Putting the “Community” in the Alaska Amphibious Community Seismic Experiment (AACSE): Alaska Peninsula and Western Gulf of Alaska, Summer 2018


The AACSE Team*

*This report was edited and compiled by Lindsay Worthington.

AACSE PI team: Geoff Abers (Lead PI, Cornell U.), Aubreya Adams (Colgate U.), Peter Haeussler (USGS), Emily Roland (U. of Washington), Susan Schwartz (U. of California Santa Cruz), Anne Sheehan (U. of Colorado), Donna Shillington (Lamont Doherty Earth Observatory), Spahr Webb (Lamont Doherty Earth Observatory), Doug Wiens (Washington U. St. Louis), Lindsay Worthington (U. of New Mexico).

2018 Apply-to-Sail Participants: Collin Brandl (Graduate Student, U. of New Mexico), Enrique Chon (Graduate Student, U. of Colorado), David Heath (Graduate Student, Colorado State U.), Robert Martin-Short (Graduate Student, U. of California Berkeley), Kelly Olsen (Graduate Student, U. of Texas), Holly Rotman (Postdoctoral Researcher, New Mexico Tech), Samantha Hansen (Associate Professor, U. of Alabama), Tiegan Hobbs (Graduate Student, Georgia Tech), Amanda Price (Graduate Student, Washington U. St. Louis), Heather Shaddox (Graduate Student, U. of California Santa Cruz), Jefferson Yarce (Graduate Student, U. of Colorado Boulder), Natalia Ruppert (Seismologist, U. of Alaska Fairbanks)

K-12 Educators On Board: Shannon Hendricks (High School Science Teacher, Anchorage School District), Bethany Essary (High School Science Teacher, Anchorage School District).

The shore-based field teams included graduate student Michael Mann (Lamont-Doherty Earth Observatory) and undergraduate student Jordan Tockstein (Colgate U.). We thank the captain and crew of the R/V Sikuliaq and the pilots, boat captains and land owners that made these deployments possible. Special thanks to Bill Danforth from the USGS for his bathymetric processing expertise aboard Leg 2 and Patrick Shore from Washington U. for coordinating onshore field logistics and preparing the data for delivery to the DMC.

If you visit Alaska and tell people that you are a seismologist, you are going to hear an earthquake story. The Alaska-Aleutian subduction system is arguably the most seismically active globally, producing more >M8 earthquakes over the last century than any other. As a result, earthquake and tsunami hazard are woven into daily life here. Near downtown Anchorage, you can visit Earthquake Park, occupying part of town that was decimated by a landslide during the 1964 M9.2 event that inspired the term “megathrust” earthquake. If you happen to be in Kodiak on a Wednesday afternoon, you will hear the weekly tsunami siren drill sound throughout the town. Earlier this year that drill was put in to practice as residents made their way through the tsunami evacuation process, meeting up at the school on high ground after midnight on January 29 following the M7.9 earthquake that occurred offshore.
So, how do you study an 800 km section of this subduction zone that is mostly offshore or only accessible via air or boat? Simple. Start with nine Principal Investigators (PIs) and dozens of conference calls; take 85 ocean bottom seismometers (OBS), thirty broadband seismometers, one fishing boat, two float planes, two fixed wing planes, a helicopter, and a 261-ft research ship; add a team of twelve OBS engineers, 24 ships crew, twelve Apply-to-Sail participants, two Alaskan K-12 teachers and two field technicians. Then make the data open and accessible as quickly as possible. This is the Alaska Amphibious Community Seismic Experiment (AACSE) and these are voices from the field.

The Alaska Amphibious Community Seismic Experiment (AACSE) deployment map prepared by Peter Haeussle

OBS Deployment Cruise Leg 1 | Seward, AK to Seward, AK – May 9-29, 2018

>> 9 May, 2018 | We are officially underway • It is 8:30am and we are departing Seward dock. We have donned our full-body immersion suits as part of a safety drill, and are now heading towards the first seismometer deployment site, lying in the Shelikof Strait just north of Kodiak Island. We are on one of the most modern and well-equipped scientific research ships in the world. The R/V Sikuliaq was built in 2014 and has a science lab, lounge, dining room, kitchen, gym, and the list goes on. There is even a sauna which apparently can double as a hypothermia recovery room – let’s hope we won’t be using it for that purpose. For cabins, we are treated to the height of oceanographic luxury. The rooms are practical and very comfortable. The Sikuliaq takes its name from the Inupiaq word that means “young sea ice”. Thanks to its round hull, the ship is capable of breaking ice up to 2.5 ft thick, which is essential on polar missions. This also gives it a tendency to move around more in high seas. As we travel, we will be collecting meteorological data such as pressure, temperature, and wind speed. We will also be recording bathymetry data to map the seafloor.

-Robert Martin-Short, University of California Berkeley

>> 10 May, 2018 | Deploying the first OBS instrument • The first OBS (Ocean Bottom Seismometer) is a shallow-water Trawl-Resistant Mounted Seismometer (TRMS), design to resist and deflect the lower leading line of bottom trawl nets. All of the OBSs are instrumented with a seismometer, batteries to last more than fifteen months, transponders to communicate with the ship and burn the wire to release the seismometer for recovery, data logger, temperature sensors, and other equipment necessary to collect these data. The shell for the TRMS itself weighs about 1,300 lbs, the whole instrument weighs about 1,800 lbs. The deployment is a success! After deploying the TRMS, we have to hide from foul weather in Larsen Bay, then assemble more TRMSs. This involves removing the doors and installing brackets to hold equipment, attaching hoods to the pop-up TRMS, checking the transponders to make sure they are properly communicating with the ship, and attaching the transponders. We will stay in the cove and work for a couple hours, then leave once the storm has passed.

-David Heath, Colorado State University

>> 12 May, 2018 | Waiting out the storm • Many of us are taking to personal hobbies and pastimes in between routine status logging. Some people are reading quietly. Others are attempting to catch up on emails, though the internet is particularly slow. Others are taking the opportunity to chat with shipmates, many of whom are still practically strangers after few days on the ship. I am learning that life on a ship provides a unique opportunity for people to connect with each other. I have spent part of the evening receiving a generous guitar lesson from the Chief Steward who is a skilled blues musician. He kindly reached out to play alongside me when he noticed me strumming out on deck. I’ve got to say, my experience thus far has been pretty great, despite the spotty weather and fits of acute nausea.

-Enrique Chon, University of Colorado

OBS Deployment Cruise Leg 2 | Seward, AK to Seward, AK; July 11-24, 2018

>> 11 July, 2018 | Educators Onboard • There are so many people involved in a research cruise like this. There is an entire ship crew, scientists, graduate students, USGS employees, OBS technicians, and, on this trip, there are even two high school science teachers and I am one of those. I am stoked to be on board. My colleague, Shannon Hendricks, and I were selected as part of the Educator Onboard K12 program. Through this program, educators are given the opportunity to participate in research to better understand current science practices. The goal is to use that knowledge to create engaging, authentic lesson plans to share with other educators. It is a little intimidating to meet all of these experts – as science teachers, we know a little bit about a lot of things, and we have a solid enough science foundation to understand what the experts are talking about (most of the time!). This also means we know enough to realize how much we don’t know! It is amazing to get to learn from scientists that have made this their life work. Getting to peek in on their ongoing research makes us better science teachers. And it is nice to know that, just like we tell our own students, there are no stupid questions.

-Bethany Essary, West High School science teacher, Anchorage, AK

>> 23 July, 2018 | The aftershock zone • Day 12 of the cruise, we have just successfully deployed our last OBS, 32 hours ahead of schedule! Half way through this cruise, we decided to move one of the instruments to near the aftershock zone of the M7.9 Offshore Kodiak earthquake. It struck about three hundred kilometers offshore Kodiak Island in the early morning hours of January 23, 2018, in the outer rise region of the Alaska-Aleutian subduction zone. It triggered tsunami warnings and prompted evacuations of thousands of people in Alaskan coastal communities. While the source parameters (such as seismic moment tensor) for the earthquake suggested strike-slip faulting (hence no significant tsunami generated), the true complexity of the source has only become evident through analysis of multiple datasets. At least four conjugate strike-slip faults were involved in the earthquake rupture. However, the distant location of the aftershock source region to the land-based stations made the data analysis and interpretation difficult. On the Leg 1 cruise, a couple of stations were serendipitously placed near or in the aftershock zone. After consultations with the PI group we moved this station to the aftershock cluster. This enhanced network of OBS sensors in the aftershock zone will help characterize the aftershock sequence with much better accuracy.

-Natalia Ruppert, University of Alaska

>> 24 July, 2018 | Good luck • For the past three years, I have been looking at OBS data off the east coast of New Zealand’s North Island, and I always wondered about the logistics behind the dataset of earthquakes. It turns out that deploying ocean bottom seismometers is a huge task that includes multiple people. This experience exceeds all my expectations. I imagined a repetitive process, but every single station has its own challenges: the bathymetry indicates a rough or steep relief so we have to move somewhere close by with a more flat and soft bathymetry; we need to be sure that the temperature sensors are the ideal for specific depths; we fill the sheets with station information and log it in our physical and digital forms, etc. This experience makes me really value all the effort that the science crew did for the deployment and recovery of the data that I am currently working on. For the future seismologists who are going to work with the data, I want to say that we did our best to make sure the seismometers were meticulously deployed and I am sure the recovery crew will be equally careful to collect the year-long log of wiggles from the stations deployed by the first and second legs. Good luck!

-Jefferson Yarce, University of Colorado

Onshore Deployment: Alaska Peninsula, Kodiak Island and Shumagin Islands; May-June 2018

>> 16 May, 2018 | A for Amphibious • The second A in AACSE stands for Amphibious – fully encompassing the entire subduction zone requires making measurements on land and at sea. The onshore part of the program involves installing instruments on Kodiak Island, the Shumagin Islands (southwest of Kodiak), the Alaska Peninsula and the region around Katmai National Park. These thirty instruments will be placed in remote locations (black circles on the map p.19) accessed by float planes or small fixed-wing planes. One team of three people is installing thirteen sites on Kodiak Island, and a second team is deploying the rest of the sites on the mainland and Shumagin Island. Today the Kodiak team started their first day of work! Like working at sea, the initial work involves unpacking all the gear shipped from across the country, and testing and assembling everything. To make sure everything is working properly, we do a “huddle test,” where we set up all of the seismometers and data loggers in one place and let them collect data for one day. We are fortunate to have been given access to some space in the Kodiak Alaska Fisheries Science Center, a research facility that provides valuable data to the fishing industry and that has a wonderful aquarium. This means we are sometimes sharing the space with sea life, like a large half-decomposed salmon shark! Tomorrow, if all goes well, we can start deploying!

