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Leveraging IODP Scientific Drilling in Support of Subduction Cycles & Deformation Science Objectives: AGU Mini-Workshop 2012

AGU Fall Meeting 2012, San Francisco, USA

Workshop Conveners: Robert Stern1, John Jaeger², Brian Jicha³, Terry Plank⁴, Dave Scholl⁵, Gene Yogodzinski⁶

¹University of Texas, Dallas; ²University of Florida; ³University of Wisconsin; ⁴Lamont-Doherty Earth Observatory; ⁵U.S. Geological Survey; ⁶University of South Carolina

About 25 scientists attending Fall AGU meeting in San Francisco took a couple hours out of their busy schedules to participate in a Thursday evening mini-workshop at the Grand Hyatt about how to best use seafloor drilling to address GeoPRISMS Subduction Cycles and Deformation (SCD) science objectives. A new decade of scientific ocean drilling will occur when the new International Ocean Discovery Project (IODP) gets underway; this is planned for 2013-2023 (For more information about IODP and GeoPRISMS, look at the GeoPRISMS Fall 2012 Newsletter). The primary goal of the AGU mini-workshop was to stimulate interested geoscientists to consider how IODP drilling in the Aleutians, Cascadia, and Hikurangi margins can attack the seven “key questions” in the SCD Initiative draft Science Plan. The two-hour brainstorming session was fueled by hors d’oeuvres, a cash bar, and six brief (5 minute presentations plus 10 minutes discussion) talks.

Figure 1. General diagram showing tectonic locations being discussed for IODP drill sites in support of GeoPRISMS science objectives. Site 1: sediment and basement inputs to subduction factory and seismogenic zone, important for Cascadia, Aleutians, and Hikurangi. Site 2: Shallow drilling to understand slow slip events, suggested for Hikurangi margin. Site 3: forearc drilling to reconstruct megathrust events and mountain growth, suggested for Aleutian and Cascadia margin. Site 4: Volcanic history (via tephra) and early arc basement, suggested for Aleutian arc. Site 5: Aleutian Basin formation and evolution.

Terry Plank discussed how to use the drillship to determine subduction zone inputs. It is essential to sample the oceanic crust and sediments that are subducted at each margin, in order to understand how these inputs affect the mechanical properties of fault zone rocks, the generation of fluids in the subduction zone, and the formation of arc magmas (Fig. 1 site 1). Terry noted that for Cascadia there are already several sediment reference sites, and there are even sites in the northern Juan de Fuca plate where basement has been well-sampled and studied hydrologically. These materials need to be analyzed in order to establish the chemical composition of what is being fed into the Cascadia subduction zone. A major uncertainty is what is accreted in the fore-arc and what is swept down to ~100 km to feed the arc magmatic system. Understanding inputs to the Aleutian-Alaskan subduction factory is a bigger problem: this convergent margin is much longer than Cascadia (~3000 km vs. ~1000 km) and sedimentation on the downgoing plate changes along strike from thick, abyssal plain and trench-axis turbidite deposits in the east to thin pelagic sediments overlain by thinning trench-axis deposits in the west. For the eastern Aleutians, we have good but very incomplete DSDP sampling of the Zodiac Fan and more sediment coring in the Gulf of Alaska is expected from scheduled drilling. In contrast, not much is known about sediments on the downgoing plate feeding the intra-oceanic Aleutian arc, west of the Bering shelf break. Fracture zones (FZ) like the Amlia FZ provide additional complexity: these may mark unusual zones of thick sediments, altered oceanic crust, and serpentinized mantle. Can we recognize these inputs in the resultant arc magmas? The subducted oceanic crust appears to become ever more important to arc outputs toward the west, but less than 20 meter of basaltic basement have been recovered from the entire 3000 km Aleutian sector. We need to recover several hundred meters of oceanic crust, because we cannot constrain how much H2O and CO2 is carried down into the subduction zone unless we understand alteration of the subducting oceanic crust. For the Hikurangi margin, ODP Leg 181 sampled the upper sediments, but the lower km (related to Hikurangi Plateau volcanism) has not yet been sampled. Plans are underway, however, to drill a new section of sediment and basement input to the Hikurangi margin (see below).

Dave Scholl outlined how we could obtain a long-term history of major Aleutian seismogenic zone earthquakes by drilling into the forearc to core the deposits of landslides and turbidites that shallow earthquakes create (Fig. 1 site 3). There are two challenges here: to distinguish seismogenic deposits from those produced by other causes, such as non-seismic forearc slope collapse; and how to date these deposits – once identified – with the precision needed at the scale of the seismic cycle? It was also noted that we have a better understanding of the Cascadia seismogenic record than we know the Alaskan record, in spite of the fact that major (M>8 to 9.2) earthquakes (eight have occurred since 1899) are more frequent along the Alaskan-Aleutian margin.

John Jaeger continued on the theme of how we could interpret tectonic history from studying deep sediment cores (Figure 1, site 3). He outlined how these sedimentary records could illuminate linkages between uplift and deformation on the one hand and climate-mediated erosion of growing mountains on the other hand. He further noted how these could combine to create a high sedimentary flux that can turn off forearc deformation.
Brian Jicha explored how the drillship could be used to understand the early Aleutian subduction zone development, and how the arc magmatic system has since evolved (Figure 1, site 4). Aleutian arc subduction is thought to have begun in Eocene time – perhaps along an E-W trending fracture zone – capturing part of the Mesozoic Kula or Resurrection plates to form the Aleutian Basin (see below). We should be able to find a suitable place in the Aleutian forearc where a continuous tephra record – the products of Aleutian and Alaskan explosive eruptions – is preserved. The tephra record – which has wind-direction and compositional bias – could be supplemented by volcaniclastic sediments, which is less compositionally biased but which would preserve the magmatic record of a few upslope volcanoes. Drilling through sedimentary cover to sample forearc basement should recover magmatic products accompanying formation of the Aleutian subduction zone. It is possible that the Aleutian Basin formed by Paleogene backarc spreading, instead of being trapped Pacific/Kula/Resurrection plate. Recovery and study of Aleutian Basin crust would be a primary constraint on timing and nature of Aleutian arc subduction initiation.

Bob Stern outlined using the drillship to understand the age and origin of the Aleutian Basin, and use this information to constrain interpretations of surrounding regions (Fig. 1 site 5), such as the early history of the Aleutian Arc as well as the thermal history of the Aleutian Basin and basement-rock beveled Beringian Shelf. The issue is that there is a lot of sediment in the Aleutian Basin (km’s), but there might be regions where the sedimentary section is thinner. By drilling to basement though 1.5 km of sediments, we should recover a complete high-latitude record of Cenozoic climate history as well as direct age of Aleutian Basin crust.
After these five samplers, we heard briefly about more advanced plans for drilling in the Hikurangi SCD focus site to understand slow slip events (Figure 1, site 2) from Laura Wallace. Hikurangi slow slip events are unusually shallow and may propagate all the way to regions near the trench that are accessible to drilling. Drilling may thus give us direct access to sampling rocks and fluids formed in association with slow-slip events. A riserless drilling proposal currently in the review and ranking process has a coring transect from the subducting plate (inputs) across the overriding plate above the SSE source. There is an input site planned: 1 km of sediments followed by ~200 m penetration into basement. The input site will provide protoliths of the fault zone rock at depth in the slow slip event source area. A proposal to drill a ~5 km riser hole will be submitted in April 2013. Hikurangi drilling will collect samples related to the former MARGINS “Source to Sink” site in the nearby Waipaoa catchment.

We were also told about an interesting Brothers volcano (Kermadec Arc) IODP pre-proposal in the works, and a full IODP proposal to drill at the Lord Howe Rise and New Caledonia Basin to look at the consequences of subduction initiation along the Tonga/Kermadec/Hikurangi subduction system. These two proposals are likely to be submitted in April 2013.

Figure 2: Participants of the GeoPRISMS/IODP mini-workshop take a break between sessions.

Following these presentations, the floor was open to other inputs. Gene Yogodzinski led the group in broad discussions, from Cascadia sediment input, the need for coring into oceanic basement at all sites, the importance of water-rich saponite in oceanic crust, the importance of studying input material to understanding the rheology of the plate interfaces, to the opportunity presented by drilling into the Amlia fracture zone because of unusual sediments and ocean crust alteration, to the importance of biogenic silica as a fluid source, to further discussion of the significance of the tephra record, to engineering considerations for drilling in the Aleutian Trench, to the Cascadia fore-arc slope basins being obvious targets for sampling the paleoseismic record.

After the open discussion, John Jaeger outlined how to propose an IODP workshop, which is useful for moving from broad ideas to specific drilling proposals. Since the workshop, we have learned that guidelines for preliminary proposals are being revised and will be in place for the Oct. 1, 2013 deadline. Some groups interested in similar drilling objectives gathered to begin planning.

Reference information

Leveraging IODP Scientific Drilling in Support of Subduction Cycles & Deformation Science Objectives: AGU Mini-Workshop 2012, Stern, R., Jaeger, J., Jicha, B., Plank, T., Scholl, D., Yogodzinski, G.

GeoPRISMS Newsletter, Issue No. 30, Spring 2013. Retrieved from http://geoprisms.nineplanetsllc.com

Workshop Report: “Ultra-Deep Drilling Into Arc Crust: Genesis of Continental Crust in Volcanic Arcs”

Waikoloa, Hawaii, 18-21 September, 2012

Workshop Conveners: Yoshihiko Tamura1, Shuichi Kodaira¹, Susan M. DeBari², Jim Gill³

¹JAMSTEC, Japan; ²Western Washington University, USA; ³University of California, Santa Cruz, USA

Compiled by Susan DeBari, Philipp Ruprecht and Susanne Straub

Figure 1. Location map of the Philippine Sea Region. Numbers show proposed drilling sites IBM-1, IBM-2, IBM-3, and IBM-4.

A workshop was held September 18-21, 2012, in Kona, Hawaii, with the goal of soliciting international support for the endeavor of understanding continental crust formation in the Izu Bonin arc in the northwest Pacific ocean. Central to this project is riser-based deep drilling into the mid-crust of the Izu Bonin arc using D/V CHIKYU. The workshop was primarily sponsored by a Grant-in-Aid for Creative Scientific Research 19GS0211 to Y. Tatsumi and JAMSTEC. Additional funds to support attendance of U.S.-based scientists were obtained from the U.S. Scientific Support Program (through the Consortium for Ocean Leadership) and the GeoPRISMS Program.

