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This Bird Flies South for the Winter

Peering Through Polar Ice - Mon, 11/24/2014 - 22:39
Skier 95 with IcePod visible beneath the rear window lands on the Antarctic ice. (photo R. Bell)

Skier 95 with IcePod visible beneath the rear emergency door lands on the Antarctic ice. Photo: R. Bell

Migrating south in the winter is a behavior that Antarctic scientists share with many species of birds, although the scientists fly just a bit further south. For the IcePod team, it was time to join the migration so they could test their equipment in the most challenging environment the Earth has to offer. After three “equipment shake down” trips to Greenland over the last two years, 20 hours of flight time have been set aside for flights in Antarctica, part of the final hurdle in the commissioning of the pod.

The team arrived early this month at McMurdo Base on a large C-17 to –14°F weather and beautiful clear blue sky as the plane touched down on the Pegasus Blue Ice Runway. The first few days were spent in training for everything from driving trucks in the cold to being environmentally sensitive to the Antarctic microbes to a crash course on interpreting the complex way trash is handled in Antarctica — an impressive 60 percent of everything is recycled. 

Loading the gravity meter on loan from the Kiwi for the Antarctic test flights. (Photo R. Bell)

Loading the gravity meter on loan from the Kiwi for the Antarctic test flights. Photo: R. Bell

The gear arrived soon after the team… first the gravity meter, borrowed from New Zealand, wrapped in a warm, manly pinkish quilt. With many boxes being stacked in the aircraft, the color was selected for its high visibility to assist with quick location and unloading. The IcePod and the equipment rack had paused on their trip down in Pago Pago, arriving a few days after the rest of the gear, but it was all quickly set up and humming in a bright yellow and blue rack tent next to the Willy Airfield on the Ross Ice Shelf. While waiting to fly, a GPS was installed on top of the tent, and equipment was set up to test performance. Both the GPS and the gravity meter measured the movement of the ice shelf as it shifted up and down on the tide ~ 1 meter a day. In addition to the rhythmic up/down movement, the tent, the airfield and the ice shelf are all moving northwards at 30 cm or 1 foot a day.

Scott Brown, Tej Dhakal and Winnie Chu prepare the equipment for take off. (photo R. Bell)

Scott Brown, Tej Dhakal and Winnie Chu prepare the equipment for take off. Photo: R. Bell

Finally, IcePod was cleared to fly and complete her first Antarctic survey mission installed on a Pole Tanker mission flying on Skier 95. The flight was delayed as the C-17 practiced airdrops over the South Pole runway, but as soon as the C-17 was out of the way, icePod took off and headed south.

Icepod flies over the Antarctic ice with Mt. Erebus visible in the background. (Photo R. Bell)

Icepod flies over the Antarctic ice with Mt. Erebus visible in the background. Photo: R. Bell

Low elevation data was collected on the way out to make sure the C-17 was clear. All the instruments worked in the flight across the very flat Ross Ice Shelf, then over the Transantarctic Mountains and across the spectacular East Antarctic Ice Sheet.

IcePod team at South Pole (left to right) Scott Brown, Chris Bertinato, Tej Dhakal, unidentified, Winnie Chu (photo by R. Bell)

IcePod team at South Pole (left to right) Scott Brown, Chris Bertinato, Tej Dhakal, a new Antarctic colleague, Winnie Chu. Photo: R. Bell

The low angle of the sun made the mountains, crevasses and wind scour areas stand out beautifully in the imagery. The deep radar imaged the structure of the Ross Ice Shelf even from 21,000 feet. The infra-red camera showed the variable temperature of the different types of ice in the Beardmore Glacier and the high plateau. The gravity meter that had rolled in on the speed pallet was extremely stable. At the South Pole, Skier 95 offloaded fuel while the IcePod team made a quick trip to the actual pole.

The flight was a success – data collected on an opportune flight and fuel delivered.

For more on the IcePod project:



The ENAM Seismic Experiment - Wed, 10/22/2014 - 12:11

After five days in North Carolina we have recovered all of the 80 stations. The stations have been recording for one month along two profiles. Now we are downloading the data at the instrument center at the East Carolina University in Greenville.  The last step is getting the equipment ready for shipping back to PASSCAL in New Mexico.

Beatrice (Bix), Dan and Ana working onsite at the first station recovered. Bix and Ana are checking the parameters of the Reftek with the CLIE, and Dan is saving the GPS waypoint of the recovery site.

