Mapping the Galicia Rift off Spain
We are collecting seismic data in the northeast Atlantic Ocean west of Spain to image faults under the seafloor that were involved in continental rifting and breakup and the initial opening of the Atlantic Ocean ~125 million years ago. This rift is notable because very little volcanism appears to have accompanied rifting, as observed in many other rifts worldwide. Instead, continental breakup here appears to have been sufficiently slow and cold that the rocks from the Earth’s mantle were exposed at the seafloor after the crust broke. Previous seismic imaging studies have revealed a continuous sub-horizontal structure that lies at the base of a series of fault blocks beneath the seafloor (called the “S reflector”), and there is significant controversy here and for similar features elsewhere on the role of this feature in accommodating extension and exposing mantle at the seafloor. This program involves collecting and analyzing a suite of geophysical data to image this structure, the overlying fault blocks, the exposed mantle and the sediments in 3D to reconstruct the evolution of the rift. We will collect 3D seismic reflection data to image faults and sediments during a 45-day cruise aboard the R/V Marcus G. Langseth, and three cruises on the F.S. Poseidon to deploy and recover ocean bottom seismometers that will be used to determine the velocity that sound travels through different layers of the earth, which yields information on their compositions.
The Langseth Galicia 3D seismic cruise is winding down. By tomorrow we will be back at the dock in Vigo. Like most seagoing science, we will miss the ship experience, we will miss the new colleagues we have met, we will look forward to getting back on shore, and for many of us the awesome multi-year task of processing, interpreting, and publishing the boatload of data we have acquired.
|This is an example of the data we have collected. Right is to the East and left is to the West. This is a cross section of the Earth about 65 km long. The blue is water. The water depth here is about 5 km. The red and gray colors are a cross section of the rocks below the water. The flat layers are sedimentary rocks. The lumpy bumps (that is a technical term!) consist of blocks of continental crust and of the mantle.|
We thank the Langseth’s Captain and crew for making this possible! These are men and women who live on the sea, and who share their ocean world with us for a month or two. Every now and then, when you can walk 100 meters in a straight line, ask yourself, “Where is the Langseth now, and who is steering the ship, or keeping the engines running, or keeping the deck ship-shape, or providing good food, or every other important task on the ship?” Under your breath say thank you for the experience you had on Langseth.
We thank Robert and his technical team. They worked tirelessly to assemble the 24 km of hydrophone streamer that hears the reflections from the Earth, the 40 or so airguns that make the booms, and all the rigging it takes to tow them spread out behind the ship over 600 meters wide and 7000 meters long. That was just the start. Then they operated the electronic equipment that received the seismic data and recorded it for the scientists. Without them we could not do the science we love.Thank you to the Science Party. We had a total of 20 scientists, including undergraduate students, graduate students, post-docs, researchers, and professors. On Leg 1 we had 14 scientists and on Leg 2 we had 10 scientists. Four scientists weathered both legs. Six joined us for Leg 2. I am very grateful for all your efforts on behalf of the Galicia 3D science. I hope that you learned a lot, had a good time, and met other scientists for the first time. I suspect that we will meet one another many times in the future.I look forward to that!
|This is the Technical team and the Science team for Langseth Leg 2.|
I want to thank the Protected Species Observers for sailing with us. They spent countless hours in the observing tower, high above any other part of the ship. They have sighted hundreds of whales, but most did not come close to the ship. It is windy and cold up there, but their role is important for making sure that collecting our scientific data does not interfere with the creatures who call the ocean home.
Thank you for sending your loved ones off on the Langseth. I can certify that they now know how to do their own laundry and to clean up their cabin before they leave the ship. During the weekly emergency drill, they run quickly up to the muster station on deck and put on safety gear. I recommend that you continue to enforce these behaviors ruthlessly! They will forget them if you let them slack-off. On the other hand, they did not have to cook their own food, or wash and dry their dishes. You will still have to work on these behaviors!
As I write this from the Langseth, we should remember that the Galicia 3D experiment goes on. Our colleagues from GEOMAR and University of Southampton will be on the FS Poseidon from 25 August to 10 September. They will be recovering the 78 Ocean Bottom Seismometers that are still on the bottom (on purpose!). They have been recording approximately 150,000 airgun array shots fired by the Langseth. I know what you are thinking. “How many total recordings of shots are recorded in all the OBS’s?” That would be about 11.7 million shot recordings. This will keep the OBS scientists busy for a while!
I particularly want to thank James Gibson for creating this blog. It has reached out to our friends and to strangers. We plan to keep the blog alive. This project will continue for years.
This week we have been exploring all the parts of the ship we have not yet discovered and were lucky enough to get shown around the engine room and the bridge. It is evident that each area of a ship (bridge, engines, science etc.) has a group of people doing those specific jobs and that the combination of everyone doing their part keeps everything running smoothly; like cogs in a massive machine.
|The engine room control panel. With that many buttons no wonder it takes so much training to work in the engine room!|
The engine room is located in the hull of the ship and is the biggest room on board by far, taking up about 2/3rds of the bottom deck. This is obviously a very important part of the ship because without it we would not be moving anywhere! The Langseth has 2 engines leading to 2 propellers and also 1 bow-thruster. There are so many different bits of machinery down there that it can take 4 years of studying to be qualified to work in the engine room. It is very loud and warm but surprisingly clean and tidy. There are also 2 compressors which are used to pressurise the air for the air guns that we tow.