The ~3000 km long intra-oceanic Izu Bonin-Mariana arc (IBM) has been long recognized as a primary site for understanding the formation of the continental crust (Fig. 1). A long history of past multidisciplinary exploration revealed the ubiquitous presence of a conspicuous low-Vp velocity (6.0-6.5 km/s) mid-crust layer that seismically resembles continental crust. This layer is common in arc crust, and, as such, is crucial in interpreting arc crustal structure globally. In the northern part of the IBM system (the Izu Bonin arc), the low-velocity mid-crust layer is within reach of ultra-deep riser-drilling and has been a dedicated target of the International Ocean Discovery Program (IODP). The IODP Science Plan for 2013-2023 “Illuminating Earth’s Past, Present, and Future” highlights the formation of continental crust as high-priority scientific Challenge 11 “How do subduction zones initiate, cycle volatiles, and generate continental crust?” as part of the main theme “Earth Connections: Deep Processes and Their Impact on Earth’s Surface Environment”.

Deep-drilling a single hole into the Izu Bonin arc is a major commitment in time and resources. Success is reliant on three companion riserless drilling expeditions in the arc by D/V JOIDES Resolution that are scheduled for 2014. These expeditions will provide crucial new data for the overarching goal of obtaining a complete temporal and spatial petrologic cross-section of Izu Bonin arc magmatism. These expeditions provide vital support for the planned CHIKYU drilling (IODP Proposal 698-Full3 at Site IBM-4) that will be discussed as a priority project at the CHIKYU+10 workshop on 21-23 April 2013 in Tokyo, Japan. This workshop will prioritize the future activities of the CHIKYU.

Overview

The workshop was attended by 58 participants (34 from US, 13 from Japan, 4 from UK, 2 from Switzerland, and 1 each from Mexico, Canada, Taiwan, New Zealand, Australia, Figure 2).

Figure 2. All participants at the conference venue, Waikoloa Beach Marriott, on the Big Island of Hawaii.

Attendees included a wide range of geophysicists, geologists, geochemists and petrologists whose research involves the genesis of arc crust. A primary goal of the workshop was to inform the broader geologic community about the goals of drilling in the Izu Bonin arc, as well as to solicit a very broad, international base of participation in proposed IODP expeditions, to rally support for the planned CHIKYU deep-drilling, and to obtain input on objectives and corollary studies.

The first day opened with background talks and discussions aimed at providing a framework for the proposed drilling. Talks focused on the physical and geochemical evolution of the Izu Bonin Mariana arc through time, the geophysical framework (including the enigmatic seismic properties of the middle crust and comparison to the Aleutian arc), and an overview of the goals of the three scheduled IODP drilling legs (subduction initiation, arc foundations, rifted rear arc).

The second day focused specifically on the CHIKYU deep drilling proposal and potential outcomes. This theme was supported by talks on the processes of crustal growth and evolution from exposed crustal sections and from thermal modeling.

The third day provided a break from talks in the conference room and allowed more informal discussions among participants during a field trip to observe the geology of the active Kilauea Volcano eruption (Figure 3).

Figure 3. Participants looking over at the summit caldera of Kilauea and the active eruption in Halema’uma’u crater during the field trip led by Don Swanson.

The forth and final day focused on specific scientific objectives for deep drilling in the Izu Bonin arc and what at-sea drilling strategies and shore-based studies would best support those objectives.

Workshop Program

The key question that motivates deep drilling in the Izu Bonin Mariana arc is how the middle crust evolves and how the processes of its growth relate to the growth of continental crust. Deep drilling in the IBM arc offers the opportunity to examine the critical relationships between magmatic processes and resulting geophysical structure. The linkages established here can also be used as a template to interpret active arc processes globally from geophysical surveys.

The workshop was structured around several key topics, and the key results are as follows:

(1) Geophysical overview of the Izu-Bonin-Mariana arc-back-arc system

More seismic surveys have been acquired over the IBM arc-back-arc system than any other island arc setting on Earth. Consequently, it is possible to contrast seismic velocity models across the arc representing different evolutionary histories, and to constrain them with strike lines where available. A multi-channel seismic reflection (MCS) survey was acquired in 2008 around the proposed drilling site of IBM-4 revealing a well-resolved domal basement high beneath the proposed drilling site. Comparison of MCS data with core recovered from ODP Site 792 indicates the section above the basement is comprised of Quaternary to upper Eocene volcaniclastic sediments. At the top of the basement high, andesitic lavas were sampled at 886 meters below seafloor (mbsf). A seismic refraction survey using densely deployed ocean bottom seismographs (OBSs) was also conducted along the MCS profile and clearly show a domal structure in the 6 km/s Vp iso-velocity contour. These Vp values, which are critical to identification of the middle crust, are located 3.5 km below sea floor at Site IBM-4, within reach of CHIKYU drilling.

(2) The generation of intermediate composition (andesitic) magmas and their relevance to growth of continental crust

The workshop presentations and discussions reinforced consensus that the Izu Bonin arc was the ideal place worldwide to study juvenile mid-crust formation, as there is minimal sediment recycling and minimal pre-existing continental crust. Hence, the net flux from the mantle/subduction zone to the crust is visible with the greatest possible clarity.

Specifically questions to address include the following:

What is the origin of the mid crust (test various hypotheses)
Are intrusive and extrusive rocks genetically related (i.e., does the mid crust form in a distinct manner from the extrusive rocks)?
Do all arc magmas stall at mid-crust levels before eruption?
How fast do magmas ascend from mantle to crust?
How are mafic magmas expressed within the crust – are they long-lived evolving bodies or rapidly solidifying small plutons?

(3) Using exposed arc sections in conjunction with IBM deep crustal drilling to understand the generation and growth of arc crust, and transferability to other active arc settings

Investigation of arc crustal sections exposed on land provide an important companion study for deep crustal drilling. The study of paleo-arcs provides a larger, more volumetrically abundant record of both the intrusive and extrusive record of the processes that generate continental crust from mantle-derived magmas. In turn, deep crustal drilling can answer many questions that remain unanswered after examination of exposed sections, the activity of which ended long before they were amassed in their current locations. For example, through the direct petrological, geochemical, and geophysical characterization of the crust at site IBM-4, a reference section of intraoceanic arc crust can be generated. The cored rocks and borehole properties can be directly linked to the seismic velocity structure of the crust, providing the first in situ test of seismic velocity models against known rock types and structures within the deep arc crust. The IBM-4 site will provide an essential reference both for active arc crust and for accreted arc crustal terranes.

(4) Other salient points related to drilling operations

Temperature estimates for the proposed drilling depth of 5500 mbsf at IBM-4 do not exceed 170°C
All coring cannot reasonably be obtained throughout the 5500 m drilling depth so borehole imaging technology will be critical. Drilling operations will also include sidewall coring (sampling from uncored intervals) and vertical seismic profiles.
Costs for drilling with Chikyu will be on the order of $600,000 – $700,000 per day, with an estimate of roughly 9 months to reach 5500 mbsf. The total cost is thus as much as $200 million.

(5) Scientific objectives

At the end of the workshop, participants formalized ten of the most important scientific objectives of drilling at Site IBM4. These objectives are as follows:

What is the tempo of constructing arc juvenile continental crust?
How does arc crust composition change with time?
Is there older (pre-51 Ma) crust that makes up significant parts of the Izu arc?
How do the results of ultradeep drilling into the Izu forearc fit with perspectives gained from other drill sites and from arc crustal sections?
What is the relationship and proportion between volcanic and plutonic rocks in ultradeep juvenile arc crust?
What was the role of fluids in the evolution of the rocks that we will penetrate?
What is the nature of the ultradeep biosphere?
What can we learn about convergent margin mineralization by ultradeep drilling into arc crust?
What is the paleomagnetic record preserved in Izu arc crust?
How well can we use surface geophysical measurements such as heat flow and seismic velocity to infer properties at depth?

Given the distinct core recovery rate in riser-drilling platforms (i.e. targeted sampling) compared to riserless drilling (i.e. almost continuously coring possible) the workshop discussions also revolved extensively around how to prioritize sample recovery strategies. Workshop participants made recommendations for prioritizing sample recovery, in particular around transitional zones derived from geophysics as well as extensive coring at the base of the drillhole. Further discussion is likely to occur at Chikyu+10.

For a more detailed report on the workshop see http://www.jamstec.go.jp/ud2012/

Roadmap to Future scientific drilling in the Izu Bonin arc

In 2014 three-riserless expeditions with JOIDES Resolution are scheduled in three sites (IBM-1, IBM-2, IBM-3) of the Izu-Bonin Arc. A call to participate in these expeditions has been made with application deadlines of May 1, 2013. The three legs (each about two month duration starting in April 2014) are designed to address key questions of crust generation and modification. The expeditions will be kicked off at site IBM-3 in the rear Izu arc to generate data on the missing half of the subduction factory, as most drilling efforts have focused on the IBM forearc. This leg will document across-arc variation in magma composition from Eocene to Neogene time to test models of mantle flow, intra-crustal differentiation, and magma generation during the arc evolution. The following two months are scheduled to drill into a section of pre-arc oceanic basement at site IBM-1 (695-Full2). This site is located beneath the 1-1.5 km of sediments in the Amami Sankaku Basin west of the Kyushu-Palau Ridge remnant arc. Such basement may make up an important part of the lower-arc crust, and contribute to arc magma chemistry through assimilation and partial melting. The 2014 drilling campaign in the Izu-Bonin arc will finish at Site IMB-2, close to the Bonin Ridge (696-Full3). The goal at this site is to unravel subduction initiation and test the supra-subduction zone ophiolite model.

Although each of the three scheduled JOIDES Resolution expeditions stand on their own merits, they will also deliver crucial complementary data for the ambitious ultra-deep drilling proposal (IBM-4; 698-Full3). The ultra-deep drilling project itself would provide first-ever in-situ unaltered samples from the region in the arc crust where crustal differentiation and evolution is most dramatic. The “transferability” of a direct view of the nature of the middle crust in the Izu-Bonin arc with crustal studies from exhumed sections has the potential of being mutually transformative. Ground-truthing potential exists for a large variety of techniques. How do seismic velocities and densities vary locally in the borehole and how are those parameters recovered from surface observations? How accurate are surface heat flow measurements in projecting the thermal evolution in the borehole? In addition, deep drilling provides tremendous opportunities to obtain new insights on fluid compositions and distribution in the crust, the presence of a deep biosphere, and the potential for observing in-situ mineralization processes.

The new data from all these drilling expeditions will provide for innovative cross-disciplinary research through the integration of many subdisciplines and multinational specialists. The extraordinary collaborative effort made at sea will culminate in extensive post-cruise shore-based studies (e.g., isotope geochemistry, thermo- and geochronology, geophysical experiments with core samples) that are set to transform our understanding how juvenile arc crust forms and differentiates with time.

