Cruise Success

Saturday August 29, 2015
By Rachel Teasdale

Axial Seamount 2015 Expedition video summary of the highlights and results from the expedition. Video by Jesse Crowell in association with Saskia Madlener at 77th Parallel Productions. Music: "Arboles by Podington Bear, https://freemusicarchive.org/music/Podington_Bear/Encouraging/Arboles"

Bathymetric map of Axial Caldera and hydrothermal vent fields visited during dive J2-825.

Cruise Success!
As the Axial Seamount 2015 Expedition comes to an end, the science team aboard the R/V Thompson is thrilled with the extensive work completed since departing Seattle on August 14. Chief Scientist Bill Chadwick was able to work around the three days of bad weather that prevented the launch of ROV Jason and AUV Sentry, and with creative rescheduling, efficient ROV Jason and AUV Sentry operations and flexibilty of the R/V Thompson crew we were able to collect the data from all pre-planned sites that were needed to accomplish the three main goals of the cruise:

Matt (green jacket) works with the R/V Thompson deck crew to deploy a bottom pressure recorder at Axial Seamount

1.    Make seafloor pressure measurements to measure volcanic inflation/deflation
2.    Complete Incubator experiments and collect samples of hydrothermal vent fluids for chemical and microbial analyses
3.    Explore the volcano to observe, sample and document the physical and biological impacts of the April 2015 eruption including new lava flows, ash, hydrothermal plumes, and micobial oraganisms

Pressure Measurements (Goal 1)
Bill Chadwick and Scott Nooner are both happy with the pressure dives (J2-823 and J2-824) during which a mobile pressure recorder (MPR) on ROV Jason collected data at 10 benchmarks (see map). Bill said this data, and data from the bottom pressure recorders (BPRs; installed two years ago and recovered during this expedition), are all of very high quality. Scott loves to process the data and is already starting to make corrections such as tidal influence so he and Bill can start to consider inflation rates since the April 2015 eruption in their ongoing work to characterize the movement of magma beneath the volcano. Matt Fowler was able to get the BPRs turned-around from instrument recovery to downloading data and installing new batteries, to re-deploying them back to the seafloor (image left), to continue monitoring the inflation and deflation of the volcano. Glenn Sasagawa’s work with the self-calibrating pressure recorder (SCPR) will continue once he’s back at Scripps, where he will process the data the SCPR collected for the last two years, and also work on improving the instrument and its ability to survive at the ocean floor for future deployments.

Kevin and Ryan prepare the RAS sampler for its year on the seafloor at Axial Seamount

Hydrothermal Vent Chemistry: CTD and RAS (Goals 2and 3)
The CTD casts were a success, with four vertical casts and four tow-yo casts over known vents as well as over the 2015 lava flows where new vents might occur. CTD data and samples will be analyzed at University of Washington by Nathan Buck and Rachel Spietz and other colleagues back on shore. Nathan’s CTD water samples will be used to characterize the plume in terms of He isotopes, metals, methane and dissolved ionic compounds. Rachel will focus on the microbes that live in the water column just above the hydrothermal plumes. Analyses of proteins in the plume will help her characterize the metabolic processes of the microbial organisms. Dave Butterfield looks forward to learning the results of Nathan and Rachel’s analyses because the new plume locations and compositions are not obviously directly linked to new lava flows, but he says the complexity of trying to interpret the plumes is part of what makes science challenging, exciting, and keeps him coming back to Axial Seamount year after year.

The remote access sampler (RAS; see image above right) that was set up by Kevin Roe, will collect samples approximately once a week for the next year when the samples will be retrieved. RAS data will help Dave and Kevin understand the longevity of the hydrothermal vents as well.  Much of Dave and Kevin’s work was also aimed at the sampling of vent fluids during the Jason dives.

Dave and Ben prepare hydrothermal vent fluid samples

Life at the Hydrothermal Vents (Goals 2 and 3)
Dave Butterfield attributes much of the success of the incubator to the hard work of Ryan Wells and Ben Larson in engineering and preparing the incubator to collect and analyze samples on the seafloor. Once the incubators were back on board, Ben collected gas from each sample (right), then the microbiology group extracted their samples for experiments that parallel those completed in the incubator on the ocean floor. Emily Reddington (below right) and Chris Algar (below left) filtered hydrothermal vent samples over pre-determined time periods, just as was done in the incubator. Microbes collected on filters of both sample sets will be analyzed once back at the Marine Biological Lab in Woods Hole, Massachusetts. Chris acknowledges that there is still a lot of lab work to be completed, but is excited to learn the results of analyses started here on the ship.   

Emily (right) and Chris (left) prepare samples for incubator experiments

Graduate student Begum Topçuoğlu and her advisor, Jim Holden have also processed microbes from hydrothermal vent fluids, and are pleased with the number and quality of samples they were able to collect while at sea. On board, they successfully cultured thermophilic (organisms that live in approximately 55°C water) and hyperthermophilic (live above 80°C) organisms, some of which are methanogens (they produce CH4) and others produce sulfur. Begum has numerous analyses to complete once back in the lab, but she and Jim are excited to learn the results of the parallel incubator experiments, which Begum calls revolutionary in terms of learning more about sampling microbes in the high pressure environment of the ocean floor.

