Tephra sedimentation during the 2010 Eyjafjallajökull eruption (Iceland) from deposit, radar and satellite observations

The April–May 2010 eruption of the Eyjafjallajökull volcano (Iceland) was characterized by a nearly continuous injection of tephra into the atmosphere that affected various economic sectors in Iceland and caused a global interruption of air traffic. Eruptive activity during 4–8 May 2010 was characterized based on short‐duration physical parameters in order to capture transient eruptive behavior of a long‐lasting eruption (i.e., total grain‐size distribution, erupted mass, and mass eruption rate averaged over 30 min activity). The resulting 30 min total grain‐size distribution based on both ground and Meteosat Second Generation‐Spinning Enhanced Visible and Infrared Imager (MSG‐SEVIRI) satellite measurements is characterized by Mdphi of about 2 phi and a fine‐ash content of about 30 wt %. The accumulation rate varied by 2 orders of magnitude with an exponential decay away from the vent, whereas Mdphi shows a linear increase until about 18 km from the vent, reaching a plateau of about 4.5 phi between 20 and 56 km. The associated mass eruption rate is between 0.6 and 1.2 × 10^5 kg s−1. In situ sampling showed how fine ash mainly fell as aggregates of various typologies. About 5 to 9 wt % of the erupted mass remained in the cloud up to 1000 km from the vent, suggesting that nearly half of the ash >7phi settled as aggregates within the first 60 km. Particle sphericity and shape factor varied between 0.4 and 1 with no clear correlation to the size and distance from vent. Our experiments also demonstrate how satellite retrievals and Doppler radar grain‐size detection can provide a real‐time description of the source term but for a limited particle‐size range.