Yanjun working on one of the stations recovered on the north line. He is performing a check with the CLIE to see the number of events recorded, the data stored on the disks and stopping the acquisition. He also checks all 3 channels on the L28 sensor. Once the acquisition has been stopped, the sensor can be pulled and the station is taken back to the instrument center.

A few of the Refteks at the instrument center. The upward cap indicates that the data have been downloaded.

Yanjun labeling Reftek flash cards that contain recordings from the past month.

Flash cards labeled with Reftek serial numbers. This is the product of our hard labor!

Being a scientist rocks!

The ENAM Seismic Experiment - Wed, 10/22/2014 - 11:57

We experienced wonderful weather during the past week working in North Carolina. The scenic countryside is filled with tobacco fields, cotton fields, and other crops. One lucky recovery team started the first day on Kitty Hawk Beach demobilizing site 101.

Beach near the easternmost station on the north line of the onshore profiles

One of the many cotton fields in the eastern North Carolina coastal plain

Langseth limericks

The ENAM Seismic Experiment - Fri, 10/17/2014 - 02:19
As we approach the end of the cruise, I think this calls for a round of salty Langseth limericks.  It helps if you imagine a round of hearty “Aye, matey!”  and “Arr!” and such between each verse.

There once was the Langseth, a ship

Over wave and trough did she skip.

Many instruments aboard

To always record

Depth, gravity, mag – every blip.

There once was the Langseth, a vessel

Where in their bunks scientists nestled.

‘Til called to their shifts

Their heads they must lift

For with errors and logs they must wrestle.

There once was the Langseth, a boat

On her airguns the crew they would dote.

Oft while in a turn

Guns were brought up astern

To ensure best acoustical note.

There once was the Langseth, seacraft.

Where we launched XBTs down a shaft.

With each probe descent

To the lab data went

So that temperature-depth could be graphed.

There once was the Langseth, a fine tub!

Where the galley crew made us good grub.

But when seas ran high

Up in knots stomachs tied

And to keep the food down, there’s the rub.

There once was the Langseth, fair barge.

To collect seismic data her charge.

Streamer 8-km long

And four gun strings strong

She’s the fleet’s seismic dreadnaught at large!

-Tanya Blacic, aboard the R/V Marcus. G. Langseth

Last Day of the Cruise!

The ENAM Seismic Experiment - Fri, 10/10/2014 - 11:58

October 10th, 2014

Three days ago, at approximately 2130, we recovered our final OBS and started our 36-hour transit back to Narragansett, RI. We began docking procedures at Senesco Marine LLC at around 1300 yesterday and were all tied up by 1400. After the lines were clear, both watches performed some preliminary breakdown of the OBS equipment to help stage it for demobilization this morning. It was impressive how fluidly we took and executed directions after a month of working together. It was clear that the trip had bonded us as a team. After everything was done, the group headed out to enjoy our first night on land, which, as anyone whose been on a ship for an extended period will tell you, is just an incredible feeling. One of the eeriest moments, however, was all of a sudden being surrounded by people besides those you’ve been on the trip with. Also, the “dock rock” is an interesting experience.

This morning, after a wonderful, final breakfast made by our steward, Mike Duffy, we packed up the final gear and the crew began lifting it off the boat, staging it on the pier. All that’s left now is to clean up my stateroom, pack up all my stuff, and head on home. This cruise has been both a great scientific and personal learning experience and I am happy to have worked with these crewmembers, techs, researchers, and students. The lab seems so empty now, as I write this post, and there’s a part of me that is sad that this adventure is ending regardless of how excited I am to get back to life on land.

Anyways, time for me to go. For those who are interested in the data we’ve collected on this cruise, look out for information concerning workshops on data access and processing in the near future.

Signing off,
Dylan Meyer aboard the R/V Endeavor

Figure 1. Evening recovery of the last OBS, there was much rejoicing!
Figure 2. A crewmember, Charlie Bean, tossing a leading line with a monkey fist to the dock.

Figure 3. The WHOI OBS van and SIO OBSs staged on the pier to be loaded onto trucks.

Figure 4. The WHOI OBS van being loaded onto a truck for transit back to Woods Hole.

Figure 5. The, now empty, lab deck of the R/V Endeavor.

Scripps OBS GoPro

The ENAM Seismic Experiment - Sat, 10/04/2014 - 05:16
I had this idea to attach our GoPro cameras to a Scripps OBS that was being deployed on the shelf nearer the coast.  These underwater housings are rated to 100 feet and we deployed them on three different sites at that depth, recording some of the coolest OBS video I have ever seen.  The stills captured from the video are pretty cool too, but one of the unexpectedly groovy features of the video is the audio.  You can hear the acoustic responses, ship noise in the shallow, ocean background biology, and current noise on the seafloor.

