Nsbuk001, Twitter asked:
What exactly are pyroclastic flows and what makes them so deadly?
We posed this question to Hazel Rymer from the Open University...
Hazel - Pyroclastic means literally broken by fire. It means broken up and exploded rocks. So when a volcano explodes, it forms a pyroclastic flow and whatís so nasty about it is that they are often very, very hot, and they are clouds of very hot ash that go bellowing very, very rapidly along the ground, engulfing everything in their path. If you've ever been to Pompeii or Herculaneum, and seen the devastation, thatís why they're so dangerous.