Transition of eruptive style: Pumice raft to dome-forming eruption at the Havre submarine volcano, southwest Pacific Ocean

Abstract

Transitions in eruptive style are common at volcanoes. Understanding how and why these transitions occur remain open questions. The 2012 eruption of the submarine Havre volcano in the Kermadec arc (South Pacific Ocean) produced a raft of floating pumice followed by a pair of domes from the same vent. Here, we used measurements on erupted magmas and constraints on the eruption rate, combined with a model for magma ascent, to identify the dominant controls on the transition in eruption style. During the raft-forming stage, magma ascent was fast enough that little gas was lost. Magma reached the seafloor with great enough vesicularity to be buoyant and produce clasts that could float. As the eruption waned, the eruption rate decreased and the conduit narrowed. Sufficient gas was then lost to the surrounding country rocks during ascent such that the erupted magma was no longer buoyant relative to seawater. Most of the original Page 2 of 19 dissolved water in the magma was lost to the crust surrounding the conduit during the dome-forming stage.

Defining Pre-eruptive Conditions of the Havre 2012 Submarine Rhyolite Eruption Using Crystal Archives

“…To date the majority of studies on the Havre 2012 submarine eruption have focused on the limited volume (< 0.1 km 3 or 7% of the total eruptive material) seafloor eruptive products (e.g., Carey et al, 2014Carey et al, , 2018Manga et al, 2018a,b;Ikegami et al, 2018;Mitchell et al, 2018Mitchell et al, , 2019Murch et al, 2019). Studies on the volumetrically dominant pumice raft (∼1.4 km 3 or 93% of total eruptive material) has been at a reconnaissance level, examined limited material (e.g., Rotella et al, 2015;Manga et al, 2018b) and focused on raft dispersion (e.g., Jutzeler et al, 2014;Carey et al, 2014;Velasquez et al, 2018). One outcome of the seafloor-focused studies has been the interpretation that the giant seafloor pumice and pumice raft were erupted contemporaneously (Manga et al, 2018a,b) given near identical whole-pumice compositions, similar mineralogy (i.e., plagioclase, orthopyroxene, clinopyroxene and Fe-Ti oxides) and textural features (e.g., banded pumice, tubed pumice and bread crusting).…”

Variability in the Gas Composition of the Popocatépetl Volcanic Plume

“…Changes in the eruptive dynamics (passive degassing, dome extrusion, or destruction) of dome-capped volcanic systems are mainly controlled by the gas content in the magma, directly affecting its viscosity and ascending speed (Martel and Schmidt, 2003;Boudon et al, 2015;Manga et al, 2018). Magma mixing in the storage reservoir (Witter et al, 2005), assimilation of the volcanic edifice basement (Goff et al, 2001), gas redox reactions and gas-rock interactions (Love et al, 1998;Mori et al, 2002;Stremme et al, 2011;Battaglia et al, 2019), conduit permeability changes (Edmonds et al, 2001;Taquet et al, 2017;Campion et al, 2018), or hydrothermal activity and gas interactions in the volcanic gas plume (Bagnato et al, 2013) are important processes contributing to changes in the gas composition from the deep to the shallow system.…”

Submarine giant pumice: a window into the shallow conduit dynamics of a recent silicic eruption

“…4 suggests greater textural maturity, i.e., continued bubble coalescence, and thus, a lack of any isolated vesicles. We infer that permeable, lateral outgassing and a breakdown of coupled gas and magma velocity (Manga et al 2018b) reduced the magma velocity (Fig. 4).…”

“…It is also possible that GP290, and other clasts that display textural banding, were generated during a later stage of the GP-forming phase as the eruption waned. Lower upward velocities at the conduit wall, gas loss, and the presence of cooler magma would allow for extended microlite crystallization (Manga et al 2018b;Sano and Toramaru 2017), as seen throughout GP290. Higher velocity and dP/dt in the conduit center, and melt viscosities < 10 7 Pa s (due to limited volatile exsolution under hydrostatic pressure) could still allow for melt domains to mingle in the shallow conduit where more viscous microlite-rich magma could be assimilated into the microlite-poor central magma body resulting in textural banding (Fig.…”