'Hovercraft effect' may explain deadly speed of volcanic gas clouds

[Judi Lynn]

Superheated gases and rock fragments can reach speeds of up to 400mph by travelling on cushion of air, say scientists
Nicola Davis
@NicolaKSDavis
Mon 8 Apr 2019 11.00 EDT Last modified on Mon 8 Apr 2019 14.25 EDT

Crouched figures, a child with its mother, a dog writhing on its back – the harrowing plaster casts of the dead of Pompeii reveal that when the end came in AD79, it was as swift as it was final.

Caught in the eruption of Mount Vesuvius, many died when buildings collapsed under heavy ash and pumice. But for those still alive, another catastrophe was about to hit as deadly currents of superheated gases, ash and rock fragments raced through the streets.

In nearby Herculaneum, the heat from such flows is thought to have been so strong that some have argued it vaporised the bodily fluids of the town’s inhabitants and exploded their skulls.

Now scientists say they have discovered how such pyroclastic flows travel so fast: the volcanic material travels on a cushion of air, rather like a hovercraft.

More:
https://www.theguardian.com/world/2019/apr/08/hovercraft-effect-may-explain-deadly-speed-of-volcanic-gas-clouds