|One of the very noisy compressors. It is hard to portray the size of these in a photo, they are huge!|
The heat from the engines is used to produce all the hot water for the ship and the engine room also has machines for desalinising our water. Fuel usage is constantly monitored and fuel moved between all the many tanks spread around the ship to ensure even weight distribution. Even though we only travel at about 4 knots whilst acquiring data we burn between 5000-6000 Gallons of fuel a day due to the massive load of the equipment we are towing behind us.
|One of the two engines|
The bridge sits at the front of the ship on top of the main living quarters. From here it seems as if practically everything can be controlled. They drive the ship when we are not driving from the main science lab during acquisition, control the speed, can manage the safety aspects including all alarms and watertight doors and keep a look out for anything floating past that might get caught up in our seismic gear (so far buoys and pallets have been sighted). One very important job of the bridge is to communicate with other nearby vessels. Nobody would expect us to be towing 6km of streamers so we have to make sure we let other ships know with enough time to arrange safe passing, therefore avoiding collisions.
|This is the main control panel in the bridge. There are screens for navigation and|
radar as well as all the speed controls. There are two smaller control panels
on the port and starboard sides of the bridge for work that
involves careful maneuvering e.g. picking up OBS's.
The last seismic line is just being finished right now and then we can get ready to begin equipment recovery. It is about 40 hours until we are back on dry land again!
University of Southampton
As we come to the end of our cruise I thought that now would be a good time to talk about the way in which both seismic and multi-beam sonar data are quantified (basically nerd out). In both cases we "bin" the data into grid cells, which are predefined based on the resolution that we expect to achieve given the ideal data density of individual cells within the grid.
|A screen capture from the multi-beam sonar Seafloor Information System (SIS).|
The image on the left shows swath coverage. The image on the right shows an active ping through the water column.
Multi-beam sonar (swath seafloor mapping) data are collected, gridded (binned) to the predefined cell size, and output in two flavors. Bathymetric grids, which are essentially 3D topographic maps, and Backscatter grids, which display the reflectivity of the seafloor. The reflectivity varies due to both incidence angle of the respective beams and the density of the surface (e.g. hard rock, sediment etc). As the ship moves along at a given velocity, the multi-beam sonar sends a "ping" from the transducers (transmitters) to the seafloor and then waits until the receipt of the last return to ping again. The ping rate (Hz or 1/seconds) is a function of the depth of the ocean as well as the sound speed through water (XBT's are useful!). The swath width also scales as a function of depth. Our average depth is ~4800m (2.98 miles), which allows for an achievable swath width of ~20km (12.43 miles!).
In order to gain insight on the density of the multi-channel seismic (MCS) data that we are collecting we use the Spectra software package. Spectra tracks the position of the ship, streamers, and air guns in real time using GPS and an acoustic network, and then bins the data accordingly within the predefined grid. The goal is to get an equal amount of seismic traces (reflected seismic waves) in each bin. The traces can then be stacked (combined), which increases the signal to noise ratio. Stacked traces within a bin are called "fold" and ideally represent traces from all offsets along the streamer in respect to the source.
|Swath coverage display of the backscatter (reflectivity of the seafloor) collected across a swath.|
|A screen capture of the Spectra display. The image on the left shows active binning of the MCS data.|
The image on the right shows the bins being infilled (filling holes).
We are getting to the end of the "No Mores," which means we are finished on Friday!! Stay tuned for a word from our Chief Scientist along with a look at the MCS data (and our cruise pic).
After all these posts about how we live and work onboard the R/V Langseth you may just be wondering what sort of sustenance keeps us going during the long hours. Well you’re in luck! The excellent cooks serve meals with a smile promptly three times a day at 7:20 am, 11:30 am, and 5:30 pm. Breakfasts always include mountains of eggs, bacon, sausages, and pancakes and on special occasions scrumptious muffins. Lunch usually comes with toasty grilled sandwiches, soup that warms your limbs, and crunchy French fries. Dinner varies but commonly consists of a juicy steak or pork chop, rice, mashed potatoes that put even your Mom’s Thanksgiving potatoes to shame, and a delicious desert like cherry pie. The salad bar is open 24 hours a day and even this far into the cruise still contains crisp spinach, olives, tomatoes, and a variety of other vegetables.
|A sampling of the meals served onboard with cooked by the always smiling galley staff. |
From left to right breakfast, lunch, and dinner.
In the center image the galley staff made up of June, Hervin, and Brian pose behind a lunch of pizza and soda.
We are now in the home stretch of our cruise, steaming furiously down our final sail lines to complete our 3D grid. Can’t believe there’s only four more dinners until we set foot back on dry land!
I was sent to join this cruise half way through because a lot of the scientific party had to leave and nobody more qualified than me could be found at such short notice! I have never been on a cruise before and had no idea what to expect, or any idea how complex and time consuming 3D seismic acquisition is. I have learnt so much about the technical side of acquisition and a little bit about the processing side; however I have also gained a lot of non-scientific tips and tricks! Here are my top 5 tips:
1) ‘Boring science is good science’ – If you are bored on a 6 hour watch that is a good thing because it means that everything is running smoothly and good data is being collected. Having things to do is always a bad sign! Things have been running pretty well recently and as a result I have greatly improved my crossword skills.
2) Things will break, don’t panic! – This is a hand me down ship filled with second-hand instruments from industry vessels. Because of this a lot of the equipment is temperamental and repeatedly needs to be fixed. However, I have also seen instruments that have been offline for days randomly start working again so you never know!
