- Email: [email protected]
Introduction to special issue on volcano–ice interactions on Earth and Mars: The state of the science
Journal of Volcanology and Geothermal Research 185 (2009) 247–250
Contents lists available at ScienceDirect
Journal of Volcanology and Geothermal Research j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / j vo l g e o r e s
Editorial
Introduction to special issue on volcano–ice interactions on Earth and Mars: The state of the science
1. Why study volcano–ice interactions? The study of volcano–ice interactions, also referred to as ‘glaciovolcanism’ (e.g., Kelman et al., 2002), has become an important topic of scientific research over the past 30 years, even though its study goes back to the early 1900s (Peacock, 1926; Noe-Nygaard, 1940; Mathews, 1947; van Bemmelen and Rutten, 1955). Four important themes drive this increasing importance: volcano hazard awareness and prevention, the Pleistocene global climate record, potential feedbacks between deglaciation and volcanism, and Martian geoscience research. As awareness, assessment and mitigation of environmental hazards becomes a dominant theme around the world, much attention has focused on hazards associated with snow and icecovered volcanoes (e.g., 2009 eruptions at Nevado del Huila in Columbia and Redoubt volcano in Alaska). The disaster at Nevado del Ruiz in 1985 was a wake-up call for the world community of disaster planners as it demonstrated that even relatively small eruptions at such volcanoes can lead to significant hazards (Major and Newhall, 1989). Such hazards are widespread, occurring at a large number of volcanoes in the North and South American Cordilleras, the northwest Pacific, Iceland and elsewhere. The potential for the sudden generation and release of large quantities of meltwater at snow- and icecovered volcanoes, either as lahars (e.g. Nevado del Ruiz) or jökulhlaups (e.g. Gjálp) is the major concern. Although hazards from volcano–ice/snow interactions are increasingly recognized by emergency planners, especially in Iceland (e.g. Eliasson et al., 2006) and the United States (e.g. Till et al., 1993), awareness and mitigation strategies elsewhere have room for significant improvement. Secondly, volcanoes that have interacted with ice may provide a unique record of changing Pleistocene ice thicknesses, which is invaluable for improving palaeo-climatic reconstructions (e.g. Smellie et al., 2008). One of the chronic problems of glacial geology is providing absolute timing constraints to differentiate periods of terrestrial ice advance and retreat. New glacial advances tend to destroy evidence of previous ones, as many of the depositional units (e.g. till and moraines) are not well preserved in areas of active ice movement. Two exceptions to this are the records preserved by glaciomarine sediments and glaciovolcanic deposits. Marine sediment cores provide a detailed chronology of ocean temperatures over the last 2.5 Ma, but this record is not easily correlated with changes in land-based ice. Products of volcano–ice interactions are increasingly playing a critical role in establishing the terrestrial record for palaeoice conditions. Pioneering work, especially in Antarctica (Smellie et al., 2008), is combining volcanological information on glacier extents and thicknesses with high precision geochronology to map out such 0377-0273/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jvolgeores.2009.06.003
fluctuations. Recent studies of glaciovolcanism in Iceland (McGarvie et al., 2006; Licciardi et al., 2007; Carrivick et al., 2009; Stevenson et al., 2009-this issue; Tuffen and Castro, 2009-this issue) are beginning to yield important new information on the mid-Pleistocene chronology of ice advance and retreat immediately south of the Arctic Circle. In western North America, work is advancing to constrain the pre-LGM positions of the Cordilleran ice sheet (Edwards et al., 2009-this issue) as well as the local effects of ice advances further south on isolated Cascade volcanoes (Lodge and Lescinsky, 2009a,b-this issue). Future work in these areas will provide critical constraints allowing us to better determine how changes in ocean temperatures are translated into changes in terrestrial ice, enabling us to better understand how ice sheets and glaciers respond to global climatic change. Convincing evidence is accumulating to indicate that past changes in the thicknesses of ice sheets have affected the activity of volcanoes beneath them in a variety of volcanic and tectonic settings (e.g. MacIennan et al., 2002; Jellinek et al., 2004; Nowell et al., 2006). The thinning and withdrawal of major ice sheets during the last glacial– interglacial transition ~ 11 ka ago lead to a dramatic acceleration in magma production and eruption in Iceland by a factor of 30 (MacIennan et al., 2002). Sub-ice volcanic activity may impact the stability and mass balance of ice sheets, primarily by facilitating basal sliding due to the production of meltwater and deformable volcanic debris (Blankenship et al., 1993; Bourgeois et al., 1998; Vogel and Tulaczyk, 2006). Positive feedback, where receding ice triggers volcanism that encourages ice recession, may therefore have been important in the past and may be important in the future as ice rapidly thins in volcanic areas such as the West Antarctic Ice Sheet (WAIS), Iceland and the Andes. Indeed, 20th century thinning of Iceland's Vatnajökull icecap may have led to an acceleration in recent volcanism in central Iceland (Pagli and Sigmundsson, 2008). A decrease in planetary albedo due to deposition of dark tephra onto the surface of ice and snow (Wilson and Head, 2009-this issue) may further amplify any positive feedback. Finally, scientists are using information from terrestrial volcano– ice interactions to study our closest planetary neighbour Mars, as many features on Mars are similar to terrestrial glaciovolcanic landforms (Allen, 1979). More recently, increasingly detailed data from Mars has provided further evidence that volcano–ice interactions have been commonplace (Chapman et al., 2000; Smellie, 2009), and areas of volcanically-triggered melting are the most likely niches for Martian life (Cousins et al., 2009). Meanwhile new types of terrestrial glaciovolcanic landform are being documented (e.g. Edwards et al., 2009-this issue; Skilling, 2009-this issue, Tuffen and Castro, 2009-this issue) that may help us to identify more Martian glaciovolcanic deposits.