The 2015 Lava Flows (Goal 3)
In addition to originally planned research at Axial Seamount, the 2015 expedition became unexpectedly well-timed for exploring the geological, chemical and biological effects of the April 2015 eruption. As noted in previous blogs, a variety of flow morphologies were observed on the 2015 flows and expert piloting of the ROV Jason facilitated the collection of nearly 30 rock samples from the 2015 lava flows (below right). In addition, a sample of ash was “slurped” from the surface of one of the pressure campaign benchmarks (AX-101, below right).  Jenny Paduan has prepared the samples for further chemical analyses to help characterize the lavas in terms of compositional variations with previous eruptions, which will provide a larger idea of the chemical processes of the magma at depth.

Rock sample (right) and ash (left) collected from the 2015 eruption

Exploration of the lava flows was facilitated by maps generated by AUV Sentry missions in and around the caldera. High resolution maps processed from AUV data have already revealed details of the lava flows such as channels that have been filled in with 2015 flows and collapse features. Multibeam surveys also discovered new areas covered with 2015 lava that were previously unknown on the NE rim of the caldera. No fissures that would have fed the flows have been identified thus far, but that area will likely be targeted for wider surveys in future expeditions.  Multibeam maps will also be used to better understand the inflation and deflation of Axial Seamount in the future because the vertical movements of the seafloor are large enough to detect by repeated surveys.  These data are yet another significant contribution to understanding the most recent eruption as well as the dynamics of this very active submarine volcano.

Here is an interesting perspective of the R/V Thompson passing through the locks and Lake Union before docking at the University of Washington:

Axial Seamount 2015 Expedition video of the R/V Thompson passing through the locks and Lake Union, and arriving at the pier at the University of Washington in Seattle at the end of our expedition. Video by Jesse Crowell in association with Saskia Madlener at 77th Parallel Productions.

Last 2 Jason Dives

August 28, 2015
By Rachel Teasdale

Weather
Bright but overcast skies with calm wind (approximately 10 knots) and calm seas.

What’s happening today?
Last night the last ROV Jason dive of the cruise ended by looking at 2015 lavas of the NRZ at midnight. We’re currently in transit back to Seattle, with an expected arrival at the University of Washington dock at 10 AM Saturday August 29.

Bathymetric map of Axial Caldera and hydrothermal vent fields visited during dive J2-825.

Last 2 Jason Dives

J2-825
Following the successful of the pressure dives (J2-823 and 824) and a quick turnaround by the Jason crew, dive J2-825 was launched Wednesday morning at the Marker 33 Vent in the southeast part of the caldera. This vent has been active since before the 1998 eruption and vent samples have been collected there nearly continuously, making it one of the best time-series sites in the caldera. Fluid samples were collected for the second round of incubator experiments  and for chemical analysis and microbial culturing on the ship.

Sampling fluids at Marker 33 Vent for the second incubator experiments during dive J2-825.

Following the fluid sampling, Jason transited to the NE caldera rim where we explored more of the 2015 lava flows that we had not yet seen or sampled.  We targeted this area because some of the earlier CTD tow-yos above NE rim of the caldera (see CTD blog) had revealed high turbidity and multi-layered hydrothermal plumes above the seafloor, suggesting that 2015 lavas, or perhaps new hydrothermal vents, were emitting vent fluids.  We spent several hours exploring the NE caldera rim and sampling the 2015 lava flows along the North Rift Zone (NRZ).

Jumbled surface (left) and ropy surface (right) on 2015 lava flows on the NE caldera rim (J2-825).

Collapsed areas of 2015 lava flows (J2-825).

Eight lava samples were collected for geochemistry and Polonium (Po) isotope dating that could provide precise ages of the samples to constrain the timing of the emplacement of lavas, possibly within the day or week of the eruption. Such precision will help constrain the eruption and emplacement dynamics and rates of lava flow emplacement. These 2015 lavas include many lava morphologies, including ropy surfaces (above upper left) jumbled flow surfaces (above upper right) and have numerous collapse areas (see lower images above).

Pillow lavas (left) and a pillow bud collected from 2015 lava flows (J2-825).

Samples includes pillow lavas (image above left), sheet flows, inflated areas (above right) and a pillow bud - the branching point where a pillow formed and then branched off (see image above right).

J2-826

RAS vent fluid sampler installed at a vent on Axial’s North Rift Zone (J2-826).

The last dive of the expedition was J2-826, which focused on collecting rocks and fluids from the 2015 lava flows of the north rift zone (NRZ), continuing the exploration of the area we started during our first Jason dive.

The first task during the dive was to position the Remote Access Sampler (RAS), which is a set of water bottles that will collect vent fluid samples in a time-series over a year when the RAS will be recovered. The RAS was deployed from the ship earlier today by placing it in the water and letting it free-fall to the seafloor with weights that increase its descent rate and remain on the seafloor. On recovery, Jason will return to manually release the anchor attached to the RAS so that glass floats attached above the RAS can lift it back to the surface.

