Quenching of steam-charged pumice: Implications for submarine pyroclastic volcanism

Grain-size distribution of volcaniclastic rocks 2: Characterizing grain size and hydraulic sorting

“…This assumption is reasonable, considering that hot pumice clasts are quickly waterlogged when put in contact with water (Whitham and Sparks, 1986;Allen et al, 2008), that >90 vol.% of the vesicles are connected in most pumice clasts (Klug et al, 2002), and that the increasing hydrostatic pressure with transport to deeper water results in the contraction and resorption of any remaining gas in the vesicle network.…”

“…Hot pumice clasts are efficiently waterlogged when quenched on contact with water (Whitham and Sparks, 1986;Allen et al, 2008), and can be deposited under water from subaqueous volcaniclastic density currents derived from subaerial pyroclastic flows that entered water (Whitham and Sparks, 1986;Freundt, 2003), or from subaqueous explosive eruptions (Allen and McPhie, 2009;Jutzeler et al, 2014a).…”

Effects of water depth on pumice formation in submarine domes at Sumisu, Izu-Bonin arc, western Pacific

“…The wide distribution of the shallower-water giant and small pumice clasts on domes A and A1 suggests that these clasts retained suffi cient heat after fragmentation to remain steam-charged and rise buoyantly (e.g., Allen et al, 2008). Even though the water-saturated giant pumice clasts were internally fractured and weighed tens to hundreds of kilograms, many remained largely intact upon settling, as their water-saturated densities would have been on average only 1.36× that of seawater.…”

“…Permeabilities and highly connected porosities suggest that ingestion of water would have been rapid once cooling commenced. Quenching causes the steam-fi lled vesicles in hot pumice to condense, promoting rapid water ingestion (Allen et al, 2008); therefore, these deep-water pumice clasts did not fl oat to the sea surface. The summits of domes B (600 m) and C (1100 m) are the shallowest depths from which the deep-water slabby giant clasts could have originated.…”

Influence of volatile degassing on initial flow structure and entrainment during undersea volcanic fire fountaining eruptions

“…This would facilitate interaction with seawater and a rapid change of clast density by quenching of steam within accessible vesicles. Allen et al [30] have shown that buoyant, vesiculated magma that comes in contact with seawater can transition to negative buoyancy relatively quickly due to the quenching of steam to water that generates negative pore pressures. However, clasts may still be able to retain sufficient heat to deform in a plastic manner and produce deformed clasts that have been attributed submarine fire fountaining under submarine conditions.…”