Time series of deployment and recovery. Photo Credit: Ernie Aaron.~Ernie
R/V Endeavor

Riding big swells and crossing the Gulf Stream

The ENAM Seismic Experiment - Fri, 10/03/2014 - 15:01

On calm days, you could almost forget that you are in the middle of the ocean.  Its sunny and calm outside, and everything is stable inside.  People get lax and leave cups and other items on table tops unsecured and unattended.  And then some big swells come, and we all remember why chairs are tied to tables, furniture is nailed down to the deck and we use bungie cords and sticky pads to keep computers and other gear in place. Today we are experiencing swells up to 5 m high, in which the ship has rolled up to 25 degrees.  Unsecured items (including people in chairs!) are rolling all over the lab.
Meanwhile, we are also crossing the Gulf Steam, which poses it own challenges to our gear. Fishermen are particularly concentrated here, and today we deviated 10 km off of our profile to avoid fishermen and their gear.  The currents are also pushing our seismic streamer around.  In the ideal case, the streamer extends straight behind the vessel and quietly rides 9 meters below the water surface.  The currents today have pushed it to the side by 70 degrees from the ideal track, and the swells generate noise on the hydrophones.  However, even though conditions may not be ideal, it is essential that we collect data here for our science goals. We think that there are thick accumulations of frozen magmas beneath the Earth’s surface here that formed when the supercontinent of Pangea broke apart to form the Atlantic Ocean.  So we shall push ahead!
Annotated screen capture from our navigation system showing the ship, the streamer, our intended profile and our deviation.
 Donna Shillington from the R/V Langseth

Working hard

The ENAM Seismic Experiment - Tue, 09/30/2014 - 16:07
September 30, 2014

It takes a team of people to get the OBS in the water and back out again. To illustrate the process of deploying a WHOI or SIO OBS, Gary Linkevich has created a time lapse video. The first part of the video captures two WHOI OBS deployments with Peter, Dave, Dylan, Gary, and Kate. The WHOI OBS are the peanut shaped yellow capsules that appear in the background next to the railing. After the WHOI OBS is in the water, we capture an SIO OBS deployment with Mark, Dylan, Gary and Kate. The SIO OBS are the rectangles with a yellow top and white base. Right after we deploy the SIO OBS, we start putting together a new one for deployment. The assembly process involves an instrument test and then attachment of the metal weight, floatation devices, light, and radio together. The deployment of this SIO OBS happened during the midnight crew shift which includes Ernie, Pamela, Afshin and Jenny. Once they pick her up and put her in, they start the assembly process all over again!

Thanks Gary for putting together this time lapse!

See you Later,

Kate Volk aboard the R/V Endeavor

Running the R/V Endeavor

The ENAM Seismic Experiment - Tue, 09/30/2014 - 15:27
September 30, 2014

One of our assistant engineer, Kurt Rethorn, gave us a tour of the engine room. Here's what we learned:

Kurt is an awesome tour guide!

The Engine
The R/V Endeavor is equipped with a two-stroke (providing more power strokes per engine rpm), diesel engine consisting of 16, 350-cubic inch, cylinders with a maximum output of 3050 horsepower. Also, this bad boy is outfitted with a turbo charger which uses the exhaust to increase pressure in the cylinders and improve the power output from the combustion stroke. The engine is kept lubricated by 500 gallons of motor oil, which is changed when the ship is in port based on the number of engine hours. We burn around 1,000 gallons of fuel a day while on station (between the generators and the main engine) and even more when we are in transit between sites. We left port with around 54,000 gallons of fuel stored beneath the berthing decks, but she can hold up to 56,000 gallons of fuel total (the additional space is left to allow for the expansion of fuel due to temperature changes). A fun fact about the R/V Endeavor is that the propeller only spins one direction, meaning that there is no reverse gear. In order to drive the ship in reverse, the pitch of the propeller blades is switched such that the flow of water is reversed. There is also a powerful bow thruster that can be engaged if necessary.

Kurt starting off the tour (Photo credit: Kate Volk)
The engine with the exhaust manifold above and access to each of the piston heads underneath the latched doors (Photo credit: Kate Volk)Fuel gauges. Fuel is consumed from both tanks at a relatively similar rate in order to keep the boat properly balanced (Photo credit: Kate Volk)
The Generators
The R/V Endeavor has four generators. Three below the water line and one above (for emergencies only). The generators produce all our electricity directly (i.e. they do not charge any batteries). In a power failure, an emergency generator will kick on in less than a minute.