Bathymetric map of Axial North Rift zone showing exploration waypoints for dive J2-826.  Only the southern half of the waypoints were visited before the dive ended.

For the rest of the dive we continued a transect across the thick 2015 lava flows on the North Rift Zone, continuing where we left off during our first Jason dive to collect samples of the 2015 lavas and any vent fluids discovered where the flows are so thick they are still cooling.

Suction sampler collecting orange bacterial mat from a site called “snow drift” on the 2015 lavas. The two red laser dots are 10 cm apart (J2-826).

Near waypoint 5 (see map), we collected a thick orange bacterial mat using the suction sampler. Nearby, we also sampled vent fluids at a temperature of 35°C and their trapped gasses.

We continued exploring the 2015 lavas of the NRZ as long as we could before it was time to recover Jason and head for home.   As usual, there is always more we would like to do if we had more time, but that’s what also keeps us coming back to Axial Seamount!  We headed to the surface with lots of samples and a much better idea of the diversity and distribution of the 2015 lava flows than we started with.  Next stop, Seattle!

Last view of 2015 lavas of the NRZ as Jason departed for the surface (J2-826).

Dive 3 & 4 Highlights

Wednesday August 26, 2015
By Bill Chadwick

3rd and 4th Jason dives 
 

Axial Seamount 2015 Expedition video highlights from ROV Jason dives J2-823 and J2-824, including pressure measurements on seafloor benchmarks, release of the SCPR mooring, and sampling of vent fluids and microbes from the ASHES vent field, and at Trevi, Marker 113, Vixen, and Casper vents. Video by Jesse Crowell in association with Saskia Madlener at 77th Parallel Productions. Music by James Andrew Menking

Map of vent sites and pressure benchmarks visited on dives 3 and 4 (J2-823 and J2-824).

The 3rd and 4th Jason dives (J2-823 and J2-824) were mainly to conduct the pressure measurements described in the Pressure Dive blog post.  However, during the last transect of the dive we released the SCPR (self-calibrating pressure sensor) mooring and also visited some of the hydrothermal vent sites that we had not yet had a chance to visit.  This allowed us to sample the vent fluids and microbes at these vents to continue our long-term time series and to look for changes in chemistry or microbial communities that might be due to the 2015 eruption.   We also recovered and deployed long-term temperature recorders in some of these vents.

This movie of dive highlights includes views of these vent sites: Virgin and Anemone in the ASHES vent field, Trevi and Spanish Steps in the eastern caldera, and Marker 113, Vixen and Casper vents in the southern caldera.

Making Lava Maps

Wednesday August 26, 2015
By Rachel Teasdale

Weather:
Overcast skies with blustery winds (up to 20 knots) and moderate (swells of 6-8 ft).

What’s happening today?
ROV Jason launched this morning on the last incubator experiment dive; AUV Sentry was launched this afternoon and a bottom pressure recorder (BPR) was acoustically released from the seafloor and recovered this evening.

Bathymetric map of Axial white box shows area discussed in high resolution maps discussed below.

Making Lava Maps
To make a map of a volcano or other feature above sea level can be done using direct observations and GPS to record geologic features directly on a base map. Unfortunately, it’s not so easy at sea, where neither light nor satellite communications penetrate the deep ocean. Even the strong lights of the ROV Jason only penetrate 10-20 m (32-64 ft).  Instead, sound waves, which are transmitted through water, are used for mapping the bathymetry of the ocean floor.

Bathymetric maps show the depth to the seafloor and at Axial Seamount they reveal the caldera, Axial’s rift zones and other topographic features (see map). Bathymetry is represented using color coding to distinguish high areas (shallow depths in warm colors) from low areas (deeper depths in cool colors). This “underwater topography” is similar to a map used to find ones way along a hiking trail, but shows the topography of the seafloor instead.

However, the resolution of bathymetric maps depends on how close to the seafloor the sonar data are collected.  Sonars on ships can map about at 30-m resolution at this depth (1500 m), whereas sonars on underwater vehicles, which can “fly” much closer to the seafloor, can map at 1-m resolution.  A high-resolution map is like focusing a blurry picture – it allows you to see much more detail.

As noted in the previous AUV Sentry blog , Sentry uses its multibeam sonar to map the seafloor using a pre-programmed set of tracks that have it systematically fly over the floor of the caldera in an overlapping zig-zag pattern, like  “mowing the lawn,” with each strip overlapping the next for thorough coverage. Once AUV Sentry returns to the ship, data from the mapping survey is processed to build bathymetric maps. To convert data into the maps, Jenny Paduan of the Monterey Bay Aquarium Research Institute (MBARI) processes the data to remove tides and other navigational effects to precisely represent seafloor depths on a bathymetric map.

On this cruise, the multibeam sonar mapping is helping to map the location of new lava flows, and the resolution is good enough to describe the morphology of those flows, which can be used to extract the volume of lava erupted, the style and the rate of emplacement.  For instance, recent mapping in the caldera has allowed a better view of the lava flows erupted there in April 2015. While lights on ROV Jason can show geologists a view of approximately 10 m (32 ft) in front of the vehicle, Jenny’s maps with AUV data reveal high resolution views of much larger areas.

