An ash-filled sky

Image: NASA/MODIS Rapid Response Team

The plume of volcanic ash that is responsible for grounding planes across northern Europe traces a dirty smear across the Norwegian Sea in this photo snapped by NASA’s TERRA satellite.

A volcano beneath the Eyjafjallajoekull glacier on the south coast of Iceland is blasting ash up to 11 kilometres into the atmosphere. At this altitude, strong winds are blowing the plume of ash south-eastwards, towards the UK and mainland Europe.

But why is volcanic ash such a problem for aircraft? The ash contains tiny particles of volcanic glass, which can be sucked into jet engines. Jet engines operate at temperatures high enough to melt the glass particles, which causes sheets of glass to form, blocking fuel nozzles and other sensitive components.

The tiny glass shards are also abrasive, and they’ll quickly damage cockpit windows – reducing visibility. The risk to aircraft from volcanic ash is so great that it is far safer to cancel all flights until the ash plume disperses. As the volcano is still erupting, this may take some time!

The volcano near Eyjafjallajoekull first erupted on the 20th March 2010, following months of small earthquakes, and caused Icelandic authorities to evacuate around500 people. The second eruption on the 14th April was ten to twenty times larger than the first because this time the magma came into contact with glacial ice, causing a powerful explosion, which threw ash high into the atmosphere.

While a potential hazard for aircraft, the ash probably isn’t a major health hazard for the UK population. The ash plume is so high that ash particles aren’t expected to reach the ground in the UK, according to a statement from the Health Protection Agency. So the only thing you need to look out for are the predicted beautiful red sunsets!