AGU Fall Meeting 2013, San Francisco, USA
1LDEO; 2University of Alaska, Fairbanks; 3USGS; 4University of Wyoming; 5University of Wisconsin; 6University of South Carolina
Aleutian-MW-AGU2013A Mini-Workshop, with support from GeoPRISMS, was organized to explore options for shared logistical support for NSF funded research in the Aleutian volcanic arc, which is part of the GeoPRISMS Alaska Focus Area. The goal is to reduce the logistical costs per project in order to enable a larger group of investigators to benefit from the opportunity that the GeoPRISMS focus is intended to foster. The workshop was held in the Fillmore ABC meeting rooms, in the Grand Hyatt San Francisco Hotel on Sunday, December 8, 2013 from 12:40 to 6:00 PM.
Despite inclement weather across North America, which prevented some registrants from attending, there were more than 90 participants from more than 60 universities and research organizations, mostly in the US.
The workshop began with a series of very short “Keynote” talks – mostly 10 minutes long, with speakers limited to 3 to 5 Powerpoint/Keynote slides, linking fundamental science problems with likely needs for logistical support in the Aleutians. These presentations were summarized by John Powers, who then outlined some end-member options for shared logistical resources.
Following the scheduled talks, there was a period for plenary discussion during which participants could present a single slide or simply comment from the floor. Including a couple of short coffee breaks, this plenary discussion occupied about three hours of the meeting. Results are summarized below.
The Aleutian arc, where the Pacific Plate subducts beneath the North American Plate, is arguably the best place on Earth to investigate several fundamental questions about arc magmatism and the conditions that create new subduction zones. It has never been rifted, so that the entire crust formed by arc processes can be geophysically imaged. Subduction erosion has exposed older sections of arc crust in the fore-arc, allowing geochronology of the entire edifice. The oceanic arc has abundant, exposed mid-crustal intrusions, providing insight into the composition of plutonic arc crust, which is almost unique among intra-oceanic volcanic arcs. The major and trace element contents of the volcanic rocks are more similar to continental crust than any other intra-oceanic arc, whereas the Sr, Nd, Hf and Pb isotopes in the western part of the arc are the most depleted of any arc, worldwide, recording a depleted mantle source with essentially no input from a terrigenous sediment component. Thus, the Aleutians represents the best place on Earth to study formation of “juvenile” arc crust, similar to continental crust, with little or no incorporation of older, inherited continental material. Pilot studies have demonstrated strong links between volatile contents, major element composition, and trace element abundance in lavas, with profound implications for magma generation and differentiation processes. The Aleutians have been the site of great earthquakes, among the largest ever recorded, and of large volume submarine landslides. They sit astride major air transportation routes, rendering the volcanic hazard particularly acute. Subduction rates, and the depth of sediments in the trench, decrease systematically from East to West, offering the opportunity to study the effect of these factors on arc magmatism and deformation.
Several participants gave brief presentations on existing Aleutian data and potential sites for future exploration in geochemistry, active and passive source seismology, geochronology, tectonics, and deformation. All provided insight on the logistical requirements for such research.
All participants were invited to submit latitudes and longitudes of sites where they wish to do geological field work or make geophysical observations.
Following science-based presentations, additional speakers described the benefits of using a shared facility for fieldwork as well as the operations of the Alaska Volcano Observatory, Earthscope, the Plate Boundary Observatory, and the German-Russian KALMAR project, which has been and will continue to be active in the westernmost Aleutian and Bering Sea regions.
Field campaigns in the Aleutians are logistically challenging and expensive unless research is conducted in the vicinity of one of the few airports, which are widely spaced along the more than 2,500 kilometers of plate boundary. Further, an amphibious approach is required for collecting geological, geophysical, and geodetic data from the numerous active volcanoes.
In the plenary sessions, attendees discussed several logistical matters: Should such a facility be used primarily for research in the oceanic Aleutian arc, or extended to include field campaigns on the Alaska Peninsula? Is there a need for shared ship support that may not require a helicopter (i.e. M/V Tiglax)? Could cost-effective research be conducted with a vessel capable of supporting helicopter operations. If so, would a small (80-120 foot) ship be sufficient, or is a larger UNOLS vessel with a helicopter required? Would it be possible to achieve most science goals with a helicopter based from commercial airstrips (in the oceanic arc away from the continental shelf, these are on Unalaska, Atka and Adak Islands, and perhaps also Attu) plus a small vessel without a helicopter?
Participants also discussed how to best share existing samples and data so as not to duplicate prior field campaigns. Workshop attendees determined that a logistics manager or office may be needed to coordinate efforts once a field facility is in place.
A key workshop outcome was a strong consensus in favor of developing shared field platforms that include a ship and helicopter. This could be in the form of a ship with a helipad, or perhaps a combination of a smaller ship and chartered helicopters based at airstrips with commercially available fuel (in the oceanic arc these are on the Unalaska, Atka and Adak Islands). When asked whether, if such support were available, participants would write proposals to NSF to take advantage of this support, 28 people present (of perhaps 50 or 60 at that point) raised their hands. At the same time, conveners asked for dissenting votes, and there were none. This highlights the potential for having about 20 proposals submitted to GeoPRISMS to make use of such shared logistical resources.
Participants in both the seismic and geodetic communities stressed that the ship/helicopter platform(s) would need to be available for a minimum of two and ideally three summers so that instruments can be deployed, collect a sufficient amount of data, and be retrieved. The distance range of helicopters based at airstrips would be insufficient to achieve optimal, uniform instrument distribution over significant distances along the arc. Bringing instruments onshore from ships using small boats would be unreliable, is dangerous, and would result in less-than-optimal instrument sites. Thus, the workshop participants who are planning onland deployment of seismic and geodetic instruments strongly favor a ship-based helicopter platform. In turn, most workshop participants favor a combined geophysical, petrological and geochemical approach for GeoPRISMS-supported work in the Aleutians, and thus there is a consensus that the ship-based helicopter platform is best for the community, though this consensus is not as strong as the overall support for shared resources in general.