These are two of the generators, aligned along the centerline of the ship (Photo credit: Kate Volk)
We use about 1000 gallons of water a day between showering, cooking, cleaning, and drinking and the ship can only hold approximately 8600 gallons of fresh water. Therefore, we must produce fresh water throughout the cruise and we have two methods of achieving that. We have a reverse osmosis machine, which takes up salt water and pushes it through a long, blue semi-permeable membrane at 800 psi. The high pressure in the membrane causes the salt to drop out of solution producing fresh water. The second way we have of producing water is an evaporator. This brings in salt water under a vacuum at 711 mmHg (13.75 psi). The water is heated up and the condensation is collected, now free of salt. The reverse osmosis machine  and evaporator can produce around 50 and 80 gallons of water per hour, respectively, so that we can theoretically make 3200 gallons of water everyday. However, the evaporative method is dependent upon the engine heat to turn the water into vapor, which means that it runs at a lower efficiency when the engine is cooler. 

Reverse Osmosis machine. You can see the blue membranes that separates the salt and water (Photo credit: Kate Volk)

Water quality (Photo credit: Kate Volk)Sea water temperatures in the Gulf Stream are pretty warm (Photo credit: Kate Volk)

See you later, 

Dylan Meyer and Kate Volk aboard the R/V Endeavor

First Look at OBS Data!

The ENAM Seismic Experiment - Tue, 09/30/2014 - 14:48

September 30th, 2014:

We have our first look at data!! Ernie Aaron merged some of the raw data from the Scripps OBSs with navigation files from the R/V Marcus Langseth such that we can start seeing the seismic waves recorded in the in ENAM project.  In Figure 1, the hydrophone record of OBS 209, which was recovered on Sept. 21st, is shown as a function of space and time. To be clear, this is original seismic data. There are still post-processing methods and inversions to apply to the data back on shore that will help extract the seismic velocity structure down to upper mantle boundary along Line 2 or any of the other seismic lines. Until then, however, here is what we learned thus far.

To remind all, the experimental setup for this study is as follows. We on the R/V Endeavorplaced OBSs on the seafloor at a spacing of approximately 15 km along Line 2. The R/V Langseth then cruised along Line 2 from ESE to WNW with airgun shots spaced every 200 meters. The OBSs were then recovered and the hydrophone and geophone data were downloaded.

Figure 1. Traces recorded from OBS 209 (bottom) with various arrivals identified by color. The dashed line shows the multiple of Slope D. Cartoon (top) shows representative raypaths of seismic waves that produced the arrivals indicated in the trace records (Figure Credit: Kate Volk).
The acoustic signal was then segmented into separate traces using the GPS-coordinated time of each shot. Ten seconds of each trace were then plotted, by shot number (Figure 1). In this data panel we see the direct wave from the R/V Langseth shots to the instrument (Figure 1; Slope B), seismic reflections and refractions from the Earth below (Figure 1; Slopes A, C, and D), and a later multiple of these seismic refractions (Figure 1; dashed magenta line), after they bounced between the seafloor and sea surface.  

The direct wave travels directly from the seismic source to the OBS, helping us identify the location of the OBS on the seismic line. Using the time it took for the direct arrival to reach the OBS at this location and the acoustic velocity of water (1500 m/s), we can estimate the depth to the OBS. In the case of OBS 209, the R/V Langseth traveled over the device around shot 2200 and it was deployed in approximately 3000 meters of water (Figure 1).

The general slope of the seismic refractions in the space-time diagram gives an indication of the speed at which these seismic waves travelled at large depth.  The data in Figure 1 have been plotted such that waves traveling with a seismic velocity of 7000 m/s, such as those turning near the crust-mantle boundary, will appear as flat events. Slower seismic waves will dip towards larger time away from the OBS, while faster waves will slope towards smaller travel times.  

The OBSs show seismic arrivals that are recorded over a very wide range of source-receiver distances. The seismic waves recorded close to the instrument (< 10 km), are the direct wave from the airguns through the water column to the instrument (Figure 1; Time 2). As you move farther from the instrument (longer offset from source to OBS), the seismic waves move through deeper materials with faster acoustic velocities and those waves reach the instrument before the direct waves (Figure 1; Times 1 and 3). At longer offsets, the primary response comes from seismic waves that travel along deep materials with very fast seismic velocities (Figure 1; Time 4). When combining all the traces together, the slope between similar acoustic responses in traces can be used to infer the seismic velocity of the seismic wave, which can be used to infer the properties of the Earth.