Reference information

Workshop Report: “Ultra-Deep Drilling Into Arc Crust: Genesis of Continental Crust in Volcanic Arcs”, DeBari S., Ruprecht P, Straub S.

GeoPRISMS Newsletter, Issue No. 30, Spring 2013. Retrieved from http://geoprisms.nineplanetsllc.com

Student Seagoing Experiences: The 2013 Cascadia Initiative Expedition Team’s Apply to Sail Program

Compiled by Emilie Hooft (University of Oregon) for the Cascadia Initiative Expedition Team

During the summer of 2013 the Cascadia Initiative Expedition Team led six oceanographic expeditions to recover and redeploy ocean bottom seismometers (OBSs) across the Cascadia subduction zone and Juan de Fuca plate. The Cascadia Initiative (CI) is an onshore/offshore seismic and geodetic experiment to study questions ranging from megathrust earthquakes to volcanic arc structure to the formation, deformation and hydration of the Juan de Fuca and Gorda plates with the overarching goal of understanding the entire subduction zone system. These objectives are all components of understanding the overall subduction zone system and require an array that provides high quality data, crosses the shoreline and encompasses relevant plate boundaries. The CI is the first to utilize a new generation of OBSs that are designed to withstand trawling by fisheries, thus allowing the collection of seismic data in the shallow water that overlies much of the Cascadia megathrust.

Figure 1. Cascadia Initiative experiment design: PBO GPS stations upgraded as part of the Cascadia Initiative (black triangles) and broadband seismometers (circles) expected to operate in the Cascadia Region between 2011 and 2015. The 2010 workshop report1 contains a detailed discussion of the color-coded seismometer experiments and the schedule of deployments.

Figure 2. Robert Anthony (New Mexico Institute of Mining & Technology) counts how many SIO Abalone remain to be deployed.

We all gathered on the deck as the persistent thumping of the Oceanus’s V16 diesel died away and the slow lapping of waves against the stern took its place. Our GPS indicating that we were in the correct spot, the crew began operating the crane to raise the oven-sized Ocean Bottom Seismometer (OBS) over the starboard side. For a second, the florescent yellow casing on the instrument was picked up by the ship’s floodlights, illuminating the instrument package against the dark, endless expanse of the Pacific Ocean. Then, just as quickly, it was released from its tether and engulfed by the swell. I leaned overboard and watched as the blinking light affixed to the top of the instrument silently faded away, eclipsed by the murky depths of the sea. Turning my back on this makeshift funeral, I imagined the OBS settling on the alien terrain of the ocean floor, perhaps on a turbidite flow. As the ship’s diesel fired back to life and set course for the next drop off location, I thought about the OBS one day disengaging from its anchor and rising back up through the water column, possibly carrying with it the key to predicting crucial properties of the next submarine landslide-triggering earthquake.Robert Anthony, Graduate Student at New Mexico Institute of Mining and Technology

The CI is a plate-scale experiment that provides a unique opportunity to study the structure and dynamics of an entire oceanic plate, from its birth at a spreading center to its subduction beneath a continental plate. Together with the land stations that are part of the amphibious array and other land networks, the OBSs will provide coverage at a density comparable to the Transportable Array of Earthscope from the volcanic arc out to the Pacific-Juan de Fuca spreading center segments.

I was a member of the first leg of the 2013 CIET cruises. I was extremely nervous about every aspect of the cruise, including the bunk rooms and food. The first few days were great. I learned about ocean bottom seismometer retrievals and a bit about each of the crew members. Then we started experiencing high winds and seas. I had stopped taking my seasickness medicine, so I spent most of the time in my bunk. During the last four days of the cruise, I helped with retrieving and securing the seismometers. I spent a lot of time talking with the crew from Woods Hole Oceanographic Institute. I also learned that the entire crew has a special skill to do what they do, especially with significant weather. Even though a few days were terrible for me, I will gladly join a scientific cruise again, as long as I don’t forget my seasickness pills.Hannah Mejia, Graduate Student at California State Polytechnic University, Pomona

Figure 3. The WHOI team recovering an OBS.

The CI is a community experiment that provides open access to all data via the IRIS Data Management Center, thus ensuring that the scientific return from the investment of resources is maximized. The Cascadia Initiative Expedition Team (CIET) is a group of scientists who are leading the seagoing expeditions to deploy and recover OBSs and the team just completed its third year of data acquisition. The CIET maintains a website for the community where information regarding CI expeditions and OBS metadata are provided.

Having sat through several planning meetings and teleconferences in which the community hashed out where exactly the ARRA Cascadia Initiative OBS units would be deployed, it was a real pleasure to actually participate in the CI Leg 5 deployment cruise. Prior to the cruise, OBSs were a bit of a mystery, and it was fascinating to see their various parts and pieces and well-engineered simplicity. Some of the pieces were familiar, such as the Trillium Compact seismometer, although its casing that houses a 360-degree gimbal was new; others were completely foreign, most notably “syntatic foam” which doesn’t significantly compress even at 6000 m, or 200 bar pressure. It never occurred to me that one can’t use any old flotation foam, nor that fishing trawler resistance is a key design criteria of OBSs in general, and particularly offshore the Cascadia margin.Tim Melbourne, Professor at Central Washington University

The CI also includes a significant education and outreach component that is providing berths for students, post-docs and other scientists to participate in either deployment or recovery legs, thus providing the seismological community with opportunities to gain valuable experience in planning and carrying out an OBS experiment. In total, 51 applicants from the US and 4 other countries applied to sail on the 2013 cruises; 21 graduate students as well as a few undergraduate students, postdocs and young scientists from the US and Canada were chosen to join the crew.

Figure 4. Tim Melbourne (Central Washington University) explains the GPS component of the Cascadia Initiative during an onboard science meeting.

My time on the R/V Atlantis showed me first hand that the geology of the sea floor is just as interesting and diverse as the geology on land. One of the most memorable things to me was our use of the bathymetry equipment to scan Hydrate Ridge, which is a formation composed of methane hydrate – a flammable substance that looks like ice. It is amazing to think that every time we sent the JASON ROV down to collect a seismometer, its cameras were looking at a part of the sea floor that had never been looked at before. This really drove home the idea that some things that we take for granted when working on land, such as orientation of the seismometer during installation and the ability to look carefully at the rock and sediment that it is installed on, are much more difficult to achieve when working at sea – it really does present a completely different set of challenges.Anton Ypma, Graduate student at Western Washington University

Sailing on the R/V Atlantis was an amazing opportunity to learn more about ocean seismology and ocean-bottom seismometers (OBS). I had little experience with in situ seismic observations and instrumentation prior to the cruise. I learned a tremendous amount about how the OBS detects movements in the Earth’s crust, the advantages of the different encasing designs (e.g. trawl resistant mounts (TRM), pop-ups & float – ups), and the recovery process for each design structure. I appreciate the folks from Lamont-Doherty Earth Observatory who answered my many questions regarding OBS’s and allowed me to get a hands-on experience helping them break down the TRM’s after recovery.Katie Kirk, Graduate Student at Cornell University and Woods Hole Oceanographic Institution

Having never done field work in seismology, what stood out most from this cruise was the incredible design and engineering that went into collecting this data. Seeing a team of scientists and engineers coordinating with the crew of a ship, I felt struck by the reality of what science in action looks like, and what can be accomplished through collaboration. I didn’t know what to expect from ship life, but to sum it up concisely: The motion of the ocean stops for no stomach. The motion of the ocean is also soothing, and often sleep-inducing after lunch, so plan accordingly. The ship is well-stocked with books, movies, games, and characters to enjoy them with. The food is very, very good. And there is nothing quite like the crashing of waves against the hull as you watch moonlit clouds float by over a landless skyline.Laura Fattaruso, University of Massachusetts Amherst

The cruises lasted from 6 to 14 days in length. OBS retrievals comprised the three first legs, of which the first two were aboard the Research Vessel Oceanus. The third retrieval leg was aboard the Research Vessel Atlantis and utilized the submersible Remotely Operated Vehicle (ROV) Jason. The ROV was used to recover 12 of the 30 seismometers for this last retrieval mission. The final three legs were OBS deployments conducted with the assistance of the Research Vessel Oceanus.

Figure 6. AB Doug Beck helps Brooklyn Gose (Undergraduate at University of Oregon) with an albacore tuna

Figure 5. Samantha Bruce (Adjunct Instructor at College of Charleston) holding a starfish in front of ROV Jason.

I woke up and immediately realized that the boat was unusually still. Even though it was nearly 11 o’clock in the morning, I felt groggy. I had volunteered for the night shift and we had only been at sea for a few days so my body wasn’t fully adjusted to the new schedule. I got dressed and made my way to the top of the steps leading to the science lab. The WHOI team had their hardhats and life vests on and were darting into the lab and back out onto the deck-clearly hard at work. We were stopped because during the last deployment one of the ARRA OBSs had failed to respond when pinged almost as soon as it was released into the water. A similar situation had happened to us the day before with the ARRA ceasing to respond about halfway through its descent. With the recent failure, there was now a major dilemma. Of the three ARRAs deployed, two were not responding. The WHOI team was busy testing the remaining OBSs by submerging them, pinging and waiting to hear a response. The chief scientists spent the day pouring over maps, sending emails and developing plans for the worst case scenario. As the day progressed, we were still no closer to understanding the problem. It was decided that the ARRA component designed to send and receive signals needed to be tested at depth. The WHOI team gutted the cage holding all the CTD equipment and attached the ARRA parts. Each ARRA was tested and each ARRA continued to function normally. By now we had an updated itinerary that paired priority sites with the KECK OBSs that seemed more stable. The cruise continued with the stipulation that if one more ARRA failed then they would no longer be deployed. It made the next few sites extremely intense, but as the days went by without incident the anxiety began to lift. In the end, the two ARRAs that failed at the beginning of our voyage were the only two to do so and we still finished ahead of schedule.Miles Bodmer, Graduate Student at University of Oregon

It took landing in the middle of the craton in Indiana at the beginning of undergrad to make me realize that I have always wanted to live and work near the ocean. My time on the R/V Oceanus was the first opportunity to spend multiple days at sea, working on a small subset of a large scientific initiative. It seemed that every time I rolled out of bed, bleary-eyed and unaware whether it was night or day, something new was happening on deck. Fishing for tuna on hand-lines tied to the back of the boat, watching a pod of orca whales gambol around our boat or playing with a makeshift cornhole set, there was always something new to see. The engineers were great, and I overheard them explaining each remarkable mechanism making up their OBS design with enthusiasm and pride. After a couple of days I was nipping into the galley for a midnight snack or popping up to the bridge with the feeling of being one of the crew, part of the ship, necessary. Though this ship will drop us off and its crew will depart again within the week leaving us to return to our mainland institutions, I am sure this will not be my last voyage.Kasey Aderhold, Graduate Student at Boston University

Figure 7. Two young orcas playing.