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2. State of the science Recently researchers interested in volcano–ice interactions have organized under the auspices of the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) to form a Commission on Volcano–Ice Interactions (CVII; http://volcanoes. dickinson.edu/), which is now co-sponsored by the International Association of Cryospheric Sciences (IACS). The aim of the Commission is to facilitate communication among scientists interested in planetary volcano–ice interactions, to sponsor meetings and special sessions, and to otherwise promote the integrated science of glaciovolcanism. This volume is a direct outgrowth of the second “Volcano–Ice Interactions on Earth and Mars” conference, held at the University of British Columbia (UBC) in June 2007, and sponsored in part by IAVCEI, as well as UBC, the University of Pittsburgh, Dickinson College, and Lancaster University. Information forming the basis of most of the papers included in this volume was initially presented at this conference. The importance of this growing science was also highlighted by the attention given to water–ice–volcano interactions at the 2008 IAVCEI general meeting in Reykjavik, Iceland, where 25 percent of the conference was focused on this and related topics. Increasingly, databases are available on the internet to assist researchers and teachers interested in volcano–ice interactions, including the CVII image database (icon.dickinson.edu), the UBC database, and the Lancaster University database. Information and resources on snow and ice-covered volcanoes can also be found on the Nordvolc website and the Alaska Volcano Observatory (www.avo.usgs.gov). 3. Outstanding issues Currently our knowledge of the physics and hydrology of volcano–ice interactions, the feedbacks between glaciovolcanism and changing ice thicknesses, and the impacts of glaciovolcanism on atmospheric and ocean chemistry has significant gaps. The techniques used to reconstruct palaeo-ice thicknesses from glaciovolcanic deposits also require revision and improvement in existing analytical and modeling methods. Fundamental physical questions include: 1) which factors control the explosivity of eruptions (Tuffen et al., 2007; is the ice thickness, subglacial hydrology, eruption rate or magmatic volatile content most important?); 2) whether brittle or ductile ice deformation predominates during eruptions and whether explosive eruptions are capable of shattering thick ice sheets, 3) whether magmatic intrusions can lift ice sheets off the bedrock (Smellie, 2008), 4) how rapidly heat is transferred from magma to ice (Guðmundsson, 2003), and 5) how potentially transient pressure changes over the course of a sub-ice eruption can affect styles of fragmentation and degrees of vesiculation (Höskuldsson et al., 2006). Unresolved issues related to subglacial hydrology include whether distributed or channelized meltwater drainage predominates during eruptions, whether low-pressure cavities develop through connection with the ice margin or surface (Schopka et al., 2006), and whether significant ice-constrained lakes develop during silicic as well as basaltic eruptions. Although we know that recession of large ice sheets can accelerate eruptive activity we do not know whether recession of ice mantling individual stratovolcanoes may have a similar effect, and therefore whether current melting of ice on Andean stratovolcanoes will increase hazards. Whereas increased meltwater fluxes are known to accelerate valley glaciers over daily or seasonal timescales (Bartholomaus et al., 2008), it is not known whether meltwater produced by volcanic activity can affect the velocity of ice sheets, even though it has been speculated that the location of ice streams may be influenced by geothermal and volcanic activity (Blankenship et al., 1993; Bourgeois et al., 1998). The impacts of glaciovolcanism on atmospheric and ocean chemistry are not well known. To date no study has addressed the volatile budget from subglacial eruptions to the atmosphere, even
though numerous papers have discussed the degassing of volatile species. It is not known whether at any point in Earth's history gas emissions from sub-ice eruptions could have significantly affected atmospheric chemistry or climate. Large volumes of meltwater that have interacted chemically with volcanic debris may suddenly be released into lakes or oceans (e.g. Gislasson et al., 2002). However, whether this meltwater input can strongly influence geochemical fluxes or, in turn, biological productivity is presently unknown. Degassing of magmatic volatiles can provide important constraints on the pressure experienced by quenching magma during eruptions and, therefore, the thickness of overlying ice (e.g. Dixon et al., 2002) or the pressure in subglacial cavities (Schopka et al., 2006). This technique relies on accurate measurement of volatile concentrations and on well-established pressure–solubility relationships for a number of volatile species (H2O, CO2, SO2, Cl and F) in different melt compositions, spanning the range of known glaciovolcanic eruptions (e.g. from basanite to rhyolite). To date only the solubility of H2O and CO2 in basaltic and rhyolitic melts is relatively well-constrained and so more experimental work, especially on the pressure-dependence of halogen solubilities, will prove useful for palaeo-environmental reconstructions at glaciovolcanic edifices. Our ability to measure trace quantities of CO2 in volcanic glasses (b30 ppm) must also be improved if we are to use H2O concentrations to accurately estimate quenching pressures, as H2O solubility is extremely sensitive to even small CO2 concentrations (Edwards et al., 2009-this issue). 4. This volume The nine research papers presented in this volume cover volcano– ice interactions at a number of different locations (Iceland, British Columbia, Washington State, Oregon and Mars), and span a wide range of magma compositions (basaltic, intermediate and rhyolitic), and deposit types (effusion-dominated, mixed effusive-fragmental, and fragmentation-dominated). The approaches used include field mapping and description of glaciovolcanic deposits (papers by Edwards et al., 2009-this issue; Lodge and Lescinsky, 2009a-this issue; McGarvie, 2009-this issue; Skilling, 2009-this issue; Stevenson et al., 2009-this issue;Tucker and Scott, 2009-this issue; Tuffen and Castro, 2009-this issue), analogue modeling of ice-contact lavas (Lodge and Lescinsky, 2009b-this issue), field- and geochemicalbased modeling of paleo-ice thickness (Edwards et al., 2009-this issue; Stevenson et al., 2009-this issue; Tuffen and Castro, 2009-this issue), and mathematical modeling of the thermal consequences of ash emplacement on ice (Wilson and Head, 2009-this issue). The entire spectrum of basaltic volcanic products, from