Three-dimensional investigation of volcanic textures by X-ray microtomography and implications for conduit processes

Synchrotron X-ray computed microtomography (mCT)
was applied for the first time to clasts of pumice and scoria
generated by active, explosive volcanoes characterized by a
range of eruptive styles (mild Strombolian to Plinian) and
magmatic composition (basaltic to trachytic). The obtained
two-dimensional (2D) tomographic images, corresponding
to sample views at different rotation angles, were processed
to reconstruct three-dimensional (3D) volumes and then
used to make 3D measurements of vesicularity, vesicle
number density, volume and connectivity for quantitative
characterization of the investigated tephras. The results
indicate a positive correlation between vesicle number
density and eruption intensity that is used to investigate
modes of magma degassing in explosive eruptions. In
addition, the vesicle geometry affecting the connected gas
flow pathways in pyroclasts from Strombolian eruptions is
determined and related to the known permeabilities.
Implications on the dynamics of explosive eruptions is
discussed and, ultimately, used to quantitatively
discriminate between different eruptive styles.