As recently witnessed during the 2010 Eyjafjallajokull eruption in Iceland, interactions between lava and ice can have devastating local and global implications. However, because these eruptions most frequently occur in remote, hard-to-access places, we do not fully understand many of the processes that can produce glaciovolcanic hazards from rapidly melting ice, such as floods and mudflows. In order to better understand the role of lava flow formation during eruptions within and beneath ice, we propose to study one of the products of subglacial eruptions, called 'pillow lavas'. Although pillow lavas are one of the most common types of lavas on the ocean floor, which covers about 70 percent of Earth's surface, their formation beneath ice is relatively unstudied. We are going to work in two areas with exceptionally well-exposed examples of glaciovolcanic pillow lavas in Iceland and British Columbia, Canada. Our work will help other scientists to better understand how heat is transferred from lava to water and ice during glaciovolcanic eruptions, which may lead to better methods for predicting the sizes of floods resulting from lava-ice interactions. Through our research, we will also have a better understanding of how to use pillow lavas from ancient deposits to unravel mysteries related to ice-age global climate. Finally, we hope that our data will also be useful for better understanding of the formation of the Earth's ocean floors, which may be important for future mineral and energy resources.
The main goals of this research are to use pillow lavas covering a range of basaltic compositions for testing hypotheses about the formation of subglacial pillow mounds, including models for lava transport within a growing pillow-dominated volcano and the potential for sudden transitions between explosive versus effusive eruption styles. Specifically we will address the following questions: i) Is the initiation of pillow lava emplacement preceded by an explosive phase? ii) How is lava distributed along and across the ridge structure? iii) What are effusion rates during subglacial, pillow-dominated eruptions? iv) Are multiple eruptive centers active along a fissure segment during a single eruptive episode?
We will pursue answers to these questions by using modern field and analytical techniques to document the three-dimensional structure, stratigraphy and geochemistry of two different pillow ridges with exceptional exposures: (1) open-pit rock quarries along a single fissure segment on the Reykjanes Peninsula in southwestern Iceland and (2) the crest of Pillow Ridge in northern British Columbia. Both locations have similar lithofacies, including a specific stratigraphic sequence of vitric tuff-breccia cut by dikes that feed pillow lava flows emplaced immediately above the tuff-breccias (TDP lithofacies association). We have established a broad-based research team, comprising US, Icelandic and Canadian scientists working in full collaboration with the PIs, to build a comprehensive database of subglacial pillow characteristics for comparison to pillow lavas produced in other environments and potentially to revise existing models for the construction of the pillow-dominated parts of subglacial volcanoes.