For example, between 60 – 80 km and 100 – 120 km, we identify acoustic responses that are relatively flat (Figure 1; Slope D), indicating that the sound wave is moving through material with an acoustic velocity of 7000 m/s. This is important because it confirms that we are imaging down to the crust-mantle boundary, which will allow us to get a well-constrained seismic velocity profile throughout the crust beneath the margin of the US East Coast.

Until next time,
Dylan Meyer aboard the R/V Endeavor

Photo Essay: Sculpting Tropical Peaks

Sculpting Tropical Peaks - Tue, 09/30/2014 - 08:21
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When glaciers retreated from Mount Chirripó at the end of the last ice age some 12,000 years ago, they left behind rocks and debris that formed a natural dam, allowing meltwater to collect and form a lake. This glacial lake at Valle de los Lagos sits at 11,000 feet, just below Chirripó’s summit. 
With a hammer, chisel and bandanna to protect his face from shattering rock, Cunningham chipped away at a boulder left by a receding glacier. Beryllium isotopes in the rock can reveal when the ice withdrew, exposing the rock’s surface to cosmogenic rays from space. (Michael Kaplan)
Two pounds of rock fragments chiseled from the surface of each boulder yields 30 grams of quartz in the lab from which millions of beryllium-10 atoms will be extracted.
Knowing when glaciers last retreated from Chirripó can help scientists pinpoint when the low-sloping “cirque” valleys just below Chirripó’s summit formed, and ultimately, how glacial landscapes erode generally. Cunningham and Kaplan sampled remnants of a large landslide in the above cirque valley to find out when the rocks came crashing down.
They stumbled on some landslides by chance. Others were identified earlier with the help of their Lamont colleague Colin Stark, an expert  in using earthquake data and satellite images to discover landslides in remote places. Picking through dense shrubs, Kaplan climbed a pile of rubble to hammer away more samples for dating in the lab. Glaciers carve out the landscape as they grow and shrink leaving a classic “U” shape on the landscape as seen here in Talari Valley.
Most of the animals on Chirripó are nocturnal, but when the sun comes out after the daily burst of rain, lizards like this one join the geologists on the rocks.
In one low-sloping valley they discovered a winding streambed paved in sharp cobble stones. The stones’ angular edges suggest they experienced minimal erosion after a landslide or eroding glacier dropped them here.  
In another spectacular landscape translating to “Valley of the Lions,” they discovered a stone marker where a man, according to the inscription, had been killed by a mountain lion in 1956. They looked for material to date this ancient valley but most of the rocks that might have established when the ice last withdrew have long eroded away.
As they analyze their rocks in the lab, Kaplan and Cunningham will look for evidence that the ice grew and retreated multiple times. They also hope to understand the processes that created the low-angle summit valleys they visited. Were the valleys eroded beneath the ice or by landslides as the ice withdrew? Future research may take them to Taiwan where similar mountain-top features have been observed.
As they analyze their rocks in the lab, Kaplan and Cunningham will look for evidence that the ice grew and retreated multiple times. They also hope to understand the processes that created the low-angle summit valleys they visited. Were the valleys eroded beneath the ice or by landslides as the ice withdrew? Future research may take them to Taiwan where similar mountain-top features have been observed.

Tropical mountain ranges erode quickly, as heavy year-round rains feed raging rivers and trigger huge, fast-moving landslides. Rapid erosion produces rugged terrain, with steep rivers running through deep valleys. However, in a number of tropical mountain ranges, landscapes with deep, steep valleys transition quickly into landscapes with low-sloping streams and gentle slopes at high elevations. This topographic contrast between high and low elevations poses a problem for geologists. Though heavy rains fall throughout the mountain range, erosion seems to sculpt parts of the mountain differently from others.

Mount Chirripó, Costa Rica’s highest peak, bears exactly this type of terrain, with flat valleys at high elevation capping rugged valleys below. The beveled summit of Mount Chirripó bears striking resemblance to summits as far away as Taiwan, Papua New Guinea and Uganda. Some geologists think that tectonic forces deep below earth’s surface pushed Chirripó into its flat-topped form about 2.5 million years ago. Others think glaciers did the work, sculpting the peak in over hundreds of thousands of years.