– Geoff Abers, Cornell University

>> 21 May, 2018 | Kodiak Island • The road network on Kodiak Island is confined to the region around the town of Kodiak, so one must travel by boat or plane to reach other parts of this rugged and beautiful island. Eight of the thirteen seismic stations that we are installing here are both off the road system and far from towns with air strips, and we have been traveling to them by float plane. One limitation of using small planes for seismic installations is that there is a weight limit on what you can bring. The float plane we have been using, a de Havilland DHC-2 Beaver, can carry 1,200 lbs. Our field team and equipment for two stations weigh 1,175 lbs! We have to do a weigh-in before our first flight – fortunately they weighed our field team together and not individually. Flying also requires better weather than simply driving to a station. So far, we have found that the weather is worse on the eastern part of Kodiak near Kodiak town but improves to the west. We feel lucky to have had three days in a row where we could fly out to some of our sites. In the last three days, we have installed five stations that have taken us to many corners of Kodiak: McDonald lagoon on the southwestern coast, small Anvil Lake in far western Kodiak and the gorgeous Uyak Bay, a fjord that connects to the ocean in the north and cuts across two thirds of the island. This fjord is enabling us to deploy closely spaced stations over a part of the subduction zone fault where large earthquakes occur, one of the primary targets of this project. Traveling by plane across Kodiak is spectacular; you are treated to stunning views of snow-capped mountains and broad valleys. Sometimes you can see mountain goats lining steep slopes, bears meandering along the shore, and frolicking otters in the water. The views from our seismic sites are really amazing, too, when we look up from orienting sensors and plugging in data loggers. Six down, seven to go for the Kodiak team!

-Donna Shillington, Lamont-Doherty Earth Observatory

>> 30 May, 2018 | Challenging Conditions • The three members of the Sand Point team set sail on the Aleut Mistress to install two strong motion sites on Nagai Island. The day started with beautiful glassy-smooth seas and a calm two hour cruise to our first site on the north side of the island. We loaded our equipment into a skiff, hopped onboard and motored to our chosen landing site. This site was chosen by satellite imagery, and as always, conditions on the ground were a little different than expected. Our landing site was a bit marshy, and we had to lug the equipment uphill through marsh grasses and bushes, and then dig through a foot-thick mat of interwoven vegetation to find a suitably dry site for burial. Anything for good data! The equipment worked like a champ, so our time spent testing it in Sand Point paid off. We left the station after five hours of work – only two-and-a-half times longer than it has taken for any other station thus far! Back on the Aleut Mistress, our captain, Boomer, had boiled some Alaskan crab for our lunch. Hard to get it any fresher!

In the afternoon, the seas started picking up with swells a little over two fathoms (that’s a little over twelve feet for you land-lubbers). While none of our crew suffered from seasickness, there were some flying objects on deck and in the cabin! We hopped back in the skiff when we reached Nagai site #2, and headed toward shore. We got so close, but in the end the boat crew felt it was unsafe to land with the high seas and changing tide. Disappointed, we made the call to cancel the site. It is a hard decision to choose not to install a station. Fortunately, an excellent Plan B fell into our laps. As luck would have it, Boomer owns property near King Cove and offered his place as a home for our new station. So, a fairly tough first day in the field ended on a high note, with the formation of plans for the future. The next three days passed slowly, as our team waited on unanticipated repairs to the plane needed for other installations out of Sand Point. Everybody wants a well-maintained plane, so we waited patiently for the repairs and sorted through and retested equipment in Sand Point. By the time the plane was ready, our team was raring to hit the field again. We hammered out four more stations in just two days, and have nearly finished our work here in Sand Point.

-Aubreya Adams, Colgate University

Get involved

This project is intended to help grow the seismological community, and includes opportunities to sail on OBS cruises and short courses for undergraduates. Upcoming opportunities for 2019 will be announced in December on the project website.

Contact members of the PI team for more information. All seismic data from the project will be open to the community upon recovery and QA/QC efforts at the IRIS DMC (OBS array has network code XD (2018-2019) and land array has network code XO (2018-2019)). The first three months of onshore data is currently online. All underway data acquired by the Sikuliaq will be archived and available at the UNOLS rolling deck to repository server.

Check out the experiment blog for more stories from the field

Reference information

A continent-scale geodetic velocity field for East Africa. R. Bendick, M. Floyd, E. Lewi, G Kianji, R. King, E. Knappe
GeoPRISMS Newsletter, Issue No. 41, Fall 2018. Retrieved from http://geoprisms.org

Revealing the secrets of the New Zealand GeoPRISMS Primary Site


Slow slip and future earthquake potential in New Zealand and Cascadia

Slow slip and future earthquake potential in New Zealand and Cascadia

Noel Bartlow (University of Missouri), Laura Wallace (UT Austin & GNS Science), Ryan Yohler (University of Missouri), and Charles Williams (GNS Science) The New Zealand and Cascadia subduction zones are two GeoPRISMS primary sites that have...
Probing the nature of the Hikurangi margin hydrogeologic system

Probing the nature of the Hikurangi margin hydrogeologic system

Evan A. Solomon (University of Washington), Marta Torres (Oregon State University), and Robert Harris (Oregon State University) Fluid generation, migration, and pore fluid pressure at subduction zones are hypothesized to exert a primary control...
Volatile cycling through the Hikurangi forearc, New Zealand

Volatile cycling through the Hikurangi forearc, New Zealand

Jaime D. Barnes (UT Austin), Jeffrey Cullen (UT Austin), Shaun Barker (Univ. of Waikato), Samuele Agostini (Istituto di Geoscienze e Georisorse), Sarah Penniston-Dorland (Univ. of Maryland), John C. Lassiter (UT Austin), Andreas Klügel (Univ. of ...
The NZ3D Experiment – Adding a new dimension for understanding slow slip events

The NZ3D Experiment – Adding a new dimension for understanding slow slip events

MGL1801 Participants - Ryuta Aral (JAMSTEC), Stephen Ball (Univ. of Wisconsin, Madison), Nathan Bangs (UT Austin), Dan Barker (GNS Science), Joel Edwards (UC Santa Cruz), Melissa Gray (Imperial College London), Shuoshuo Han (UT Austin), Harold Leah...
IODP tackles the Hikurangi Margin of New Zealand with two drilling expeditions to unlock the secrets of slow-slip events

IODP tackles the Hikurangi Margin of New Zealand with two drilling expeditions to unlock the secrets of slow-slip events

MGL1801 Participants - Ryuta Aral (JAMSTEC), Stephen Ball (Univ. of Wisconsin, Madison), Nathan Bangs (UT Austin), Dan Barker (GNS Science), Joel Edwards (UC Santa Cruz), Melissa Gray (Imperial College London), Shuoshuo Han (UT Austin), Harold Leah...
Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip (HOBITSS) - Revealing the environment of shallow slow slip

Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip (HOBITSS) - Revealing the environment of shallow slow slip

Susan Schwartz (UC Santa Cruz), Anne Sheehan (University Colorado, Boulder), Rachel Abercrombie (Boston University) In the last fifteen years, it has become evident that slow slip events (SSEs) are a common and important part of the subduction process....
Sizing up the Taniwha: Seismogenesis at Hikurangi Integrated Research Experiment (SHIRE)

Sizing up the Taniwha: Seismogenesis at Hikurangi Integrated Research Experiment (SHIRE)

Jeff Marshall (Cal Poly Pomona) andJessica Pilarczyk (University of Southern Mississippi) “A Live Dragon” Beneath the Sea In Māori culture, the Taniwha is a dragon-like beast that lives beneath the water, sometimes protecting seafarers, whil...
Assessing changes in the state of a magma storage system over caldera-forming eruption cycles, a case study at Taupo Volcanic Zone, New Zealand

Assessing changes in the state of a magma storage system over caldera-forming eruption cycles, a case study at Taupo Volcanic Zone, New Zealand

Kari Cooper (UC Davis), Adam Kent (Oregon State University), Chad Deering (Michigan Tech), and collaborator Darren Gravley (University of Canterbury, New Zealand) The largest volcanic eruptions are rare events but when they occur can represent a...
SISIE: South Island Subduction Initiation Experiment

SISIE: South Island Subduction Initiation Experiment

Erin Hightower (Caltech) and Brandon Shuck (UT Austin) The South Island Subduction Initiation Experiment (SISIE) was an international collaborative active-source seismic survey of the Puysegur subduction margin conducted aboard the R/V Marcus G....

Magnetotelluric and Seismic Investigation of Arc Melt Generation, Delivery, and Storage beneath Okmok Volcano


Kerry Key (Scripps Institution of Oceanography) and Ninfa Bennington (University Wisconsin-Madison)

It all sounded so easy when we were writing the proposal. Sure, we can deploy 54 seafloor magnetotelluric (MT) instruments around a remote Aleutian island, no problem, we have done lots of marine MT surveys before. Add on an array of onshore magnetotelluric and passive broadband seismic stations covering the flanks and caldera of a volcano that erupted without almost no warning back in 2008? Sure, that won’t be too hard either since we will have a helicopter transporting the field teams and science equipment, and we can base our camp at a remote cattle ranch used by previous field teams studying Okmok volcano. So we worked up a budget, wrote the proposal text and submitted it to the July 2014 target date for proposal submissions to the National Science Foundation’s GeoPRISMS program.

Fast forward to early January 2015 when we received an email from Bil Haq, then one of the two NSF Program Managers for GeoPRISMS, stating “Your proposal did well in the competition for GeoPRISMS funds and I plan to fund it at this time”.

Yes!!!!! Woohoo!!!!!! Seriously, this was good news.

Then comes the word that the field work will start in mid-June. We were supposed to get everything in place for two short cruises and three weeks of onshore field work in just a few months. Time to get moving!

The Logistics

We started a seemingly endless chain of emails and conference calls to work out the logistics for the onshore field work. We would be working out of a field camp at Bering Pacific Ranch on the abandoned WWII military base Fort Glenn, located on the eastern flank of Umnak island. Our tasks were to get a helicopter, about fifty barrels of helicopter fuel, seismometers, magnetotelluric instruments, cooking supplies and food for about 160 person-days delivered by the start of field operations around June 20th. The tiny city of Dutch Harbor, conveniently located about 100 km away on neighboring Unalaska Island, is the country’s largest fishing port by volume, so we planned to ship our stuff from the lower 48 states up to Dutch Harbor, where it would be consolidated and then shipped to Fort Glenn. Easy right?

Amazingly, this plan actually worked out. Once all the geophysical equipment, batteries, helicopter fuel, non-perishable food and cooking supplies arrived in Dutch Harbor, it was loaded onto the Island Packer, a small landing craft, and then ferried on a 60-km journey from Unalaska Island to a makeshift dock at the beach near Fort Glenn. Then two ranch hands transported it 5 km up to the field camp at the ranch.

By comparison, preparing for the marine part of the project was relatively straightforward since the Scripps lab does this routinely and all we had to do was get the marine MT equipment to the ship. By coincidence, our deployment cruise was scheduled on the RV Thompson, which happened to be passing through San Diego on its way north, so we lucked out and loaded the marine MT gear onboard for a free ride up to the Aleutians.

