Mountains Under the Sea
By Bridgit Boulahanis
The biggest question driving the OASIS mission is simple: how old are the lava flows along the 8°20’N Seamount Chain. Answering that question is far from simple, requiring a plethora of data, multitudinous methods of sample collection, and many experts in order to conduct the analysis.
We can get information about the magnetic polarity of the rocks below us from our magnetometer, allowing us to understand the relative age of the seafloor in relation to known magnetic pole reversals. We can use shipboard multibeam and autonomous underwater vehicle multibeam to gain an idea of the character of the seafloor we survey, generating maps of the major features and preliminary analysis of the sediment cover in the region. We can use dredges, large metal baskets lowered overboard with weights, to pick up rocks across a broad area in order to characterize the chemical composition of lavas in that region. Each of these forms of data collection is adds an important piece to the puzzle we are trying to solve.
However, the most exciting form of data collection is the sampling we can do with Human Occupied Vehicle (HOV) Alvin. Alvin allows us to get precise samples of specific lava flows and morphological features, ensuring that we know exactly where the rocks we chemically analyze come from. Beyond its incredible sampling capabilities, it is the most exciting way to learn about the seafloor. Last week, I had my first opportunity to dive in the submersible, and while the science is what drew me here, it was the thrill of seeing firsthand what was on the bottom of the ocean that had me wide awake many hours before launch, standing on deck as the sun came up, staring over the side into the depths that I would soon be exploring. In the morning air it was hard to imagine that soon I would be under thousands of meters of water, seeing with my own eyes what I have been studying for years.
After a small breakfast and what felt like years of excited pacing, we entered the submersible. I was diving with Alvin pilot Jefferson Grau and Dr. Mike Perfit, Distinguished Professor of Geology at University of Florida. The tight space that makes up the human occupied space of Alvin has just enough room for three, and so as the submersible was lowered into the sea off of the R/V Atlantis, we settled in for a cozy nine hours.
After bobbing with the waves on the surface for several minutes as the pilot and crew did their final safety checks, we began our descent. Almost immediately upon leaving the surface the motion of the waves faded away and the submarine felt still enough to almost trick me into believing we weren’t moving at all. However, soon the bright blue of the shallow ocean faded to the black of the deep, and bursts of bioluminescence surrounded the submersible. More seasoned colleagues had told me that I should keep an eye out for bioluminescence, but there was so much of it that it would have been hard to miss! It looked as if we were descending through a field full of fireflies, with occasional fireworks popping up as we passed larger organisms bursting out of the darkness.
It took us almost 90 minutes to reach the seafloor, and I spent the entire time looking out the two portholes I could reach from my side of the submersible. I was already enamored with the experience, and we hadn’t even gotten to the ocean bottom. During our final approach we turned on all of Alvin’s external lights, suddenly bringing daytime to a previously eternally dark part of the world. Jefferson and Dr. Perfit, both veterans of Alvin exploration, advised that I look out my side porthole to catch the soonest glimpse of the seafloor. For several minutes I waited, staring down to where light blue faded to darkness. Then, suddenly, it was there – sandy sediment extending in every direction with pillow basalts peaking out around.
Immediately we began collecting samples of the rocks around us using Alvin’s two manipulator arms, while writing descriptions of the area and recording audio descriptions of everything we saw. Following a dive track laid out before our descent, we traversed up the side of Avery Seamount while noting the characteristics of everything we passed. Dr. Perfit pointed out rocks for Jefferson to sample, while I operated cameras to ensure we attained high quality footage of each sampling location. Our conversations were filled with preliminary analysis, with Dr. Perfit guiding me in identifying the differences between the various rocks outside our window.
Midway through our dive we came to a steep wall approximately 30 meters high, a cliff face at a 90 degree angle to the seafloor. Even in the best multibeam maps of the ocean floor we cannot represent such rapid depth changes accurately – our sonar will smooth even the largest crags automatically, making knowing about these sorts of cliff faces elusive without underwater vehicles. Despite my years of looking at these maps, I never pictured vertical cliffs rising off of the seafloor. To say this realization rocked my world would not be hyperbole, but it would be a bad pun.
Our dive track took us past the steep wall, and so Alvin rose up, floating along the cliff face that seemed to climb endlessly from the sediment below. Soon the dark pillow basalts became speckled with sea life – corals and anemones, starfish and sponges. Everywhere we looked, life was not only present but appeared to be thriving. While as geologists and geophysicists we do not sample any of the living organisms we find, it was very exciting to see, and we noted their location to pass on to biologist colleagues who might return.
Alvin’s sample basket was almost completely full by the time we approached the summit of Avery Seamount, and we spent our last moments on the seafloor extracting one last rock for later analysis. Though the dive lasted its full nine hours, it passed far too quickly. Too soon we were rising to the surface, passing back up through the bioluminescence and the lightening shades of blue until we were again hoisted on board the ship.
