Surtsey Island is a UNESCO World Heritage site located off the south coast of Iceland. This protected island is recognized worldwide as a natural laboratory for investigating processes of rift zone volcanism, hydrothermal alteration and biological colonization of basaltic tephra, and development of industrial resources using palagonitic tuff as a prototype for sustainable, high performance concretes.
An 181m hole was drilled in 1979 (Jakobsson & Moore 1986) and provided a petrological, mineralogical, and thermal framework to understand early eruptive and hydrothermal processes in tephra and feeder dikes and the structure of the volcano above and below sea level. Subsurface microbiota have now been observed in fluids extracted below the 120 °C thermal barrier of microbial life.
In 2016, DOSECC was retained as part of the SUSTAIN drilling program (Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative concretes) to core two holes while protecting the sensitive wildlife and vegetative habitats of the Surtsey Natural Reserve. A clean, 200-meter-deep vertical hole with anodized aluminum casing will be used to explore pore water chemistry, microbiota-water- rock interactions, and seawater compositional modifications over time.
After drilling is complete, a Surtsey Subsurface Observatory will be installed in this hole for long term monitoring and in situ experiments. A 300-meter- long angle hole with steel casing inclined west toward the eastern volcanic vent axis will intersect dike intrusions, provide additional information on deep stratigraphy and structure, and investigate higher temperature zones of the hydrothermal system.
The SUSTAIN drilling program will be the first to sample microbial colonization of tephra, together with its pore water, through a neo-volcanic island from the surface to the seafloor with all precautions taken to avoid contamination from the surroundings. The subseafloor pressure at the Surtsey Microbial Observatory at 0.2 km depth will be lower than that typical of the neovolcanic zone of mid-ocean ridges at ~2.5 km depth. More phase separation (boiling) can therefore occur in this shallow environment at temperatures relevant to microbial metabolism.
Because many of the energy-rich substances capable of supporting autotrophic life (e.g. H 2 , H 2 S, CH 4 ) partition into the vapor phase, there may be higher redox gradients and more spatial diversity in microhabitats in this environment compared to those on the ridge crest. Studies of microbial colonization of the altered subterrestrial tephra and hydrothermal fluids could provide new insights into archaeal lineages in the very young biosphere and, possibly, contribute to understanding the nature of the archaeal ancestor of eukaryotic organisms.
The Surtsey hydrothermal system is one of the few localities worldwide that is actively producing a rare authigenic Al-tobermorite and zeolite assemblage (Jakobsson and Moore, 1986). Tobermorite, Ca 5 Si 6 O 16 (OH) 2 ·4H 2 O, with 11 Å c-axis interlayer spacing, is formed by the action of hydrous fluids on basic igneous rocks. It also occurs among the alteration products at the cement–rock interface of toxic and nuclear waste repositories. It is a candidate sorbent for nuclear and hazardous waste encapsulation owing to its ion-exchange behavior which arises from the facile replacement of labile interlayer cations.
Al-tobermorite and phillipsite also occur as the principal cementitious mineral phases in the volcanic ash-lime mortar of 2000-year-old Roman concrete harbor structures. Little is known about how hydrothermal chemistry and phase-stability relationships in Al-tobermorite and zeolite mineral assemblages evolve as a function of time, temperature, fluid interactions, and microbial activity. The new cores will therefore provide a real-time geologic analog for understanding the evolving microstructures and macroscopic physical properties of tuff and sustainable concrete prototypes with pozzolanic pyroclastic rocks under the variable hydrothermal conditions of the engineered barriers of waste repositories.
Deepening of the inclined hole may resolve the disparity in the two models regarding the width of the subseafloor diatreme structure underneath Surtsey, and possibly intersect the outer wall of the diatreme if it is sufficiently narrow. Analyses of core from the inclined hole should also provide information about how the onset of fragmentation, submarine transport of tephra, and deposition in the submarine environment differs from what is represented in subaerial deposits.
The extent to which Surtsey’s activity was predominantly phreatomagmatic, versus the degree to which it involved substantial volatile-driven magmatic explosivity has important implications for predicting potential hazards to air traffic from future Surtseyan-type eruptions. These processes can be clarified with rigorous analysis of deposits combined with experiments using remelted material from the island.
The unique and distinguishing feature of the drilling program is to apply volcanological, geochemical, mineralogical, microbiological and geoarchaeological perspectives to create a new diagenetic and biogenetic paradigm for pyroclastic rock concretes with cation-exchange properties and long term societal benefits for human and earth ecology. Drilling is expected to take place in the summer of 2017.
Jakobsson, S., and Moore, J. G. (1986) Hydrothermal minerals and alteration rates at Surtsey volcano, Iceland. GSA Bulletin, 97, 648–659.