June 16-17, 2015 | Making it to Dutch Harbor

Dutch Harbor was also the port of departure for the marine MT deployment cruise so we flew into Anchorage and then boarded connecting flights to Dutch Harbor. While anywhere else in the US this would likely be an easy connection, flights to the Aleutian islands are unpredictable due to frequent low hanging clouds and fog. When the planes take off in Anchorage, they don’t know how the weather will be in Dutch Harbor so they load enough fuel on board to make the return trip if visibility is so bad they can’t see the Dutch Harbor runway. This was indeed the case for several of our connecting flights, and so it took a few attempts spread out over a few days for everyone to finally make it to Dutch Harbor. At the local grocery store Safeway, which was unexpectedly well stocked with a cornucopia of fresh produce, we gave the manager a lengthy shopping list of fresh produce, dairy, meat and seafood and he promised it would be delivered to the airport on the morning of June 22, where it would be loaded onto the charter flights taking us west to Fort Glenn.

June 18-21, 2015 | Deployment Cruise

We pushed off the dock around mid-day on the 18th and by 01:00 on the 19th the ship arrived at the first station, located on the northern end of the survey profile in the Bering Sea. By 10:00, we had already deployed seventeen seafloor MT receivers. The sky was filled with low hanging clouds so we couldn’t see Umnak Island, but the lack of view was made up for by the lack of wind and almost no swell – perfect conditions for the maiden marine flight of our consumer-grade drone, allowing us to capture some 4K high definition videos of ship and the science team deploying MT receivers. While waiting in port during the previous days, we had done a lot of prep work, including putting batteries in the 54 data loggers for the MT receivers, synchronizing their crystal oscillator clocks with GPS time and programming them to startup around the time we predicted they would be on the seafloor. So now for each receiver deployment, all we had to do is mount the magnetic field induction coil sensors on the receiver frame along with the two long electric dipole arms, attach the external electronic compass, plug in all the sensor cables, secure the concrete anchor strap, test the acoustic release system, test the stray-line buoy’s radio and finally attach the bright orange flag to the frame. There is a well-developed procedure for all these steps and checklist to make sure nothing is skipped, so it all goes like clockwork thanks to the careful efforts of the students, postdocs and technicians working either the noon-to-midnight or midnight-to-noon shifts (ship-time is not cheap so the vessel works 24 hours a day).

The clouds partially lifted in the late afternoon of the 19th as we entered Umnak Pass, a narrow channel that separates Umnak Island on the west from Unalaska Island on the east. The MT deployment carried on like clockwork and by the 20th we were making way into the Pacific Ocean, which was starting to kick up with strong winds and some moderate swell. We finished the last MT deployment about twelve hours ahead of schedule so we decided to use the extra time to collect high resolution multibeam bathymetry on the forearc slope before heading back to Dutch Harbor. Our journey back to port went about the northern shore of Unalaska, and with luck the clouds lifted partially to give some nice views of Mount Makushin volcano. As usual, soon after the ship tied up most of the crew and science party headed to the local bar to re-equilibrate after a few days on a dry ship.

June 21-July 8, 2015 | Onshore field work

The next phase of the project started with flights from Dutch Harbor to Fort Glenn that transported the science party, two ranch hands, and the perishable food that Safeway had just delivered. From the gravel landing strip (left over from WWII) at Fort Glenn, a ranch hand drove the science party and food up to the camp house where we would stay. The camp house was basically three trailer units arranged in a u-shape with an aluminum roof overtop and a giant garage door on the open side of the U. One unit was a cooking trailer with full kitchen and dinner area. Another was a bunk house and the third was a bathroom, shower and laundry facility. While we weren’t going to exactly be roughing it, nobody had stayed here in several years and everything was covered in mold and black volcanic dust, and the window sills were graveyards of giant fly corpses. We spent much of the first day cleaning up the place, stocking the kitchen and setting up workbenches for the geophysical equipment in the enclosed space in the middle of the three trailers. Sometime during the first day the helicopter arrived and everything was coming together for us to begin operations the next day.

Our seven-person science team would helicopter into and around Okmok volcano. Half of the crew carried out an onshore magnetotelluric survey collected in an array using a combination of long-period and wide-band MT systems, with nineteen stations within the caldera and ten stations outside. The remainder of our field team installed thirteen temporary broadband seismometers both in and around the volcano. The temporary seismic array recorded seismic data until its retrieval in summer 2016. In tandem with the Alaska Volcano Observatory’s twelve permanent seismic stations, there were twelve seismic instruments within/at the rim of the caldera and fourteen seismic instruments outside the caldera.

Both the seismic and MT teams operated in parallel so the helicopter went back and forth ferrying the teams around. That meant we always had to be prepared to be left overnight (or longer) at field stations if the fog came in and the helicopter couldn’t return to pick us up (luckily this never happened, despite a few close calls). We also had to be prepared for being chased by one or more of the ~7000 feral cattle that roam the outer flanks of the caldera. We quickly developed a protocol where after dropping off a team, the helicopter would fly in a 1-km circle around the station chasing away any nearby cattle. Despite this, there was an occasion where the seismic team had to make haste into a ravine to get away from an angry bull. While the MT systems only needed to record data for a few days and thus were all recovered by the end of the first field season, the broadband seismic systems were going to record seismic waves for the next year and would be picked up during the second field season.

July 9-14, 2015 | Recovery cruise

For the marine MT recovery cruise, we were on a different ship, the newly built RV Sikuliaq. Recovering the marine MT receivers meant driving up to them in the ship, sending an acoustic command that tells the instrument to let go of its anchor and then waiting for the instrument to rise to the sea surface. Once on the surface, the instrument’s stray line buoy radios the ship with its GPS position. The ship then drives up to the floating instrument from the downwind side and once its alongside the ship, we toss a grapnel around the stray line and use that to attach the instrument to the ship’s remotely operated crane, which then lifts it aboard. We successfully recovered all instruments except one that was deployed in a dicey location in Umnak Pass where there were strong currents that we suspect carried the instrument away after it released its anchor.

July 29 – Aug 6, 2016 | Recovery of seismic instruments

In summer 2016, we returned to Umnak Island to recover the seismic instruments. This time our operations were based on marine vessel Maritime Maid. Operations continued in a similar fashion to the previous field season with helicopter providing the team’s transportation to and from Okmok. However, this year there was an added level of excitement as take-offs and landings were carried out on the ship’s small helipad. Due to unusually cloudless blue skies and warm temperatures, we demobilized all thirteen seismic sites in a matter of several days. Amazingly, and quite happily, we found that the majority of stations were still up and running when returning to the sites for demobilization. After a rapid and successful field season, we departed from the wonderful Maritime Maid crew and made our way back home. ■

“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.org. This opportunity is open to anyone engaged in GeoPRISMS research, from senior researchers to undergraduate students.
We hope to hear from you!

Reference information
Magnetotelluric and Seismic Investigation of Arc Melt Generation, Delivery, and Storage beneath Okmok Volcano. K. Key, N. Bennington
GeoPRISMS Newsletter, Issue No. 38, Spring 2017. Retrieved from http://geoprisms.org

Seeking the origins of continents in the western Aleutian island arc


Elizabeth Cottrell (Smithsonian Institution), Katherine A. Kelley (University of Rhode Island), Michelle Coombs (USGS Alaska Volcano Observatory), Elizabeth Grant (University of Washington), Mattia Pistone (Smithsonian Institution), and Katherine Sheppard (UC Santa Barbara)

The origin of Earth’s continents is among the most fundamental of questions facing geoscientists today. Though andesitic in composition, continental crust shares many geochemical characteristics with basaltic lavas erupted at subduction zone arc volcanoes, suggesting that subduction zone magmatism somehow manufactures Earth’s continents. Our project goal is to examine one particular attribute shared by arc magmas and continents, unusually low iron contents (sometimes referred to as “calc-alkaline affinity”). Our work will test the roles of magmatic water content, oxygen availability, and parent magma composition on the development of low iron in arc magmas. With this goal in mind, we conducted a three-week field campaign, from September 4-23, to the far Western Aleutian islands of Buldir, Kiska, Segula, Little Sitkin, Semisopochnoi, Gareloi, Tanaga, and Kanaga, home to some of the most calcalkaline lavas on Earth. The goals of the field program were to collect samples of volcanic airfall deposits (tephra), which may preserve glass inclusions within the igneous phenocrysts that will reveal the water contents and oxygenation conditions of these end-member magmas. We conducted our field work from the home base of the R/V Maritime Maid, which anchored in four harbors among these islands, and used a Bell 407 helicopter to access field sites on these eight volcanoes. On the Maid, our GeoPRISMS team of five (Liz Cottrell, Michelle Coombs, Mattia Pistone, Elizabeth Grant, and Katherine Sheppard) was joined by a team of volcanic gas scientists supported by the Deep Carbon Observatory (Tobias Fischer and Taryn Lopez) and a team of geophysicists and field technicians from the Alaska Volcano Observatory (John Lyons, Dane Ketner, and Adrian Bender) who serviced the USGS seismic network on several of these volcanoes for the first time in more than ten years. Project PI Katie Kelley could not be in the field, but participated remotely via satellite phone and internet tools that allowed her to track the ship, helicopter, and us in nearreal time. Our voyage is a great example of how multiple teams can work together to achieve great things.


– Liz Cottrell

Preparing for Danger: Training in Anchorage

2 September 2015 | Anchorage, AK • We’re here. Anchorage, Alaska. Months of planning and training are behind us. In three days we will take a three hour jet flight to the airstrip that is both farthest East and farthest West in the United States (figure out that riddle!). From there, we will board a small boat, The R/V Maritime Maid, and steam West into the uninhabited islands of the Western Aleutians. We will only have what is in our suitcases and what we shipped months ago – and I am scared. I am scared I didn’t prepare my team. I am scared I don’t have the right equipment. I am scared I will make poor decisions. But I am most scared of this pool I’m in. This is the Learn to Return Aviation Land and Water Survival School, more commonly known as “dunker” training, with the unfortunate slogan “Be the One to Come Home!” And I’m thinking “Can’t we all come home?” In this course, we get strapped into metal seats with five-point
harnesses meant to mimic the fuselage of a plane or helicopter. We hover above the water. My instructor, Clint, barks, “Mayday Mayday! This is Echo Alpha Romeo 289 with two souls on board. We are ditching! Ditching! Ditching!” And then WHAM! The seats flip and I impact the water. I can’t see. I can’t breathe. I follow the routine. (0) Don’t panic. (1) Slide my hand. Find the door latch. (2) Open the door. (3) Anchor my hand in the door frame. (4) Slide my other hand to unfasten my belt and pull myself out. Even now, dry, thinking of Clint’s voice sends chills down my spine. One team member doesn’t pass the course. I think of my two kids and wonder if I should just get on a plane home. But somehow, tomorrow I board my flight to Adak. The R/V Maritime Maid and “2-Mike-Hotel” (the Helicopter)

3 September 2015 | Adak, AK • The heli pad on the Maid looks to be about the size of my desk at work. I wonder how it is that my first ever helicopter experience will be taking off from the back of a boat and going over the Bearing Sea to the rim of a volcano. Am I crazy? Our pilot, Dan Leary, is the most experienced pilot at Maritime Helicopters and the absolute best pilot I could ever have hoped for. I soon understand that Captain George Rains, who has sailed these waters for longer than I’ve been alive, isn’t going to take any unnecessary risks.