3) Duck tape has a million uses – There is no end to the list of things duck tape is used for on this ship: keeping weights in place on streamers, keeping your laptop on the desk during bad weather, taping your ladder to your bunk so it doesn’t bang during rough weather and keeping ropes in place on the deck to name a few. It seems like any problem can be fixed with tape.
|If you don't want your office chair rolling around or you need a cable tie just use tape!|
4) Hoard food – When food you like is put out in the mess then take it while you can. A few days ago a gigantic tub of mini snickers and bounty bars was put out in the mess….I have never seen chocolate disappear so fast!
5) Taking a shower is the most dangerous activity on the ship – I recommend keeping either an elbow or hand on the wall at all times so you can feel when you start to move. I think taking a shower is probably the best form of exercise on the ship because of the amount of effort and energy it takes just to balance. Also, never soap the bottom of your feet in rough seas. That is probably classified as an extreme sport!
University of Southampton
As Natalie told you, the Main Lab operates for 24 hours a day, but we have a 6 hour shift (nobody can work for 24 hours of course!). So, what are we going to do in our free time? That is a great question! Let me show you the Marcus Langseth's free-time facilities.
Located next to the Galley we have our Library which has a lot of good books (I was reading the Che Guevara's travel book before the beginning of this part II, I really want to finish it!) and these excellent chairs...they're really comfortable, believe me. You can also find a variety of mystery, fiction and scientific books on the shelves.
|The library with a wide variety of books|
Yeah, but John actually I'm not a book lover ...
No problem! This is what you need! A 42-inch TV screen and a big collection of movies and TV shows. Ah, and don't forget the PS3, which makes the crew's free-time fun. I have to admit something to you, I've never used the movie room, but maybe sometime I will go there to catch a movie or documentary.
|The movie room with seating for plenty|
But if you're an athletic person, this is your place, the gym!
It's a little bit small, but if you think we're in the middle of the ocean, the luxury of having some equipment must be appreciated.
|The gym ... be careful when the ship is moving!|
So, there is a treadmill, some free weights, etc. Be aware of the pitch, roll and heave! These are the movements made by the ship. Instead of explaining them, I'll post an image which can perfectly illustrate what I'm trying to say.
|The differences between pitching, rolling, and heaving|
For those who appreciate an indoor sport, we also have a ping-pong table. It's located one level below the Galley, at the Main Deck. I didn't use this table either, but I'll launch a challenge: Try to play ping-pong during rough seas! Imagine how cool a ping-pong game is inside a ship facing waves of 5 or 7m (or even higher).
|The ping pong table ... this could get interesting in rough seas|
Thank you...or should I say Obrigado?
João (John) Pedro T. Zielinski
Complutense University of Madrid/Federal University of Santa Catarina
Today marks the final day before we start the infamous "No Mores". No more Saturdays, then no more Sundays, and on and on until it is time for us to set a course towards dry land. With almost two weeks behind us on this second half of the cruise we have only a handful of sail lines left to complete (see figure below). Once we finish the lines we will head back down to the bottom half of our work site to fill in holes; isolated spots where we were unable to collect data due to strong currents or short-lived equipment problems. After that it's back to port where we will wave farewell to the R/V Langseth as it steams towards the waters offshore of Iceland for another scientific adventure.
Don't forget to check out our progress as we fill in the sail lines here
|A panorama view of the main science lab|
We left off last time with a tour of our sleeping quarters thus it seems only appropriate to now walk through the room where we spend most of waking hours; the main science lab. Located one level below the gun deck, the main lab operates 24 hours a day controlling every aspect of data acquisition from monitoring the multichannel streamers and air-gun arrays to building the computers needed to process the terabytes of data that barrel in.
|An up close view of the numerous computer screens in the main lab|
It can safely be said that when acquiring 3D seismic data during which approximately 6.5 terabytes of raw data will be recorded over 43 days you can never have enough computers.
In the main lab, laptops and computers occupy every surface.
Stand-alone computer monitors duck taped onto desks sit next to laptops anchored by bungee cables.
Power cords, Ethernet cables, and USB connections snake across tables in every direction periodically diving down into a dark power outlet. A bank of computer screens approximately 12 monitors wide and 3 monitors tall encircles nearly half of the lab.
These screens (39 in total) act as terminals that allow us to monitor and control a myriad of processes that are summarized in the image below.
Possibly of greatest importance are the terminals dedicated to “driving the ship.”
We aim to always have the four streamers following in perfect straight lines behind the ship however, cross-currents make this is a difficult charge.
Given the length of 6 km (3.7 miles!) and the weight of the streamers, it is akin to a toy boat towing four 23 m (75 ft) fishing lines straight behind it on a windy day. Thus to keep the streamers in the optimum orientation with respect to our acquisition line we continuously nudge the ship north and south while pulling the heads of the streamers with us. All of the steering is done from a combination of three monitors with the use of the software package “Spectra,” which in the simplest sense determines real time data coverage given the location of the air guns and the streamers.
|A labeled view of the bank of computer monitors that dominates the lab|
Of equal importance are monitors that display the health of the four streamers and the two air-gun arrays.
We aim to keep the streamers at a constant depth relative to the air-gun arrays and also at a depth that keeps them protected from passing ship traffic.
In this part of the Atlantic fishing vessels are common and with our gear sitting kilometers behind our ship and 12 m (40 ft) beneath the sea surface one could see how a vessel might not know that it is there.
