VOLCANOES have more in common with monster thunderstorms than we thought. Their plumes swirl like cyclones, which could explain why they have been seen spawning tornadoes and sheet lightning.
It is conventionally thought that a rises straight up and spreads out in a rough circle. But when at the University of Illinois at Urbana-Champaign and colleagues studied hourly satellite photos of the 1991 eruption of in the Philippines, they noticed that the margins gradually separated into five lobes. They saw similar shapes in photos of five other volcanoes.
The team’s calculations show that this…