effusiondominated pillow lava (Edwards et al., 2009-this issue) and subaerial lava caps (Skilling, 2009-this issue) to ash-dominated eruptions (Wilson and Head, 2009-this issue) are possible during volcano–ice interactions. The products of two contrasting, Pleistocene, basaltic eruptions beneath thick ice are described in papers by Edwards et al. and Skilling. Edwards et al. have studied an englacial tindar formed at the Mount Edziza volcanic complex in British Columbia, which is dominated by pillow lava and surtseyan basaltic breccia. Skilling presents observations from Hlöðufell, a tuya in south-western Iceland whose eruption culminated in the emplacement of a subaerial lava cap. Both eruptions were complex, comprising multiple phases of activity and probably involving significant changes in the amount of meltwater collected at the vent. Edwards et al. use elevations of pillow horizons and dissolved water contents to estimate the palaeo-ice thicknesses during the ~ 900 ka eruption and find them consistent with a substantial regional ice sheet. Skilling argues that some distinctive features in subaqueously-emplaced lavas at Hlöðufell indicate the presence of stoped blocks of ice that were fractured and detached from the ice roof during subglacial phases of the eruption. Wilson and Head (2009-this issue) focus on the consequences of pyroclastic eruption products (airfall ash and PDC deposits) for rates
Editorial
of ice sublimation on Mars. Their modeling is consistent with thick deposits of ash acting to insulate martian ice from sublimation, with important consequences for rates of ice survival at planetary poles and the flanks of stratovolcanoes. Intermediate volcanism is covered by the contributions from Lodge and Lescinsky (2009a,b-this issue) (Kokostick Butte, Or and Mount Rainier, Wa), Stevenson et al. (2009-this issue) (Kerlingafjöll central volcano in central Iceland) and Tucker and Scott (2009-this issue) (Mt Baker, Wa). Lodge and Lescinsky and Tucker and Scott document distinctive fracture patterns in lavas at stratovolcanoes in the western US. Although some of the described fracture patterns have similar characteristics, they also show significant differences that reflect the contrasting emplacement environments (ice-contact versus subaerial to lacustrine). Lodge and Lescinsky use detailed data on fracture orientations and morphologies to assess how flow-related and cooling-related stresses combined to produce the distinctive fracture populations found in ice-contact lavas. The work by Tucker and Scott demonstrates that, because similar fracture types may develop in icecontact and subaerial lava flows (e.g. pseudopillows and columnar joints), information about the flow morphology and geological setting are needed for robust palaeo-environmental reconstructions from lavas alone. In contrast Stevenson et al. describe mostly fragmental lithofacies dominated by vitriclastic tuffs that were formed during explosive, monogenetic intermediate eruptions in Iceland. Their study demonstrates for the first time that andesitic-to-dacitic eruptions may involve significant interactions with meltwater, as previous studies (Mathews, 1951; Kelman et al., 2002) had documented lavadominated glaciovolcanic edifices. The papers by McGarvie and Tuffen and Castro document the wide range of products of evolved, rhyolitic glaciovolcanism in Iceland. Tuffen and Castro document the emplacement of a sub-ice rhyolitic dyke in northern Iceland in exacting detail, and present evidence that the dyke was emplaced in very thin and permeable ice/firn. Their detailed mapping and descriptions of crystallization textures show the textural complexity possible during a relatively simple sub-ice eruption. In contrast, McGarvie presents a broad, comprehensive overview of all rhyolitic glaciovolcanism in Iceland. His descriptions include lava- and tephra-dominated rhyolitic edifices as well as rhyolitic deposits extant on larger stratovolcanoes. Both studies highlight the geochronometric importance of using the evolving subject of glaciovolcanism for palaeo-climatic reconstruction. Common themes that emerge from the contributions are 1) that interactions between volcanoes and overlying ice/snow can produce massive and fragmental deposits with highly distinctive and heterogeneous textures, 2) interpretation of ice thicknesses is at best a complex processes that requires a combination of field- and geochemical-constraints and usually results in constraints on either minimum or maximum ice/snow thicknesses, and 3) the overall importance of studying glaciovolcanism for obtaining detailed records of terrestrial and martian glaciation. References Allen, C.C., 1979. Volcano–ice interactions on Mars. Journal of Geophysical Research 84, 8048–8059. Bartholomaus, T.C., Anderson, R.S., Anderson, S.P., 2008. Glacier sliding response to transient water storage. Nature Geoscience 1, 33–37. Blankenship, D.D., Bell, R.E., Hodge, S.M., Brozena, J.M., Behrendt, J.C., Finn, C.A., 1993. Active volcanism beneath the west Antarctic ice sheet and implications for icesheet stability. Nature 361, 526–529. Bourgeois, O., Dauteuil, O., VanVlietLanoe, B., 1998. Pleistocene subglacial volcanism in Iceland: tectonic implications. Earth and Planetary Science Letters 164, 165–178. Carrivick, J.L., Russell, A.J., Rushmer, E.L., Tweed, F.S., Marren, P.M., Deeming, H., Lowe, O.J., 2009. Geomorphological evidence towards a deglacial control on volcanism. Earth Surface Processes and Landforms 34, 1164–1178. doi:10.1002/esp.1811. Chapman, M.G., Allen, C.C., Guðmundsson, M.T., Gulick, V.C., Jakobsson, S.P., Lucitta, B.K., Skilling, I.P., Waitt, R.B., 2000. Volcanism and ice interactions on Earth and Mars. In: Zimbelman, J.R., Gregg, T.K.P. (Eds.), Environmental Effects on Volcanic Eruptions. InNew York, Kluwer Academic/Plenum Publishers, pp. 39–74.