Therefore, whenever we see an approaching boat we implore them to keep a safe distance away both for the safety of their vessel and for our gear.
|The back of the lab where most of the preprocessing and quality control is done.|
Additionally, we use this bank of terminals to monitor for the presence of critters in the water, the weather and sea conditions, and the health of the EM122 multi-beam. Sitting back from the semi-circle of computers is another set of desks where the we, the students and scientists, stake our claim. Outfitted with no-slip fabric and duck tape, we have covered the back of the room with our computers, which we use for pre-processing and quality control (QC) of the incoming data.
That about covers the main lab, they keep it pretty cold down here for the sake of the computers so I’m headed up to grab another sweatshirt before I get frost bite.
Stay warm out there!
For those of you who have been following our adventure here's a comparison of the sea-state. I know that the few of us who have been out here for both halves definitely appreciate the difference, and for those joining for the second half it looks like smooth seas ahead!
Also, we have now reached 10,000 page views!! So thanks Mom (and everybody else).
|Our home away from home at sunset|
We started our tour of the R/V Langseth almost a month ago with a walk through of the mess hall and now with our return to the high seas are excited to pick back up where we left off. Let’s begin with our sleeping quarters.
As we all know, the most important aspect of real estate is location, location, location and the same can be said for room assignments when at sea. On first glance, you might be tempted to opt for a room on a higher floor accompanied by a nice porthole to allow full view of the spectacular sea outside. However, hold that thought! Remember that the further above sea level you are, the more you will move with each passing wave. What may feel like a peaceful sway down on the lower levels can turn into a ferocious veer strong enough to topple chairs on the top deck. Thus, if you have any inclination that you could succumb to seasickness it is probably best to pass on the picturesque vista and opt instead for a windowless cabin below. Fortunately, for many of the scientists mental struggles over room selection never occurred as cabins had been assigned to us before we walked up the gangway. Most of the students aboard are sleeping in a suite of cabins that share a common living space endearingly termed the “Snake Pit”. The origin of the room’s namesake remains mysterious, perhaps previous groups of students did some sort of battle there? Or fought snakes? Who knows, for now though it represents a comfortable room where many spend their off time reading books from the library or taking short siestas in between work.
|The "Snake Pit" where students read and lounge between shifts|
All of the cabins aboard share similar features such as a set of bunk beds and matching closets. Depending on the individual setup, you might find yourself lucky enough to also have a set of desks and perhaps even a small couch though these furnishings are found mostly in the higher rooms reserved for the principle scientists and the superior ship mates. Given that work continues around the clock on the Langseth, all bunk beds include an individual light for private reading and also black out drapes to both prevent any light from your bed reaching your room mate and conversely any light from your room mate reaching you. Additionally, all rooms come with either adjoining shared or private bathrooms (termed “heads”). Given the combination of rolling waves and slippery tiles, it could easily be said that the heads may be some of the most injury prone rooms aboard. Thus whenever attempting to take a shower, remember to always keep one hand on the hand rail and if the ship starts swaying don’t neglect to hold on tight otherwise you might suddenly find yourself autonomously ejected onto the cold, wet floor.
|Our cozy cabin equipped with bunk beds and closets|I think that about does it for now, dinnertime is just around the corner and I can smell the ahi tuna from here. Buenas Noches!
As Dale said we are back to work!! We have now completed 3 lines of the ~25 that we hope to cover during this second half.
Being at sea again allows me to look back at our extended stay in Vigo
(Galicia). The port city of Vigo is a unique and beautiful place. The summer months are particularly nice as this part of the Atlantic coast is rainy most of the year. Vigo is just about 2hrs north of Porto (Port wine
), which is in Portugal. The proximity to Portugal and the fact that in the past teaching the English language was not stressed within the school system leads to a population that speaks a mixture of Portuguese and Spanish, but not much English. As a result my (poor) Spanish was definitely put to the test as well as my ability to communicate using what are best described as elementary level sketches.
What Vigoites lack in English they make up in hospitality and a relaxed outlook on life. In short, the idea of a "siesta" is not lost on them. While the bars (and there are hundreds if not thousands) are usually open, the restaurants do not open until 8:30 p.m., and generally not at all on Sunday. However, we did manage to find one that is, and it happened to have very good (and cheap) Tapas. Although off the beaten path it quickly became one of our favorites.
|A view down the alley to one of our favorite bar/restaurants.|
Vigo also has some amazing beaches! After what amounted to a 45 minute walk or a 6 Euro (~$8) cab ride from the ship we could either lay a towel down and get some sun or grab a drink at one of the bars that are literally on the sand. I was shocked to say the least in the shear number of people that were at the beach, and it seemed like there were more during the weekdays than the weekends. Must have something to do with the laid back lifestyle (?)
|Playa Samil on a Tuesday.|
The best beach (Rodas) in the world (The Guardian, 2007) can be found on one of three islands about 45 minutes (16 Euro, ~$20) by ferry named Illas Cies
. The archipelago of Cies is also a Spanish National Park. An interesting thing about these islands is that they look like an above sea analog to what we are seeing sub-seafloor in the data. That is to say that they consist of a series of faulted crustal blocks (granite). The style of faulting is termed "Normal
," which means that the hanging wall moved down relative to the foot wall. This type of faulting is indicative of extension and is expected along the length of this margin.
|A view of Cies from Playa Samil with faults indicated by the arrows.|
The part that we had been so patiently waiting for arrived after almost 3 weeks in this unique place. While I will not miss being in port, I am happy to have had the chance to see and experience this part of the world as it truly is a beautiful place.
|Arrival of "La Cabeza" (the head).|
Welcome back to our blog! As of yesterday morning, we are back at sea and shortly we will resume acquiring 3D data. The repairs to the engine were more difficult than originally thought. We had the Rolls Royce engineers with us for the whole time, working with our fine engineers on the ship. You may not know that Rolls Royce makes really big engines like those in the Langseth. They worked to clean out the engine, ordered a number of parts, and the parts gradually arrived in Vigo. The engine was reassembled and tested at the dock. It worked again!