More descriptions and pictures of individual at-sea experiences are on the CIET Website. The 21 Apply-to-Sail participants for 2013 listed in the order of cruise participation are: Hannah Mejia, California State Polytechnic University Pomona; Sara Kowalke, University of Minnesota; Stanislav Edel, New Mexico Institute of Mining and Technology; Laura Fattaruso, University of Massachusetts Amherst; Lexine Black, California State University, Northridge; Anton Ypma, Western Washington University; Samantha Bruce, College of Charleston; Katie Kirk, Cornell University & Woods Hole Oceanographic Institution; Christina King, University of Rhode Island; Ye Tian, University of Colorado at Boulder; Miles Bodmer, University of New Mexico; Robert Skoumal, Miami University; Kasey Aderhold, Boston University; Robert Anthony, New Mexico Institute of Mining and Technology; Shannon Phillips, University of Oregon; Tim Melbourne, Central Washington University; Brooklyn Gose, University of Oregon; Xiaowei Chen, Woods Hole Oceanographic Institution; Yajing Liu, McGill University; Harmony Colella, Miami University of Ohio; Martin Pratt, Washington University in St. Louis. ■

“Report from the Field” was designed to inform the community of real-time, exciting GeoPRISMS -related research. Through this report, the authors expose the excitement, trials, and opportunities to conduct fieldwork, as well as the challenges they may have experienced by deploying research activities in unique geological settings. If you would like to contribute to this series and share your experience on the field, please contact the GeoPRISMS Office at info@geoprisms.nineplanetsllc.com. This opportunity is open to anyone engaged in GeoPRISMS research, from senior researchers to undergraduate students.
We hope to hear from you!

Reference information

Student Seagoing Experiences: The 2013 Cascadia Initiative Expedition Team’s Apply to Sail Program , Hooft E. for the Cascadia Initiative Expedition Team

GeoPRISMS Newsletter, Issue No. 31, Fall 2013. Retrieved from http://geoprisms.nineplanetsllc.com

Report: ExTerra 2013 – Understanding Subduction through the Study of Exhumed Terranes

August 24-25, Florence, Italy

M. Feineman¹ & S. Penniston-Dorland²

¹Pennsylvania State University; ²University of Maryland

Figure 1. ExTerra 2013 workshop participants.

On August 24-25, 2013, geoscientists met in Florence, Italy for the ExTerra 2013 workshop prior to the Goldschmidt conference. In all, there were 33 participants from 9 countries, including 11 students, 2 post-docs, and 5 early-career faculty. Workshop participants divided into three groups based on different types of exhumed terranes: subducted slab, mantle wedge, and arc crust. The groups were tasked with refining the key scientific questions previously identified in the ExTerra White Paper (2012) and discussing future directions for ExTerra.

What is ExTerra?

ExTerra is a group of individuals interested in studying exhumed rocks of ancient subduction zones in order to understand the processes that operate deep within subduction zones. Our ongoing mission is to explore how we can best organize research on exhumed terranes such that we might accomplish more as a group than we can as individuals working independently. Three target areas have been identified as significant to improving our understanding active subduction processes by the study of exhumed terranes:

Subducted slab, including HP and UHP rocks such as blueschists, eclogites, and metapelites;
Mantle wedge, including serpentinites, ophiolites, and peridotites; and
Middle and lower arc crust, including granitoids, gabbros, migmatites, gneisses, amphibolites, granulites.

Workshop summary

Figure 2. ExTerra 2013 workshop participants learn about US examples of exhumed arc crust sections from Mihai Ducea.

Day 1: Science Questions

The first day consisted of a full day of scientific presentations with ten keynote talks followed by an evening poster session. The talks were chosen to emphasize cutting-edge research on the processes and materials found deep within subduction zones and ultimately exhumed at the Earth’s surface, and to stimulate discussion of the Big Science Questions that can be addressed using rocks from exhumed terranes. The keynote speakers and topics are listed in the table below.

Day 2: Planning for the Future

The second day was focused on the future of ExTerra and included presentations on potential field institute localities and a discussion of sample and data management led by Kerstin Lehnert, Director of Integrated Earth Data Applications (IEDA). The workshop participants then separated into breakout groups by target area to refine the key scientific questions identified in the first ExTerra white paper (2012), and to discuss future directions for ExTerra, including potential field institute localities.

Table 1. List of speakers and presentations

Speaker	Institution	Talk Title
Subducted Slab
Ethan Baxter	Boston University	The growth of garnet and the chronology of slab dehydration
Philippe Agard	UPMC (Paris VI)	Into the subduction plate interface?
Horst Marschall	WHOI	The importance of hybrid rocks for transient trace-element and volatile storage at the slab-mantle interface
Mantle Wedge
Peter Kelemen	LDEO – Columbia	Field observations and thoughts about carbon transfer from metasediments into the mantle wedge in oceanic subduction zones
Jaime Barnes	UT, Austin	Geochemical signature of a serpentinized mantle wedge
Katherine Kelley	URI – GSO	Mantle wedge oxygen fugacity
Sarah Brownlee	Wayne State University	Seismic signatures of a hydrated mantle wedge from antigorite crystal preferred orientation (CPO)
Arc Crust
Mihai Ducea	Univ. of Arizona	A review of some of the most important exhumed crustal sections and xenolith localities from the Americas
Josef Dufek	Georgia Tech	Magmatic connections: The interplay of magmatic systems with their crustal containers
Olivier Jagoutz	MIT	The formation of continental crust: the seismological perspective

Big Science Questions

Workshop participants continued to explore and refine the Big Science Questions regarding subduction zones that can be addressed through the study of exhumed high- and ultrahigh-pressure rocks and terranes. A few of the many emergent and re-emergent themes include:

What are the timescales of fluid release and transport in the slab and mantle?
What is the physical nature of the slab-mantle boundary?
What is the relative importance of mechanical vs. chemical mixing across the slab interface?
How are volatiles (including CO₂, H₂O, and O₂) stored and transported in the mantle?
What is the extent of mass exchange between arc magmas and arc crust?
Is the erupted component at volcanic arcs representative of the stored plutonic component in the middle-to-lower arc crust?
How different is the bulk composition of continental vs. oceanic arc crust?
How can we best relate observables from exhumed rocks to seismic observations and geodynamic models?

ExTerra Field Institutes

One proposed extension of ExTerra in the coming years is a series of field institutes that would gather groups of researchers (~20 participants) at a few world-class exhumed subduction localities with the purpose of exploring some of the key scientific questions identified in the ExTerra white papers. The field institutes would focus on targeted sample collection, supported by careful sample registration and data management. Institutes might also include field techniques such as LiDAR, handheld XRF, and in situ measurement of physical properties. After an initial time period (~18 months) during which samples would be preferentially accessible to field institute participants for analysis, all samples would be made publicly available for research purposes following a model similar to that employed by the Ocean Drilling Program. Proposed sites for future field institutes include Santa Catalina Island, CA; Santa Lucia Mountains, CA; Fiordlands, New Zealand; Sierra Valle Fertil, Argentina; and Monviso, Italian Alps.

Get Involved!

If you are interested in contributing to the discussion or joining the ExTerra mailing list, please contact us at: mdf12 (at) psu.edu or sarahpd (at) umd.edu For more information, visit the ExTerra webpage

Reference information

ExTerra 2013: Understanding Subduction through the Study of Exhumed Terranes, Feineman M., Penniston-Dorland S.

GeoPRISMS Newsletter, Issue No. 32, Fall 2013. Retrieved from http://geoprisms.nineplanetsllc.com

The New Zealand Primary Site Implementation Planning Workshop Report

Wellington, New Zealand, April 14-16 2012

Workshop conveners: Laura Wallace¹, Susan Ellis², Adam Kent³, Nicola Litchfield², Kathleen Marsaglia⁴, Jeff Marshall⁵, Demian Saffer⁶, Susan Schwartz⁷, Richard Wysoczanski⁸

¹University of Texas, Austin; ²GNS Science, New Zealand; ³Oregon State University; ⁴California State University at Northridge; ⁵Cal Poly Pomona; ⁶Pennsylvania State University; ⁷University of California, Santa Cruz; ⁸NIWA, New Zealand

An implementation planning workshop was held for the New Zealand Primary Site on 14-16 April, at Te Papa Museum in Wellington, New Zealand. There were ~170 participants from ten different countries, demonstrating the outstanding opportunities for international collaboration at this Primary Site. The large number of participants and high-quality white papers submitted (38 white papers – more than for any of the other GeoPRISMS Primary Site Workshops) reflected the high level of enthusiasm among both the US and international subduction zone communities for future studies in New Zealand. The workshop consisted of a number of keynote and invited talks, and break-out sessions to discuss and prioritize the main scientific objectives and most suitable GeoPRISMS goals.

Figure 1. Group picture in front of the colorful Marae at Te Papa Museum, Wellington

Workshop topics and agenda

After a welcome to the workshop from Prue Williams (New Zealand Ministry for Business, Innovation, and Employment), Kelvin Berryman (New Zealand Natural Hazards Platform), Bilal Haq (NSF) and Julia Morgan (GeoPRISMS Program), the science program kicked off with a keynote presentation from Nick Mortimer (GNS Science) on the history of subduction in New Zealand since the Paleozoic. For much of the remainder of the first day, we heard from keynote speakers on the four main topics to be addressed at the New Zealand Primary Site. These include:

What are the geological, geochemical and geophysical responses to subduction initiation and early arc evolution and how do they affect subduction zone formation?
What are the pathways and sources of magmas and volatiles emerging in the arc and forearc, and how do these processes interact with upper plate extension?
What controls subduction thrust fault slip behavior and its spatial variability?
What are the feedbacks between climate, sedimentation, and forearc deformation?

Figure 2. Participants at the New Zealand Planning Workshop in Wellington, 2013.

The keynote talks provided background on how these questions could be addressed in New Zealand, as well as global perspectives on the important outstanding questions. Keynote talks on the first day helped to set the stage for discussions held during the rest of the workshop. On the afternoon of Day 1, we held our first set of breakout sessions. The sessions were organized around the four key topics above, and were focused on identifying the most exciting science that can be done in New Zealand to address these topics.