Weather Orphans the Helicopter

5 September 2015 | Constantine Harbor, Amchitka, AK • The Maritime Maid left port in Adak yesterday destined for harbor in Amchitka. At the time of our departure, the weather was beautiful with sunny, blue skies and a clear view of a steaming white fumarole at the summit of Kiska. The Maid does not sail with the helicopter parked on the deck. Instead, the helicopter normally flies when the boat is underway and they meet up again in harbor. Our plan yesterday was for the helicopter to meet us when we moored in Constantine Harbor, Amchitka but, as we sailed, fog closed in at Adak and kept the helicopter from following us. We have no scientific interest in Amchitka, so we must wait for the helicopter to join us.

8 September 2015 | Kiska Harbor, Kiska, AK • After four days of separation, we are finally reunited with the helicopter! Two days ago, we decided to lift anchor and head to Kiska harbor in the hopes of starting work, with or without the helicopter, and left a fuel cache on Amchitka so the heli could catch up with us as soon as weather permitted. We made the most of our idle time at Amchitka by taking a small skiff to shore, doing a gear shakedown, and taking some “practice” samples. Likewise at Kiska, we were able to skiff to shore yesterday and explore the area around the harbor, view and sample some distal volcanic deposits, and try not to set of any unexploded ordinances leftover from World War II. Kiska was a WWII battleground, occupied by the Japanese for a time before being re-taken by the US, and the historical remnants litter the ground and harbor.

9 September 2015 | Segula Volcano • My first day of real field work! Because of the remoteness of this region, few geological studies have been done here. Today’s target, Segula, hasn’t been visited by geologists since the 1940’s and there are only three known rock analyses from this volcano. We find a gorgeous exposed tephra section in a wide gully and greedily fill our bags with this “black gold.” By the end of the day, I realize with satisfaction that our work will return precious samples from this volcano ripe for new discoveries. – Liz Cottrell


– Elizabeth Grant

Minefield Kiska

9 September, 2015 | Kiska Island • Team tephra is in search of olivine in mafic tephra and we have split up into two sub-teams today so we can cover more ground. Mattia and I are on Kiska, the third westernmost island in the Aleutian chain. The helicopter drops us off on a relatively flat, topographic low near the northern flank of Kiska Volcano, next to a recent lava flow. As the helicopter flies off to assist the other teams, Mattia and I survey the landscape and geologic map to get our bearings. We quickly realize that what we had assumed to be a relatively easy passing is actually a literal and figurative minefield. Instead of consisting of relatively young olivine-rich basalt, the flow is actually composed of older blocks of andesite, twice as wide as we are tall and covered with plants and grasses that reach up to our waists. Not only that, but Kiska is littered with “UXO,” unidentified explosive ordinances, which could be anywhere. From our topographic low, it takes us 45 minutes to scramble the 40 meters to the top of the lava flow, and we arrive at the top sweating and out of breath. As we survey our progress, it dawns on us that we will not be able to cross the rest of this flow; it’s too large and too dangerous. From the comfort of the ship’s galley, we had routed our path across the map’s page, talking about sampling along the way. In reality, the unexpected size of the lava flow provided us with some much-needed perspective about the unforgiving scale of nature and the long-reaching consequences of human activity.


– Katie Kelley

The Virtual Aleutians

10 September 2015 | Narragansett, RI • I wish I were there. And I don’t. Staring at the computer screen, I wonder for the umpteenth time if I made the right decision to stay home. My baby daughter, Miranda, is only four months old, so I couldn’t have gone. Still, I can’t help but have this internal debate daily. It is mid-afternoon here and they will be starting their day in the field soon. I login to a website to check the location of the Maid and the helicopter, both of which pop up on an animated map of our field area. When the helicopter is in flight, it lights up pink and its little propeller turns as it moves across the screen. Watching this is the most exciting part of my shore-based experience.

My phone rings and the caller ID shows “Liz Sat Phone.” Liz says it is raining and I can hear the raindrops over the phone. It seems always to be raining there; she says the volcanoes make their own weather. We quickly debrief on yesterday’s work and go over a plan for the coming day’s activities: our party will deploy one team to Kiska, and the other to Buldir. Buldir is the riskiest flight of the trip, partly because the flight itself is extremely dangerous and partly because they might not find anything useful when they get there, so they are risking life and limb possibly for naught. I am incredibly nervous for them. After we hang up, I login to another website to track Liz’s InReach device, which sends her location every ten minutes. I leave the office just as the helicopter leaves the Maid for Buldir.

Of course, Liz tried to contact me from Buldir while I picked up my children from day care, during the only ten-minute window of my day when I had to pocket my phone. They made it safely there, which is a relief, and I briefly text with Liz’s husband, who is also closely tracking her steps, about how wild it is to watch her walking around. When I get home, we setup my laptop at the dinner table (the only time a computer has ever been allowed at the table, mind you) so my whole family can watch the “action” as it happens. My three year-old daughter has learned the names of all of the volcanoes on the itinerary and asks where Liz and the helicopter are today.


– Mattia Pistone

Kiska Volcano: Ascensus ad coelum et descensus ad Inferos

10 September 2015 • Thirty minutes prior to sunrise. From the vessel bow, while sipping hot tea, I observe that low-elevation clouds still seal the sky. These are not ideal conditions for helicopter flight but this is our last day on Kiska Island and, despite numerous attempts on the flanks, we have yet to find any of the rocks (mafic tephra) that we are looking for. We can only hope to find a fissure in the cloud barrier and find a way to the volcano summit. The wind is with us, however, and it is rapidly clearing up the sky from the dusty clouds. Today, the first team to be deployed by helicopter is the gas team (Tobias Fischer, Taryn Lopez) supported by Adrian Bender, the sedimentologist of “tsunamites” and “stormites,” who is going to be the “radio antenna man” in contact with the Maid while the group collects dangerous volcanic gases on the southwest flank of the volcano summit. The helicopter is fully packed with people, backpacks, and field instruments. There is only one free seat for one person with a backpack. After briefing with the other members of team tephra, it is unanimously decided that I will join the gas team today. I will be tasked with finding and returning rocks from the volcano summit back to the research vessel. I am thrilled! After taking off, our helicopter pilot Dan Leary is like a hawk looking for prey; he finds a spot with broken clouds and steers into it. Thanks to the ascending winds increasing while approaching the hidden east flank of the volcano, we are promptly above the clouds – the sky can also be blue here in the Aleutians. While ascending, the northwest wind is too strong to make any attempt for landing at the volcano summit. Therefore, we are all deployed at about a thousand feet below the volcano summit. It looks like we will have to reach the summit only with some effort and sweat. After a short briefing about work tasks and timetable, and radio communications, the gas team and myself initiate our hike up. Lava flows, loose volcanic bombs and blocks dominate the landscape. After several days at low elevation, I can enjoy this hike without fear of encountering UXO. I am at the top of the crater rim and the landscape in front of me is gorgeous! The volcano crater is in front of me and I feel so small and insignificant. Clusters of loose rocks cover the internal flanks of the volcano. The crater floor is filled with fine volcanic material; it looks like mud. The western side of the volcano has no rim and from there, low-elevation clouds ascend and enter this amphitheater while the northwestern winds blows. I am the lonely spectator of this volcanic show and feel like an explorer – I am the first one to set foot in this volcanic crater… well, after the geologist Robert Coats, who most probably came here during his mapping work in the early 50’s… but, for sure, I am the first Italian here! That’s exciting! Now, back to work. I report the GPS coordinates and field
observations in my book and start to hammer the samples I need. Any sample I take looks beautiful and full of precious information. I wish to take any and all specimens with me since this is the first and last chance we have to collect rocks in the crater of Kiska Volcano during this field mission. But I have to face the reality: I am by myself and cannot carry too many rocks. How time flies! I am quick to collect samples, observations, and data because I have to go back soon. We have now 70 kg of rocks to hike to our helicopter rendez-vous location and I anticipate a very negative reaction from the gas team, who have worked hard for many hours. Instead, I receive generous support, which is typical of an enthusiastic team of people. This is the best reward after a long day of work between volcanic rocks and wind gusts. Together, we march back to the pick-up point. I think this is the greatest day of the field mission here in the Aleutians.


– Katherine Sheppard

On the Edge

10 September 2015 | Kiska Harbor, Kiska, AK • Buldir is a tiny speck of an island about halfway between the much larger masses of Kiska and Attu, all the way out in the far Western reaches of the Aleutian chain. How far out? Let’s just say we didn’t have our passports with us, so we couldn’t except to legally get much further west. There are 45 miles of open water to the east and west of Buldir, which was about a 45-minute flight for our Bell 407 helicopter. This is a perfect amount of time to reminisce about three things: we would be among only a few geologists to visit the volcano in decades, we only had one day to do as much work there as we possibly could, and if anything went wrong while on the island we were all royally screwed. Our day on Buldir had the potential to be the most dangerous day of the trip, mostly due to the long over-water helicopter flight and the remote location. If the helicopter landed but couldn’t take off due to bad weather,
we would be stuck out there until the weather cleared or the boat came to get us. As anyone familiar with the weather in the Aleutians knows, this could take a very, very long time.

As it turned out, we landed, did our work and I soaked in the glory of feeling like a real life explorer. The fog stayed at a respectful distance, the wind stayed manageable, and we were able to take off at the end of the day with minimal excitement. When we landed on the boat 45 minutes later, however, we were ecstatic. We had found amazing tephra samples that suggested an explosive, volatile-rich history for Buldir. Not at all as we were led to expect before the trip, so a resounding success! Only when we had unpacked all the rocks and rid ourselves of our protective gear did our helicopter pilot turn to Liz, let out a breath he seemed to have been holding all day, and say “I am never, ever, ever doing that again.”


– Liz Cottrell

12 September 2015 | Semisopochnoi • With the stressful overwater flight to Buldir behind me, I find myself relaxed and enjoying the flight to Semisopochnoi Volcano. A survey from the air reveals beautiful sections of tephra cut from the vegetated landscape. Michelle and I are able to sample meticulously here all day.

17 September 2015 | Gareloi • I am standing waist-deep in olivine scoria and loving it. Katherine and I fill our sampling bags to bursting and I know we have gotten what we came for. I then hike up to the crater rim – just to take a peek. I am stunned at what I see… a crater lake and active fumaroles! This appears to be a new development since the last time geologists visited this place in 2005 and I am reminded that these are indeed very active volcanoes.