Max Cunningham, a graduate student at Columbia University’s Lamont-Doherty Earth Observatory, traveled to Chirripó this past summer to test the idea that mountain glaciers carved the summit we see today. Working with his adviser Colin Stark, a geomorphologist, and Michael Kaplan, a geochemist, both at Lamont-Doherty, Cunningham chiseled away samples of glacial debris to take home for analysis. The researchers hope to eventually pin down when the high-elevation valleys capping Mount Chirripó’s summit eroded into their current form. Read more about their work in the above slideshow.

Photos by Max Cunningham unless otherwise credited.

XBT (a short story)

The ENAM Seismic Experiment - Tue, 09/30/2014 - 00:53
            “Twenty shots until the next XBT.”
            It was nearing time to launch the next expendable bathythermograph probe, or XBT.  The software was readied and two scientists headed out of the lab, radio in hand.  They donned lifejackets that had once been bright orange but were now closer to a dull rust color from long and dirty use on the deck and selected a T-5 probe from the box.
            Out on the deck they were alone, perched partway up the stack of levels in the stern of the ship, the gun deck below them and the paravane deck above.  It seemed that the others working the graveyard shift were all inside, perhaps wrestling with some mechanical puzzle or else simply keeping watch to make sure all was well, sipping strong coffee, playing cards to pass the time.  The scientists snapped the probe into the gun-shaped launcher.  They removed the plastic end cap from the black cylinder that housed the probe and its spool of fine copper wire.
            “We’re in position.”
            There was a pause, then the radio crackled back, “Launch probe.”
            In a moment the probe was sliding down the long tube that extended out and downward from the starboard side.  With a small splash it plunged from the end of the tube into the inky deep.  Now to wait while it made its journey towards the bottom, more than 4000 meters below.  Despite the very late (or very early, depending on your point of view) hour, it was warm.  The air was muggy – not exactly a welcome change from the air-conditioned lab, although the tinge of diesel fumes was less out here in the relative open.  There was little wind and the seas were calm.  Standing on the moving island of light that was the ship the sea quickly disappeared into the surrounding void.  What surface that could be seen appeared to rise disturbingly close up alongside them, like a churning wall of water.  It was only visible at all by the few swirls of foam formed by the ship’s passage and a reflection here and there off the constantly moving face of the black oily-looking water.  They waited for the go ahead to terminate the probe.
            Down in the lab, there was a strange blip on the screen showing the multibeam bathymetry data, but no one noticed as they were too busy entering in location data for the XBT or scrutinizing the movement of the streamer birds that regulated the depth of the hydrophone streamer.  There were, after all, 36 other monitor screens to watch.
            Outside there was a louder than usual splash.  The two scientists peered into the gloom.
            “Dolphin?” one wondered out loud.
            “While we’re shooting?  I hope not,” the other replied, “We’ll end up having to interrupt the line.”
            Was there something just under the water surface?  A pale sinuous shape at the very edge of the ship’s halo of light?  No, it must be a trick of the light and the weird perspective engendered by the lack of any sense of distance.  Perhaps more coffee was in order when they got back inside.
            The radio crackled again, “Terminate probe.”
            The scientists broke the wire that was still spooling out to the probe that was now falling behind them.  “Probe terminated,” they reported.  They were just turning to leave when it emerged.
            At first it looked like a whale back, though pale milky green in color rather than the expected grey.  As it lifted free from the surface it became clear that it was much longer than an orca or even a grey whale, more like an ancient marble column turned soft and rubbery.  It tapered as more of its length was exposed until the tip broke free of the clinging water.  One side of the enormous snake-like shape was covered with round suckers the size of dinner plates in a poisonous green color.  The cyclopean tentacle towered out of the water, waving gently with a sickening sort of grace ten meters or more above the uppermost deck.  Here and there along its length were clots of a coppery tangled substance, almost like seaweed wrapped around it.  “The XBT wire,” one of the scientists realized from the midst of her fascinated horror.
            The tentacle hovered for another movement before swooping down with surprising swiftness.  The two scientists were neatly plucked from the ship in the blink of an eye.  With a clatter, the radio fell to the deck.  They were held above the water for a long moment, crushed together so tightly they couldn’t speak and could barely draw breath.  Then, slowly, the tentacle disappeared beneath the smoothly rolling waves.

            Two hundred and sixty-seven shots until the next XBT.