At the beginning of the second day, the breakout session leaders reported back to the rest of the workshop on the outcomes of their breakout session discussions. Following the breakout leader reports, we heard a series of talks on existing infrastructure and datasets in New Zealand that could be brought to bear on any future GeoPRISMS studies at the New Zealand Primary Site. The range of datasets and available infrastructure at the New Zealand Primary Site is particularly impressive. Among these are comprehensive cGPS and seismic networks (www.geonet.org.nz), extensive, high-quality marine geophysical data that is publicly available, recent geological mapping of the entire country at a 1:250,000 scale, and a world-class database of active faults. Participants also heard about IODP projects and proposals that are in the works for the New Zealand region that have strong relevance to the SCD topics.

The IODP efforts included:

Drilling at the offshore Hikurangi subduction margin to understand slow slip events,
Drilling in the Lord Howe Rise area between New Zealand and Australia to investigate the consequences of Tonga-Kermadec-Hikurangi subduction initiation, and
Drilling at Brother’s Volcano in the Kermadec Arc to understand submarine volcano hydrothermal processes.

After lunch on Day 2, we were also reminded of the potentially important societal implications of future GeoPRISMS SCD research in New Zealand by a series of talks on the role of science in the understanding of seismic (Russ Van Dissen, GNS Science), volcanic (Gill Jolly, GNS Science), and tsunami hazards (David Johnston, Massey University) in the New Zealand region. These talks were followed by a series of short, topical science talks on a variety of studies being undertaken in New Zealand and elsewhere to address questions relevant to the GeoPRISMS SCD. For the rest of the afternoon on Day 2, participants divided into four breakout sessions that represented the four main geographical areas of the New Zealand Primary Site:

Hikurangi Margin,
Fiordland,
Kermadec Arc, Havre Trough, and vicinity,
The Taupo Volcanic Zone.

These breakout sessions discussed the main science priorities in each of these geographic areas, and identified data gaps that need to be filled to undertake the science. Synergies that exist across the four Topics in each of these locations were also discussed.

Figure 3. Animated discussion around the giant geological map of New Zealand.

At the beginning of Day 3, we heard reports from the Day 2 breakout leaders, and had a plenary discussion on the Day 2 outcomes. Following the reports, we heard a series of talks from potential international partners in Japan (Shuichi Kodaira, JAMSTEC), Germany (Achim Kopf, Bremen), the UK (Lisa McNeil, Southhampton), and Canada (Kelin Wang, Pacific Geoscience Center) about their countries’ ongoing research interests in subduction and the potential infrastructure that they could bring to bear on studies at the New Zealand Primary Site. Bilal Haq also gave an overview on the structure of GeoPRISMS, and potential NSF infrastructure, such as marine geophysical vessels, that could be utilized for NSF-funded studies in New Zealand. One of the most exciting aspects of the New Zealand Primary Site is the huge potential for US collaboration with New Zealand and other international partners which will greatly amplify the outcomes of any GeoPRISMS-funded studies conducted in New Zealand.

The remainder of the final day was spent in Breakout sessions and plenary discussions to refine the plans for future GeoPRISMS-funded studies within the main geographic focus areas. For the final set of breakout sessions, the conveners decided to stray from the original plan and organized the breakouts into geographic regions (rather than topically), so that the participants could focus in on planning for the main experiments to be conducted at the New Zealand Primary Site. One very controversial decision by the conveners was to put the Hikurangi and Taupo Volcanic Zone participants together in a single breakout session to discuss potential corridors across from the subduction thrust through to the arc to consider the Hikurangi subduction zone as a complete system. Although forcing these two groups together was a challenge, we hope that it initiated some discussions that will lead to more thinking about the Hikurangi subduction zone as a complete system in the future.

Identification of geographic corridors and priorities within those corridors

Four geographic regions emerged as focus areas where several of these topics could be well addressed.

The Puysegur Trench

The Puysegur Trench elicited significant enthusiasm at the workshop, as it is arguably the best-expressed example on Earth of a subduction zone being “caught in the act” of initiating, providing a globally unique opportunity to define the geodynamic boundary conditions to test models for subduction intiation. Key questions include: How does the new slab first enter the mantle? What is the fluid expression and thermal structure of subduction initiation? Focused geophysical surveys can tackle fundamental questions about the onset of convergence and associated vertical motions, offshore thermal and crustal structure, newly developing arc volcanism, as well as the geometry of subduction initiation. These new datasets will be underpinned by the uniquely well-constrained plate kinematic history during subduction development and a complete Miocene rock uplift history onshore Fiordland that records the vertical deformation response to subduction intiation.

The Hikurangi subduction margin

The Hikurangi subduction margin offers an outstanding opportunity to address the controls on variability in megathrust slip behavior, due to strong along-strike variations in interseismic coupling and slow slip event behavior observed there. Participants also recognized the outstanding opportunities to assess feedbacks between climate, sedimentation and forearc deformation, which can build upon previous MARGINS S2S studies in the Waipaoa catchment. Other questions to be addressed at Hikurangi include: How do topography, thermal structure, and material properties of incoming plate control fault zone structure, slip behavior, accretionary wedge evolution, and uplift and erosion of the forearc? What are the pathways and timescales of sediment input? What is the slip behavior and rheology of the near-trench portion of subduction fault?

Discussions for future work emphasized integrated geophysical, geological, and geochemical studies of the onshore and offshore forearc and incoming plate to discern the major controls on variations in subduction interface behavior and overall margin evolution. Moreover, a series of IODP proposals are currently in the system to investigate the mechanisms behind shallow slow slip event occurrence at North Hikurangi, and these provided an important focal point for discussions on future studies. Future studies at Hikurangi will leverage on existing datasets and scientific infrastructure such as a comprehensive geodetic and seismic network (www.geonet.org.nz), as well as significant ongoing and planned efforts by international partners in NZ, Japan, and Europe.

The Taupo Volcanic Zone

The Taupo Volcanic Zone elicited significant excitement as the most productive rhyolitic system on Earth, which also coincides with an extensional fault system. Some of the major questions to be addressed there include: How does the mafic flux from the mantle translate to voluminous rhyolitic magma production? How does arc volcanism interact with upper plate extension? World-class datasets bearing on the distributions, age, geochemistry, physical volcanology and petrology of many rocks from the Taupo and adjacent arc volcanoes have already been acquired by New Zealand-based researchers. As a result, substantial scope exists to supplement and synthesize these data and combine them with integrative geophysical and geochemical investigations. Moreover, comparison of the Kermadec Arc corridors with outcomes from the TVZ affords an opportunity to assess the influence of the continental/oceanic crust transition in the overlying plate on arc development, as well as changes in the nature of the subducting plate. An opportunity to link with the Hikurangi margin group also exists, and a targeted geochemical, geophysical, and geological corridor would enable assessment of controls on magmatism and volatile cycling for the entire subduction system, from the incoming plate and forearc through to the arc.

The Kermadec Arc

The Kermadec Arc offers a prime setting for addressing questions relating to magmatic and volatile fluxes at a well-developed volcanic arc from the forearc through to the backarc. The Havre-Lau backarc system, which progresses from oceanic spreading in the north to rifting and disorganised spreading in the south, also offers insights into backarc extension dynamics and the reorientation of arc systems. The effect of Hikurangi Plateau subduction on the magmatic products of the arc is also a topic of interest, requiring some along-strike comparisons. Moreover, it was also recognized that an outstanding record of Eocene subduction initiation at the Tonga-Kermadec-Hikurangi Trenches exists in the region west of the Kermadec Trench. The Kermadec Arc working group recognized that a key initial part of the project will be to identify corridors across the arc in which to target their field programs. Targeted field programs would include shipboard geophysics (passive and active seismic, electromagnetic, among others), rock sampling for geochemistry, petrology, and chronology, and hydrothermal fluid sampling. Results from an upcoming GeoMar/Sonne cruise in the Kermadec Arc will provide results to help define which corridor(s) should be focused on. The marine-based science plan developed by a Kermadec working group would complement ongoing and planned efforts by New Zealand, Japanese and German colleagues, and these international collaborations will amplify outcomes of GeoPRISMS goals in the Kermadec Arc.

In addition to these geographically-focused efforts, there was strong support for GeoPRISMS studies of exhumed terranes in New Zealand, which provide unique exposures of Mesozoic subduction in the Fiordland and Otago regions of the South Island, as well as parts of the eastern North Island. It was recognized that the only pristine Cretaceous arc section in the Circum-Pacific exists in Fiordland in the South Island, offering a prime locale to investigate the root zones of an ancient arc, at outcrop scale.

International Collaborations

The New Zealand Primary Site already is the focus of significant research efforts within the international community. This affords a wide range of opportunities for linking GeoPRISMS studies with a vast body of previous work on subduction systems in NZ, leveraging existing infrastructure, and collaboration in numerous ongoing and planned investigations. These ongoing endeavors include significant investments from the NZ government and efforts within the highly productive NZ geosciences community, as well as active research programs led by Japanese and European- based investigator groups. Any GeoPRISMS studies in New Zealand should build on these substantial existing and ongoing studies. We were pleased to see concrete plans for future experiments develop between the international partners and US investigators during the workshop. Although the science priorities identified at the New Zealand Primary Site are many and varied, we expect that most of these can be realistically accomplished due to the additional resources of the broader, international community that can be brought to bear on these topics.

Figure 4. Students gathered around Nicola Litchfield and Tim Little at Petone Wharf – Upper Hutt. Major uplift of the Wellington Basin occured after the 1855 Wairarapa Earthquake.

Student Participation

20 students from the US, New Zealand, and the United Kingdom participated in the workshop. A student symposium was held the day before the workshop, on the campus of Victoria University in Wellington. A series of talks were given by some of the conveners and other invited scientists to introduce the students to the New Zealand subduction setting and outline the GeoPRISMS scientific goals. The students brought posters on their research which they each presented to the group in two minutes pop-up talks. The student presentations were extremely informative and polished. On the last day of the main workshop awards for poster presentation were given to 6 students (Best Overall Poster & Presentation: Katie Jacobs, Besim Dragovic, Melissa Rotella; Honorable Mention for Verbal Presentation: Laurel Childress; Honorable Mention for Poster Layout & Visual Aesthetics: James Muirhead, Simon Barker). After the student symposium, Tim Little (Victoria University) and Nicola Litchfield (GNS Science) led an outstanding fieldtrip to see the Wellington Fault (an active dextral strike-slip fault) at various locations throughout the Wellington region.

Overall, the extremely high level of engagement and input at the workshop by the students was impressive. On the final day, the students presented a well-organized implementation plan for the New Zealand Primary Site, which was a valuable guide in the crafting of the final implementation plan.

