A new International Continental Drilling Program (ICDP)
project will drill through the 50-year-old edifice of Surtsey Volcano, the
youngest of the Vestmannaeyjar Islands along the south coast of Iceland, to
perform interdisciplinary time-lapse investigations of hydrothermal and
microbial interactions with basaltic tephra. The volcano, created in
1963–1967 by submarine and subaerial basaltic eruptions, was first drilled
in 1979. In October 2014, a workshop funded by the ICDP convened 24
scientists from 10 countries for 3 and a half days on Heimaey Island to
develop scientific objectives, site the drill holes, and organize logistical
support. Representatives of the Surtsey Research Society and Environment
Agency of Iceland also participated. Scientific themes focus on further
determinations of the structure and eruptive processes of the type locality
of Surtseyan volcanism, descriptions of changes in fluid geochemistry and
microbial colonization of the subterrestrial deposits since drilling 35
years ago, and monitoring the evolution of hydrothermal and biological
processes within the tephra deposits far into the future through the
installation of a Surtsey subsurface observatory. The tephra deposits
provide a geologic analog for developing specialty concretes with
pyroclastic rock and evaluating their long-term performance under diverse
hydrothermal conditions. Abstracts of research projects are posted at
The location of Surtsey Volcano within the southernmost extension of the Eastern Icelandic rift zone (scale bar of 50 km; after Trønnes, 2002). Colors refer to compositional trends in basaltic rocks (Jakobsson et al., 2008).
The very young volcanic island of Surtsey, which formed over a 3.5-year episode of eruptions along the southern offshore extension of the SE Icelandic volcanic rift zone (Figs. 1, 2), represents a world-class example of a rift zone volcano that has grown from the seafloor in historic time. The Surtsey eruption was thoroughly documented beginning in November 1963, when a plume of ash first broke the sea surface, until the termination of subaerial lava flow activity in June 1967. Surtsey was designated a UNESCO World Heritage site in 2008 and “has been protected since its birth, providing the world with a pristine natural laboratory” for study of earth and biological processes (Baldursson and Ingadóttir, 2007). An International Continental Drilling Program (ICDP) workshop on Heimaey Island in October 2014 convened 24 scientists from 10 countries and representatives from the Surtsey Research Society, who developed the scientific objectives of the Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative Concretes (SUSTAIN) drilling project (Jackson, 2014). The project will include the eventual installation of an in situ Surtsey subsurface observatory for monitoring hydrothermal microbial life and changes in the physical and compositional properties of associated hydrothermal fluids, which will complement the 50 years of observations of plant and animal life on the surface of Surtsey.
Surtsey Volcano in eruption, 30 November 1963 (Terry Mann, courtesy of Robert Carson).
The 181 m deep hole drilled within the eastern tephra cone in 1979 (Fig. 3a) was sponsored by the US Geological Survey and the Icelandic Institute of Natural History. It has provided well-constrained information about the substructure and stratigraphy of the volcano, as well as the nature of its hydrothermal system, which continues to be manifested by steam vents at the surface (Jakobsson and Moore, 1986, 1992; Jakobsson et al., 2013). Investigations of the core and downhole temperature measurements described the petrologic characteristics of the basaltic tephra, partially altered to palagonite tuff, the thermal conditions and nature of hydrothermal alteration, and the authigenic mineral growth of a rare aluminous calcium-silicate-hydrate and zeolite mineral assemblage above and below sea level (Fig. 3b). These minerals, Al-tobermorite and phillipsite, have cation exchange capabilities for certain radionuclides and heavy metals and have been the focus of laboratory syntheses of concretes for hazardous waste encapsulations (Komarneni and Roy, 1983; Komarneni, 1985; Trotignon et al., 2007; Cappelletti et al., 2011; Coleman et al., 2014). In the SUSTAIN drilling project, time-lapse investigations of dynamic secondary mineral assemblages in the altered tephra deposits will yield information from a geological analog for the long-term performance behavior of specialty concretes formulated with pyroclastic rock. The results of these investigations will advance technological developments initiated by ancient Roman engineers, who developed pozzolanic concretes with this same mineral assemblage that have maintained their integrity despite centuries-long exposure to seawater (Brandon et al., 2014). A recent study of hot fluids in the 1979 drill hole (Fig. 3b) has identified for the first time potentially indigenous thermophilic bacteria and archaea deep in the center of an isolated Neogene volcanic island (Marteinsson et al., 2015). In the SUSTAIN project, 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 eukaryote organisms (Spang et al., 2015).
