Japan's Ontake Erupts, Hikers Trapped and Injured

Hikers trying to escape from the unexpected eruption on Ontake in Japan on September 27, 2014. Photo by YouTube (Kuroda Terutoshi) video capture Today, Ontake (also known as Ontakesan) erupted unexpectedly trapping hundreds of people who were hiking on Japan's second tallest volcano. The eruption appears to have been highly explosive, with pyroclastic flows and an ash column that topped over 5.5 kilometers (18,000 feet). You can see some stunning video of the pyroclastic flows roaring down the valleys on the side of the volcano. It appears that this had to be a fairly large eruption to produce the massive pyroclastic flows captured in the video (although scale is a little hard to discern; see below). UPDATE 1:15 PM EDT: First take on the eruption from Dr. Koshun Yamaoka from Nagoya University is that it may have been a phreatic (steam-driven) eruption. From what I've seen, it seems big to ...