An example of this resolution is in a series of maps below. On the left is a map of an area in the NE part of the caldera (see location box in map at top of this page), mapped before the April 2015 eruption. Jenny generated the middle map from AUV Sentry data from August 2015. Areas in the white boxes (A and B) are notably different from the pre 2015 eruption map, as seen in the Difference map on the right, which is developed by subtracting the “Before Eruption” data from the “After Eruption” data.

Maps of small area in the NE caldera (shown in white box in map at top of blog, before the 2015 eruption (left), after the eruption (middle) and the difference between the two maps (right) and image of an example of a small collapse pit in a lava flow (right). Details described in the text; maps courtesy of Jenny Paduan, MBARI

The area enclosed by Box A contains a new flow lobe emplaced during the 2015 eruption and is shown at a larger scale in the image below (left), which also reveals a collapse area at the center of the large flow. An example of a much much smaller but similar collapse is shown below right.


Similarly, the area enclosed in Box B was filled with narrow flow lobes and channels (“Before Eruption”) but those channels are now filled in and flattened out by the 2015 lavas. This can also be seen in the “Difference” map, which depicts more shallow areas (higher sea floor topography shown with warmer colors) after the eruption.

Box C in the “After Eruption” map above is shown at larger scale in the map below (left), which reveals a top-view of vertical pillars that were once channels for water to flow vertically though the lava flow. Those vertical channels were preserved when the molten interior of the flows drained, leaving the pillars left standing in the flow field (see image below right).


The high resolution multibeam sonar data collected by AUV Sentry allows fine details of new lavas to be resolved in the resulting maps. While ROV Jason can photograph similar features, it cannot access the extensive areas that AUVs can map, so often the AUV maps are used to identify features that merit detailed exploration with ROV Jason. The combination of widespread, high resolution mapping is a critical contribution to the characterization of the distribution of the 2015 lava flows, yet another important step towards understanding this active submarine volcano. 

In addition to creating high-resolution bathymetric maps, another goal of the sonar mapping by AUV Sentry is to look for changes in seafloor depth due to deformation related to inflation and deflation since previous surveys were collected. This data will be used to complement the pressure measurements  and expand the spatial coverage of the deformation measurements in the future.

Facilitating Science

Tuesday August 25, 2015

By Rachel Teasdale

Facilitating Science: 

Axial Seamount 2015 Expedition video showing how the R/V Thompson supports all the various science operations at sea. Video by Jesse Crowell in association with Saskia Madlener at 77th Parallel Productions. Music by James Andrew Menking

The R/V Thompson Crew The crew of Research Vessel, Thomas G Thompson (see image below) operated by the University of Washington is a dedicated group of mariners who are keen on ensuring that the ship serves as a floating research station where diverse scientific research projects can be completed successfully and efficiently. Each crew member brings their expertise and creativity to accomplishing tasks dreamed up by scientists on the cutting edge of Marine Geology, Biology, Chemistry, Engineering and more.

R/V Thompson in port on Friday August 14, 2015 just prior to departing Seattle, WA.

Chief Mate Bree Ogden- Bennett on the bridge of the R/V Thompson.

The crew on this expedition is led by Captain Russell DeVaney who is essentially responsible for everything that happens on the ship, but he considers his most important task to be the safe operation of the ship and scientific activities. The team of ship’s Mates stand navigational watches around the clock to keep the ship on course.

Chief Mate Bree Ogden-Bennett, a graduate of the California Maritime Academy, has worked at sea for six years. Among her many duties, she stands navigational watch (see photo right) and oversees all deck operations. One advantage of working on research vessels for Bree is that the point of her work is to conduct operations at sea, whereas other maritime industries are focused on racing from port to port. Bree, Second Mate Tom Drake, and Third Mate Josh Woodrow stand two four-hour watches each day (e.g. noon to 4pm and midnight to 4am). In addition to standing watch on the bridge, Tom also maintains navigational information and nautical logs.

Z -drive propeller (from R/V Thompson stock images.

With its specialized “Z-drive” propellers and dynamic positioning system the ship can maintain position with great precision, which is necessary for ROV Jason to work on the seafloor. The Z-drives allow the ship’s propellers to face any direction, for 360° propulsion (see photo left). With the help of the bow-thruster for lateral positioning, the ship can move in any direction or hold a specific position, even against the wind and waves. The Z-drives and the ship’s engines are maintained by the eight member- Engineering Department, led by Chief Engineer, Mark Johnson. Oiler, Mario Yordan runs the diesel engines that produce power to run generators that power the ship.

Mario Yordan inspects the engines.

Third Engineer Doug O’Neill oversees the water for the ship, which is desalinated seawater. He first sends seawater through a strainer then pumps it at high pressure through five stages of reverse osmosis in which the salt is removed from the water. The final purification comes from a dose of 0.3 ppm chlorine. The ship can make 4,000 gallons each day and can store up to 12,000 gallons, but Doug says we typically only use 3,000 gallons per day. The ship undergoes almost constant preventative maintenance, but the Engineering Department has a machine shop in which almost any part on the ship can be fixed.

