This ash cloud fom Eyjafjallajokull volcano is streaming across the Atlantic towards Britain and Europe and it's the reason why all flights have been cancelled. The ash is not the kind of powdery grey stuff left over after a fire but it full of tiny pulverised particles of rock which can stop jet engines and strip the paint from the fuselage. The tan colour of the cloud indicates a fairly hight ash content.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this natural-colour image on April 15, 2010.
This eruption started on March 20, and comes from a stratovolcano which means alternating layers of ejected ash, lava and rocks. It is erupting underneath the ice of the glacier, melting the ice which is causing the violent explosions as water hits the molten lava. The original fissure was about 1000 metres long has joined two more fissures and is now a single erupting vent.