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Cousins, C.R., Ward, J.D., Crawford, I.A., Towner, M.C., Jones, A.P., 2009. Life in subglacial lavas as an analogue for life on Mars. 19th Annual V. M. Goldschmidt Conference, Davos, Switzerland, Abstract 945. Dixon, J.E., Filiberto, J.R., Moore, J.G., Hickson, C.J., 2002. Volatiles in basaltic glasses from a subglacial volcano in northern British Columbia (Canada): implications for ice sheet thickness and mantle volatiles. Volcano–Ice Interaction on Earth and Mars: In: Smellie, J.L., Chapman, M.G. (Eds.), Geological Society, London, Special Publications, vol. 202, pp. 255–271. Edwards, B.R., Skilling, I.P., Cameron, B., Lloyd, A., Haynes, C., Hungerford, J.H.D., 2009. Evolution of an englacial volcanic ridge: Pillow Ridge tindar, Mount Edziza volcanic complex, NCVP, British Columbia, Canada. Journal of Volcanology and Geothermal Research 185, 251–275 (this issue). Eliasson, J., Larsen, G., Gudmundsson, M.T., Sigmundsson, F., 2006. Probabilistic model for eruptions and associated floods events in the Katla caldera, Iceland. Computational Geosciences 10, 179–200. Gislasson, S.R., Snorrason, A., Kristmannsdottir, H.K., Sveinbjornsdottir, A.E., Torsander, P., Olafsson, J., Castet, S., Dupre, B., 2002. Effects of volcanic eruptions on the CO2 content of the atmosphere and the oceans: the 1996 eruption and flood within the Vatnajokull Glacier, Iceland. Chemical Geology 190, 181–205. Guðmundsson, M.T., 2003. Melting of ice by magma–water interactions during subglacial eruptions as an indicator of heat transfer in subaqueous eruptions. In Explosive Subaqueous Volcanism. Geophysical Monograph 140, 61–72. Höskuldsson, A., Sparks, R.S.J., Carroll, M.R., 2006. Constraints on the dynamics of subglacial basalt eruptions from geological and geochemical observations at Kverkfjoll, NEIceland. Bulletin of Volcanology 68, 689–701. doi:10.1007/s00445-005-0043-4. Jellinek, A.M., Manga, M, Saar, M.O., 2004. Did melting glaciers cause volcanic eruptions in eastern California? Probing the mechanics of dike formation. Journal of Geophysical Research 109, B09206. doi:10.1029/2004JB002978. Kelman, M.C., Russell, J.K., Hickson, C.H., 2002. Effusive intermediate glaciovolcanism in the Garibaldi volcanic belt, southwestern British Columbia, Canada. Volcano–Ice Interaction on Earth and Mars: In: Smellie, J.L., Chapman, M.G. (Eds.), Geological Society, London, Special Publications, vol. 202, pp. 195–212. Licciardi, J.M., Kurz, M.D., Curtice, J.M., 2007. Glacial and volcanic history of Icelandic table mountains from cosmogenic 3He exposure ages. Quaternary Science Reviews 26, 1529–1546. Lodge, R.W.D, Lescinsky, D.T., 2009a. Fracture patterns at lava–ice contacts on Kokostick Butte, OR, and Mazama Ridge, Mount Rainier, WA: implications for flow emplacement and cooling histories. Journal of Volcanology and Geothermal Research 185, 298–310 (this issue). Lodge, R.W.D., Lescinsky, D.T., 2009b. Anisotropic stress accumulation in cooling lava flows and resulting fracture patterns: Insights from starch–water desiccation experiment. Journal of Volcanology and Geothermal Research 185, 323–336 (this issue). MacIennan, J., Jull, M., McKenzie, D., Slater, L., Gronvold, K., 2002. The link between volcanism and deglaciation in Iceland. Geochem Geophys Geosyst 3. doi:10.1029/ 2001GC000282. Major, J.J., Newhall, C.G., 1989. Snow and ice perturbation during historical volcanic eruptions and the formation of lahars and floods. Bulletin of Volcanology 52, 1–27. Mathews, W.H., 1947. “Tuyas,” flat-topped volcanoes in northern BC. American Journal of Science 245, 560–570. Mathews, W.H., 1951. The Table, a flat-topped volcano in southern BC. American Journal of Science 249, 830–841. McGarvie, D.W., 2009. Rhyolitic volcano-ice interactions in Iceland. Journal of Volcanology and Geothermal Research 185, 367–389 (this issue). McGarvie, D.W., Burgess, R., Tindle, A.J., Tuffen, H., Stevenson, J.A., 2006. Pleistocene rhyolitic volcanism at the Torfajökull central volcano, Iceland: eruption ages, glaciovolcanism, and geochemical evolution. Jökull 56, 57–75. Noe-Nygaard, A., 1940. Subglacial volcanic activity in ancient and recent times: Folia Geographica Danica, v. 1, no. 2, K. Dansk. Geog. Selsk. Nowell, D.A.G., Jones, M.C., Pyle, D.M., 2006. Episodic Quaternary volcanism in France and Germany. Journal of Quaternary Science 21, 645–675. Pagli, C., Sigmundsson, F., 2008. Will present day glacier retreat increase volcanic activity? Stress induced by recent glacier retreat and its effect on magmatism at the Vatnajokull ice cap, Iceland. Geophysical Research Letters 35. doi:10.1029/ 2008GL033510. Peacock, M.A., 1926. The geology of Vijey, southwest iceland: a record of igneous activity in glacial times. Transactions of the Royal Society of Edinburgh 54, 441–465. Schopka, H., Gudmundsson, M.T., Tuffen, H., 2006. The formation of Helgafell, southwest Iceland, a monogenetic subglacial hyaloclastite ridge: sedimentology, hydrology and volcano–ice interaction. Journal of Volcanology and Geothermal Research 152, 359–377. doi:10.1016/j.jvolgeores.2005.11.010. Skilling, I.P., 2009. Subglacial to emergent basaltic volcanism at Hlöðufell, South-west Iceland: A history of ice-confinement. Journal of Volcanology and Geothermal Research 185, 276–289 (this issue). Smellie, J.L., 2008. Basaltic subglacial sheet-like sequences: evidence for two types with different implications for the inferred thickness of associated ice. Earth Science Reviews 88, 60–88. Smellie, J.L., 2009. Terrestrial sub-ice volcanism: landform morphology, sequence characteristics and environmental influences, and implications for candidate Mars examples. Special Paper — Geological Society of America 453, 55–76. Smellie, J.L., Johnson, J.S., McIntosh, W.C., et al., 2008. Six million years of glacial history recorded in volcanic lithofacies of the James Ross Island Volcanic Group, Antarctic Peninsula. Palaeogeography Palaeoclimatology Palaeoecology 260, 122–148. Stevenson, J.A., Smellie, J.S., McGarvie, D.W., Gilbert, J.S., Cameron, B.I, 2009. Subglacial intermediate volcanism at Kerlingarfjöll, Iceland: Magma–water interactions beneath thick ice. Journal of Volcanology and Geothermal Research 185, 337–351 (this issue).
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Till, A.B., Yount, M.E., Riehle, J.R., 1993. Redoubt Volcano, Southern Alaska: A Hazard Assessment Based on Eruptive Activity Through 1968. U.S. Geological Survey Bulletin, 1996. Washington, USA. Tucker, D.S., Scott, K.M., 2009. Structures and facies associated with the flow of subaerial basaltic lava into a deep freshwater lake: The Sulphur Creek lava flow, North Cascades, Washington. Journal of Volcanology and Geothermal Research 185, 311–322 (this issue). Tuffen, H., Castro, J.M., 2009. The emplacement of an obsidian dyke through thin ice: Hrafntinnuhryggur, Krafla Iceland. Journal of Volcanology and Geothermal Research 185, 352–366 (this issue). H.Tuffen, H., J.S.Gilbert, J.S., D.W.McGarvie, D.W., 2007. Will subglacial rhyolite eruptions be explosive or intrusive? Some insights from analytical models. Annals of Glaciology 45, 87–94. Vogel, S.W., Tulaczyk, S., 2006. Ice-dynamical constraints on the existence and impact of subglacial volcanism on West Antarctic ice sheet stability. Geophysical Research Letters 33, L23502. doi:10.1029/2006GL027345. Wilson, L., Head, J.W., 2009. Tephra deposition on glaciers and ice sheets on Mars: influence on ice survival, debris content and flow behavior. Journal of Volcanology and Geothermal Research 185, 290–297 (this issue). R.W.van Bemmelen, R.W., M.G.Rutten, M.G., 1955. Tablemountains of Northern Iceland. E.J. Brill, Leiden. 217 pp.
Benjamin R. Edwards Department of Geology, Dickinson College, 5 North Orange Street, Carlisle, PA, 17013, USA Corresponding author. E-mail address: [email protected].