-by Tanya Blacic aboard the R/V Langseth (with a wink to H. P. Lovecraft)

Life at Sea

The ENAM Seismic Experiment - Sat, 09/27/2014 - 22:34
September 27, 2014

Our small ship is in a state of endless motion with pitch, roll, yaw, and heave. We continuously experience a feeling of fluctuating gravity at sea, as one minute we are several pounds heavier and the next we are several pounds less. We’re tossed about endlessly like riders at the fair. It’s a feeling that can turn the stomach of the saltiest of sailors, but more often disturbs the newbies the most. At sea there is also no such thing as silence. Out here the engines are always running, hydraulic pumps are always droning, and ships operations occur around the clock. From my bunk I can feel us lurch forward and lean into a turn to starboard, or port, and then they reverse the pitch of the propeller as if applying an emergency brake to slow the ships forward motion. This reverse pitch causes a shudder in the hull that shakes us like a cheap hotel vibrating bed and it chatters every moveable thing. From my bunk I can also hear the acoustic pings emanating from the hull-mounted transducers. Speaking to me in code, they tell me if OBS operations are going well.  Based on the ping styles I can also discern the acoustic techniques used by WHOI and Scripps, so that I know which instrument type is being talked to. All of this information creates a movie in my mind that plays out until I fall asleep. Life on a ship is a constant immersion in all that is going on and for 30-days there will be no escape.

-Ernie Aaron

And then there was data…..

The ENAM Seismic Experiment - Fri, 09/26/2014 - 21:10

It’s been a week since we deployed all of our gear and started steaming along our lines, so now we have amassed a lot of data!  Although we can only steam at very low speeds while towing the equipment (~4.5 nautical miles an hour or  ~5 mph), each time we fire the air gun array, the 636 channels on the seismic streamer listen for returning sound waves for 18 seconds and record a total ~25 Mb of data. Repeat that every 30 seconds for 7 days, and it begins to add up!  We now have 400 Gb of seismic data alone, not including all of the other types of data we collect while underway (bathymetry, magnetics, gravity).  We are a data-collecting machine.  

Matt, Jenna and Derek sit  back and watch the data roll in from the Main Lab
Not only are we collecting data, we are also doing some preliminary data analysis to get a first look at the geology hidden below the ocean, which is always exciting.

Kara and Matt are entranced by velocity analysis
Although we are only a week in, our data collection has already taken us through water depths as shallow as 20 m and as deep as 6000 m.  At the edge of the continental shelf, water depths change rapidly from ~500 to ~3000 m over just 20 km – a slope of 10%.  For perspective, that’s very similar in elevation change and slope to the course for the Pikes Peak marathon.

Perspective view of seafloor depth from MGDS across the continental slope overlain by a higher resolution swath of bathymetric data that we acquired along our transect, which is also shown projected onto the seafloor.
We have also traveled over widely variable geology – from 35-km-thick continental crust to ~7-km-thick oceanic crust, and from sediment thicknesses of 5 m to over 7 km.   Our data are also revealing cool structures in the sediments and crust – faults, sediment waves, and more.  Below is a picture of a salt diapir that we imaged at the edge of the continental margin.  The salt was probably first deposited at least 150 millions years ago in a flat layer, but as more sediments were deposited on top of it, it got squeezed up and out into dramatic diapirs.

Preliminary image of a salt diapir in seismic reflection data near the base of the continental slope. The y-axis shows the time it takes for a sound wave to travel down in the earth and back again. This images shows about ~5 km down into the earth below the seafloor. Donna Shillington aboard the R/V Langseth

First day of land deployment - showing kids how cool seismology is - by Kara Jones

The ENAM Seismic Experiment - Fri, 09/26/2014 - 16:32

(Originally posted on September 12)

Today was the first day of the onshore deployment of the RT130s through southern Virginia and North Carolina. My partner, Yanjun Hao, and I, were just one of five teams working to deploy instruments along the two survey lines. We deployed the first two instruments at West Harnett Middle School and South Hartnett Elementary School, both outside of Lillington, NC. In both case, the fifth and sixth graders were very interested in learning about what we were doing and eager to participate. I explained to them the basic concept of P and S-waves and then asked the children to jump so that we could test that each of the channels on the sensors was working correctly. They very much enjoyed getting to see on the clié exactly what the signal they generated looked like. At both schools, I was surprised how much the children, and the teachers, knew about earthquake seismology and the intelligent questions they asked. A teacher asked whether they would detect the explosives detonated at nearby Fort Bragg, and a sixth grader named Gauge blew me away when he asked if the sensors would be able to record the sound waves generated by the planes or nearby explosions! In total, we probably spoke to 100 kids about the project today. It was a very encouraging to see how excited and interested they all were in the science. When we first arrived and explained that we would be installing a seismometer, a 5th grade teacher looked at us with wide eyed and asked "Are you seismologists?!" I nodded yes and she was so excited she started jumping up and down. Despite some rain and GPS trouble later in the day, the excitement that the elementary and middle schoolers showed about seismology was enough to make it a great start to the deployment.