– Michelle Coomb

20 September 2015 | Kanaga • Gas team and two tephra teams got set on Kanaga in the morning, and then boat transited from Hot Springs Bay on Tanaga to the Bay of Islands on the west side of Adak. This was the most spectacular day of the trip so far. Kanaga was completely out and cloud free and I took many beautiful photos. Kanaga is a great island and volcano – deep blue lake in the caldera, spectacular lava flows, deep green grass everywhere. Kanaton Ridge is just screaming out for more and better work, as is the entire island. Visited a few tephra sections as guided by CW’s paper and found some big lapilli pumice falls. No mafic scoria to speak of, unlike Tanaga, and much to our team’s disappointment. I think I found two mafic ashes that may be from Tanaga, which will be interesting to see. We ended the day around 5 pm at the hot springs.■

 

“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.org. This opportunity is open to anyone engaged in GeoPRISMS research, from senior researchers to undergraduate students.
We hope to hear from you!

Reference information
Seeking the origins of continents in the western Aleutian island arc
GeoPRISMS Newsletter, Issue No. 36, Spring 2016. Retrieved from http://geoprisms.org

Investigating older rocks in the oceanic Aleutian volcanic arc east of Adak


Peter Kelemen (Columbia University, LDEO) on behalf of Merry Yue Cai (Columbia University, LDEO), Emily H.G. Cooperdock (UT Austin), Steve Goldstein (Columbia University, LDEO), Matt Rioux (UC Santa Barbara), and Gene Yogodzinski (University of South Carolina)

Benefiting from the NSF GeoPRISMS community platform in the Aleutian volcanic arc in the summer of 2015, our group from the University of South Carolina and Columbia University had a
matchless opportunity to study and sample outcrops of pre-Holocene volcanic and plutonic rocks on Unalaska, Umnak, and Atka Islands. Speaking for myself, at the age of 59 and having worked in the field in a lot of spectacular places – every year for forty years – this was one of the most memorable and rewarding field seasons of my life.

The older rocks in the Aleutian volcanic arc are notable because they include the most extensive outcrops of plutonic rocks in any oceanic arc, worldwide. Aside from the visionary work of Sue and Bob Kay and their colleagues, these plutonic rocks have not received much attention since pioneering USGS studies were completed in the 1950’s (Umnak), 1960’s (Unalaska), and 1970’s (Atka). This prior work demonstrated that the Eocene to Miocene plutonic rocks east of Adak Island were more strongly “calc-alkaline”, with higher SiO2 at a given Mg/Fe ratio, compared to the “tholeiitic”, Holocene volcanic rocks on the same islands.

In a recently published pilot study using USGS samples (Cai et al., Earth Planet. Sci. Lett. 2015), we found that these plutonic rocks are also isotopically distinct from the lavas on the same islands, demonstrating that the two suites were generated by melting of two distinct sources.

Our field season in the summer of 2015 was designed to investigate whether these differences in source composition were the result of :

  1. temporal evolution of the arc, in which case Miocene to Eocene lavas should have isotope ratios similar to those of calc-alkaline plutons, and perhaps will also mirror the calc-alkaline compositions of these plutons, or
  2. distinct processes, in which viscous, SiO2– and H2O-rich, calc-alkaline, andesitic magmas tended to stall and form mid-crustal plutons, while relatively low viscosity, SiO2– and H2O-poor, tholeiitic, basaltic magmas tended to erupt on the surface, in which case Miocene to Eocene lavas may be isotopically (and compositionally?) distinct from coeval plutons.

To this end, we hoped to sample coeval plutonic and volcanic arcs on several Aleutian islands where the plutons are well-exposed.

Our starting plan was to set up fly camps in the alpine terrain on the islands, which is underlain by extensive outcrops of granodiorite and diorite plutons. We assumed that we would have difficulty obtaining ages on highly altered volcanic rocks, whereas it would be relatively easy to date zircons from the large plutons. Thus, we expected to sample volcanic rocks where they are intruded by plutons of known age. Frankly, my expectations about the field work were not high. I imagined we would be semi-lost in perennial fog, while disconsolately scraping moss, lichen, and tundra grasses off texture-less, fine-grained, grey-green outcrops, and spending a lot of time arguing about whether a specific sample was volcanic, plutonic, or even sedimentary!

Merry Cai, Steve Goldstein, Gene Yogodzinski, and I flew to the commercial airport in Dutch Harbor on Unalaska Island on August 5, where we were joined by pilot Sean Charlton in Pollux Aviation’s R44 helicopter. Sean had flown out from the mainland, with floats fully inflated. I had never used such a small, gasoline-powered helicopter, with an engine not much larger than a lawnmower, so I was a bit skeptical at first. We initially focused on the Shaler pluton on Unalaska, which is the largest in the Aleutians, and hence in any oceanic volcanic arc, worldwide. The weather was quite good when we were there, which allowed us to fly every day. Everyone says the Aleutian weather is bad and unpredictable, and of course, it is, but not always. Working there can often be quite nice. We set up a couple of fly camps, and ranged through the beautiful alpine terrain, examining complex border facies of granodiorite, diorite and volcanic hornfels. We also took advantage of the helicopter on re-supply days to make ground stops along the coast. There, we found exceptional outcrops, including surprisingly fresh volcanic rocks with chilled margins, suitable for 40Ar/39Ar geochronology.

After a while, the exceptional coastal exposures, coupled with the convenience of the helicopter, induced a change in our plans. We moved into the hotel in Dutch Harbor, and flew every day. It
turned out that world-class sea cliff outcrops, coupled with wave cut terraces that offered ideal helicopter landing sites at all but the highest tides, provided a spectacular opportunity for us to conduct comprehensive sampling.

As the photos accompanying this article show, the Aleutian sea cliffs revealed spectacular sequences of pillow lavas, pyroclastic deposits, and columnar-jointed sills. Indeed, photos in the USGS Bulletins showed some of these exceptionally well-exposed features, but in earlier years, without a helicopter, these outcrops were very difficult to access from small boats. In addition, there were few opportunities to obtain reliable ages on the lavas. With the helicopter, and some confidence about 40Ar/39Ar dating of fine-grained volcanic rocks, we were in heaven. Further, as it turns out, our samples from the many sills intruding the volcanics will provide plenty of opportunities to check the Argon ages using U/Pb in zircon.

As it turned out, the R44 helicopter was perfect for us, fitting easily into small landing spots, often within ten meters of the Pacific surf. Unfortunately, Steve Goldstein came down with shingles and had to convalesce in Dutch Harbor, sampling volcanic rocks from the extensive road network when he could. However – sorry Steve! – this did reduce our helicopter-supported group to three, who just fit into the three passenger seats in the R44, enabling ultra-efficient field work. We would leapfrog along the coast, setting out one or two people at each landing spot, and scheduling pickups a few hundred meters further along the coast.

In the middle of August, we moved from Unalaska to Umnak Island, where we were fortunate to stay in a bunkhouse at Bering Pacific Ranches, Ltd., near the abandoned WWII airfield at Fort Glenn. This is a fascinating operation; while we were there, Ranch owner Pat Harvie and his crew were preparing to round up thousands of “organic, free-range” cattle from across the island, using a fleet of R22 helicopters, plus a lot of bailing wire and duct tape. These animals were destined for shipment to Canadian markets in the late summer and early fall. We all hope this visionary operation ended in great success!

From this spectacular basecamp, we spent several productive days sampling along the north and southeast coasts of the island, with a side-trip to the rim of the giant Okmok caldera during a clear spell. We also used the opportunity to access the westernmost peninsula of Unalaska Island, completing our extensive sampling there. All too soon, it was time to leave the Ranch. We returned to Dutch Harbor, where we met Captain George Rains, the crew of the R/V Maritime Maid, and pilot Dan Leary with Maritime Helicopters’ Bell 206 Long Ranger. We also rejoined a rejuvenated Steve Goldstein, together with his daughter, Emily Cooperdock, who had flown up to join us. This increase in our group size corresponded with the change from the four-seat R44 to the six-seat 206, and as a result we remained a highly efficient, helicopter-supported team!

We moved into comfortable quarters onboard the Maid and, delayed by weather, spent a few more days living on the ship in Dutch Harbor, continuing to sample on Unalaska Island. Until this point, we had not lost a single day to weather, though we had gotten wet on a couple of days.

However, our transit to Atka Island, and our work there, were substantially delayed by wind, then fog. A side benefit was a spectacular morning at anchor among the Islands of Four Mountains,
where we photographed the perfect strato-volcanoes there while we waited for the helicopter to catch up with the ship. Finally, the weather cleared and we spent a highly productive day and a half
racing along the western peninsula of Atka Island, acquiring a fantastic set of samples, including previously dated intrusions that span the range from the youngest (9 Ma) to oldest (39 Ma) plutons known in the arc east of Adak.

We then set out for Adak Island. In the airport there, we greeted the next group who would use the GeoPRISMS community platform onboard the Maid, led by Liz Cottrell. We wished them all the best and, sadly, began the long trip home.

In addition to the pilots, and the crew of the Maritime Maid, we would like to express deep gratitude to Program Manager Jenn Wade at NSF, who worked tirelessly to make the community platform concept come alive, and to Christie Haupert, Alaska Science Project Manager for Polar Field Services, Inc., who provided flawless logistical support.

Preliminary data on a few 2015 samples, Unalaska Island.

PS: Since that time, we’ve been working hard processing our samples and obtaining initial data. On the left is a plot of some early, major element analyses of our samples from Unalaska Island. Note that, as for the USGS samples we analyzed for our pilot study (Cai et al., Earth Planet. Sci. Lett., 2015), most of our 2015 plutonic samples are calc-alkaline and most of our 2015 mafic lava samples are tholeiitic, despite the fact that the 2015 lavas and plutons are approximately coeval. This suggests that the chemical differences documented by Cai et al. (2015) are present among coeval igneous rock suites in the Aleutians, and did not arise as a result of temporal evolution of both volcanic and plutonic magmatism.

In addition to our main line of inquiry, outlined above, we are evaluating the potential for study of detrital zircons in volcanoclastic sediments, while Emily Cooperdock is preparing a proposal to study the uplift and denudation history of the Aleutians via U-Th-He thermochronology as well as fission track and 40Ar/39Ar analyses. ■

A) Schematic map of the Aleutian island arc, sampled areas are highlighted in black. B) Wt% SiO2 versus Fe/Mg ratio of studied Aleutian igneous rocks. By convention, the Fe/Mg ratio is calculated using wt% MgO and FeO, with all Fe as FeO. C) Present-day Nd and Pb isotope ratios of Aleutian igneous rocks vs. longitude and vs. age. Circles are central and eastern Aleutian volcanics: Yellow = Rat and Delarof Islands, Green = Adak and Kanaga, Blue = Atka, Purple = Umnak, White = Unalaska. Error bars are smaller than the symbols. In 3) and 4), the Holocene volcanics are separated by location only without age differences. Figures from Cai et al., Earth Planet Sci. Lett. 2015.

“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.org. This opportunity is open to anyone engaged in GeoPRISMS research, from senior researchers to undergraduate students.
We hope to hear from you!