Hugh Tuffen Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ , UK Ian P. Skilling Department of Geology and Planetary Science, 200 SRCC Building, University of Pittsburgh, Pittsburgh, PA, 15260, USA Lionel Wilson Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ , UK 9 June 2009
Contents lists available at ScienceDirect
Journal of Volcanology and Geothermal Research j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / j vo l g e o r e s
Editorial
Introduction to special issue on volcano–ice interactions on Earth and Mars: The state of the science
1. Why study volcano–ice interactions? The study of volcano–ice interactions, also referred to as ‘glaciovolcanism’ (e.g., Kelman et al., 2002), has become an important topic of scientific research over the past 30 years, even though its study goes back to the early 1900s (Peacock, 1926; Noe-Nygaard, 1940; Mathews, 1947; van Bemmelen and Rutten, 1955). Four important themes drive this increasing importance: volcano hazard awareness and prevention, the Pleistocene global climate record, potential feedbacks between deglaciation and volcanism, and Martian geoscience research. As awareness, assessment and mitigation of environmental hazards becomes a dominant theme around the world, much attention has focused on hazards associated with snow and icecovered volcanoes (e.g., 2009 eruptions at Nevado del Huila in Columbia and Redoubt volcano in Alaska). The disaster at Nevado del Ruiz in 1985 was a wake-up call for the world community of disaster planners as it demonstrated that even relatively small eruptions at such volcanoes can lead to significant hazards (Major and Newhall, 1989). Such hazards are widespread, occurring at a large number of volcanoes in the North and South American Cordilleras, the northwest Pacific, Iceland and elsewhere. The potential for the sudden generation and release of large quantities of meltwater at snow- and icecovered volcanoes, either as lahars (e.g. Nevado del Ruiz) or jökulhlaups (e.g. Gjálp) is the major concern. Although hazards from volcano–ice/snow interactions are increasingly recognized by emergency planners, especially in Iceland (e.g. Eliasson et al., 2006) and the United States (e.g. Till et al., 1993), awareness and mitigation strategies elsewhere have room for significant improvement. Secondly, volcanoes that have interacted with ice may provide a unique record of changing Pleistocene ice thicknesses, which is invaluable for improving palaeo-climatic reconstructions (e.g. Smellie et al., 2008). One of the chronic problems of glacial geology is providing absolute timing constraints to differentiate periods of terrestrial ice advance and retreat. New glacial advances tend to destroy evidence of previous ones, as many of the depositional units (e.g. till and moraines) are not well preserved in areas of active ice movement. Two exceptions to this are the records preserved by glaciomarine sediments and glaciovolcanic deposits. Marine sediment cores provide a detailed chronology of ocean temperatures over the last 2.5 Ma, but this record is not easily correlated with changes in land-based ice. Products of volcano–ice interactions are increasingly playing a critical role in establishing the terrestrial record for palaeoice conditions. Pioneering work, especially in Antarctica (Smellie et al., 2008), is combining volcanological information on glacier extents and thicknesses with high precision geochronology to map out such 0377-0273/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jvolgeores.2009.06.003
fluctuations. Recent studies of glaciovolcanism in Iceland (McGarvie et al., 2006; Licciardi et al., 2007; Carrivick et al., 2009; Stevenson et al., 2009-this issue; Tuffen and Castro, 2009-this issue) are beginning to yield important new information on the mid-Pleistocene chronology of ice advance and retreat immediately south of the Arctic Circle. In western North America, work is advancing to constrain the pre-LGM positions of the Cordilleran ice sheet (Edwards et al., 2009-this issue) as well as the local effects of ice advances further south on isolated Cascade volcanoes (Lodge and Lescinsky, 2009a,b-this issue). Future work in these areas will provide critical constraints allowing us to better determine how changes in ocean temperatures are translated into changes in terrestrial ice, enabling us to better understand how ice sheets and glaciers respond to global climatic change. Convincing evidence is accumulating to indicate that past changes in the thicknesses of ice sheets have affected the activity of volcanoes beneath them in a variety of volcanic and tectonic settings (e.g. MacIennan et al., 2002; Jellinek et al., 2004; Nowell et al., 2006). The thinning and withdrawal of major ice sheets during the last glacial– interglacial transition ~ 11 ka ago lead to a dramatic acceleration in magma production and eruption in Iceland by a factor of 30 (MacIennan et al., 2002). Sub-ice volcanic activity may impact the stability and mass balance of ice sheets, primarily by facilitating basal sliding due to the production of meltwater and deformable volcanic debris (Blankenship et al., 1993; Bourgeois et al., 1998; Vogel and Tulaczyk, 2006). Positive feedback, where receding ice triggers volcanism that encourages ice recession, may therefore have been important in the past and may be important in the future as ice rapidly thins in volcanic areas such as the West Antarctic Ice Sheet (WAIS), Iceland and the Andes. Indeed, 20th century thinning of Iceland's Vatnajökull icecap may have led to an acceleration in recent volcanism in central Iceland (Pagli and Sigmundsson, 2008). A decrease in planetary albedo due to deposition of dark tephra onto the surface of ice and snow (Wilson and Head, 2009-this issue) may further amplify any positive feedback. Finally, scientists are using information from terrestrial volcano– ice interactions to study our closest planetary neighbour Mars, as many features on Mars are similar to terrestrial glaciovolcanic landforms (Allen, 1979). More recently, increasingly detailed data from Mars has provided further evidence that volcano–ice interactions have been commonplace (Chapman et al., 2000; Smellie, 2009), and areas of volcanically-triggered melting are the most likely niches for Martian life (Cousins et al., 2009). Meanwhile new types of terrestrial glaciovolcanic landform are being documented (e.g. Edwards et al., 2009-this issue; Skilling, 2009-this issue, Tuffen and Castro, 2009-this issue) that may help us to identify more Martian glaciovolcanic deposits.
