Ash could cause spectacular sunset

For air passengers that will be little consolation, with thousands grounded across the UK.

But Dr David Rothery, from the department of earth and environmental sciences at The Open University, said flight restrictions were an essential safety precaution.

He said: “The eruption of the Eyjafjallajokull volcano in southern Iceland, which climaxed yesterday with flooding and a tall eruption column driven by expanding steam, distributed fine rock particles known as ’volcanic ash’ as high as 11km into the atmosphere.

“This ash cloud is now drifting with the high altitude winds.

“The main mass is over Scandinavia, but it is also over the north of Great Britain and is likely to spread south over the whole island by the end of the day.

“This is not a dense cloud, and is unlikely to be noticed by people on the ground, though we may have a spectacularly red sunset this evening.

“However, air traffic restrictions have very properly been applied, resulting in closure of airports and airspace.

“This is because if volcanic ash particles are ingested into a jet engine, they accumulate and clog the engines with molten glass.”

Emergency procedure manuals have been changed in the wake of various volcanic ash incidents.

In 1982, a British Airways plane dropped to within a few thousand feet of the ground after flying into an ash cloud over Indonesia.

Dr Rothery said: “Previously, when engines began to fail the standard practice had been to increase power. This just makes the ash problem worse.

“Nowadays, a pilot will throttle back and lose height so as to drop below the ash cloud as soon as possible.

“The inrush of cold, clean air is usually enough to shatter the glass and unclog the engines.

“Even so, the forward windows may have become so badly abraded by ash that they are useless, and the plane has to land on instruments.”