An eruption began in Grímsvötn, beneath Vatnajökull ice cap, 21st May 2011 at around 19:00 hrs. Tremors had began at 17:30. This eruption was powerful for the first 24 hrs. In the early hours of 22nd May the ash plume reached 15-19 km height. The eruption was over 25th May. This photo is taken 22nd May at 10:20, showing reduced visibility due to great quantities of ash in the air. It is assumed that as much ash was released into the air during the first 24 hours of this eruption as in total during the 40 days of the Eyjafjallajökull eruption a year earlier, i.e. in spring 2010.