We sailed from Vigo at 0700 on 15 July with a partially new science team. Several people left the ship because they had conflicts with the extended cruise. They were Donna, Tim, Cesar, Mari, Brian, Steve, Luke, Marianne, Miguel, and Toby. Remaining were Dale, James, Raj, and Sarah. We could hardly do with a science team of four, so we recruited six newcomers. They are Natalie Accardo (Lamont), Milena Marjonovic (Lamont), Gaye Bayrakci (Southampton), Joao Pedro Tauscheck Zielinski (Madrid), Tessa Gregory (Southampton), and Katherine Coates (Southampton). We will try to get photos and bios up shortly.
We are deploying the seismic gear now. We have two streamers out and the third almost out. We hope to begin acquisition in the morning.
We are all excited about continuing our cruise and completing the 3D survey.
June 22 was officially hump day – we were halfway through our 43-day cruise. Happily, we were also about halfway through our data collection; we had just finished acquiring the primary lines in the southern part of our survey area, which was a major milestone.
The data are looking very nice (stay tuned for an upcoming post with some of the first images of features below the seafloor here from our new data!).
Now that we have been out for a while and the survey was proceeding smoothly, everyone had settled into their shifts and routines, and the science party was consumed with onboard processing and archival of the incoming data stream. Funny enough, hump day and the near completion of half of our survey almost coincided with the summer solstice and a very full moon
It seemed like the convergence of many lucky omens.
Alas, it was not so. In the wee hours of the morning on June 24, the port engine failed as we were steaming along collecting data. The ship has two engines (partially in case of just such an event!). Fixing things at sea is obviously more complicated than fixing them on land, and the engineers onboard determined that the damage was significant and not quickly repaired. While we have the parts onboard to replace most of the known broken pieces, making the repairs and assessing the full extent of the damage is best done dockside. Thus we decided to pick up all our seismic gear and head back to Vigo to make the repairs. It took us >3 days to deploy all of the streamers, paravanes, and associated kit, but only about 12 hours to recover them! Now we are limping back to Vigo through relatively rough (3-4 m) seas powered by one engine. Once the damage and remedies for the port engine can be fully assessed, we can figure out our next move. Wish us luck!
All of us on the science team have had our turn being indoctrinated in the "perils" of XBT
deployment. In this video, Luke demonstrates the proper technique for launching an XBT.
We’re starting a new series of posts here on the Galicia 3D blog to give our readers a piecemeal tour of our home away from home, the R/V Marcus G. Langseth. Every few days or so, you will see new parts of the ship with detailed descriptions and hopefully a few interesting stories to go with them. Today we focus on the mess and galley (dining area and kitchen), arguably the most important area of the ship, but stay tuned for the engine room, bridge, the rack, main lab, aft decks, gym, steel beach, the ping pong table and more!
Prior to boarding the Langseth, my expectations of the food on board were clouded with visions of elementary school cafeteria slop doled out in aluminum trays and eaten with sporks and a side of plastic bag infused with milk. Little did I know that the folks on board take their food quite seriously. The three meals prepared each day are easily the most anticipated events of a crews’ day.
The galley (a.k.a. the kitchen in land dweller speak) is manned by a cook and steward who are responsible for sustaining the morale for the 53 people on board. The mess is regularly stocked with snacks like crackers, raisins, peanuts, dried prunes (yuck!), popcorn, cold cereal, microwave pasta, deli meats and cheeses, an assortment of milks and juices, coffee, tea, ice cream, and “fresh” fruits and vegetables (which will slowly be replaced with canned fruits and vegetables as the days go by). Cookies and pastries are also available at select times during the day if one is lucky enough to get there before they’ve all been consumed.
Between snacking times are the three glorious meals. Breakfast has the most stable menu of all the meals with a selection of eggs, potatoes, hot cereal, pancakes, French toast, bacon, sausage, ham, and a fruit platter that is now transitioning from fresh to canned fruits. Lunch generally consists of a type of sandwich, soup, French fries and/or onion rings, hot vegetables, rice, and other unpredictable delights. Supper has been quite intriguing as of late. We’ve been blessed with several kinds of steak, beef tenderloin, meatloaf, spaghetti, and many other varieties of taste bud tantalizing foods. For those who sleep during dinner and require a stomach recharge at 3am (yours truly and a good number of the crew on the midnight to noon shift), the galley staff save plates of dinner for “breakfast” that can be eaten during off times – I like to call this meal “brupper”, but am having difficulty getting the name to stick.
|Lunch at the mess with Luke, Sarah, and Tyler.|It has been entertaining to watch our young British colleagues become exposed to American cuisine for the first time with foods like peanut butter and jelly sandwiches, meatloaf (although they’ve been informed that it’s never as good as my mom’s – love you mom!), French toast, sausage in patty form, and Hershey’s chocolate syrup. It is also quite obvious that a 2,000 mile pond provides for the generation of different mealtime habits. For example, Luke was quite disgusted that I would dip a chocolate-chip cookie in a cold glass of milk; I shared his disgust when he spiced his French toast (sans-syrup) with salt and pepper and ate it like a normal piece of toast (apparently this was his first French toast experience). I’m guessing there will be some sort of payback if we ever meet in England sometime. Well folks, speaking of the devil, I’m off to the mess for a warm breakfast. I hope you enjoyed the tour and stay tuned for the next one!