Reference information
Investigating older rocks in the oceanic Aleutian volcanic arc east of Adak
GeoPRISMS Newsletter, Issue No. 36, Spring 2016. Retrieved from http://geoprisms.org

Islands of Four Mountains to Unimak: From the slab to the surface


Report retrieved from the website of the Department of Terrestrial Magnetism Carnegie Institution of Washington and the Facebook page of the field mission (IFM-Unimak 2015: From the Slab to the Surface)

Scientists have a relatively good understanding of the processes occurring in the upper portions of the Earth’s crust that lead to volcanic activity. However, much remains unknown about
how these shallow processes are controlled by the large-scale tectonics and deep mantle processes that are ultimately responsible for volcanism.

A NSF-funded group led by DTM seismologist Diana Roman headed to Alaska for three weeks,two of which were spent on the research vessel Maritime Maid, to collect seismic data in the Islands of the Four Mountains and tephra samples throughout the eastern Aleutians. The group included Roman and DTM postdoc Amanda Lough, as well as Dan Rasmussen, Alex Lloyd, and Terry Plank from Columbia University’s Lamont-Doherty Earth Observatory, Pete Stelling from Western Washington University, and John Power, John Lyons, Christoph Kern, and Cindy Werner from the U.S. Geological Survey.

The goal of their work is to determine how the amount of water dissolved in magma affects where, and for how long, magma is stored in Earth’s crust. This information is critical for accurately
forecasting volcanic eruptions and understanding the large-scale processes that lead to volcanism in Earth’s subduction zones. The volcanoes targeted in this study have a wide range of magma water contents, magma storage depths, and depths of seismic activity, making them ideal candidates for this research.

Roman led another trip in the summer of 2016 to retrieve seismic equipment from the Islands of the Four Mountains. ■

“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.org. This opportunity is open to anyone engaged in GeoPRISMS research, from senior researchers to undergraduate students.
We hope to hear from you!

Reference information
Islands of Four Mountains to Unimak: From the slab to the surface
GeoPRISMS Newsletter, Issue No. 36, Spring 2016. Retrieved from http://geoprisms.org

Magnetotelluric & seismic investigation of arc melt generation, delivery, and storage beneath Okmok volcano


Ninfa Bennington (U. Wisconsin-Madison), Kerry Key (Scripps Institution of Oceanography), and USGS Investigators Matthew Haney and Paul Bedrosian

Okmok Volcano - Umnak Island in the eastern Aleutian islands of Alaska
Fore more information about the project, videos, photos, updates, visit the blog at http://okmok.ucsd.edu/

Okmok is one of the most active volcanoes in the Aleutian arc and hosts a 10 km diameter caldera. The subdued topography of Okmok, relative to other Aleutian volcanoes, improves access and permits dense sampling of the volcanic edifice. We have selected Okmok as the site of study for this project due to frequent volcanic activity and the presence of a crustal magma reservoir as inferred from previous seismic studies. At least two caldera forming eruptions are recognized and Okmok is believed to be representative of volcanoes both within the Aleutian arc and worldwide, where long periods of effusive eruptions are punctuated by much larger explosive caldera forming eruptions.

We are applying geophysical techniques to characterize the magmatic system beneath Okmok. During the summer of 2015, we collected onshore and offshore magnetotelluric (MT) data and installed a temporary year long seismic deployment. The seismic instruments will be retrieved in summer 2016. These new geophysical data will be used to test hypotheses regarding the role of slab fluids in arc melt generation, melt migration within the crust, and the crustal magmatic plumbing and storage system beneath Okmok Caldera.

Offshore MT Field Deployment

After numerous delays due to thick fog typical of the Aleutians, the entirety of the offshore MT crew arrived to Dutch Harbor, AK and was assembled on the R/V Thompson. A video of the research vessel captured by a morning drone flight can be viewed here. On June 18, 2015, the team departed Dutch Harbor for their first offshore MT site. The offshore crew spent the day preparing receivers so that there were only a few remaining steps to complete before deploying them over the side of the ship. By June 20, all 54 MT receivers had been deployed well ahead of schedule.

With the MT deployment complete, the team collected multi-beam bathymetry data on the upper forearc slope south of Umnak Island using the ship’s EM302 multi-beam echo sounder. On top of mapping the bathymetry of the ocean floor, the intensity of these recordings can be used to help determine the nature of the seabed (e.g. sediments versus hard rock). On June 21, the offshore team transited back to Dutch Harbor via Umnak pass. This return route included spectacular views of Mount Makushin Volcano on Unalaska Island.

Onshore MT and Seismic Deployments

On June 23, having returning to Dutch Harbor from offshore MT work, co-PI Key and Scripps graduate student Georgiana Zelenak joined up with the rest of the onshore team (PI Bennington, UW-Madison post-doc Summer Ohlendorf, and USGS collaborators Matthew Haney and Paul Bedrosian) and departed for Umnak Island. The onshore work was based out of Bering Pacific Ranch at Fort Glenn, an abandoned WWII military base, with a helicopter transporting the seismic and MT teams and equipment during the 19 days of field operations.

After the team arrived at Fort Glenn, the camp house was set up and seismic and MT equipment were prepared for the start of field operations the following day. Seismic and MT field operations commenced on June 23 and extended until July 11. The seismic team installed thirteen temporary broadband seismometers both in and around the Okmok Caldera. In tandem with the Alaska Volcano Observatory’s twelve permanent seismic stations, there are now twelve seismic instruments within or at the rim of the caldera and 14 seismic instruments outside the caldera. The temporary array will record seismic data until its retrieval in summer 2016. Onshore magnetotelluric data were collected in a 3D array using a combination of long-period and wide-band MT systems, with 19 stations within the caldera and ten stations outside. Following the completion of onshore fieldwork, part of the onshore team (PI Bennington, Summer Ohlendorf, and USGS collaborators Matthew Haney and Paul Bedrosian) caught a charter flight back to Dutch Harbor. Co-PI Kerry Key and graduate student Georgie Zelenak hitched a more unconventional ride when the rescue boat from the RV Sikuliaq picked them up from Umnak Island.

Offshore MT Instrument Recovery

Following completion of onshore MT work, the offshore MT team made a six day cruise on the new R/V Sikuliaq to recover offshore MT instruments. Of the 54 offshore deployments, 53 instruments were successfully recovered while one instrument was lost in Umnak pass due to strong tidal currents in the shallow water. ■

“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.org. This opportunity is open to anyone engaged in GeoPRISMS research, from senior researchers to undergraduate students.
We hope to hear from you!

Reference information
Magnetotelluric & seismic investigation of arc melt generation, delivery, and storage beneath Okmok volcano
GeoPRISMS Newsletter, Issue No. 36, Spring 2016. Retrieved from http://geoprisms.org

A Field Campaign to the Aleutians


Field work in the Aleutian Islands is complex, expensive, and thoroughly exciting. When the community suggested to NSF that we facilitate a collaborative field platform to get safely to and from the many islands of interest along the arc, we turned to our colleagues in the Division of Polar Programs (PLR). They helped us coordinate, along with the USGS and Alaska Volcano Observatory (AVO), a combined logistics platform of ship and helicopters that could support the science proposed by our eager PIs.

Planning began in the summer of 2014, as we looked at the proposals that had come into the GeoPRISMS deadline focused on work in Alaska and the Aleutians. What was funded from that round was a group of well-reviewed proposals that together we felt had a chance to make real progress on the goals laid out in the Science and Implementation Plan. We got to work with the PIs, the USGS & AVO, Polar Field Services (who would manage the logistics), and PLR to set up the work, get everyone permitted, and get our scientists in the field. We leveraged funds from a number of places to make this work. EAR and OCE, via the GeoPRISMS Program, funded the bulk of the platform. The Directorate for Geosciences (GEO) contributed funds as well. The GeoPRISMS project shared mobilization costs with a previously-funded Arctic Social Sciences project. The Polar Geospatial Center generated DEMs and maps to help researchers better target their time on these remote islands.

In the summer of 2015, three teams of academic researchers along with scientists from the USGS & AVO set off on unprecedented coordinated research in the Aleutian Islands. They shared ship and helicopter time aboard the Maritime Maid, a helicopter-capable research vessel that traveled along more than 800 miles of volcanic arc, from Dutch Harbor in the east to Buldir Island in the west, transporting scientists and equipment on and off the islands. The USGS, already involved in assisting our scientists with permitting and field expertise, also funded their own helicopter time to service monitoring stations on volcanoes, some of which hadn’t been visited in many years. The Deep Carbon Observatory, funded by the Sloan Foundation, provided additional support for a fourth team of researchers to occupy the remaining free berths on the Maritime Maid, maximizing the efficiency of the ship and the potential for real scientific progress.

Field work included rock and gas sampling from numerous volcanoes, as well as geophysical deployments (seismic and magnetotelluric) via this joint logistics platform and parallel-funded projects in the eastern part of the arc. The scientists involved were interested in a range of topics, including magma storage beneath the volcanoes, the chemistry and style of eruptions, and earthquake and tsunami hazards in the Pacific.

This multidisciplinary, multi-scale, collaborative work has already and will, in the future, yield remarkable results that help forward the goals laid out in the GeoPRISMS Science and Implementation Plan. The researchers returned home (mostly) unscathed and very scientifically successful, and both NSF and the USGS have praised the endeavor which uniquely coordinated resources to accomplish the goals of two federal agencies. The GeoPRISMS Program estimates that we saved nearly a million dollars by leveraging what we could, partnering with experts, and being strategic in our thinking, funding, and planning.

– Maurice Tivey
GeoPRISMS Program Manager, National Science Foundation

Magnetotelluric & seismic investigation of arc melt generation, delivery, and storage beneath Okmok volcano

Magnetotelluric & seismic investigation of arc melt generation, delivery, and storage beneath Okmok volcano

Ninfa Bennington (U. Wisconsin-Madison), Kerry Key (Scripps Institution of Oceanography), and USGS Investigators Matthew Haney and Paul Bedrosian Okmok is one of the most active volcanoes in the Aleutian arc and hosts a 10 km diameter caldera....
Islands of Four Mountains to Unimak: From the slab to the surface

Islands of Four Mountains to Unimak: From the slab to the surface

Report retrieved from the website of the Department of Terrestrial Magnetism Carnegie Institution of Washington and the Facebook page of the field mission (IFM-Unimak 2015: From the Slab to the Surface) Scientists have a relatively good understanding...
Investigating older rocks in the oceanic Aleutian volcanic arc east of Adak

Investigating older rocks in the oceanic Aleutian volcanic arc east of Adak

Peter Kelemen (Columbia University, LDEO) on behalf of Merry Yue Cai (Columbia University, LDEO), Emily H.G. Cooperdock (UT Austin), Steve Goldstein (Columbia University, LDEO), Matt Rioux (UC Santa Barbara), and Gene Yogodzinski (University of South...
Seeking the origins of continents in the western Aleutian island arc

Seeking the origins of continents in the western Aleutian island arc

Elizabeth Cottrell (Smithsonian Institution), Katherine A. Kelley (University of Rhode Island), Michelle Coombs (USGS Alaska Volcano Observatory), Elizabeth Grant (University of Washington), Mattia Pistone (Smithsonian Institution), and Katherine Sheppard...

