Eyjafjallajökull crater situation during 8 to 10 May 2010. Specific features (labelled ‘A’ to ‘D’) visible in an aerial image taken at 8 May can also be identified in an airborne SAR image taken 3 days later (inlet), suggesting that the crater geometry has not significantly changed during this period. The green arrow indicates the angle of view of the video camera which was placed at 850-m distance from the center (‘D’) of the active vent. Based on such images and radar maps, it was possible to estimate the outer vent radius R and the angle of repose β. Image courtesy of Thórdís Högnadóttir.