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2. State of the science Recently researchers interested in volcano–ice interactions have organized under the auspices of the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) to form a Commission on Volcano–Ice Interactions (CVII; http://volcanoes. dickinson.edu/), which is now co-sponsored by the International Association of Cryospheric Sciences (IACS). The aim of the Commission is to facilitate communication among scientists interested in planetary volcano–ice interactions, to sponsor meetings and special sessions, and to otherwise promote the integrated science of glaciovolcanism. This volume is a direct outgrowth of the second “Volcano–Ice Interactions on Earth and Mars” conference, held at the University of British Columbia (UBC) in June 2007, and sponsored in part by IAVCEI, as well as UBC, the University of Pittsburgh, Dickinson College, and Lancaster University. Information forming the basis of most of the papers included in this volume was initially presented at this conference. The importance of this growing science was also highlighted by the attention given to water–ice–volcano interactions at the 2008 IAVCEI general meeting in Reykjavik, Iceland, where 25 percent of the conference was focused on this and related topics. Increasingly, databases are available on the internet to assist researchers and teachers interested in volcano–ice interactions, including the CVII image database (icon.dickinson.edu), the UBC database, and the Lancaster University database. Information and resources on snow and ice-covered volcanoes can also be found on the Nordvolc website and the Alaska Volcano Observatory (www.avo.usgs.gov). 3. Outstanding issues Currently our knowledge of the physics and hydrology of volcano–ice interactions, the feedbacks between glaciovolcanism and changing ice thicknesses, and the impacts of glaciovolcanism on atmospheric and ocean chemistry has significant gaps. The techniques used to reconstruct palaeo-ice thicknesses from glaciovolcanic deposits also require revision and improvement in existing analytical and modeling methods. Fundamental physical questions include: 1) which factors control the explosivity of eruptions (Tuffen et al., 2007; is the ice thickness, subglacial hydrology, eruption rate or magmatic volatile content most important?); 2) whether brittle or ductile ice deformation predominates during eruptions and whether explosive eruptions are capable of shattering thick ice sheets, 3) whether magmatic intrusions can lift ice sheets off the bedrock (Smellie, 2008), 4) how rapidly heat is transferred from magma to ice (Guðmundsson, 2003), and 5) how potentially transient pressure changes over the course of a sub-ice eruption can affect styles of fragmentation and degrees of vesiculation (Höskuldsson et al., 2006). Unresolved issues related to subglacial hydrology include whether distributed or channelized meltwater drainage predominates during eruptions, whether low-pressure cavities develop through connection with the ice margin or surface (Schopka et al., 2006), and whether significant ice-constrained lakes develop during silicic as well as basaltic eruptions. Although we know that recession of large ice sheets can accelerate eruptive activity we do not know whether recession of ice mantling individual stratovolcanoes may have a similar effect, and therefore whether current melting of ice on Andean stratovolcanoes will increase hazards. Whereas increased meltwater fluxes are known to accelerate valley glaciers over daily or seasonal timescales (Bartholomaus et al., 2008), it is not known whether meltwater produced by volcanic activity can affect the velocity of ice sheets, even though it has been speculated that the location of ice streams may be influenced by geothermal and volcanic activity (Blankenship et al., 1993; Bourgeois et al., 1998). The impacts of glaciovolcanism on atmospheric and ocean chemistry are not well known. To date no study has addressed the volatile budget from subglacial eruptions to the atmosphere, even
though numerous papers have discussed the degassing of volatile species. It is not known whether at any point in Earth's history gas emissions from sub-ice eruptions could have significantly affected atmospheric chemistry or climate. Large volumes of meltwater that have interacted chemically with volcanic debris may suddenly be released into lakes or oceans (e.g. Gislasson et al., 2002). However, whether this meltwater input can strongly influence geochemical fluxes or, in turn, biological productivity is presently unknown. Degassing of magmatic volatiles can provide important constraints on the pressure experienced by quenching magma during eruptions and, therefore, the thickness of overlying ice (e.g. Dixon et al., 2002) or the pressure in subglacial cavities (Schopka et al., 2006). This technique relies on accurate measurement of volatile concentrations and on well-established pressure–solubility relationships for a number of volatile species (H2O, CO2, SO2, Cl and F) in different melt compositions, spanning the range of known glaciovolcanic eruptions (e.g. from basanite to rhyolite). To date only the solubility of H2O and CO2 in basaltic and rhyolitic melts is relatively well-constrained and so more experimental work, especially on the pressure-dependence of halogen solubilities, will prove useful for palaeo-environmental reconstructions at glaciovolcanic edifices. Our ability to measure trace quantities of CO2 in volcanic glasses (b30 ppm) must also be improved if we are to use H2O concentrations to accurately estimate quenching pressures, as H2O solubility is extremely sensitive to even small CO2 concentrations (Edwards et al., 2009-this issue). 4. This volume The nine research papers presented in this volume cover volcano– ice interactions at a number of different locations (Iceland, British Columbia, Washington State, Oregon and Mars), and span a wide range of magma compositions (basaltic, intermediate and rhyolitic), and deposit types (effusion-dominated, mixed effusive-fragmental, and fragmentation-dominated). The approaches used include field mapping and description of glaciovolcanic deposits (papers by Edwards et al., 2009-this issue; Lodge and Lescinsky, 2009a-this issue; McGarvie, 2009-this issue; Skilling, 2009-this issue; Stevenson et al., 2009-this issue;Tucker and Scott, 2009-this issue; Tuffen and Castro, 2009-this issue), analogue modeling of ice-contact lavas (Lodge and Lescinsky, 2009b-this issue), field- and geochemicalbased modeling of paleo-ice thickness (Edwards et al., 2009-this issue; Stevenson et al., 2009-this issue; Tuffen and Castro, 2009-this issue), and mathematical modeling of the thermal consequences of ash emplacement on ice (Wilson and Head, 2009-this issue). The entire spectrum of basaltic volcanic products, from effusiondominated pillow lava (Edwards et al., 2009-this issue) and subaerial lava caps (Skilling, 2009-this