Two holes through the 50-year-old deposits, designed in collaboration with
the Icelandic National Planning and Environment Agencies to protect the
sensitive habitats of the Surtsey Natural Reserve, will be drilled at a site
within
Hydrothermal alteration of Surtsey deposits (after Jackson, 2014).
Structural models of Surtsey, showing the shallow crater
hypothesis
The SUSTAIN drilling project will use the natural laboratory of the Surtsey tephra above and below sea level, and interdisciplinary volcanological, microbial, geochemical, mineralogical, and geoarchaeological research programs to undertake scientific investigations situated within the larger ICDP research themes of the evolution of hydrothermal seawater–rock interactions in rift zone volcanism, the succession of early microbial life, and the development of industrial resources, using the alteration processes of palagonitized tuff as models for creating sustainable, high-performance concretes with pyroclastic rocks.
Descriptions of the episodic eruptions at Surtsey from 1963 to 1967 provide the most comprehensive record of Surtseyan-style emergent volcanic activity and island rift zone volcanism in the world (Thórarinsson, 1967). Questions remain, however, about the earliest submarine part of the edifice, which was not observed during initial studies of the volcano (Fig. 4). The role of seawater interaction with hot magma and temporal variations in magmatic volatile content in driving subaerial explosive eruptions will also be investigated. New drilling will clarify Surtsey's early history and submarine structural anatomy and provide interdisciplinary perspectives into explosive eruptive processes and how volcanic facies, structural discontinuities, pyroclast size and vesicularity provide a template for hydrothermal fluid flow, heat transfer, diagenetic and biogenetic alteration processes, and temporal changes in porosity and rock physics properties.
Surtsey is an isolated oceanic island that has provided an exceptionally
well-monitored laboratory of world-wide significance for the investigation
of biological colonization and succession on and in basaltic tephra
deposits. Furthermore, the temperature range recorded in the 1979 hole (Fig. 3b) is ideal for studying the extreme temperature conditions of
chemosynthetic life. A subsurface biome comprising bacteria and archaea has
recently been observed in fluids extracted from the 1979 hole below 145 m depth (Fig. 3b). This subsurface microbial community is quite possibly
indigenous, since it occurs below a > 120
Comparisons of new cores with the 1979 core and original samples of the
newly erupted deposits will give precise information about the
time-integrated evolution of fluid–rock interactions. These include the
alteration of basaltic glass to form palagonite, at variable temperature and
fluid chemistry, and associated secondary mineral nucleation and growth
(Fig. 3a). Palagonite is a metastable alteration product of fresh basaltic
glass that has interacted with aqueous solutions and lost Si, Al, Mg, Ca, Na
and K, gained H
The collaborative research investigations to be undertaken by the scientific team of the SUSTAIN drilling program focus on three ICDP research themes: volcanic systems and geothermal regimes, the geobiosphere, and natural resources as applied to pyroclastic rock concretes in the sustainable built environment.
