SPARTAN MAN RANDOM COMMENTS CORNER - Page 72

Volcanic ash has long been identified as a mortal hazard to aircraft, but whether the cloud spreads further across Britain depends on wind speed and direction.

Magma usually lies as pressurised pools of molten rock deep beneath the Earth's surface. During an eruption it rises. This drops the pressure and gas dissolved in the magma starts to emerge and forms bubbles, just as it does in champagne when a cork is released.

The bubbles cause the magma to froth violently and burst out as a volcanic eruption. When the boiling fragments of liquid magma hit the cold air they freeze into individual dust particles, driven upwards towards the high atmosphere by the power and heat of the eruption.

As the turbulent torrent rushes out it rips and pulverises rocks from the volcano, adding to the growing cloud of ash.

"Think about when you cough. Not all of the material that comes out is from lower down, some is dragged from further up as well," says Colin Macpherson, a volcano expert at Durham University.

Even if it does spread, the high-altitude ash cloud is unlikely to settle on the ground or even be visible from it. The curious are advised to wait until sunset, when they could be in for a treat. The retreating light could be scattered as it bounces from the shiny dust particles, which can enhance the red colour and bring stunning displays. The gigantic eruption of Mt Krakatoa in Indonesia in 1883, the loudest recorded bang in history, threw out so much ash that spectacular sunsets were recorded for years afterwards