Fig. 3. Schematic diagram of the inferred processes underlying impulsive seafloor events.

(A) At shallow depths, rapid expansion of bubbles formed from vaporized seawater (blue) by hot erupted lava and volatiles exsolved from magma (yellow) can generate explosive signals. (B) At intermediate depths, implosions of predominantly vaporized seawater and some exsolved volatiles due to high hydrostatic pressure generate implosive signals. The depth boundary for transition (wavy line) from explosion-dominated to implosion-dominated regime remains to be determined though implosions were observed as shallow as ~1,600 m in this study. (C) At >~3,000 meters depths, vaporization of seawater by hot erupted lava is inhibited so proportionately fewer and smaller bubbles reach the lava surface, resulting in fewer detectable implosive events.