Pyroclastic flows are the infamous deadly avalanches of superheated gas and debris that killed thousands at Pompeii and in the 1902 Mount Pelée eruption on Martinique. Now, thanks to a very brave scientist, you can watch a pyroclastic flow up close.
This is one of several videos taken during the recent eruption of Guatemala's Santiaguito (or Santa Maria) volcano. At the Eruptions blog, Erik Klemetti explains the background of how this footage was made, what it shows, and why it's so important.
So, when faced with a pyroclastic flow, why would you try to get up close to one? Julio Cornejo, an INSIVUMEH observer from the Santiaguito volcano observatory (OVSAN), did just that to capture some video (see top and below) that has surprised everyone that has seen it. Cornejo was able to film the very far end of a pyroclastic flow generated by the dome collapse at Santiaguito (see above), when it had lost most of its energy but was still moving. At this point a flow is likely still capable of engulfing and suffocating someone in hot ash and gasses, as happened to many people in the 1902 eruption of Mont Pelee. So, Cornejo is very lucky to have made it out alive with this footage, but what he got was remarkable.
Rudiger Escobar Wolf, a volcanology post-doctoral researcher at Michigan Tech who studies volcanoes in Guatemala, posted a sequence of videos from Cornejo and INSIVUMEH and annotated some of the video to understand what we're seeing. I've also watched the video closely and have two here that show some likely never-before-filmed examples of how pyroclastic flows can be destructive even after they slowed to a snail's pace relative to their usual speed.