Velocities in the plume of the 2010 Eyjafjallajökull eruption

The eruption of the Icelandic volcano Eyjafjallajökull in the spring of 2010 lasted for 39 days with an explosive phase (14–18 April), an effusive phase (18 April–4 May) and a phase with renewed explosive activity (5–17 May). Images every 5 seconds from a camera mounted 34 km from the volcano are available for most of the eruption. Applying the maximum cross-correlation method (MCC) on these images, the velocity structure of the eruption cloud has been mapped in detail for four time intervals covering the three phases of the eruption. The results show that on average there are updrafts in one part of the cloud, and lateral motion or downdrafts in another. Even within the updraft part, there are alternating motions of strong updrafts, weak updrafts and downward motion. These results show a highly variable plume driven by intermittent explosions. The results are discussed in the context of integral plume models, and in terms of elementary parcel theory.