issue) to ash-dominated eruptions (Wilson and Head, 2009-this issue) are possible during volcano–ice interactions. The products of two contrasting, Pleistocene, basaltic eruptions beneath thick ice are described in papers by Edwards et al. and Skilling. Edwards et al. have studied an englacial tindar formed at the Mount Edziza volcanic complex in British Columbia, which is dominated by pillow lava and surtseyan basaltic breccia. Skilling presents observations from Hlöðufell, a tuya in south-western Iceland whose eruption culminated in the emplacement of a subaerial lava cap. Both eruptions were complex, comprising multiple phases of activity and probably involving significant changes in the amount of meltwater collected at the vent. Edwards et al. use elevations of pillow horizons and dissolved water contents to estimate the palaeo-ice thicknesses during the ~ 900 ka eruption and find them consistent with a substantial regional ice sheet. Skilling argues that some distinctive features in subaqueously-emplaced lavas at Hlöðufell indicate the presence of stoped blocks of ice that were fractured and detached from the ice roof during subglacial phases of the eruption. Wilson and Head (2009-this issue) focus on the consequences of pyroclastic eruption products (airfall ash and PDC deposits) for rates
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of ice sublimation on Mars. Their modeling is consistent with thick deposits of ash acting to insulate martian ice from sublimation, with important consequences for rates of ice survival at planetary poles and the flanks of stratovolcanoes. Intermediate volcanism is covered by the contributions from Lodge and Lescinsky (2009a,b-this issue) (Kokostick Butte, Or and Mount Rainier, Wa), Stevenson et al. (2009-this issue) (Kerlingafjöll central volcano in central Iceland) and Tucker and Scott (2009-this issue) (Mt Baker, Wa). Lodge and Lescinsky and Tucker and Scott document distinctive fracture patterns in lavas at stratovolcanoes in the western US. Although some of the described fracture patterns have similar characteristics, they also show significant differences that reflect the contrasting emplacement environments (ice-contact versus subaerial to lacustrine). Lodge and Lescinsky use detailed data on fracture orientations and morphologies to assess how flow-related and cooling-related stresses combined to produce the distinctive fracture populations found in ice-contact lavas. The work by Tucker and Scott demonstrates that, because similar fracture types may develop in icecontact and subaerial lava flows (e.g. pseudopillows and columnar joints), information about the flow morphology and geological setting are needed for robust palaeo-environmental reconstructions from lavas alone. In contrast Stevenson et al. describe mostly fragmental lithofacies dominated by vitriclastic tuffs that were formed during explosive, monogenetic intermediate eruptions in Iceland. Their study demonstrates for the first time that andesitic-to-dacitic eruptions may involve significant interactions with meltwater, as previous studies (Mathews, 1951; Kelman et al., 2002) had documented lavadominated glaciovolcanic edifices. The papers by McGarvie and Tuffen and Castro document the wide range of products of evolved, rhyolitic glaciovolcanism in Iceland. Tuffen and Castro document the emplacement of a sub-ice rhyolitic dyke in northern Iceland in exacting detail, and present evidence that the dyke was emplaced in very thin and permeable ice/firn. Their detailed mapping and descriptions of crystallization textures show the textural complexity possible during a relatively simple sub-ice eruption. In contrast, McGarvie presents a broad, comprehensive overview of all rhyolitic glaciovolcanism in Iceland. His descriptions include lava- and tephra-dominated rhyolitic edifices as well as rhyolitic deposits extant on larger stratovolcanoes. Both studies highlight the geochronometric importance of using the evolving subject of glaciovolcanism for palaeo-climatic reconstruction. Common themes that emerge from the contributions are 1) that interactions between volcanoes and overlying ice/snow can produce massive and fragmental deposits with highly distinctive and heterogeneous textures, 2) interpretation of ice thicknesses is at best a complex processes that requires a combination of field- and geochemical-constraints and usually results in constraints on either minimum or maximum ice/snow thicknesses, and 3) the overall importance of studying glaciovolcanism for obtaining detailed records of terrestrial and martian glaciation. References Allen, C.C., 1979. Volcano–ice interactions on Mars. Journal of Geophysical Research 84, 8048–8059. Bartholomaus, T.C., Anderson, R.S., Anderson, S.P., 2008. Glacier sliding response to transient water storage. Nature Geoscience 1, 33–37. Blankenship, D.D., Bell, R.E., Hodge, S.M., Brozena, J.M., Behrendt, J.C., Finn, C.A., 1993. Active volcanism beneath the west Antarctic ice sheet and implications for icesheet stability. Nature 361, 526–529. Bourgeois, O., Dauteuil, O., VanVlietLanoe, B., 1998. Pleistocene subglacial volcanism in Iceland: tectonic implications. Earth and Planetary Science Letters 164, 165–178. Carrivick, J.L., Russell, A.J., Rushmer, E.L., Tweed, F.S., Marren, P.M., Deeming, H., Lowe, O.J., 2009. Geomorphological evidence towards a deglacial control on volcanism. Earth Surface Processes and Landforms 34, 1164–1178. doi:10.1002/esp.1811. Chapman, M.G., Allen, C.C., Guðmundsson, M.T., Gulick, V.C., Jakobsson, S.P., Lucitta, B.K., Skilling, I.P., Waitt, R.B., 2000. Volcanism and ice interactions on Earth and Mars. In: Zimbelman, J.R., Gregg, T.K.P. (Eds.), Environmental Effects on Volcanic Eruptions. InNew York, Kluwer Academic/Plenum Publishers, pp. 39–74.
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Cousins, C.R., Ward, J.D., Crawford, I.A., Towner, M.C., Jones, A.P., 2009. Life in subglacial lavas as an analogue for life on Mars. 19th Annual V. M. Goldschmidt Conference, Davos, Switzerland, Abstract 945. Dixon, J.E., Filiberto, J.R., Moore, J.G., Hickson, C.J., 2002. Volatiles in basaltic glasses from a subglacial volcano in northern British Columbia (Canada): implications for ice sheet thickness and mantle volatiles. Volcano–Ice Interaction on Earth and Mars: In: Smellie, J.L., Chapman, M.G. (Eds.), Geological Society, London, Special Publications, vol. 202, pp. 255–271. Edwards, B.R., Skilling, I.P., Cameron, B., Lloyd, A., Haynes, C., Hungerford, J.H.D., 2009. Evolution of an englacial volcanic ridge: Pillow Ridge tindar, Mount Edziza volcanic complex, NCVP, British Columbia, Canada. Journal of Volcanology and Geothermal Research 185, 251–275 (this issue). Eliasson, J., Larsen, G., Gudmundsson, M.T., Sigmundsson, F., 2006. Probabilistic model for eruptions and associated floods events in the Katla caldera, Iceland. Computational Geosciences 10, 