Reverse osmosis system converts sea water to drinking water.

Deck operations include launching and recovering instruments with cranes and winches as well as assisting AUV Sentry and ROV Jason launches and recoveries. Dana Africa has worked as one of the able-bodied seamen (AB) on the R/V Thompson for nearly eight years. She and five other on the deck crew says the job is to “sweep, swab, paint, chip, run cranes and winches and sometimes steer the ship.”

In some cases scientists at sea attempt to use existing methodologies in new ways or are inventing brand new methods for investigating biological, geological and chemical characteristics of the world’s oceans. Brandi Murphy and Jen Nomura help facilitate their work as marine techs on the R/V Thompson.

AUV Sentry recovery with Bree (white hard hat), Brandi (in her pink hard hat), AUV Sentry Group (blue hard hats) and R/V Thompson deck crew (white and orange hard hats, and in the crane)

They help scientists do their work on the ship and serve as the liaisons between the ship’s crew and science party. Most days Brandi and Jen spend time on deck (see photo right) helping launch or recover vehicles and instruments for work on the ocean floor. Brandi is familiar with the scientific equipment from her work on research expeditions in graduate school. She and Jen help develop and implement work plans to deploy or recover sensitive instruments.

Chief Steward India Grammatica with one of the mess crew’s delicious meal.

In addition to accomplishing scientific goals, a constant morale booster comes from the kitchen. Not only are India Grammatica, Liz Zacharias and Kelly Darrah always happy and outgoing, their food is amazing. When not talking about science, the main topic of conversation usually pertains to the previous and next meals - or both!

The science team of the Axial Seamount 2015 Expedition is grateful for the hard work and dedication contributed by these folks, and all of the R/V Thompson crew who ensure the success of the scientific goals of our work at sea.

Forecasting Eruptions

Tuesday August 25, 2015 

Weather: 
Overcast skies with calm winds (less than 15 knots) and relatively calm seas (swells of 6-8 ft).

What’s happening today? 
 ROV Jason continues with the last stages of the pressure dive and has resumed collecting fluid samples where hydrothermal vents are near pressure benchmarks. AUV Sentry continued mapping the caldera, then was recovered at this afternoon.

 Forecasting eruptions
 By Bill Chadwick

Graphic showing magma intruding into the volcano causing inflation.

Volcanoes like Axial Seamount inflate and deflate like a big balloon in response to magma going into or out of a reservoir located beneath the summit caldera. Between eruptions the volcano slowly inflates (and the seafloor gradually rises by 10s of cm/yr) as magma is injected into the reservoir from below. Then during eruptions, the volcano rapidly deflates (and the seafloor drops by 2-3 m over a few days) as magma is removed from the reservoir to erupt as lava on the seafloor.

Graphic showing magma erupting to the surface of the volcano, causing deflation.

The pressure measurements we are making during the current Jason dive measure this vertical movement at many locations on the volcano and they are useful in several ways. They allow us to estimate the depth, size, and shape of the magma reservoir that is pushing the seafloor up and down from below. For example, from the depths determined by the pressure measurements we know the magma reservoir is located a few kilometers (~1 mile) below the seafloor and is centered on the caldera. We can also use the measurements to estimate the supply rate of magma into (or out of) the reservoir. For example, we know that the magma supply at Axial has been continuous for the last 18 years, but the rate of that supply has changed with time. After the 2011 eruption the supply rate was 4 times larger than before the 2011 eruption. That is why the time interval between the 2011-2015 eruptions was shorter (4 yrs) compared with the previous interval (13 yrs between 1998-2011). The inflation and deflation measurements can also be used to anticipate when the next eruption might occur.

Plot of bottom pressure recorder (BPR) mobile pressure measurement data (MPR) with time, showing repeated pattern of rapid deflation during eruptions (drop of the seafloor), followed by slow inflation between eruptions (uplift of the seafloor). These data plus the MBARI AUV data allowed us to forecast an eruption in 2015.

To attempt to forecast eruptions at Axial, we’ve used the simple idea that the volcano should be ready to erupt again when its level of inflation reaches the same threshold it reached when the previous eruption was triggered. That idea is based on the concept that as the magma reservoir inflates with magma, the pressure inside gradually builds (like more and more air forced into a balloon). Eventually the pressure gets so high that magma forces its way out of the reservoir (like a balloon popping or springing a leak). That’s when an eruption happens. Of course, not all volcanoes are that “well behaved,” and their pattern of inflation and deflation is not necessarily repeatable or predictable from one eruption to the next. But we wondered if a submarine volcano like Axial might have a predictable pattern since the ocean crust is so thin and the magma “plumbing system” is relatively simple. Once we started measuring the pattern of inflation and deflation at Axial we decided to give it a try.

