Dynamics of Individual Eruptive Pulses and their Contribution to the Total Mass Flux – Case Study of the 2nd Explosive Phase of the 2010 Eyjafjallajökull Eruption (Iceland)

Abstract:

The 2010 Eyjafjallajökull eruption was characterized by pulsating activity, where emissions from the vent occurred in frequent but discrete bursts with pulses in the order of seconds that then merged at higher altitude in a sustained eruption column. High resolution near-field video recordings of the vents, taken from a distance of ~850 m from 8 – 10 May (during the second explosive phase), were used as a case study to describe the mechanism of such pulsating eruptions and their contribution to the total mass flux of ash injection in the atmosphere. The dynamics of discrete overpressured jets were quantified during the intial gas thrust stage, i.e. between discharge and the height of transition into a convective buoyant regime (at ~100 m above the vent). By applying a straight-forward volumetrical calculation model, the volume and pressure history of eruptive pulses could be reconstructed. Then the mass flux of individual pulses was determined by exploiting the fact that the pressure at the transition height is known to be at ambient pressure. Based on our results we examine how to link the eruption source parameters of multiple discrete expansive jets to the overall mass eruption rate deduced by “classical” continuous ash plume models (being ~4*10⁴ kg/s). In addition we discuss the implications for a real-time assessment of eruption source parameters by using near-field monitoring systems under pulsatory eruption conditions.