The subaerial tuff cones of Surtsey are constructed from deposits produced by intermittent tephra-finger jets and from continuous uprush eruptions. Continuous uprush lasted for several minutes to several hours and produced eruption jets 100–250 m in diameter and 500–2000 m in height forming up to 9 km high eruption columns (Thórarinsson, 1967). The new drill holes should clarify whether the lower part of the edifice contains a mound of submarine pillow lavas (Fig. 4a) (Thórarinsson, 1967) or tephra (White and Houghton, 2000) that preserves the initial submarine depositional phase of the eruption, or a deep funnel filled with slumped and downfaulted subaerial deposits (Fig. 4b) (Moore, 1985). We can therefore test which of two contrasting models best represents the true structure of the island: the shallow crater model (Fig. 4a) (Thórarinsson, 1967; Jakobsson and Moore, 1992; Jakobsson et al., 2013) where any diatreme that may have formed is narrow, leaving the pre-eruption seafloor relatively intact underneath the volcanic edifice, or the diatreme model (Fig. 4b) (Moore, 1985) that has wide, funnel shaped, tephra-filled diatremes that extend a few hundred meters into the pre-eruption seafloor. The new oriented cores should help us define these volcanic structures. For example, do the primary layering and pre-solidification slump planes dip steeply inward toward the vent of the volcano (Fig. 4e) as observed in unoriented cores from the 1979 drill hole (Moore, 1985) or do beds dip gently outward away from the vent (Fig. 4d) as suggested by a shallow crater model? Deepening of the inclined hole may resolve the disparity in the two models regarding the width of the subseafloor diatreme structure and may 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 (e.g., Schipper et al., 2010, 2015) combined with experiments using remelted material from the island (Büttner et al., 2002).
The current model for Surtsey's hydrothermal system hypothesizes that
cooling of dike intrusions in the eruptive centers of the eastern and
western craters (Stefansson et al., 1985) provides the heat to drive
hydrothermal convection, which results in palagonitization of the tephra and
induration of the core of the island (Fig. 3a). The high heat of
vaporization of water means that significant heat transfer occurs
isothermally by release of steam through the tephra pile, as indicated by
the isothermal (100
In recent years the deep biosphere has been shown to be an immense habitat for microbial life, and these findings have wide reaching implications for global geochemical cycling (Orcutt et al., 2011). Although there is increasing exploration of the deep biosphere, mainly due to advances in drilling technologies and underwater equipment, one fundamental environment remains unexplored: the “zero age” upper crust. This province is exceptionally interesting since it is here that the first microbial colonization and interaction with basaltic rocks takes place. Exploration of the microbial colonization of Surtsey tephra could therefore give otherwise unavailable insights into the origins of rock-dwelling microorganisms. The diversity, abundance, and function of potentially endemic communities of microorganisms will be analyzed by DNA extraction and next generation sequencing of metagenomes and 16S rRNA genes. The functioning of the microbiome will be investigated by transcriptomic analysis and strain isolations (Marteinsson et al., 2015).
Assessments of the geochemical composition of hydrothermal seawater, reaction progress associated with water–rock–microbiological interaction and inorganic chemical energy available in the hydrothermal system, will be combined with equilibrium reaction models to describe affinities for chemosynthesis and tephra alteration and provide constraints on the potential energy available for microbial metabolism. The design of the Surtsey subsurface observatory is similar to that of observatories installed during recent IODP expeditions (Fisher et al., 2011; Edwards et al., 2012). After drilling, incubation chambers (e.g., Toner et al., 2013) will be deployed inside slotted sections of the aluminum casing to facilitate further microbial, geochemical and hydrological studies in isolated sections of the drill hole above sea level (< 60–70 m below the surface (mbs) at the drill site), in the highest temperature regime (70–140 mbs), and below the high temperature regime (> 140 mbs) (Fig. 3b). The new studies of potentially indigenous subsurface microbial life in the vertical hole will be the first systematic, longitudinal study of microbial colonization of an isolated neovolcanic island at successive depths from the surface to the seafloor.
The drilling project collaborators and science team, as well as abstracts
describing scientific objectives, are posted at
We thank the ICDP for their generous support of the 2014 workshop and SUSTAIN drilling program. Sveinn Jakobsson, Icelandic Institute of Natural History, Hallgrímur Jónasson, The Icelandic Centre for Research, and Ingvar A. Sigurðsson, South Iceland Institute for Natural History, took part in the workshop and contributed their expertise. Þórdís Bragadóttir, Environment Agency of Iceland, explained regulations on conservation and project permission procedures in Iceland. Edited by: T. Morishita Reviewed by: M. Jutzeler and one anonymous referee