Same plot as above with deflation pressure data that was recorded during the 2015 eruption by an instrument on the Ocean Observatories Initiative Cabled Array network (in orange). We are collecting data during the Axial Seamount 2015 expedition that will more closely tie data recorded during the April 2015 eruption to the previous time-series. More information at: pmel.noaa.gov/eoi/axial_blog.html.

Our first attempts were complicated by the fact that we started with a gap in the pressure data after the 1998 eruption and our early ROV-based pressure measurements had relative high errors as we learned how refine the technique. Despite those uncertainties, in 2006 we made a forecast that we thought Axial would erupt again “before 2014”. Our anticipated eruption occurred in 2011 – and even though the forecast window was pretty wide (several years), we were encouraged by this success. Since then, our measurement techniques have continued to improve, which allowed us to make a forecast with a narrower time window before the 2015 eruption. In September 2014, we issued a forecast that Axial would erupt again sometime in 2015, and that eruption occurred in late April. Another success! A critical piece of information to that successful forecast was repeat bathymetry by our colleagues at MBARI with their AUV that showed that the rate of inflation we had measured with our pressure sensors in 2013 was continuing into 2014. Our hope is that by studying how eruptions can be forecast at Axial Seamount we will learn valuable lessons that can be applied to predicting volcanic eruptions on land.

To learn more about the 2015 Axial eruption, see the video from the earlier posting about the eruption.

Skyping from Sea

Monday August 24, 2015 
By Rachel Teasdale

Weather
Bright but overcast skies with moderate wind (5-15 knots) and relatively calm seas (swells of 6-8 ft).

What’s happening today? 

Many of us awoke this morning to find Jason on the deck, which was not planned. At approximately 3:00 this morning a problem with the hydraulic system of the sample basket (where the mobile pressure recorder is stowed) developed, which forced the dive to end early. Fortunately the Jason group was able to fix the problem quickly and Jason was back in the water at noon to continue the long dive to measure pressure at a series of ten benchmarks. We’re on the third and final circuit of the campaign. AUV Sentry was launched this afternoon on a mission to continue multibeam sonar mapping of the caldera.

Skyping from Sea

Chemist Dave Butterfield (Univ Washington/NOAA), geologist Bill Chadwick (Oregon State University/NOAA, and microbiologist Jim Holden (University of Massachusetts, Amherst) talk via Skype video connection with students at Lindhurst High School in Marysville, CA.

Working at a volcano that is 1.5-2.2 km (0.9-1.3 mi) under the sea might be difficult to imagine for non-scientists, but to encourage broader understanding of the type of work we’re doing and the various instruments we use, we have been talking to school-aged groups by Skype while at sea. Following a similar program we began in 2013, we organized Skype calls with west coast middle and high school classrooms, summer camps, and with the Visitor’s Center at the Hatfield Marine Science Center (HMSC) in Newport, Oregon.

During the Skype calls, scientists on board the Thompson at Axial Seamount can conduct a video call to shore, more than 400 km (250 mi) away via the ship’s satellite-based internet. In spite of the distance, scientists and engineers on board the Axial Seamount 2015 Expedition have been able to share some of their science goals for the cruise, provide updates of some of the progress we’ve made, and then answer questions.

Chief Scientist, Bill Chadwick, microbiologist Jim Holden, and chemist Dave Butterfield are often on the Skype calls to explain their work here at Axial Seamount and also some of the research they’ll continue to do once back at their home institutions. The majority of time during the calls is spent answering questions from kids with whom we are Skyping.

Teachers prepare their students to talk with scientists by having them read the cruise blog entries (http://axial2015.blogspot.com). Most are curious about the ROV Jason and AUV Sentry dives, and also have more detailed questions about the 2015 lava flows and the microbes that manage to survive in the hydrothermal vent environments.

2015 Axial Seamount lava morphologies, including pillows (left), jumbled flows (center) and lobate sheet flows (right).

For example, a student from Chico Junior High School in California asked Chadwick to compare the explosivity of eruptions on land with the 2015 eruption given the high water pressure in which it erupted. Chadwick answered that at Axial Seamount, lavas typically erupt in the form of thin fluid sheet flows or thicker pillow lavas (see images above) rather than explosively and drew some comparisons to other volcanoes like Kilauea on the Big Island of Hawaii, and in contrast to more explosive volcanoes like Mt. St. Helens.

In a conversation with the HMSC Visitor Center, a room of more than 35 visitors peppered scientists with questions ranging from the possible connections between Axial Seamount’s geologic activity and earthquake hazards along the coast, to the diversity of animal and microbial life that live at the hydrothermal vents (see image below).

Tubeworms (left) thrive on hydrothermal vent chimneys in the CASM hydrothermal vent field where we sampled hot spring fluids during Dive J2-822 on 21 August 2015.

In a Skype call with a STEM Marine Science Camp for girls at the Hatfield Marine Science Center, AUV Sentry engineer Loral O’Hara explained that she works with colleagues on board to process mapping data from the submersible as well as to plan future missions. Biologist Emily Reddington responded to questions to explain the work she and her colleagues do with fluid samples from the hydrothermal vents to identify and characterize the activities of specific microbes by sequencing their DNA and RNA.

