Surtsey volcano, now 50 years old, represents a world-class example of island formation through rift zone volcanism. The 181 m hole drilled in 1979 (Jakobsson & Moore 1986) provides a comprehensive petrological, mineralogical, and thermal framework to understand the structure of the volcano, and early eruptive and hydrothermal processes in the parent tephra and feeder dikes. 

The drilling project used the natural laboratory of the Surtsey tephra above and below sealevel and the thermal profile of a basalt dike swarm below sea level to describe how the hydrothermal alteration of tephra drilled 40 years ago at ~25–140 °C has evolved.  It refined our understanding of seawater-rock interactions that influence diagenetic and microbial alteration of tephra to produce lithified tuff; it described how rift zone volcanic islands form, lithify, and are ultimately destroyed; and explored how explosive magma interactions with seawater send tephra into the jet stream, leading to health risks and airplane encounters with airborne ash.

Keywords: Europe, Iceland, Basalt, Hydrothermal Alteration, Microbial Life, Rift Zone Volcanism, Surtsey, Tuff