Brian JordanRice University
We made it! According to the 30 minute log, which is one of the duties that we are given while on watch, we sustained up to 40 knot (74 km/hr, 46 mph) winds and ~7m (23 ft) seas for a few hours last night. That said, and aside from a relative lack of sleep, most of us seem to be no worse for wear. We also managed to travel north of our next sail line by almost an entire degree of latitude, which translates to ~111km (69 miles). We have now turned around, and are heading back to the survey area while working on streamer one. We will then re-deploy the air guns, and re-engage the survey in a couple of hours.
|Same view taken this morning.|
As a follow up to Donna's post, we are making individual preparations, which include taking the motion sickness medicine of choice or default depending on where you come from.
|Spanish, English, and American motion sickness remedies.|
We are also securing (tying down) our stuff and preparing our beds, which includes a new to us method coined "tacoing." To "taco" a bed means to use whatever you can find e.g. dirty clothes, luggage, random foam (Luke found some foam in the bird lab) in order to form a taco shape between your mattress and the wall. This way the roll has less of an affect on you as you try to get some sleep.. At least that's the theory.
|My laptop's ready!|
|Brian in a reasonably "taco'd" bed... And Luke's version.|
Will update from the other side of the storm.
For the last week, we have been enjoying relatively calm seas. Swells rolled in from distant storms, but the local weather was quite enjoyable. Now the storm that pummeled the east coast of the US last week is headed our way. This storm is expected to give us winds up to ~36 knots and ~7-8 m (~21-24 ft) waves! This is too rough for the more vulnerable components of our gear such as the airguns, which are dangling beneath floats behind the ship. Additionally, our data quality suffers when the weather worsens. When the winds pick up to ~25 knots, we’ll pull in some of our gear, and then turn around to face the storm and ride it out. In the meantime, we are preparing by strapping things down in the main lab and stowing loose items that might roll around and fall over once the ship really starts to roll.
Wish us luck!
|Map of forecast wave heights posted in the main lab. The big bulls-eye is right over our field area...| We have been at sea for nearly two weeks, and during this time we have seen many things… the hints of exciting geologic structures under the seafloor in our data, waves, whales, gear going off the stern. But we have seen very little of the sun, until today. Most days have been overcast and grey. Now that all the equipment is deployed, there is nothing requiring us to be outside except for the occasional XBT launch, so it’s easy for a day or two to go by without going outside at all. It is even possible to be totally unaware of the weather for long stretches of time since the main lab, where we spend most of our time, is windowless and below the water line. Instead of windows, we have monitors showing what is happening out on various decks from a series of cameras around the ship. Today they showed bright sunshine reflecting off the water behind the ship. After spending a few minutes out in the sun on the deck, my unaccustomed eyes are still seeing spots…. Back to the lab!
|Bern and James are on watch, so they can only watch the sun on TV from the lab.|
After days of uneventful and productive data acquisition, a pall fell over the R/V Langseth. Early Sunday morning, one of the streamers began to report communication errors and soon failed to communicate at all. A series of tests over the ensuing hours revealed that the problem was not on the ship but in the equipment out in the water. Recovering and repairing seismic gear is not a quick task. To access this streamer, we had to undo many of the steps required to put it out to begin with: recover the port paravane, shift Streamer 3 starboard and out of the way, and then reel in part of Streamer 4. After hours of troubleshooting, the technical staff of the Langseth brought Streamer 4 back to life. All of the equipment on the Langseth is… not new, and this certainly applies to the seismic streamers. The technical staff on the ship are pros at keeping this equipment alive (and many cases bringing it back from the dead). Twelve hours after the problems with Streamer 4 began, it was back in the water, and we were ready to start collecting data again. But no sooner had one problem been solved, another appeared. This time the trouble arose from the failure of a piece of equipment on the ship that is at the heart of our acquisition system – the real time navigation unit (or RTNU, for those in the know). This component gathers satellite and other navigational information from the seismic equipment and delivers it to the navigation software on the ship so that we can determine the positions of all of our equipment in the water, and where and when we need to be shooting. Once again, the dedicated technical staff of the Langseth came to the rescue. Painstaking checking and double-checking of each component in the RTNU began last night and continued into the early hours of the morning. In the wee hours, it’s easy to get a little superstitious. Did all these problems arise because Tim Reston and I each accidentally drew in lines on our chart indicating that we’d completed lines in our 3D box before we actually had? Or was it the curse of Costa da Morte (Coast of Death)? This part of the Galician coast is known for its shipwrecks and nicknamed accordingly. Of course, the real culprit was the non-newness of the gear in question. Once again, the Langseth’s miracle workers saved the day by assembling the working parts of various old RTNU’s into one working unit. Thanks to their efforts, we are up and running again….
|RTNU carnage on a table in the main lab.|
Donna Shillington10th June
One of the secondary activities on the cruise has been the deployment of XBTs off the stern. XBTs are a standard oceanographic tool designed to measure the variation of water temperature with depth, providing information on mixing processes within the water column. As temperature is one of two primary controls on velocity of sound in water (the other being salinity), it is also of interest in the processing of our bathymetric data.
