Fig. 6: Morphological and physical features of ash and lapilli.

a–b SEM images of selected LP clasts from the two paroxysms, showing external morphology and internal texture (left and center columns), and binary images (right column; vesicles in black with Φ = vesicle area fraction %, and N_{A bulk} = total number of vesicles per mm⁻² within each class). c 2D distribution of the major axis of the best-fit ellipse (L) for Type1 (lines) and Type2 (bars) vesicles in number density (N_A mm⁻²). d 3D volume distribution of Type1 vesicles (VVD). Arrows point to nucleation events. e Log-plot of the cumulative vesicle size distribution (CVSD), i.e., the number density of 3D (N_v, Type1) vesicles larger than L (major axis of the vesicle best-fit ellipse) against L. Equations of power-law (dashed) and exponential (solid) curves fitting the data are shown together with the R². For comparison, published data on 0.01–1 mm vesicles data Stromboli 2003 and 2007 paroxysms²⁹ (black lines) and experiments³⁰ (green lines) are shown. f Density distribution of lapilli in the size range 8–16 and 16–32 mm and corresponding estimated vesicularity distributions for 3 July (red lines) and 28 August (blue lines, See “Methods” section).