Concluding Remarks

We would like to thank the meeting attendees for their enthusiastic participation, which made the workshop a great success. We would also like to thank the speakers for the stimulating and informative talks, and the breakout leaders for their key role in steering discussions. The white paper authors made major contributions by sharing their ideas for future work, which have also provided an important resource for development of the draft implementation plan. The enthusiastic participation of the graduate students and post-docs was extremely impressive, and bodes well for the future of subduction studies in the New Zealand region. The draft implementation plan has been released for public comment, and should be finalized by the end of the year, if not sooner, well in time for the upcoming GeoPRISMS NSF deadline of July 1, 2014. Finally, a successful workshop would not have been possible without generous financial support from NSF/GeoPRISMS, the New Zealand Ministry for Business, Innovation and Employment, the Consortium for Ocean Leadership, GNS Science, and the New Zealand Earthquake Commission.

The GeoPRISMS Implementation Plan for the New Zealand Primary Site is now available!

The GeoPRISMS Science Plan has been revised based on the outcomes of the GeoPRISMS Workshop on New Zealand, held in Wellington in April 2013

Reference information

The New Zealand Primary Site Implementation Planning Workshop,Wallace L., Ellis S., Kent A., Litchfield N., Marsaglia K., Marshall J., Saffer D., Schwartz S., Wysoczanski R.

GeoPRISMS Newsletter, Issue No. 31, Fall 2013. Retrieved from http://geoprisms.nineplanetsllc.com

A Geophysical and Hydrogeochemical Survey of the Cascadia Subduction Zone

H. Paul Johnson¹, Evan A. Solomon¹, Robert Harris², Marie Salmi¹, Richard Berg¹

¹ School of Oceanography, University of Washington, Seattle, ² COAS, Oregon State University, Corvallis

Modified from H.P. Johnson, E.A. Solomon, R.N. Harris, M.S. Salmi and R.D. Berg, Heat Flow and Fluid Flux in Cascadia’s Seismogenic Zone, Eos, Nov 2013.

The R/V Atlantis

Our 204 heat flow and 23 fluid flux stations survey along a single cross-margin profile is the highest resolution series of such measurements ever made on a subduction zone accretionary wedge. Combined with previous R/V LANGSETH multi-channel seismic data previously acquired along the same profile, these measurements reveal a wealth of detail of active fluid pathways, tectonic complexity, and diverse thermal environments for the previously unstudied accretionary prism off the Washington coast. Processing of these rich data sets is just beginning but preliminary analysis of the results reveals several unexpected findings. These include the inflow of seawater into at least the uppermost sediment layers above the deformation front and first anticlinal ridge, higher temperatures (~225°C) of the sediment-basement interface at the deformation front than previously recognized and methane-rich fluid flux with a geochemical signature indicating that these fluids originate from a deep source at temperatures greater than 80°C within the accretionary prism. The Cascadia Subduction Zone (CSZ) that dives beneath the North American continent is relatively quiescent but poses a great seismic hazard to the NE Pacific coast. Although the northern and southern portions of the CSZ off-shore the Vancouver Island and Oregon coasts have been studied over the past 50 years, detailed geophysical studies of the section off the Washington State margin have been limited until recently due to its proximity to sensitive U.S. Navy access routes. With the lifting of the ban on high resolution multi-beam bathymetry maps of the area and the recognition that the CSZ is a quiet but active fault zone, the 250 km length of the Washington portion has received new attention, which included its election as a focus site for the National Science Foundation GeoPRISMS Program, a target area for the Cascadia Initiative Expedition Team Ocean Bottom Seismic array, and the focus of two multi-channel seismic surveys using the R/V LANGSETH in 2012. In August, 2013, we conducted a 30-day detailed heat flow and fluid flux survey along a single across-strike profile of the Washington margin from the abyssal plain west of the deformation front of the accretionary wedge at 3000 meters depth to the continental shelf at 160 meters water depth using the R/V ATLANTIS and the ROV JASON II. The scientific goals of this cruise were to:

Determine the temperatures along the décollement of the CSZ megathrust fault, since temperature is an important influence on the locked portion of the fault.
Identify and quantify both shallow and deep-seated fluid flow within the accretionary sediment wedge that overlies the megathrust fault zone.
Test the hypothesis that active hydrothermal circulation within the subducting oceanic crust is occurring and if so, whether this oceanic plate aquifer is mining heat from deep within the subduction zone and serving as a ‘cold-finger’ for thermal processes beneath North American margin.

Figure 1. Top Image shows heat flow instrument sites from August 2013 GeoPRISMS cruise, including Jason short-probe, thermal blanket deployments, and OSU long-probe sites. Light grey lines are LANGSETH MCS 2012 survey lines. Insert shows general location of survey area. Lower map shows fluid flow sampling sites, including Mosquito flow meters, Jason push cores and multi-corer sediment coring sites.

Figure 2. Top panel shows JASON short-probe heat flow data over the Deformation Front and First Anticlinal Ridge shown in Figure 1. Red bars show locations of reduced heat flow areas hypothesized to be areas of fluid inflow into the upper sediment layers. Lower LANGSETH seismic profile is co-registered with the heat flow stations and shows the Juan de Fuca plate entering the CSZ from the right and the deformation front and First Anticlinal Ridge. The x-axis is MCS Common Depth Point where 400 CDPs represents 2700 meters.

Although designed as a stand-alone research experiment, our field program is integrated with other recent and continuing GeoPRISMS and Department of Energy Hydrate Programs on Cascadia Subduction Zone. This integration is both a benefit and a necessity given the complex interdisciplinary scientific processes that are presented on the Washington margin. For example, we took advantage of the LANGSETH 2012 Multi-Channel Seismic (MCS) lines to identify sub-surface structures in our survey area and conducted heat flow and fluid flux measurement profiles over Line 4 from that cruise. Our data will also be eventually linked to the Cascadia Initiative Expedition Team (2011-2014) Ocean Bottom Seismometer data to help understand CSZ seismic behavior and hazards and to the planned Department of Energy cruise on the R/V THOMPSON (Solomon and Johnson) that focuses on understanding the response of upper slope gas hydrates to the observed warming of intermediate depth water temperatures off the Washington margin. In order to construct a single high-resolution profile of heat flow and fluid flux measurement across the Washington accretionary prism and adjacent abyssal plane we employed the entire suite of geophysical and hydrological tools available in order to approach the above scientific problems with a comprehensive program. Using the ROV JASON II, we deployed short heat flow probes (204 measurements), 28 thermal blankets, 23 Mosquito flow meters, and took 20 push cores to sample near-surface sediments for pore water chemistry. From the ATLANTIS surface ship we conducted EM122 detailed bathymetry and acoustic backscatter images from the abyssal plain to the shallow continental shelf, 9 CTD casts, 15 multi-core sediment recoveries, and 36 Oregon State University long-probe heat flow insertions.

Figure 3. (left) JASON photo of Mosquito flow meter (left) and thermal blanket (right). (middle) Deployment of dual JASON short probe heat flow instruments, used for redundant measurements at a single heat flow site. (right) Frame grab of JASON video image of actively-forming authigenic carbonate deposit at a methane bubble emission site at 1000 meters water depth. Vertical dimension of photo is about 3 meters.

Remotely Operated Vehicle Jason II deployment operations during the R/V Atlantis cruise off the Washington Coast. Photo Credit Una Miller, UW/Oceanography student.

While these data sets are still being analyzed some results reveal the potential for preliminary interpretation. At the Juan de Fuca oceanic plate approach to the Washington CSZ heat flow data from all three applied methods (JASON short-probe, thermal blankets, OSU long-probe) yield a consistently high heat flow average value of near 100 mW/m2. When this value is downward continued through the incoming sediment column using in situ near-surface thermal conductivities combined with deeper values derived from LANGSETH seismic velocities it yields a basement-sediment interface temperature just west of the deformation front of 225°C. This newly estimated temperature substantially exceeds the canonical values of 100-150°C for fluid production from the smectite-illite transition previously used to define the up-slope boundary of the locked portion of megathrust faults. As our survey moves eastward across the deformation front and up-slope over the ‘second anticlinal ridge’, the closely-spaced heat flow measurements illuminate high spatial variability. This is caused by fluid flow that previously could not be resolved with widely-spaced surface ship measurements. These data show two narrow zones of dramatically decreased heat flow values over the summits of the two westernmost structures that can be interpreted as the inflow of seawater into the dilated uppermost sediment layers. Seismic profiles from the LANGSETH 2012 MCS survey also show structures resembling keystone graben faults at the summits of these western anticlinal ridges, which is consistent with a dilating upper sediment section. Ongoing processing of data from our Mosquito flow meters, sediment cores, and additional heat flow stations will further test this hypothesis. The Washington margin has been recognized for over 50 years as a methane-rich accretionary prism and recent studies have strongly reinforced this view. Our initial EM122 profiles of the survey area at the beginning of the cruise prior to launching our first JASON dives located several active methane emission sites with active bubble plumes rising hundreds of meters into the water column. During the course of the deployment of heat flow and fluid flux stations along the profile we encountered extensive areas of calcium carbonate pavements at the seafloor which in some areas resisted penetration of our heat flow probes and sediment coring instruments. At a thousand meters water depth we discovered several areas of active methane gas emissions and actively forming authigenic carbonate deposits, with delicate aragonite precipitation structures currently forming on the edges of massive carbonate slabs that were several meters thick and hundreds of meters in horizontal dimension. The basic heat flow and fluid flux work are the central data sets for two University of Washington PhD theses (M. Salmi and R. Berg). Processing of the abundance of diverse data collected over our 30-day field program is in progress and will be a fertile data set upon which to base future studies of the Cascadia Subduction Zone. An extension of the original NSF proposed work is a high resolution video survey as an experiment-of-opportunity of three of these methane emission sites and carbonate formation zones with the JASON video camera during the 2013 cruise. These video data and returned carbonate samples are now the core of a previously unplanned UW undergraduate (U. Miller) research project. ■

Funding was through the NSF GeoPRISMS Program with grateful acknowledgement to the crews of R/V ATLANTIS and ROV JASON II. Scientific Party Team listed alphabetically consisted of Rick Berg, Tor Bjorklund, Rick Carlson, Dan Culling, Rob Harris, Casey Hearn, Kira Homola, Paul Johnson, Peter Kalk, Alex Mesher, Una Miller, Brendon Pratt, Adrian Rembold, Marie Salmi, Evan Solomon, and Jon Yang. The cruise investigators subscribe to the NSF Open Access policy and after initial processing the full suite of data will be available online.

Reference information

A Geophysical and Hydrogeochemical Survey of the Cascadia Subduction Zone, Johnson, H.P., Solomon, E.A., Harris, R., Salmi, M., Berg, R.