Upon exiting Alvin we were met with a cheering science party, a tradition every time the submersible comes back on deck. After applause and hugs we scientists did what we do best – got straight to work on the analysis. We classified the samples we had collected and began the description and photography process, logging each rock carefully so when they get back to a laboratory on land the geochemists have all of the information they might need.
The descriptions and samples we collected while on the bottom will help us to characterize how old Avery Seamount might be, providing valuable insight into the processes that formed this expansive seamount chain. Having contributed to increasing scientific understanding in such a hands on way is absolutely thrilling. Now when I look over the edge of the ship it is impossible not to picture of the varied terrain that must be slipping past me deep below, teeming with life and calling out for me to visit again soon.
Bridgit Boulahanis, a graduate student at Columbia University’s Lamont-Doherty Earth Observatory, is in the eastern Pacific Ocean aboard the R/V Atlantis on an expedition to investigate a chain of submarine volcanoes along the East Pacific Rise. Learn more about the expedition in her blog and on the OASIS Facebook page and YouTube channel.
We are in the midst of a four-day transit from our study site on the East Pacific Rise to the Atlantis’ next port of call in Costa Rica. All of the scientists aboard will depart for home from there, while many of the crew will stay on for another leg of the cruise. The transit thus far has been long and boring and slightly rough, but such transits give us plenty of time to write cruise reports, pack up our gear, and get ready for the next stage of our journey home.
There is also time to reflect on the past few days and weeks of work, which by and large have gone well (and have been anything but boring). Scott accomplished all of his scientific goals with his pressure measurements, Monika collected copious biological samples that will keep her group busy for some time, and as you know if you’ve been following along, the VentCam worked better than we could have hoped. Sometimes cruises do not go this well, so we have been sure to be thankful for our good fortunes. We are also indebted to the captain and crew of the Atlantis, and all the members of the Alvin group. Each of them deserves enormous credit for taking us safely to sea and helping us accomplish our scientific goals. Obviously we couldn’t have done it without them.
On a related note, one highlight worth mentioning occurred on the last dive of the cruise. A few days ago Scott held a drawing to give away the starboard observer position on the final dive — normally reserved for a scientist — to a member of the ship’s crew. The contest was open to any crew member who had not yet had a dive in Alvin. Most of the crew qualified for this contest, because the science party rarely has a slot available to give. Scott drew lots from a bag and the winner of the free trip to the bottom of the ocean was wiper Leroy Walcott from the engine department. He seemed more than enthused about the opportunity and word has it that he had a spectacular dive. He was also quite proud to be the first person from his home country of Barbados to dive in Alvin.
It has been an enjoyable and productive cruise that none of us will soon forget. But life on a research vessel can be difficult, and being away from friends and family is not always easy. So even though the forecast for New York has temperatures below freezing in the coming days, I am actually looking forward to being back home! See you all back in the cold cold city.
As you know yesterday was Christmas, and things are just a little bit different on such a holiday aboard a research vessel. Although the sub was in the water, many of the crew had the day off. As far as I can tell, most of them work around the clock, so such a rest was clearly in order. Dinner yesterday was also something special. Steward Carl Wood, Cook Mark Nossiter, and Mess Attendant Richard Barnes created a most delicious meal from scratch, including roast beef, turkey, stuffing, mashed potatoes, and all sorts of veggies and fixins. We ended the evening with a white elephant gift exchange on the fantail. Alvin looked on from inside the hanger while sporting a giant Santa hat made for the occasion by the group from Austria. A jolly good time was had by all.
But the highlight of my day was the return of the VentCam. Project engineer Carl Robinson dove in Alvin along with pilot Bruce Strickrott and geophysicist Milene Cormier of the University of Missouri. They carried a set of glass-ball floats down with them and when they reached the seafloor attached these floats to the VentCam tripod to send it toward the surface. About an hour and a half later, officers on the bridge spotted the yellow glass balls bobbing up and down, and maneuvered the ship in close. Bosun Wayne Bailey and members of his deck crew brought the instrument onboard without any shouting or hollering. Anyone who has ever done any oceanography knows that this is the ultimate sign of a well-executed recovery.
After an initial look at the video we collected, it looks like the deployment was a success. The camera’s light balancing routine worked very well, and all indications suggest that the flow rate analyses will work just fine. Carl and I will now begin the process of breaking down our gear and boxing it up for the shipment back home. I will also start planning for the next VentCam deployment, which might come as early as July. It’s never too early to start preparing for a cruise.
Meanwhile, Scott still has four dives left for making pressure measurements, so his work will continue. I’ll be in the ball once more tomorrow as a supporting member of his team, and I’m looking forward to another dive. So far Scott’s project has also gone well, and I hope to help continue the trend.
