Think You Can Drive Fast Enough to Escape an Erupting Volcano?

A massive pyroclastic flow from a 2014 eruption of Sinabung in Indonesia. James Reynolds, used by permission. Imagine being near a volcano when it unleashes a gigantic eruption. I'm not talking something fairly piddling like the 1980 eruption of Mount St. Helens or even the 1991 eruption of Pinatubo in the Philippines. I'm talking one of these eruptions that the tabloids and conspiracy websites say will destroy civilization, like Yellowstone or Toba. The common response is that everyone within hundreds of kilometers of the volcano would be killed almost instantly thanks to the fast moving pyroclastic flows that can rush outward from the caldera volcano for more than 150 kilometers (~100 miles). That idea is based on what we can see from these flows at smaller eruptions, where they race down the sides of the volcano at speeds over 500 kilometers per hour (300 mph). Cities like Pompeii and St. Pierre were wiped out mere moments after an eruption thanks to these avalanches of hot volcanic debris and ash. However, we've never been able to examine first-hand the results of a really giant eruption that puts Vesuvius and Pelée to shame. So, we need to look at the deposits left by such gargantuan events to figure out how they might be similar or different than their smaller brethren. Do the pyroclastic flows race out at the same speeds and are these flows the same mix of hot gasses and ash? The answer to those questions can help us better prepare for such an eruption and interpret the deposits left by these monsters in the past. A new study in Nature Communications by Olivier Roche (Université Blaise Pascal), D.C. Buesch (USGS) and Greg Valentine (University at Buffalo) has taken a stab at quantifying the speed of one of these massive eruptions and the results surprised me: Maybe we wouldn't be so doomed?