Figure 6. Estimates of distribution outside Iceland and the volume of tephra erupted.

The tephra from 14–16 April is estimated seperately since it forms a well defined sector and was responsible for the first ash transported to Europe. (a) Tephra thickness as a function of square root of area within each isopach, using fallout in the Faroe Islands, satellite data and the established first order behaviour of tephra thicknesses declining exponentially with distance from source³,³⁷,³⁸. (b) Estimated cumulated bulk volume of fallout volume and its distribution with distance. The volume within Iceland is found by direct integration of the onland part of the maps in Fig. 4. The volume outside Iceland is found by integrating the exponential curves (e.g. ref. 37). (c) Estimate of volume (left axis) and mass (right axis) that was transported beyond a specified area. The volume is found by integrating the exponential curves for 14–16 April and the whole eruption from the point on the square root of area axis on (a) out to infinity, using eqs. 13 and 14 in ref. (35). Values outside A^1/2 = 300 km are rough order of magnitude estimates.