We all recognize that one of our duties as scientists is to explain to non-scientist what we do and why we think it’s important.  These Skype calls are a great way to do that, in addition to this cruise blog.   And who knows, they just might inspire the next generation of scientists to explore the natural world and try to answer important questions on land, or maybe even at sea.

Detecting Deformation

Sunday August 23, 2015
By Rachel Teasdale

Weather 
Bright but overcast skies with calm wind and seas.

What’s happening today? 
The Jason pressure dive continues for the second day. This morning the SCPR (Self Calibrating Pressure Recorder) was recovered, after two years on the seafloor. This afternoon AUV Sentry will be recovered after nearly 24 hours of mapping in the caldera.

Bathymetric map of the Axial Seamount caldera (horseshoe shape open to the south) with north and south rift zones and lavas of the April 2015 eruption outlined with black lines.

Detecting Deformation
As previously discussed, the goal of the pressure dive is to use the array of the Bottom Pressure Recorders (BPRs) to precisely measure the depth of the seafloor at Axial Seamount over time. As magma moves up from deeper sources, the seafloor rises, in a process referred to as inflation. When magma erupts (or moves laterally in the volcano), the seafloor lowers, known as deflation. Following a series of pressure dives in 2011 and 2013, Bill Chadwick, Scott Nooner and their colleagues used their high precision pressure data to determine that since the 2011 eruption, Axial Seamount had inflated approximately 60 cm/yr (1.9 ft/yr).

As pressure surveys have continued to monitor the movement of magma at Axial Seamount, colleagues at the Monterey Bay Aquarium Research Institution (MBARI) have used sonar instruments to map the surface of the seafloor. Multibeam sonar mapping like that described for AUV Sentry (< link to Sentry blog 16 August), works by emitting sound waves that are reflected from the ocean floor and returned to receivers. The time between the emitted and received reflected pulses is used to determine the distance the sonar traveled to the seafloor and back. Maps of the seafloor are color coded, usually with warm colors representing shallow (or high seafloor topography) and deeper (lower) seafloor topography represented by cool colors (see map above).

Image of MBARI’s AUV D. Allan B in 2006.

Axial Seamount is one of the few places where high resolution mapping has been completed prior to and after an eruption. Multibeam sonar surveys before and after the 2011 eruption were completed by MBARI. Their AUV, D. Allan B (see photo left) collected sea floor depth data with 20 cm (0.6 ft) vertical resolution. By subtracting the pre-eruption bathymetry from that collected after the 2011 eruption, they were able to detect depth changes on the sea floor that are greater than 20 cm, including the dimensions of new lava flows and locations of eruptive fissures (see maps below).

Maps of 2011 Axial Seamount lava flows (c) defined from differencing of pre- and post-eruption bathymetry. Right side (d) is 2011 bathymetry with interpreted flow margins (black lines), eruptive fissures (red) and lava flow channels (blue). Ashes is a hydrothermal vent field. Topography is color coded, in m below sea level. Figure modified from Caress et al., 2011.

Given their success with high resolution mapping and improved data processing, David Caress and David Clague of MBARI had the idea that their multibeam sonar mapping might be able to capture the same inflation and deflation measured by Chadwick and Nooner. To test this hypothesis, Caress and the AUV, D. Allan B re-mapped Axial’s surface in 2014. They then subtracted the 2011 survey from their new 2014 mapping and found there had been 1.8 m (5.8 ft) of uplift at the center of the caldera in the three years between surveys, which was consistent with the deformation observed by Chadwick and Nooner from 2011-2013 using pressure sensors. Thus two independent methods for measuring the deformation of the seafloor yielded the same rates of inflation. These two methods are now being used in tandem for the first time during this expedition, because they are complimentary and together can provide new insights into the extent of deformation.

Based on the continuous inflation rates observed from 2011-2013 by the pressure sensors and the continued inflation measured by the MBARI AUV into 2014, Chadwick and Nooner were able to successfully forecast that the next eruption at Axial Seamount would occur sometime in 2015. The April 2015 eruption proved their forecast correct. We will explore more about eruption forecasting at Axial Seamount in an upcoming blog.

Pressure Dive

Saturday August 22, 2015
By Rachel Teasdale

Weather
Overcast skies with calm wind and seas (finally!)

What’s happening today?

Axial Seamount 2015 Expedition video describing the various kinds of pressure measurements being conducted on this cruise to measure inflation and deflation of the volcano. Video by Jesse Crowell in association with Saskia Madlener at 77th Parallel Productions. Music by James Andrew Menking

Bathymetric map of Pressure Dive benchmarks and BPR locations, including reference site AX-105

This morning the Pressure Dive began with the launch of ROV Jason approximately 8 km south of the caldera, then moved into the caldera midday. AUV Sentry was launched this afternoon for a 24 hour mapping project in the caldera.

Pressure Dive
Today we started the Pressure Dive - this is a 3 ½ day campaign in which ROV Jason will visit 10 sites in a circuit that will be completed three times.