AACSE:  The Alaska Amphibious Community Seismic Experiment


******* NEWS *******

In June 2019, seven undergraduate students, selected from a national pool of 54 applicants, participated in an AACSE short course in Kodiak, AK, led by PI Aubreya Adams (Colgate University). During the week-long experience, participants were first immersed in a short but intensive course introducing topics in seismology, plate tectonics, and the tectonic history of Alaska. A fieldtrip led by Peter Haeussler (USGS) and Gary Carver (Humboldt State University) introduced students to the geology of accretionary prisms. Finally, the group joined PI Lindsay Worthington (UNM) in the recovery of 398 nodes in eastern Kodiak. To summarize and share their newfound knowledge and experience with others, students from the course built a story map, highlighting the history and goals of the AACSE as well as their own experiences in Kodiak.

icon-chevron-right AACSE story map

North America’s largest recorded earthquakes and largest documented volcanic eruptions both take place in southwest Alaska. A major shoreline-crossing community seismic experiment commenced in 2018, focused on the Alaska Peninsula subduction zone. Alaska is a GeoPRISMS primary site and current EarthScope target. The deployment is augmented by deployment of EarthScope Transportable Array (TA) seismic stations, earthquake and volcanic monitoring networks, and the recent development of a large pool of ocean bottom seismographs (OBSs). Together, these resource provide a unique opportunity to advance understanding of Alaska and subduction processes generally.

AACSE collects seismic data remotely onshore and offshore, all of which will be freely released to the community as rapidly as possible. The array includes 75  broadband OBSs and 30 land broadband sensors, recording for 15 months beginning May-June 2018. The array covers a broad area that spans the incoming plate, the megathrust and volcanic arc to the distal backarc, and includes a dense transect in the Kodiak/Katmai region. When integrated with the TA, the array extends 1500 km from incoming plate to the Arctic coast and spans 700 km along strike. The OBSs include 20 shielded sensors for deployment in shallow water. Many OBSs include absolute pressure gauges to capture possible slow slip events, while five OBSs and six land sites will include accelerometers to record large local earthquakes without clipping.

The AACSE broadband OBS deployment completed on July 20, teams of scientists deployed 75 instruments across two sailing legs aboard the R/V Sikuliaq. Twelve Apply-to-Sail participants and two K-12 teachers from Alaska participated in the deployment cruises by performing watchstanding duties, helping prepare instruments for deployment and maintaining the project blog.

The Sikuliaq runs multiple acoustic and oceanographic sensing systems while underway including: ocean current measurements (ADCP), seawater temperature, conductivity and density (CTD), echo sounder for fisheries research (EK60), multibeam bathymetry (32kHz Kongsberg EM302), parametric sub-bottom profiler for shallow subsurface imaging (Kongsberg TOPAS PS 18), R2R event logger, expendable bathythermograph for measuring water temperature (XBT). All data will be archived and available via the UNOLS R2R server. Additionally, multibeam data will be archived via the MGDS and sub-bottom data will be archived at the UTIG Academic Seismic Portal. For access to the data prior to archiving, contact the cruise co-chief scientists: Leg 1 – Lindsay Worthington (lworthington (at) unm.edu) and Leg 2 -Anne Sheehan (anne.sheehan (at) colorado.edu). Cruise reports available here: link to cruise report

The onshore broadband seismometers were deployed May-June 2018, with 29 stations installed on Kodiak, the Shumagin Islands, and the Alaska Peninsula. All stations include Nanometrics posthole PHQ-120 sensors recorded on Quanterra Q330 data loggers placed in low-profile aluminum boxes; the blog shows some photographs of installations. Six of those sites also record Titan accelerometers, all at 100 sps. The first onshore data were recovered during a service run in August-September 2018, and are NOW AVAILABLE at the IRIS DMC, network code XO. OBS data will be available after recovery in 2019.

A map of the current deployment plan and a detailed deployment plan can be found on the links below. The project is intended to help grow the seismological community, and includes opportunities to sail on OBS cruises and short courses for undergraduates – 2019 opportunities to be announced in December 2018!  Feel free to contact members of the PI team for more information.

 

Deployment and DataPI teamAnnouncementsDocumentsWebinarUpdatesApply to SailUndergrad short course

Alaska Amphibious Community Seismic Experiment (AACSE)

 icon-chevron-right Download the Deployment map (PDF, last update September 18, 2018)

Preliminary station locations

These locations are based on initial surveys only, and will be superseded by metadata generated when data are submitted to the IRIS DMC. They are provided for reference. Please use the metadata at the DMC for all analyses, once it is available.  List of land stations, and of OBSs.

Data Availability

  • All earthquake seismic data will be made available as it is retrieved and archived, through the IRIS DMC – OBS array has network code XD (2018-2019) and land array has network code XO (2018-2019).
  • Underway marine data including multibeam bathymetry are being made available through MGDS and embedded into the GMRT grids, available through GeoMapApp and other interfaces. The deployment cruises are SKQ201811S and SKQ201816S.
  • Sub-bottom TOPAS profiler data was collected on the Sikuliaq during both 2018 deployment cruises, and are being made available through the Academic Seismic Portal at UTIG.

 icon-link Project web page: http://geoprisms.org/research/community-projects/alaska/

The AACSE PI Team at the Portland (ME) OBS Workshop in September 2017. From left to right, top to bottom: Lindsay Worthington, Susan Schwartz, Anne Sheehan, Spahr Webb, Emily Roland, Donna Shillington, Aubreya Adams, Doug Wiens, and Geoff Abers.

PI team for the Alaska Amphibious Community Experiment proposal:
Geoff Abers (Cornell University, abers@cornell.edu)
Douglas Wiens (Washington University in St Louis, doug@wustl.edu)
Susan Schwartz (UC Santa Cruz, syschwar@ucsc.edu)
Emily C. Roland (University of Washington, eroland@uw.edu)
Anne Sheehan (University of Colorado Boulder, anne.sheehan@colorado.edu)
Aubreya Adams (Colgate University, aadams@colgate.edu)
Donna Shillington (LDEO, Columbia University, djs@ldeo.columbia.edu)
Spahr Webb (LDEO, Columbia University, scw@ldeo.columbia.edu)
Peter Haeussler (USGS, pheuslr@usgs.gov)
Lindsay Worthington (University of New Mexico, lworthington@unm.edu)

icon-chevron-right First land data now available!  All data are at the IRIS DMC, network code XO for land data and XD for OBS data

AACSE is deployed! The land array was deployed May-June 2018, and the OBSs finished deployment on July 20 2018

The AACSE deployment has been funded and is scheduled for spring, 2018 deployment!

The AACSE plan will be presented and discussed at the September 2017 OBS Workshop in Portland, Maine!

The AACSE project team convened a GeoPRISMS MiniWorkshop just prior to the 2017 AGU in New Orleans

A webinar (April 25, 2016) introduced the community to the exciting scientific opportunities that this DCL offers and to outline general strategies for achieving them. Watch the record of the webinar below.

 icon-download Download the slides of the webinar (PDF, 8Mb)

Presenters: Susan Schwartz, Geoff Abers, Emily Roland, Rob Evans, Doug Wiens, Jeff Freymueller

Apply to Sail with the Alaska Amphibious Community Seismic Experiment.

Application Deadline is now passed

Cruise Dates (+/- 5 days; arrive 2 days before departure date):

  • Leg 1: June 6 – June 24, 2019 (R/V Marcus G. Langseth: active source seismic survey)
  • Leg 2: Aug 10 – Aug 29, 2019 (R/V Sikuliaq: passive OBS recovery)
  • Leg 3: Aug 27 – Sep 12, 2019 (R/V Marcus G. Langseth: passive OBS recovery)

Graduate students and scientists at all career stages are invited to sail with the Alaska Amphibious Community Seismic Experiment (AACSE) aboard one active source seismic cruise during late Spring 2019, and two OBS recovery legs during the late summer and early fall of 2019. The AACSE is major shoreline-crossing community experiment focusing on the subduction zone offshore the Alaska Peninsula, which has been the site of North America’s largest recorded earthquakes as well as major volcanic hazards.  Data are collected during the 15-month experiment using 75 broadband ocean bottom seismometers (OBS) and 30 land stations.

  • OBSs will be recovered by two legs in August aboard the Global-Class R/V Sikuliaq and in September aboard the R/V Langseth. Participants will be involved with all aspects of the scientific process by assisting in OBS recoveries and with multibeam bathymetry data, documentation of the expedition, preparation of cruise reports, and documenting the cruise via social media.
  • An active source seismic cruise will be conducted aboard the R/V Langseth in June. This cruise will include an educational component for those interested in learning about marine active source imaging methods.  Duties of participants on this cruise will include keeping acquisition logs, acquiring multibeam bathymetry and 3.5 KHz data, documentation of the expedition, preparation of cruise reports, and documenting the cruise via social media.

The PI team anticipates that berths for 4 to 6 additional students or scientists will be available on each leg.  The cruises will be aboard working vessels with 24-hours operations, and participants will be unable to return to shore during the expedition. Participants should anticipate difficult conditions including rough seas, long hours, close quarters, constant noise, foul odors, and limited medical facilities.  Travel costs to and from the departure and arrival ports, meals, and lodging will be paid for Apply to Sail participants, but no stipend is included.

To apply to sail with the AACSE cruise, each applicant should submit a 2-page CV, a brief statement of interest, and a statement of relevant experience. Applicants who will be graduate students during the summer/fall of 2019 should also submit a letter of support from their graduate advisor. Applications are now closed.  Please direct any questions about the Apply to Sail application process to Aubreya Adams (aadams (at) colgate.edu).  Questions specific to the passive source cruises should be directed to Aubreya Adams, and questions regarding the active source cruise should be directed to Anne Becel (annebcl (at) ldeo.columbia.edu).

Applications are now closed

The Alaska Amphibious Community Seismic Experiment (AACSE) Team is pleased to invite applications from undergraduate students to join a short course on the Tectonics and Seismicity of the Alaskan Subduction Zone. The short course will be based in Kodiak, Alaska June 14-23 (±2 days) and will include a three-day workshop followed by field work with seismic instrumentation.

During the workshop, participants will learn earthquake science and tectonics, will be introduced to seismic theory and data, and will explore the earthquake geology of the Kodiak region. Following the workshop, students will join in the recovery of a 400 station nodal array across Kodiak with members of the science team.

Applicants should anticipate that this short course will require a 24/7 commitment during the course, will involve work early in the morning and late at night, and require shared accommodation. This no-credit short-course is tuition free, and transportation, room and board will be provided for approximately six students selected to attend the short course, but no stipend is included.

