Syn-Eruptive Conditions of the AD 1530 Sub-Plinian Eruption of La Soufrière of Guadeloupe (Lesser Antilles)

A prerequisite in refining volcanic hazard at explosive volcanoes is a better quantification of the timescales syn-eruptive processes, such as magma degassing and crystallization prior to eruption. To this aim, new data on matrices (microlites, residual glasses, bubbles) pumice, scoria, dense clasts erupted during AD 1530 andesitic eruption La Soufrière Guadeloupe are combined with published from phase-equilibrium kinetic experiments, order estimate pressures microlite ascent rates. From timescale data, we infer that started phreatomagmatic explosions tapping magmas ascended about 1 month (decompression rate ?50 Pa/s) coldest parts reservoir (?825°C 74 wt% SiO 2 melt). These continuously crystallized microlites (?25 vol% plagioclase, orthopyroxene, clinopyroxene, magnetite, quartz, apatite), but did not outgas likely due sealed conduit margins. The flank collapse (preexisting “cold” edifice) followed phase triggered sub-Plinian progressively tapped hotter main (?875°C 71 interstitial melt), emitting banded homogeneous pumice. pumice significantly mostly lack decompression-induced microlites, suggesting short durations 0.5–1 day rates 1,400–4,000 Pa/s). following Strombolian emitted dark scoria only rare duration days ?550 terminal lava dome growth involved fully outgassed more than month, giving time for (?40 cristobalite). detection any shallow magmatic intrusion crucial, since it can trigger sequence processes leading an marked by succession different disastrous eruptive styles, scenario similar Overall, provide approach petrological, geochemical, experimental may be used conditions other systems.