|Poseidon's Zodiak on the way over to exchange supplies.|
A few years ago, it was realised that seismic provides a method of directly observing the mixing processes, as the different water layers have sufficiently different seismic velocity and salinity for reflections to be generated at their boundaries: we have already seen reflections in the water column of our data, probably from boundaries between North Atlantic water and warmer, more saline Mediterranean water. However there have been relatively few studies of these processes using traditional oceanographic and seismic techniques, a deficiency being rectified by the deployment of XBTs at regular intervals during our cruise.
|A successful exchange on medium-high seas!!|
In addition to deploying ocean bottom seismometers to record our seismic shots, the German research vessel F.S. Poseidon has been carrying out oceanographic measurements, mainly using CTD casts (conductivity-temperature-depth), which provide more information than XBTs. As a result they had several XBTs left over. These they transferred to us this morning: Poseidon came within about 1 km of the Langseth and sent the XBTs over in a small boat. A real bumpy ride!
|Goodbye, until we meet in Vigo!|
University of Birmingham
After days of uneventful and productive data acquisition, a pale fell over the R/V Langseth. Early Sunday morning, one of the streamers began to report communication errors and soon failed to communicate at all. A series of tests over the ensuing hours revealed that the problem was not on the ship but in the equipment out in the water. Recovering and repairing seismic gear is not a quick task. To access this streamer, we had to undo many of the steps required to put it out to begin with: recover the port paravane, shift Streamer 3 starboard and out of the way, and then reel in part of Streamer 4. After hours of troubleshooting, the technical staff of the Langseth brought Streamer 4 back to life. All of the equipment on the Langseth is… not new, and this certainly applies to the seismic streamers. The technical staff on the ship are pros at keeping this equipment alive (and many cases bringing it back from the dead). Twelve hours after the problems with Streamer 4 began, it was back in the water, and we were ready to start collecting data again.
But no sooner had one problem been solved, another appeared. This time the trouble arose from the failure of a piece of equipment on the ship that is at the heart of our acquisition system – the real time navigation unit (or RTNU, for those in the know). This component gathers satellite and other navigational information from the seismic equipment and delivers it to the navigation software on the ship so that we can determine the positions of all of our equipment in the water, and where and when we need to be shooting. Once again, the dedicated technical staff of the Langsethcame to the rescue. Painstaking checking and double-checking of each component in the RTNU began last night and continued into the early hours of the morning. In the wee hours, it’s easy to get a little superstitious. Did all these problems arise because Tim Reston and I each accidentally drew in lines on our chart indicating that we’d completed lines in our 3D box before we actually had? Or was it the curse of Costa de Morte (Coast of Death)? This part of the Galician coast is known for its shipwrecks and nicknamed accordingly. Of course, the real culprit was the non-newness of the gear in question. Once again, the Langseth’s miracle workers saved the day by assembling the working parts of various old RTNU’s into one working unit. Thanks to their efforts, we are up and running again….
|RTNU carnage on a table in the main lab|
On 5th of June, Poseidon deployed her last three OBH instruments. The crew then spent the next two days doing CTD ("conductivity, temperature, depth") measurements of the water column. They typically recovered good measurements of conductivity and temperature for depths down to 1000 m. These measurements can be used to monitor mixing of different water bodies (such as warmer Mediterranean waters with the cold Atlantic) and to calculate variations in velocity within the water column to compare with seismic reflections we observe within the water column. Rough seas for the last 1.5 days have made the CTD measurements challenging.
Today the Poseidon is recovering eight OBH to download the data they recorded and redeploy them elsewhere within the 3-D box. It will be exciting to see the first OBH data! We won't see the rest of the data until the remaining OBS and OBH are recovered in August and September.
Despite being in the same area, here on the Langseth the science party hasn't seen the Poseidon since our first day passing them on the way out to sea from Vigo. However, this may be because we are all busy below deck in the main lab (with no windows) processing data!
For the last couple of days, we have been slowly (very slowly) steaming along at 4 knots (~4.6 miles an hour) towing all of the gear behind the ship and collecting seismic data. A lot of data! Each of the four seismic streamers behind the ship records returning sounds waves on 468 channels. Every time one of our air gun arrays fires, we collect 60 Mb of data. Repeat that every 16 seconds for a few days, and it adds up. Even though we have only been at it for a few days, we have already generated 405 Gb of raw seismic data, and that does not include all of the other types of marine geophysical data that we collect (bathymetry, magnetics, etc). Nonetheless, there are many reminders that we still have a long ways to go. For example, a large map on a table in the main lab shows all 56 profiles that we plan to acquire during this cruise in our target area for 3D imaging (black horizontal lines in the image below). As we complete them, we draw a green line along the profile on the map. Four down, fifty-two to go!
*Follow our progress on the "Survey Area" page as we update the sail lines every ~4 days.
|Map in the main lab showing planned profiles. The ones we've already completed are in green|
Our fourth (and final) gun array was deployed last night!! This means that all of the hard work that the crew has performed (with our help, of course) will begin to pay off as the data streams in while we traverse east along the western most extension.Marine reflection seismology involves actively generating soundwaves (rather than waiting for earthquakes as in many other types of seismology). The ideal seismic source is as close to a “spike” as possible. Sound waves from the source travel into the Earth, where they reflect off sedimentary layers as well as hard-rock surfaces. The returning reflections are recorded by over a thousand hydrophones (underwater microphones that gauge pressure changes created by the reflected seismic waves) in the streamers that we have been deploying for the last four days.
