Lucky Shot

Satellite catches pyroclastic flow in motion

An image of a pyroclastic flow, one of the quickest and deadliest phenomena related to volcanic eruptions, has finally been caught by a satellite. These ground-hugging avalanches of hot ash and rocks can sweep down a volcano’s slopes at more than 100 kilometers per hour. They last no more than a few minutes, says Avijit Gupta, a geomorphologist at the University of Leeds in England.