The depth to the seafloor can be extracted from the water pressure of the overlying water column. At the surface, atmospheric pressure is 14.5 psi (pounds per square inch) and that increases by an additional 14.5 psi every 10 m (33 ft) of water depth. Bill Chadwick and Scott Nooner use the water pressure on the seafloor to determine the precise depth of the seafloor at an array of seafloor monuments and then they look for changes in the depth of the monitored sites over time. This is important for understanding whether magma is welling up in the volcano, a process known as inflation, or if magma is moving out of the volcano, known as deflation. Prior to the April 2015 eruption, the caldera gradually inflated at a rate of 60 cm/yr (2 ft/yr) for several years, and then deflated suddenly by 2.4 m (8 ft) over just a few days during the eruption.

Photo of mobile pressure recorder (being placed with the Jason manipulator arm) at benchmark AX-310.

Pressure measurements are made at nine sites in and around the caldera. A tenth site (AX-105) is located approximately 10 km (6 mi) south of the center of the caldera and is assumed to be stable and serves as a reference site.  During the pressure dive, the depth of the 9 monitoring sites in the caldera is precisely determined relative to the reference site.

Three instruments are involved in monitoring the “bottom pressure” to help Bill and Scott accurately detect vertical movements of the volcano. The pressure at the ten sites will be measured for 20 minutes per visit, during each of three circuits by ROV Jason’s “Mobile Pressure Recorder” (MPR; see image at left). Repeated measurements during the three circuits help to reduce errors in the measurements. Pressure sensors are more stable when kept at depth, so ROV Jason (and the ship) will move back and forth between each site, rather than bringing the ROV (with the pressure sensor) up and down between sites.

Photo of a mini-pressure recorder (in green and blue cylinder) and the mobile pressure recorder (in orange housing) being placed with the Jason manipulator arm at benchmark AX-105.

A second way to measure pressure is with Bottom Pressure Recorders (BPR), which record continuously and are installed at multiple sites in the caldera and remain on the seafloor for years at a time. These battery-operated BPRs are attached to moorings with weights attached that are deployed by dropping them from the surface and letting them sink to the seafloor. When it is time to recover the BPR, an acoustic signal can be transmitted to trigger the release of the anchor, which allows the BPR and its flotation to rise back to the surface where they are retrieved by the ship. Data is downloaded from the BPRs and they are redeployed to continue the long-term measurements. Six of the ten MPR sites on the pressure dive circuit have not previously had BPRs installed, so mini-pressure recorders will be placed on the MPR benchmarks during our 2015 campaign (see image at right). The mini-pressure recorders will measure pressure for approximately two years until retrieved by a submersible during a future expedition.

Bathymetric map of Axial Seamount caldera showing the cabled network (black lines), 2011 lava flows (white outlines) and locations of cabled BPR instruments (red circles) of the Ocean Observatory Initiative (OOI); from http://www.pmel.noaa.gov/eoi/rsn/

A third set of BPRs are part of the Ocean Observatories Initiative Cabled Array, which were installed in a network of instruments in 2014 by the University of Washington.  These BPRs are cabled for power and data transmission between Axial Seamount and the Oregon coast (see photo atbelow).

Bottom Pressure Recorder of the OOI Cabled network.

The three cabled BPRs are located near benchmarks of our pressure dive transect (see photo above right and map above left). Cabled BPRs send data to shore in real-time and helped detected the April 2015 eruption.

Glenn Sasagawa, Bill Chadwick, and Matt Heintz in 2013 just prior to the launch of the Self-Calibrating Pressure Recorder (SCPR) in Axial Seamount’s caldera.

Axial Seamount is also a test site for instruments under development, such as the Self-Calibration Pressure Recorder (SCPR) that Glenn Sasagawa and his colleagues at Scripps Institution of Oceanography at UC San Diego have developed to eliminate drift issues with pressure recorders. Glenn is looking forward to Sunday August 23rd when he plans to retrieve and download data from the experimental SCPR that was installed in the caldera during the previous ROV Jason pressure dive in 2013 (see photo below right).

The suite of pressure recorders are used collectively because the measurements of each can be compared to each other and have different strengths. The BPRs collect data continuously but the pressure sensors have a tendency to drift mechanically at a rate similar to the annual uplift of the caldera during non-eruptive stages. Data collected in the MPR campaign are used to compare and correct the BPR drift but are collected only during expeditions with submersibles like ROV Jason, so are expensive and infrequent. Measurements from the cabled network provide real-time data but are currently only available at three sites in the caldera and will not operate if power or communication is interrupted.

Use of multiple data sets that are collected at a variety of sites around the summit of the volcano provides the best possible data to help Bill, Scott, Glenn and numerous colleagues understand how the volcano inflates and deflates in response to magma supplied from below.  These movements give information about how much magma is moving in or out of the volcano, how eruptions are triggered, and also can be used to forecast when the volcano is ready to erupt again.

Find more information about the OOI cabled network, see:
http://oceanobservatories.org/ 
and BPR data from the OOI cabled network are displayed at:
http://pmel.noaa.gov/eoi/rsn/