The source consists of a series of air guns of varying sizes, which are hung at a depth of 9m (~30 feet) below large inflatable tubes. The tubes are 60m (~200 feet) long and each has 9 active air guns (10 with one to spare). In our case there are two sets of air guns being towed 150m (~500 feet) behind the ship, that alternately fire. To create a strong source that is as spike-like as possible, the guns are carefully arranged and fire almost simultaneously. The air is released from the chamber of the air gun, creating a 3300 cubic inch bubble pulse, which collapses to create the sound waves.
|Orientation of the streamer and gun arrays being towed by R/V Langseth.|
The red circles indicate the location of the gun arrays.
We are making sound in the ocean, where many mammals use sound to communicate and hunt for food. In order to ensure we are operating responsibly and minimizing our impact on mammals, we have five Protected Species Observers (PSO’s) onboard who both watch and listen for (from the observation deck in Donna’s previous post) any marine mammal that comes close to the ship. If any are spotted or heard within a specified radius around the ship, we power down the guns until they leave the area.
Most of the science team came out on deck this afternoon to watch the starboard-side paravane deployed in relatively calm waters under partly cloudy skies. The technical and engineering crew proceeded slowly and carefully through the deployment procedure, and after about a couple of hours the paravane and attached streamer were over 300 m off the starboard side of the Langseth.
The second paravane went in the water at 22:00 this evening, and streamer 2 is currently being uncoiled into the water behind the ship. Despite a few delays, we are making good progress!
It's 6:30am ship time (Spanish time). The 12am-4am shift finished deploying streamer 4 at about 12:30am, and since then we've been waiting for the sun to rise and the seas to calm before putting out the paravanes and continuing to deploy streamers 2 and 3.
Most of the science group has been working in 4 hour shifts thus far - 4 hours of work and then 8 hours of time for other things each 12 hour period. The last day or two, I was using my 8 hour rest periods to eat a couple of saltines, lie down, and attempt to ignore the rocking of the ship, but I must be getting used to the seas (and they are calmer!) because I can now do other things like read papers and look at a computer screen.
We have been collecting data almost since we left port. We are mapping the bathymetry, collecting gravity data, recording ocean current directions, etc. Since we entered our 3-D box area yesterday, it's been exciting to identify fault scarps in the bathymetry.
Donna mentioned in her previous post that once a streamer is in the water, its location is monitored and it can be moved around using winged devices called "birds" that are attached to it. Imagine a number of actual birds holding a cable in their talons at an even spacing while flying. Our mechanical birds are not so different, except they are flying the streamer through the water. We can see where the birds are on a computer screen in the lab, and we can control the depths of the birds by remotely moving their wings. When a streamer goes into the water, it can take some time to get the weighting right and then for the birds to dive the streamer down to the desired depth (generally 8-12 meters below the sea surface).
3rd June (posted late due to internet outage)
|Assembing a bird to be attached to the streamer.|
|Birds for streamers 2 and 3 waiting to be deployed.|
After steaming for twelve hours out of port, we started the long process of putting out all of the seismic gear needed for this program. The weather worsened as we headed towards the field area, and we have been deploying equipment in 3-4 meter swells for the last 18 hours. This ship can roll by up to 10-15 degrees in these conditions (and more than a couple of people are feeling sea sick as a result). On the deck, ropes and cables connected to equipment towed off the back of the ship lurch and clank rhythmically, and water commonly washes over the lower deck. Down in the main lab, stray items that aren’t properly stowed or strapped down start to roll back and forth, the ship creaks and groans, and office chairs swivel with each swell.
For this program, we will be towing an enormous amount of gear behind the ship to enable us to image faults involved in rifting, the exposure of mantle rocks and continental breakup in 3D. Four 6-km-long seismic ‘streamers’ filled with pressure sensors (which can detect returning sound waves) will be towed 200 m apart, for a full spread of 600 meters. As we deploy the streamers, we add weights to ballast the streamer, acoustic units to determine the locations of the streamers, and ‘birds’ that enable us to control the depth of the streamer remotely. We also swap out broken pieces. The streamers are held apart by two gigantic paravanes, which are like large metal kites that fly out from either side of the ship. Each one weighs an astonishing 7.2 tons and is ~7.5x6 meters in size. There are also myriad floats, cables and ropes to maintain the correct geometry of the entire array. The streamers will record returning sound waves generated by two arrays of air guns, which will be towed 100 m apart and fired separately. We expect that it will take us 3 days to deploy this complicated array of equipment behind the ship. The weather is expected to start improving tomorrow afternoon, which will help us greatly!
|Looking forward on the Langseth as she takes a roll in the swell.|
|A streamer with a 'bird' being deployed off the Langseth's stern into the waves.|
The R/V Marcus G. Langseth pushed away from the docks of Vigo at 8 am local time. The sun was shining, and the views of the rugged cliffs, forests and Galician towns along the coastline were spectacular. We will only be able to see land at the very beginning and very end of this 45-day cruise. We steamed out of the protected waters around Vigo and out into the open Atlantic Ocean a few hours later, and happily were met by relatively calm seas (1-2 meter swells), although its quite brisk compared to summer weather back home. We actually saw the F.S. Poseidon in the distance as she headed back to Vigo at the end of the first OBS cruise of this program. We only have a relatively short transit of ~10 hours before we begin to deploy the extensive suite of scientific equipment behind the ship needed to image the structures beneath the seafloor in 3D. Putting out the seismic streamers and associated gear will take 3 days!
|The science party on deck as the ship departs Vigo.|