Weather expert describes flying near Iceland's ash cloud
The Icelandic authorities have shut the country's main airport after the nation's most active volcano, Grimsvotn, began erupting.
A plume of smoke rose 20km (12 miles) into the sky but is now said to have fallen to around half that height.
Matthew Roberts works for the Icelandic Meteorological Office and spoke to the BBC shortly after returning from an observation flight.
He reported seeing "plumes of steam, volcanic lightning strikes and enormous quantities of ash being ejected into the air.
22 May 2011