s a lot smaller than it’s catastrophic predecessor. I like to think of it as Baby Krak--because babies are totally not threatening.

Between 2007 and 2009, seven volcanoes erupted in Indonesia. That doesn’t count the ones that are just belching sulfurous smoke. So far in 2010, there have been five erupting, most more than once, which appears to be quite common. The news reports say numerous small eruptions are a good thing because they release the pressure building under the surface so that the larger eruptions are forestalled.

So, mostly I go on with my day giving volcanoes the same consideration I give to terrorism. It happens here, but what are the chances? Every so often though, a terrifying thought enters my brain: Pompeii. I mean, yikes. I don’t know about you, but I’m frankly not that interested in being buried under four to six feet of ash. I don't think it would be good for my complexion.