Lava bubble-wall fragments formed by submarine hydrovolcanic: explosions on L(o)over-bar'ihi Seamount and Kilauea Volcano

Glassy bubble-wall fragments, morphologically similar to littoral limu o Pe le, have been found in volcanic sands erupted on Lo'ihi Seamount and along the submarine east rift zone of Kilauea Volcano. The limu o Pele fragments are undegassed with respect to H2O and S and formed by mild steam explosion s. Angular glass sand fragments apparently form at similar, and greater, de pths by cooling-contraction granulation. The limu o Pele fragments from Lo' ihi Seamount are dominantly tholeiitic basalt containing 6.25-7.25% MgO. No ne of the limu o Pele samples from Lo'ihi Seamount contains less than 5.57% MgO, suggesting that higher viscosity magmas do not form lava bubbles. The dissolved CO2 and H2O contents of 7 of the limu o Pele fragments indicate eruption at 1200+/-300m depth (120+/-30 bar). These pressures exceed that g enerally thought to limit steam explosions. We conclude that hydrovolcanic eruptions are possible, with appropriate pre-mixing conditions, at pressure s as great as 120 bar.