GeoPRISMS Newsletter, Issue No. 32, Spring 2014. Retrieved from http://geoprisms.nineplanetsllc.com

Report: Workshop on Field Logistics for GeoPRISMS in the Aleutian Arc

AGU Fall Meeting 2013, San Francisco, USA

Workshop Conveners: Peter Kelemen1, Geoff Abers¹, Jeff Freymueller², Paul Haeussler³, Steve Holbrook⁴, Brian Jicha⁵, John Power³, Gene Yogodzinski⁶

¹LDEO; ²University of Alaska, Fairbanks; ³USGS; ⁴University of Wyoming; ⁵University of Wisconsin; ⁶University of South Carolina

Modified from: B. Jicha, G. Yogodzinski and P.B. Kelemen, Sharing Resources for Aleutian Arc Research, Eos, 2014

The Aleutian Arc (Photo Google Earth)

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.

Science

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.

Logistics

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.

Go to the Mini-Workshop webpage

Reference information

Field Logistics for GeoPRISMS in the Aleutian Arc, Kelemen P., Abers G., Freymueller J., Haeussler P., Holbrook S., Jicha B., Power J., Yogodzinski G.

GeoPRISMS Newsletter, Issue No. 32, Spring 2014. Retrieved from http://geoprisms.nineplanetsllc.com

Report: Kermadec Arc-Havre Trough Planning Mini-Workshop

AGU Fall Meeting 2013, San Francisco, USA

Workshop Conveners: Adam Kent¹, Mark Reagan², Laurent Montési³, Kaj Hoernle⁴

¹Oregon State University; ²University of Iowa; ³University of Maryland; ⁴GEOMAR, Germany

Attendees of the Kermadec Arc – Havre Trough Mini-Workshop on Sunday morning

On Sunday December 8, 2013 a diverse group of international researchers gathered at the Grand Hyatt, San Francisco for a GeoPRISMS-sponsored Mini-Workshop aimed at advancing collaborative science within the Kermadec-Havre Trough system (KAHT), part of the SCD New Zealand Focus Site. This followed from the successful New Zealand Planning Workshop held in Wellington in April 2013. The primary goal of this Mini-Workshop was to bring representatives of international groups together to discuss recent results, review ongoing science plans, and to identify area for future work under the aegis of GeoPRISMS.

Following an introduction from the organizers and short presentations by NSF and GeoPRISMS representatives, a keynote presentation by Ian Smith, University of Auckland, provided background on the KAHT system as a classic intra-oceanic arc, and emphasized some of the key science opportunities such as progressive changes in convergence rate and continental contributions along strike from North to South, the significant proportion of felsic rocks that are present, and the possibility for studies of arc initiation in older preserved arc remnants.

These opportunities were also discussed and expanded on by reports from a number of international groups that are either already working in the region or that have well advanced plans. Most of these groups are actively seeking collaborators, reinforcing the potential of the KAHT system for driving multidisciplinary collaborative research. Kaj Hoernle (GEOMAR, Germany) discussed results for upcoming cruises aimed at understanding the inception and evolution of the Vitiaz Arc that was subsequently split into the Tonga-Kermadec and Lau-Colville Ridges. These ridges offer important targets for understanding the timing of initiation and evolution of the KAHT system – particularly in comparison with recent results from the Izu-Bonin-Mariana Arc (IBM) to the North. This point was also emphasized by Mark Reagan (U. of Iowa), who summarized advances in understanding of arc initiation in the IBM – and there may be close parallels between the KAHT and IBM. Yoshi Tamura (JAMSTEC) outlined ambitious plans for ROV studies of arc initiation, origin of basalts, caldera volcanism, and hydrothermal fluids associated with submarine volcanism within the KAHT. This proposed project would be conducted by a Japanese-led team of international researchers. Adam Kent (Oregon State U.) presented results provided by Richard Wysoczanski (NIWA, New Zealand) of sampling cruises to a number of submarine KAHT volcanoes as well as a number of regional and focused geophysical surveys. Many of these data sets will provide valuable for future selection of targets for detailed study. Erin Todd (USGS) discussed trace element and isotopic variations in dredged lavas from the Havre Trough – focusing on the interplay between tectonic and magmatic processes. Erin emphasized the importance of the KAHT for resolving the effects of melting styles, tectonic settings, and mantle thermal conditions on magma production during the rifting phase of backarc basin evolution.

These presentations were followed by a number of “pop up” talks – short presentations detailing other opportunities presented by KAHT research. These included Fernando Martinez (U. of Hawaii) discussing the large difference in spreading rates between the Lau Basin and Havre Trough. Samer Naif (Scripps Institution of Oceanography) described the potential for use of marine EM techniques and Dan Bassett (U. of Oxford) discussed the interplay between structure, mechanics, and seismicity. Jessica Warren (Stanford) detailed a global data base of abyssal and forearc peridotite compositions and Ken Rubin (U. of Hawaii) and Osama Ishizuka (GSJ/AIST) showed results from recent cruises to the northern Lau and the Tonga Trench respectively, that provided additional information on the range of mantle compositions and magmatic processes in the Kermadec-Tonga system.

The final part of the workshop was spent discussing future plans for KAHT research, with a consensus that the system offers many exciting new opportunities for international collaborative research.

Go to the Mini-Workshop webpage

Reference information

Kermadec Arc-Havre Trough Planning Mini-Workshop Report, Kent A., Reagan M., Montési L., Hoernle K.

GeoPRISMS Newsletter, Issue No. 32, Spring 2014. Retrieved from http://geoprisms.nineplanetsllc.com

Report from the Field – Katmai, Alaska

Taryn Lopez, GeoPRISMS Posdoctoral Fellow (University of Alaska Fairbanks)

Fluid movement in the subsurface of active volcanoes is frequently thought to produce abundant seismicity, but the actual type of fluid, including magma, volcanic gases, or hydrothermal waters, cannot yet be constrained from seismic data. Knowledge of the type of fluids in the subsurface can be determined through chemical and isotopic analysis of volcanic gases. In this project, we aim to combine high temporal resolution measurements of volcanic gas composition and seismicity to help constrain the type of fluid associated with these unique seismic signatures. A two-week field campaign was conducted between July 10 – 24, 2013 at three persistently degassing and seismically active volcanoes within the Katmai Volcanic Cluster (KVC), Alaska, to address this problem. The aims of this work were to collect samples of volcanic fluids for chemical and isotopic analyses and to install campaign instruments to measure gas composition, seismicity, and SO₂ flux at high temporal resolution at Mount Martin, Mount Mageik and Trident Volcano.

Another day on the field. Francesco Capecchiacci, (from National Reseach Council, Italy) hikes along Mount Martin’s crater rim. Mount Mageik can be seen in the background. The photo was taken in July 2013 by Taryn Lopez during a two-week field campaign conducted in the Katmai Volcanic Cluster in Alaska.

Part 1:
Volcanic gas and seismic instrument installation

July 10, 2013 – After months of planning, the field campaign for my NSF GeoPRISMS postdoctoral fellowship project was about to get underway. Things were off to a reasonably smooth start with both my field partners Bo Galle (Chalmers University Sweden) and Francesco Cappechiacci (National Research Council, Italy) having arrived safely to Alaska and our team en route to King Salmon, Alaska, the closest town to the KVC. We were met in King Salmon by my Alaska Volcano Observatory (AVO) colleagues Dane Ketner and Max Kaufman, who would be conducting maintenance on the AVO Katmai seismic network and assisting with the instrument installations that were critical to my project. After making some last-minute purchases at the local store, my team headed to the hangar of Egli Air Haul, the local company that has provided helicopter and fixed wing service to AVO for fieldwork in Katmai for over 20 years. Our plan was for Francesco, Bo and I, along with our 600+ lbs. of instruments, food, and field gear to get transported to the famous Valley of Ten Thousand Smokes (VTTS), the site of the largest volcanic eruption of the 20th century, the 1912 Katmai-Novarupta eruption. We would set up our base camp at the USGS Research station on Baked Mountain. Dane and Max would be staying in King Salmon for the next six nights and would fly in each day with Sam Egli, our helicopter pilot. Due to weight restrictions my team would be shuttled to the VTTS on a fixed-wing airplane in two shifts and would then have to hike our gear two horizontal miles and 400+ vertical feet from our landing spot to our base camp. We decided that Francesco and I would go in the first shift and start shuttling our most critical assets to camp. The trip to the VTTS was beautiful and we were lucky to have fantastically clear skies allowing for impressive aerial views. Francesco and I began the first of three slow slogs to camp, while our pilot returned for Bo. By 11:00 PM (or approximately 7 hours after departing King Salmon) we had finally transported ourselves and all our gear to camp. We were exhausted, but happy to be there, and had arrived just in time for a beautiful sunset!

Figure 1. View of Mount Mageik (center) and Mount Martin (right, with plume) as seen from Baked Mountain on 11 July 2013. Photo credit T. Lopez

July 11, 2013 – We awoke to beautiful clear skies, low winds and open-summits at both Martin and Mageik (Fig. 1). Favorable weather conditions like this are atypical of the Alaska Peninsula and we were feeling optimistic that we would complete our field objectives. It was our first of seven days of helicopter support (shared with AVO) during which time we aimed to complete the following tasks: (1) Install MultiGas instruments for measuring volcanic plume composition (CO₂, SO₂, H₂S, and H₂O) and broadband seismometers on the summits of Mount Martin, Mount Mageik, and Trident’s southeast fumarole field; (2) Install scanning NOVAC instruments for measuring continuous SO₂ flux downwind from Mount Martin and Mount Mageik; and (3) Directly sample the fumarolic emissions from Mount Mageik, Mount Martin and Trident Volcano. Additionally, our USGS colleagues also needed to service several seismic stations. Our plan was ambitious but if the weather cooperated it would be achievable.
At 8:00 AM I made my morning check-in call to Dane, who reported that the weather was also clear in King Salmon and he hoped that they would be flying soon. While much of the first day was spent shuttling batteries, instruments, and station enclosures from King Salmon to the Baked Mountain Camp, by 7 PM that evening, Dane and I finally arrived on the summit of our first target, Mount Mageik. With help from Sam, our pilot, we managed to get much of the hardware for our co-located seismic and MultiGas station installed by 9 PM.