Applications from current sophomores, juniors, and seniors pursuing a degree in geoscience, physics, computer science, applied mathematics, engineering or related majors at a US institution are encouraged.

Applicants should submit the following information by April 1:

  • No more than 2-page resume
  • No more than 1-page Statement of Interest
  • List of relevant classes
  • Name and email address for one professional reference. Applicants should ask the reference writer to submit a letter of reference via email to aadams (at) colgate.edu by April 1.


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Evolution of the Chemically Diverse Aleutian Island Arc


Brian Jichaand Suzanne Kay2

1Department of Geoscience, University of Wisconsin-Madison, Madison, WI, 2Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY

Figure 1. Google Earth image of western Aleutian arc showing islands studied as part of this project.

The Alaska-Aleutian Arc extends for more than 3500 km westward from central Alaska to the Kamchatka Peninsula. The timing of Aleutian Arc inception and subsequent compositional evolution through the initial stages of arc growth are poorly known. Early estimates of Aleutian Arc inception varied from 70 to 40 Ma (e.g., Grow and Atwater, 1970; Scholl et al., 1986), but were based on very little data. Determining precisely how and when the Aleutian Arc began to form was one of the initial goals of this project. By addressing a central question of the GeoPRISMS Program (What are the physical and chemical conditions that control the development of subduction zones, including subduction initiation and the evolution of mature arc systems?) we intended to help link subduction initiation in the Aleutians with similar tectonic events at subduction zones in the western Pacific.

We identified outcrops on several islands that appeared to have a high probability of providing new limits on the timing of arc inception. Specifically, we focused on mafic ‘basement’ rocks and intrusives that cut the mafic lavas on Amatignak, Ulak, and Amchitka Islands (Fig. 1). These islands were interpreted to host remnants of the very early growth of the Aleutian Arc prior to northward arc migration. We also aimed to acquire new samples of the Vega Bay formation on Kiska Island and investigate the Finger Bay Volcanics on Adak Island (Rubenstone, 1984; Kay and Kay, 1994) from the extensive sample suite in the collections at Cornell University.

Figure 2. Allen Schaen (top) and Suzanne Kay (bottom) collecting samples from Rat and Skagul Islands, respectively in 2013.

Figure 2. Allen Schaen (top) and Suzanne Kay (bottom) collecting samples from Rat and Skagul Islands, respectively in 2013.

Two reconnaissance field campaigns were conducted in the summer of 2012 and 2013 with the help of the U.S. Fish and Wildlife service vessel M/V Tiglax. In 2012, we (Jicha and Cornell Ph.D. student Ashley Tibbetts) spent two weeks in the central and western Aleutians sampling lavas from Adak, Kiska, Ulak, Amatignak, and Kagalaska islands. Initial 40Ar/39Ar incremental heating experiments and geochemical analyses revealed that most of the subaerial samples of the older portions of the central and western Aleutians are < 40 Ma and thus provide little information on subduction initiation. As a result, we refocused our priorities and aimed to constrain the along- and across-arc chemical evolution of the central and western Aleutians over the last 40 Myr of arc history (e.g., Kay and Kay, 1994). In August 2013, we (Jicha, Kay, UW-Madison M.S. student Allen Schaen) conducted another sampling campaign with an emphasis on two regions: a SW-NE trending transect from the southern (Amatignak and Ulak) and central (Kavalga, Ogliuga, and Skagul) Delarof Islands to the Pleistocene-Holocene volcanoes on Gareloi and Tanaga Islands, and the Rat Island to Attu island segment of the western Aleutians (Figs. 1, 2). The first transect is the focus of the Master thesis of UW-Madison student Allen Schaen, which aims to compare the temporal evolution of igneous and tectonic processes in the Delarofs with similar studies on the Adak Island to the east (e.g., Kay and Kay, 1994) and the Attu Island to the west (e.g., Yogodzinski et al. 1993). The thesis of Tibbetts focuses on the evolution of the Aleutian basement on the islands of Attu, Kiska and Rat.

Overall, we have conducted 40Ar/39Ar laser incremental heating experiments and major, trace-element, and Sr and Nd isotope analyses on more than 130 samples. A summary of the findings is provided here:

Twenty-two 40Ar/39Ar ages reveal that magmatism in the Delarof region spanned 37 million years and was coincident with two arc-wide magmatic flare ups in the late Eocene/early Oligocene and latest Miocene/Pliocene (e.g., Jicha et al., 2006). A significant transition in arc chemistry of the lavas in this region occurs in the Pleistocene where lavas from nearby volcanoes Gareloi and Tanaga exhibit higher sediment signatures (e.g., Th/La) and lower 143Nd/144Nd compared to older Delarof Islands closer to the trench. Similar findings from Eocene-Miocene lavas within the western Aleutians from Amchitka to Adak suggest that a sediment melt component was unavailable early in the development of the western Aleutian Arc, but has become more pronounced in the Quaternary.

As part of our attempt to understand the evolution of the Central Aleutian arc lower crust we have studied and dated gabbroic composition granulite xenoliths from the Cornell collection of ~200 samples from Kanaga Island. The mafic xenolith suite is composed of plagioclase-clinopyroxene ±orthopyroxene-titanomagnetite-bearing gabbroic xenoliths with rare olivine and adcumulate textures, pyroxene granulites with granoblastic textures, and deformed recrystallized mafic granulites. The variable textures, mineral chemistries and isotopic ratios of these xenoliths show they had experienced a complex history before being incorporated into their ~7 Ma Mg-rich basalt host lava. These mafic xenoliths, along with the ultramafic xenoliths, are interpreted as lower crustal cumulates of basaltic to mafic andesitic arc magmas (e.g., Kay et al., 2013). It is from a mafic two-pyroxene granulite xenolith that we have surprisingly obtained the oldest ages yet reported in the Aleutian arc. This age comes from extremely challenging 40Ar/39Ar incremental heating experiments on low K (~An68Or0.4 Ab31.6) plagioclase, which yield complicated spectra, but give a plateau age of 47.8±4.3 Ma. We interpret this age as a time of metamorphism and recrystallization of mafic arc cumulates by younger arc magmas intruding the existing arc crust.

Calc-alkaline I-type plutons, like those thought to be major crustal building blocks of continental margins are rare in oceanic island arcs, but are present in the pre-Pliocene record of the Aleutian arc (e.g., Kay et al., 1990). The oldest and most calc-alkaline of these is the ~10 km wide Hidden Bay pluton on Adak Island, which intrudes the early Tertiary Finger Bay Formation. Published K-Ar (Citron et al., 1980) and new 40Ar/39Ar and U-Pb zircon ages from 16 gabbro, porphyritic diorite, diorite, granodiorite, leucogranodiorite and aplite units show the pluton evolved from 34.6 to 30.9 Ma in a series of events during a waning magmatic phase. The similarity of chemical analyses of the isotropic gabbros with modern Aleutian high-Al basalts supports minimal evolution of the central Aleutian magmatic source since at least 34 Ma. Mineralogical, trace element, and isotopic evidence suggest the plutonic units largely evolved in the deep crust with final crystallization and segregation of aplites occurring at shallow levels. Overall, the diorites are cumulates, whereas the volumetrically dominant granodiorites (58-63% SiO2) along with the leucogranodiorites (67-70% SiO2) approach melt compositions. The presence of calc-alkaline plutons in the central Aleutian arc by 34 Ma requires stability of pargasitic hornblende, crustal thicknesses approaching those of the modern arc by 34 Ma (~37 km on Adak; Janiszewski et al., 2013), a parental magma similar to that from the present-day arc, and a contractional stress regime. Such a scenario requires a very rapid build-up of the Aleutian ridge in the Eocene.

Building on the model of Yogodzinski et al. (1993), we have also been investigating the early evolution of the western arc. Our new chemical and 40Ar/39Ar analyses show that both the host rock (40.3±0.1 Ma) and the gabbroic units (34.7 to 27.2 Ma) have depleted epsilon Nd values (+9-10.8) and Marianas-like trace element chemistry (e.g., depleted LREEs). These NE-striking units are bordered on the west by 35.6 to 28.8 Ma altered MORB-like pillow lavas, breccias and dikes. Still further west lies a band of MORB-like rhyolite-albite granites with one rhyolite giving a 40Ar/39Ar age of 16.2±0.1 Ma. Thus, our new data indicates the oldest units on Attu formed in a Marianas-like arc between 40 and 16 Ma. To our knowledge, similar magmatic rocks are virtually unknown east of Attu. In contrast, the youngest Attu volcanic rocks form an east-west trending band of 8-6 Ma calc-alkaline andesites with lower eNd (+7.5-9.0) that erupted as calc-alkaline volcanism was occurring all along the arc. Combining this change in the strike of magmatic centers on Attu with published paleomagnetic data from Kiska (Minyuk and Stone, 2009) suggests a ~40-50° clockwise rotation of the western Aleutians along with uplift on Attu after 16 Ma and before 8 Ma.

Our ongoing and future efforts for the samples collected in 2012 and 2013 coupled with the vast collection at Cornell University will be focused on quantifying subduction erosion and subsequent northward migration of the arc with time, and evaluating the evolution of the different parts of the central and western Aleutian arc in comparison to the Attu-Rat, Delarof, and Kanaga-Adak segments.

References
Citron, G.P., Kay, R.W., Kay, S.M., Snee, L., Sutter, J. (1980). Tectonic significance of early Oligocene plutonism on Adak Island, central Aleutian Islands, Alaska, Geology, 8, 375-379.
Grow, J.A., Atwater, T. (1970). Mid-Tertiary tectonic transition in the Aleutian arc, Geological Society of America Bulletin, 81, 3715-3722.
Janiszewski, H.A., Abers, G.A., Shillington, D.J., Calkins, J.A. (2013). Crustal structure along the Aleutian island arc: New insights from receiver functions constrained by active-source data, Geochem. Geophys. Geosys., 14(8), 2977–2992, doi:10.1002/ggge.20211.
Jicha, B.R., Scholl, D.W., Singer, B.S., Yogodzinski, G.M., Kay, S.M. (2006). Revised age of Aleutian Island Arc formation implies high rate of magma production, Geology, 34, 661-664.
Kay, S.M., Kay, R.W., Citron, G.P., Perfit, M. (1990). Calc-alkaline plutonism in the intra-oceanic Aleutian Arc, Alaska, In Kay, S. M. and Rapela, C.W. (eds.), Plutonism from Antarctica to Alaska, Geol. Soc. Spec. Pap., 241, 233-255.
Kay, S.M., Kay, R.W. (1994). Aleutian magmas in space and time, in Plafker, G., and Berg, H.C., eds., The Geology of Alaska: The Geology of North America, v. G-1: Boulder, Geological Society of America, p. 687-722.
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Reference information
Evolution of the Chemically Diverse Aleutian Island Arc, Jicha, B., Kay, S.

GeoPRISMS Newsletter, Issue No. 34, Spring 2015. Retrieved from http://geoprisms.org