Fig. 1: Characteristics of the main pumice types from the 2012 Havre eruption.

a–d Stereoscope images showing the representative colours and textures of the 4 pumice types analysed in this study; white and pink refer to pumice raft material. Note the grey and white pumice bands in the seafloor pumice. e–h XFM-Fe, Ti, Ca-RGB stacked elemental maps for the different pumice types. Boundary between white and grey pumice domains for the seafloor pumice indicated by white dashed line in (e). XFM elemental maps are colour-coded based on a RGB triangle where red, green and blue are end members correlating to high Fe, Ti and Ca, respectively. Where multiple elements are co-located, the pixel displays a colour that represents the relative proportion of each element’s concentration. For example, Fe–Ti oxides will appear yellow, orthopyroxene crystals will appear pink and plagioclase crystals blue. i–l Corresponding XFM Fe elemental maps for the areas outlined by white boxes in (e–h). Fe elemental maps are set to a fire colour scale (µg*cm⁻²) where white pixels correlate to areas of high Fe-intensity, indicating Fe–Ti oxide microlites. Yellow pixels represent either orthopyroxene microlites or Fe–Ti nanolite glass mixtures. Scale bars in top row (a, e, i) applies to the entire column below (e.g., a, b, c, d are in the same scale as presented in (a).