@article{fdi:010090279, title = {{P}re-eruptive outgassing and pressurization, and post-fragmentation bubble nucleation, recorded by vesicles in breadcrust bombs from vulcanian activity at {G}uagua {P}ichincha volcano, {E}cuador}, author = {{C}olombier, {M}. and {M}anga, {M}. and {W}right, {H}. and {B}ernard, {B}. and de{G}raffenried, {R}. and {C}áceres, {F}. and {S}amaniego, {P}ablo and {V}asseur, {J}. and {J}akata, {K}. and {C}ook, {P}. and {D}ingwell, {D}. {B}.}, editor = {}, language = {{ENG}}, abstract = {{B}readcrust bombs formed during {V}ulcanian eruptions are assumed to originate from the shallow plug or dome. {T}heir rim to core texture reflects the competition between cooling and degassing timescales, which results in a dense crust with isolated vesicles contrasting with a highly vesicular vesicle network in the interior. {D}ue to relatively fast quenching, the crust can shed light on pre- and syn-eruptive conditions prior to or during fragmentation, whereas the interior allows us to explore post-fragmentation vesiculation. {I}nvestigation of pre- to post-fragmentation processes in breadcrust bombs from the 1999 {V}ulcanian activity at {G}uagua {P}ichincha, {E}cuador, via 2{D} and 3{D} textural analysis reveals a complex vesiculation history, with multiple, spatially localized nucleation and growth events. {L}arge vesicles ({T}ype 1), present in low number density in the crust, are interpreted as pre-eruptive bubbles formed by outgassing and collapse of a permeable bubble network during ascent or stalling in the plug. {H}aloes of small, syn-fragmentation vesicles ({T}ype 2), distributed about large vesicles, are formed by pressurization and enrichment of volatiles in these haloes. {T}he nature of the pressurization process in the plug is discussed in light of seismicity and ground deformation signals, and previous textural and chemical studies. {A} third population ({T}ype 3) of post-fragmentation small vesicles appears in the interior of the bomb, and growth and coalescence of {T}ype 2 and 3 vesicles causes the transition from isolated to interconnected bubble network in the interior. {W}e model the evolution of viscosity, bubble growth rate, diffusion timescales, bubble radius and porosity during fragmentation and cooling. {T}hese models reveal that thermal quenching dominates in the crust whereas the interior undergoes a viscosity quench caused by degassing, and that the transition from crust to interior corresponds to the onset of percolation and development of permeability in the bubble network. {P}lain {L}anguage {S}ummary {B}readcrust bombs are volcanic ejecta formed during explosive volcanic eruptions by rapid cooling of the exterior (the crust) and slow cooling of the interior that causes gas loss, bubble growth and cracking of the exterior. {T}he rapidly cooled crust preserves characteristics of the magma prior to explosion. {W}e study here the variations in porosity and vesicle properties from crust to interior in breadcrust bombs from the {G}uagua {P}ichincha volcano in {E}cuador. {O}ur results shed light on the pre-eruptive conditions in the magma prior to explosive activity, and on the post-fragmentation evolution of the bomb interior by bubble formation.}, keywords = {breadcrust bombs ; {V}ulcanian eruptions ; vesicle number density ; vesiculation ; bubble nucleation ; fragmentation ; {EQUATEUR}}, booktitle = {}, journal = {{J}ournal of {G}eophysical {R}esearch : {S}olid {E}arth}, volume = {128}, numero = {9}, pages = {e2023{JB}026775 [16 p.]}, ISSN = {2169-9313}, year = {2023}, DOI = {10.1029/2023jb026775}, URL = {https://www.documentation.ird.fr/hor/fdi:010090279}, }