At South Hartnett Elementary School in Anderson Creek, NC. I am showing one fifth grade class what the seismic signal they just generated looks like on the clié.

The land instruments

The ENAM Seismic Experiment - Fri, 09/26/2014 - 16:26
The insulation was tough but gratifying. The weather in North Carolina is unpredictable. At times it was hot and humid. I was drenched in sweat burying the sensors. Other times we were caught in torrential downpours working under a tarp; terrified by the sound of thunder. The sites were located on mostly private property, hosted by people who were eager to help with the experiment. The interaction with the local people enriched the experience. Many of them showed true southern hospitality. 
Station deployed!
From an academic prospective I learned about survey design, instrument deployment and the logistics. This provided a distinctly unique experience that is unavailable in the classroom environment. Beatrice and Dan were tremendously helpful and supportive. I learned a great deal about active seismic from my conversations with them. They’re passionate about nurturing future geophysicist. The GeoPRISMS is an altruistic endeavor for them. I am thankful to them for investing so much of their time and expertise into the project. 

The GeoPRISMS experiment has been an overwhelmingly positive experience. I am grateful to have been given the opportunity to help with the deployment and look forward to my involvement in the recovery of the instruments! A future workshop will be held for processing the data and the inversions. This pre to post educational approach is invaluable to me as a future geophysicist.

Posted by Christopher Novitsky 

The Land Deployment Team!

The ENAM Seismic Experiment - Fri, 09/26/2014 - 15:30
From L-R: Yanjun Hao, David Boyd, Dam Lan, Ana Corbalan, Christopher Novitsky, Pnina Miller, Jason Leiker, Kara Jones, Beatrice Magnani (front), James Farrel (back), Dan Lizarralde.It took us a while, but here we are, the team that deployed the land seismometers on Sept 12-15. The instruments are now continuously recording the Langseth shots and will continue recording for few more weeks. The East Carolina University in Greenville, NC graciously allowed us to use one of the research facilities on their West Campus (a place with a fascinating story - blog on that coming soon!) as the headquarter for operations. We will be back to the field at the end of October to pick up the instruments, download/save the data and demob.

Posted by Beatrice Magnani

The Night Watch in Action!

The ENAM Seismic Experiment - Fri, 09/26/2014 - 12:29
We've captured the process of recovering and deconstructing a Scripps OBS thanks to Harm's nifty GoPro camera attached to the crane. This OBS was a little tricky to hook, but otherwise it was a smooth recovery!

Time series of the recovery after the OBS has been attached to the crane. Photo Credit: Ernie Aaron.

See ya'll later,
Jenny Harding
R/V Endeavor

What are we up to

The ENAM Seismic Experiment - Thu, 09/25/2014 - 16:09
September 25, 2014

        For those of you following at home, it might be a bit confusing on which ship is doing what and where. I've made a little cartoon timeline that will hopefully illuminate our progress so far.
       There are two ships currently in the Atlantic: the OBS deploying R/V Endeavor and the seismic shooting R/V Langseth. The R/V Endeavor has been putting OBS down and picking them back up again on lines 2, 3, and 4 while the R/V Langseth has shot seismic along line 2 and 3, and is going to head over to shoot on line 4 soon.

See you later,

Kate Volk aboard the R/V Endeavor

Group photo time

The ENAM Seismic Experiment - Wed, 09/24/2014 - 13:30

September 24, 2014

Well we have finished deploying OBS on line four and are now transiting back to the beginning of line 3 to start picking OBS back up again. At this point, we've all fallen into our jobs and are working like a well oiled machine. Each shift was able to deploy around 9 or 10 OBS in 12 hours time, moving smoothly from one site to the next. To celebrate our progress so far, I've got some group photos to share.

The science party from left to right: Gary, Dylan, Afshin, Harm, Brandon, Pamela, Jenny, and Kate (Photo credit: Dave DuBois, edited by Gary Linkevich)
The WHOI and SIO OBS technicians from left to right: Ernie, Peter, Mark, and Dave (Photo credit: Gary Linkevich)

The whole science group (Photo credit: Ethan, edited by Gary Linkevich)

The science group in the WHOI van with the WHOI OBS (photo credit: Dave DuBois)See you later,

Kate Volk aboard the R/V Endeavor



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