When lava erupts underwater, contact with cold seawater causes rapid cooling on the outside of the lava, forming a quenched crust and pillow-like shapes as the surface hardens while the interior stays molten for longer.
Cooling time scales
- Surface crust: forms in seconds to minutes after contact with seawater.
- Outer crust cooling to near seawater temperature: minutes to hours, depending on depth, water movement, and lava type.
- Full solidification of the eruption (including the bulk interior): days to weeks; larger flows can keep heat in the core for weeks to months.
Biological colonization on fresh lava
- Initial microbes and biofilms can begin within hours to days, using minerals in lava and energy from hydrothermal fluids.
- Microbial mats and small organisms may appear over days to weeks.
- Small invertebrates and larger organisms can establish over weeks to months; a mature vent-like community often takes years and depends on energy sources and stability.
Note: These are broad ranges. Real times vary with depth, eruption style, water chemistry, currents, and the availability of chemical energy sources.