179–200. Gislasson, S.R., Snorrason, A., Kristmannsdottir, H.K., Sveinbjornsdottir, A.E., Torsander, P., Olafsson, J., Castet, S., Dupre, B., 2002. Effects of volcanic eruptions on the CO2 content of the atmosphere and the oceans: the 1996 eruption and flood within the Vatnajokull Glacier, Iceland. Chemical Geology 190, 181–205. Guðmundsson, M.T., 2003. Melting of ice by magma–water interactions during subglacial eruptions as an indicator of heat transfer in subaqueous eruptions. In Explosive Subaqueous Volcanism. Geophysical Monograph 140, 61–72. Höskuldsson, A., Sparks, R.S.J., Carroll, M.R., 2006. Constraints on the dynamics of subglacial basalt eruptions from geological and geochemical observations at Kverkfjoll, NEIceland. Bulletin of Volcanology 68, 689–701. doi:10.1007/s00445-005-0043-4. Jellinek, A.M., Manga, M, Saar, M.O., 2004. Did melting glaciers cause volcanic eruptions in eastern California? Probing the mechanics of dike formation. Journal of Geophysical Research 109, B09206. doi:10.1029/2004JB002978. Kelman, M.C., Russell, J.K., Hickson, C.H., 2002. Effusive intermediate glaciovolcanism in the Garibaldi volcanic belt, southwestern British Columbia, Canada. Volcano–Ice Interaction on Earth and Mars: In: Smellie, J.L., Chapman, M.G. (Eds.), Geological Society, London, Special Publications, vol. 202, pp. 195–212. Licciardi, J.M., Kurz, M.D., Curtice, J.M., 2007. Glacial and volcanic history of Icelandic table mountains from cosmogenic 3He exposure ages. Quaternary Science Reviews 26, 1529–1546. Lodge, R.W.D, Lescinsky, D.T., 2009a. Fracture patterns at lava–ice contacts on Kokostick Butte, OR, and Mazama Ridge, Mount Rainier, WA: implications for flow emplacement and cooling histories. Journal of Volcanology and Geothermal Research 185, 298–310 (this issue). Lodge, R.W.D., Lescinsky, D.T., 2009b. Anisotropic stress accumulation in cooling lava flows and resulting fracture patterns: Insights from starch–water desiccation experiment. Journal of Volcanology and Geothermal Research 185, 323–336 (this issue). MacIennan, J., Jull, M., McKenzie, D., Slater, L., Gronvold, K., 2002. The link between volcanism and deglaciation in Iceland. Geochem Geophys Geosyst 3. doi:10.1029/ 2001GC000282. Major, J.J., Newhall, C.G., 1989. Snow and ice perturbation during historical volcanic eruptions and the formation of lahars and floods. Bulletin of Volcanology 52, 1–27. Mathews, W.H., 1947. “Tuyas,” flat-topped volcanoes in northern BC. American Journal of Science 245, 560–570. Mathews, W.H., 1951. The Table, a flat-topped volcano in southern BC. American Journal of Science 249, 830–841. McGarvie, D.W., 2009. Rhyolitic volcano-ice interactions in Iceland. Journal of Volcanology and Geothermal Research 185, 367–389 (this issue). McGarvie, D.W., Burgess, R., Tindle, A.J., Tuffen, H., Stevenson, J.A., 2006. Pleistocene rhyolitic volcanism at the Torfajökull central volcano, Iceland: eruption ages, glaciovolcanism, and geochemical evolution. Jökull 56, 57–75. Noe-Nygaard, A., 1940. Subglacial volcanic activity in ancient and recent times: Folia Geographica Danica, v. 1, no. 2, K. Dansk. Geog. Selsk. Nowell, D.A.G., Jones, M.C., Pyle, D.M., 2006. Episodic Quaternary volcanism in France and Germany. Journal of Quaternary Science 21, 645–675. Pagli, C., Sigmundsson, F., 2008. Will present day glacier retreat increase volcanic activity? Stress induced by recent glacier retreat and its effect on magmatism at the Vatnajokull ice cap, Iceland. Geophysical Research Letters 35. doi:10.1029/ 2008GL033510. Peacock, M.A., 1926. The geology of Vijey, southwest iceland: a record of igneous activity in glacial times. Transactions of the Royal Society of Edinburgh 54, 441–465. Schopka, H., Gudmundsson, M.T., Tuffen, H., 2006. The formation of Helgafell, southwest Iceland, a monogenetic subglacial hyaloclastite ridge: sedimentology, hydrology and volcano–ice interaction. Journal of Volcanology and Geothermal Research 152, 359–377. doi:10.1016/j.jvolgeores.2005.11.010. Skilling, I.P., 2009. Subglacial to emergent basaltic volcanism at Hlöðufell, South-west Iceland: A history of ice-confinement. Journal of Volcanology and Geothermal Research 185, 276–289 (this issue). Smellie, J.L., 2008. Basaltic subglacial sheet-like sequences: evidence for two types with different implications for the inferred thickness of associated ice. Earth Science Reviews 88, 60–88. Smellie, J.L., 2009. Terrestrial sub-ice volcanism: landform morphology, sequence characteristics and environmental influences, and implications for candidate Mars examples. Special Paper — Geological Society of America 453, 55–76. Smellie, J.L., Johnson, J.S., McIntosh, W.C., et al., 2008. Six million years of glacial history recorded in volcanic lithofacies of the James Ross Island Volcanic Group, Antarctic Peninsula. Palaeogeography Palaeoclimatology Palaeoecology 260, 122–148. Stevenson, J.A., Smellie, J.S., McGarvie, D.W., Gilbert, J.S., Cameron, B.I, 2009. Subglacial intermediate volcanism at Kerlingarfjöll, Iceland: Magma–water interactions beneath thick ice. Journal of Volcanology and Geothermal Research 185, 337–351 (this issue).
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Till, A.B., Yount, M.E., Riehle, J.R., 1993. Redoubt Volcano, Southern Alaska: A Hazard Assessment Based on Eruptive Activity Through 1968. U.S. Geological Survey Bulletin, 1996. Washington, USA. Tucker, D.S., Scott, K.M., 2009. Structures and facies associated with the flow of subaerial basaltic lava into a deep freshwater lake: The Sulphur Creek lava flow, North Cascades, Washington. Journal of Volcanology and Geothermal Research 185, 311–322 (this issue). Tuffen, H., Castro, J.M., 2009. The emplacement of an obsidian dyke through thin ice: Hrafntinnuhryggur, Krafla Iceland. Journal of Volcanology and Geothermal Research 185, 352–366 (this issue). H.Tuffen, H., J.S.Gilbert, J.S., D.W.McGarvie, D.W., 2007. Will subglacial rhyolite eruptions be explosive or intrusive? Some insights from analytical models. Annals of Glaciology 45, 87–94. Vogel, S.W., Tulaczyk, S., 2006. Ice-dynamical constraints on the existence and impact of subglacial volcanism on West Antarctic ice sheet stability. Geophysical Research Letters 33, L23502. doi:10.1029/2006GL027345. Wilson, L., Head, J.W., 2009. Tephra deposition on glaciers and ice sheets on Mars: influence on ice survival, debris content and flow behavior. Journal of Volcanology and Geothermal Research 185, 290–297 (this issue). R.W.van Bemmelen, R.W., M.G.Rutten, M.G., 1955. Tablemountains of Northern Iceland. E.J. Brill, Leiden. 217 pp.
Benjamin R. Edwards Department of Geology, Dickinson College, 5 North Orange Street, Carlisle, PA, 17013, USA Corresponding author. E-mail address: [email protected].
Hugh Tuffen Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ , UK Ian P. Skilling Department of Geology and Planetary Science, 200 SRCC Building, University of Pittsburgh, Pittsburgh, PA, 15260, USA Lionel Wilson Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ , UK 9 June 2009