From top to bottom: Figure 2. (a) Francesco Capecchiacci samples volcanic gases in the crater of Mount Mageik. (b) Francesco Capecchiacci hikes up from the crater of Mount Mageik. (c) Sam Egli and Taryn Lopez on the crater rim of Mount Martin. Photos credit T. Lopez

July 12, 2013 – The next morning, we awoke to similarly glorious conditions! By noon, Sam had dropped Dane and I off at Mageik’s summit to complete our work. While we continued working on the installation, Sam shuttled Max and Bo to the proposed site for installing the Mageik NOVAC station and then brought Francesco to join us at the summit. Francesco and I were hoping to hike down into the crater of Mount Mageik to sample the fumarolic gases and crater lake water. Working on active volcanoes can be a hazardous job, especially for gas geochemists who often need to spend time within active craters to get the most useful samples. Mageik’s steep-sided crater walls and abundant gas emissions which could eliminate visibility with the slightest wind-change, induced what I hoped was just the right amount of caution to allow us to be successful and stay safe. The wind was blowing the plume to the south, which meant that we had good visibility and access to the fumaroles on the north crater wall. We scrambled fairly easily down the soft, highly altered volcanic rock that comprised the crater walls and set up to begin sampling the gas and steam condensate from a boiling point temperature fumarole (Figs. 2a, 2b). Two hours later we had completed sampling of two fumaroles and took advantage of a brief parting of the plume to scramble down to the crater floor and quickly sample the quite warm and acidic crater lake water. At 5:30 PM we rejoined Dane on the crater rim who had much of the instrument installation completed. After configuring and acquiring the first test data from our instruments, we headed back to camp. Bo and Max had been equally successful and installed the NOVAC instrument in under three hours. It was a good day!

July 13, 2013 – We woke up on our third helicopter day to another beautiful day. The summit of Mount Martin, our next target, was open providing nice views of its persistent plume, and we were eager to begin our work. We adopted the same plan as the previous day and were almost as successful. The one major disappointment of the day was that Francesco and I were unable to sample the vigorously degassing and audibly jetting fumaroles within Mount Martin’s steeply sided crater. We scouted our options from multiple vantage points along the crater rim. Unfortunately most of the crater walls were nearly vertical and comprised of highly weathered, unconsolidated material, with regular outcrops of overhung volcanic rock. We realized that rock falls would be a hazard for all viable routes. With much disappointment, we decided that sampling the Martin fumaroles was not feasible. We were successful in installing the summit seismometer and MultiGas instrument as well as the down-wind NOVAC station and concluded that it was still a very successful day (Figs. 2c, 3)!

Figure 3. Mount Martin co-located seismic and MultiGas station with Mount Mageik in the background. Photo credit T. Lopez

July 14-18, 2013 – The weather conditions over the next several days deteriorated, with high clouds covering most of the summits, and a dense cloud build-up behind Katmai Pass – the gate to our last field target, Trident Volcano’s southeast fumarole field. Bo, Francesco and I spent much of this time at camp, downloading data from the NOVAC stations, and allowing Max and Dane to work on AVO seismic network maintenance. Luckily we had a few nice windows of opportunity during this time period and were able to install the MultiGas sensor and collect fumarole samples at Trident Volcano before having to say goodbye to Bo, Max, Dane, and Sam on July 18. Francesco and I had four more days to hike around the VTTS and collect water samples.

At the end of the July field campaign we had completed 7/8 of our proposed instrument installations and collected gas samples at 2/3 of the proposed volcanic fumarole fields. This was the most ambitious volcanic gas geochemistry effort to take place in Alaska since the 1990’s and we felt very happy with our accomplishments! Our plan was to leave the campaign instruments running over the next two months of summer and then to retrieve the instruments and data before fall arrived in September.

Figure 4. Summit of Mount Mageik as seen flying in on 4 September 2013. Figure 5. (left) The Mount Mageik MultiGas station as found on 4 September 2013. Photos credit T. Lopez

Part II:
Two days stranded on Mount Mageik

September 4, 2013 – I was back in King Salmon with my AVO colleague, John Paskievitch, who had offered to help me retrieve the instruments that my team had installed earlier that summer and who would also conduct some additional AVO maintenance on the Katmai seismic network. It was our first of three scheduled helicopter days to conduct this work and, unfortunately, the weather forecast for this field campaign was not encouraging. After running a few errands around town, John and I headed to Egli Air Haul to meet Sam and to weigh and organize our field gear. By early afternoon, the fog had thinned and we decided to fly to the VTTS to see if any fieldwork would be possible. To our surprise, the valley was clear and Mount Mageik’s summit was open (Fig. 4). After a quick stop at the Baked Mountain Huts to drop off any unnecessary weight and to get into our warmest clothes, we flew to Mount Mageik’s summit, arriving at ~3 PM.

Our station was located on a small hill between Mount Mageik’s four summits, on the rim of the actively degassing crater and surrounded on three sides by heavily crevassed glaciers. Upon our arrival to the station, John and I found that the station enclosure had become unlatched, was open, and the instruments and the station antenna mast were completely covered in thick rime ice (Fig. 5). We had blue skies above us but a dense wall of clouds was building up on the south side of Mount Mageik, and we knew that we had to watch the weather closely, as conditions could change very quickly. Sam stayed in the helicopter and watched the weather while John and I began to extract the instruments from the frozen ground. Approximately 30 minutes later Sam told us that the weather had deteriorated and we needed to leave NOW!

Clockwise from top left: Figure 6. (a) John Paskievitch as seen on 4 September 2013 after securing the helicopter with snow anchors in preparation for spending the night. (b) Helicopter covered in thick rime ice after ~16 hours on the summit of Mount Mageik (5 September 2013). (c) Alaska Air National Guard Rescue team and Pavehawk helicopter on Mount Mageik. Photos credit T. Lopez

John and I grabbed our equipment and helmets and were back in the helicopter in less than four minutes. Unfortunately, in those few minutes the clouds had rolled in, bringing with them freezing rain. Sam powered up the helicopter and we sat ready to take off at the first sign of improved visibility, while the helicopter blades were gradually accumulating ice. Approximately 15 minutes later, having had no improvement in visibility, Sam realized that the rotor blades had too much ice to fly. Sam powered down the helicopter and John and I made several futile attempts to scrape ice off the rotor blades. Conditions continued to deteriorate, and we realized that we would have to spend the night on the mountain and we would likely require rescue as our helicopter would probably not be flyable due to ice accumulation. We called Egli Air Haul and the AVO duty scientists to inform them of our situation and to ask them to notify the Alaska State Troopers.

In any survival training course you will learn that the first thing you should do in an emergency situation is to secure shelter. We were lucky to have brought our shelter with us, but with the high winds our helicopter was at risk of being blown down into the crater. Therefore, with Sam and I sitting in the helicopter to keep it weighed down, John spent several hours securing the helicopter with “dead-men” snow-anchors (Fig. 6a). By 9 PM our shelter was secure. Our next priority was simply to stay warm and dry, conserve energy, and wait for rescue. Thankfully we were well prepared for an emergency situation and had sufficient clothing, sleeping bags, sleeping pads, bivy-sacks, food, water, and communication supplies to keep us comfortable, at least in the short term. We also had a combination of ~55 years of experience doing field work in Alaska and I was very grateful for my highly experienced and resourceful comrades!

September 5, 2013 – After a fitful night of sleep with strong winds peaking at 75 mph, we woke to similarly dismal conditions, with continued freezing rain and poor visibility. We also found that the entire helicopter was covered in ~8 inches of rime ice, making it difficult to open the doors and even causing the helicopter’s frame to distort under the excess pressure (Fig. 6b). We passed the day quietly, dozing a lot, talking some, going outside as infrequently as possible, and looking forward to our regular satellite phone check-in calls with Egli Air Haul. By 5:00 PM that day, there was no improvement to the weather and no external rescue efforts had been planned. We realized that our situation could easily go from uncomfortable to life threatening if we were not rescued soon, especially considering that our shelter was at risk of being compromised with the increasing ice-load. At that point Sam turned on the helicopter’s Emergency Locator Transmission. Within an hour we received word that the Alaska Air National Guard (AANG) was mobilizing rescue teams. At 9:00 PM that evening we first heard the comforting sounds of our rescue aircraft nearby. The AANG had deployed two rescue teams to assist us. One team based on a C-130 airplane was flying over our position, looking for any potential breaks in weather, while the second aircraft, a Pavehawk helicopter, contained our ground-support team. Using our helicopter’s radio we were able to directly speak with the AANG pilots and set up regular check-in times to communicate with them in case of potential weather breaks. Unfortunately, a thick layer of clouds continued to keep us trapped through the night. We spent a second night in the helicopter, colder and less comfortable than the first, but encouraged by the regular sound of our rescue aircraft nearby.

Panoramic view from the North of the Katmai Volcanic Cluster. Photo credit T. Lopez

September 6, 2013 – By 8:00 AM the next morning, the winds had dropped significantly and the temperature was rising. Most encouraging of all was that visibility had increased to ~20 m and the sky was brighter indicating a thinner cloud deck. By noon, the ice on the helicopter frame had begun to melt. Over the next three hours the Pavehawk helicopter flew back and forth over our location hoping to catch a break in the clouds and sweep in to rescue us. Using our hand-held USGS radios and the sound of their rotors, we helped them narrow in on our position. The clouds continued to thin and we were finally rewarded with the welcome sight of their massive helicopter! Minutes later, the Pavehawk had landed on the glacier below us and two of our rescuers, tethered to the Pavehawk, quickly crossed the glacier to meet us and escorted us back to safety (Fig. 6c)!
Our experience on Mount Mageik went about as well as it could have thanks to Sam’s resolve to not fly in unsafe conditions, John’s resourcefulness in anchoring the helicopter, our preparation with survival gear and training, an excellent support/communication team at home, and the competency and bravery of the AANG rescue team. I feel very lucky that all of these things came together so that I have the opportunity to share my story today. While I learned many important life lessons during this experience, I would like to share two of them here: (1) Spend as much time as possible with your loved ones as you never know what day will be your last, and (2) Fieldwork in Alaska should never be taken lightly, so ALWAYS carry your survival gear and have proper training! ■

Reference information

Report from the Field – Katmai, Alaska, Lopez T.

GeoPRISMS Newsletter, Issue No. 32, Spring 2014. Retrieved from http://geoprisms.nineplanetsllc.com

Overview

Roadmap to Future scientific drilling in the Izu Bonin arc

What is ExTerra?

Workshop summary

Big Science Questions

ExTerra Field Institutes

Workshop topics and agenda

Identification of geographic corridors and priorities within those corridors

International Collaborations

Student Participation

Concluding Remarks

Science

Logistics

Part 1: Volcanic gas and seismic instrument installation

Part II: Two days stranded on Mount Mageik

Part 1:
Volcanic gas and seismic instrument installation

Part II:
Two days stranded on Mount Mageik