Showing posts from March, 2017

Why did Etna's lava flow explode?

- Dr. Alison Graettinger There is something powerful about understanding that something can happen, and then seeing it happen. Today a video on BBC showed what happens when a lava flow moving gently down a snow-covered slope suddenly becomes very dangerous. The video clip shows a white plume of steam with some dark streaks in it, then suddenly there are loud wooshing noises and bangs. The rising plumes are black and brown. The camerawoman needed to run to escape. The group thankfully all made it away from the scene and down slope.  Video from BBC from March 16, 2017. Click link to view due to updated permissions.  So what happened? How does a lava flow suddenly explode? It is all about the snow. The lava flow is very hot > 1,000 C and the snow is frozen, so 0 C. That big difference represents all the energy in the lava flow in the form of heat. We complain when the weather is above 37 C (98.6 F; or hotter than our inside body temperature), so you can appreciate that there