Not everything on a research vessel always goes according to plan. Today we awoke to find out that during the night the primary CTD winch failed, leaving about 2000 meters of cable and a large instrument package over the side. Alvin cannot dive when we have a wire in the water, so this situation is going to delay today’s launch, and we may even need to scrap it altogether. Hopefully this won’t happen.
At night while Alvin is sleeping we use the CTD, which measures things like temperature, pressure and turbidity, to map the extent and intensity of hydrothermal venting above the ridge. Since Alvin can only dive during daylight hours, this is an excellent way to use the ship’s resources while we wait for the dawn. On rare occasions though there is an issue with the winch that can cause a delay.
Crew members from the engine room, the deck crew, mates, and the captain have been working through the night to move the spool from the faulty winch to a backup winch on the aft deck of the 02 level. These wire spools weigh many thousands of pounds, and it takes an extremely competent and experienced crew to change them out while the ship is rolling at sea. Thankfully, that is what we have on this ship. The crew is doing their best and doing it as fast as safely possible. Hopefully within another hour or two we’ll be winding in the CTD and preparing for a belated dive in the sub.
After a search during dive 4576, Scott finally found a suitable site for the VentCam deployment, and later that evening we launched the system overboard for its first trip to the seafloor. The next day, with the help of pilot Bruce Strickrott and pilot-in-training Anton Zafereo, we dove in Alvin to recover the device and position it at a black smoker vent called Bio9. It was a lovely sight to see it shining its light into the darkness as we approached. Intermittently flashing at programmed intervals, it looked like some kind of lunar lander examining a distant world. In a way, I suppose it was.
We used Alvin’s manipulator to carry the VentCam from the landing site over to Bio9, and after only about 30 minutes or so, Bruce had it all set up and ready to record video. If all goes according to plan, it will record 15 seconds of video at 75 frames per second every 10 minutes. I will be able to process this data using an image analysis technique that will tell me how fast the fluid is flowing out of the vent and how the flow is changing over time.
Once we iron out all the wrinkles, we hope to eventually build many of these devices and place them at many vents for long term deployments. By comparing changes in flow rate through different vents in response to events like earthquake swarms, we will begin to unravel more of the mystery of the subseafloor plumbing system, and better understand how heat and chemicals are transferred between Earth’s lithosphere and the overlying ocean. Such information will be critical as we work to understanding how mid-ocean ridge hydrothermal systems support deep sea ecosystems and how they fit into the global climate system. We’ll just take it one step at a time though.
Monika Bright of the University of Vienna had the first dive of the expedition yesterday and brought back with her all sorts of squishies both tiny and small from sites of diffuse venting around the high-temperature hydrothermal vents far below the ship. Being that I am a geophysicist, I don’t fully understand all the biological-type analyses her group is doing with the captured creatures, but word has it that they are studying succession processes (how organisms colonize new sites and how those communities change over time), and infection processes (how young tube worms that start their lives without their required compliment of chemosynthesizing microbes eventually acquire them). Pretty interesting work!
Meanwhile, Carl and I have been making final adjustments to the camera system before its scheduled deployment on Sunday. We are making small tweaks to the code that controls the automatic exposure routine so the video we collect will be suitable for the image analyses we’ll complete after recovery. Although we hope to get good science from the data we collect, this is the maiden voyage for this particular instrument, and our attention is mostly directed at making sure that the apparatus is properly configured for easy positioning by the sub’s manipulator arms and that we get a few days worth of good video with good light levels. Many more adjustments will probably be required before the system is ready for a long term deployment.
On yesterday’s dive Monika spent some time scouting around for a good location to place our camera system, but none of the sites she visited will do the trick. This is a bit of a problem for me because I need to know a little about the geometry of the environment around the vent so that I can adjust the tripod accordingly. For this reason my dive has been bumped back one slot and Scott’s dive has been rescheduled for tomorrow. Scott has has agreed to do a little more scouting for me before he gets on with his pressure measurements. Problem solved. Hopefully.
Scott’s work is also pretty cool. This is the second year of his three-year campaign to take pressure readings at
a set of concrete benchmarks that he placed along the ridge axis and off to one side. The pressure at the bottom of the ocean changes slightly over time because the shape of the seafloor changes as magma moves around below. Scott’s experiment will help us better understand the dynamics of plate tectonics and how new crust is formed at mid-ocean ridges. I’ll try to keep you posted on how this project and all the others go during the cruise.
The first day of any UNOLS cruise is filled with myriad meetings, briefings, and safety courses. All new crew members and scientists are provided a comprehensive orientation to introduce them to many of the ships operations, safety equipment, and procedures. Among other things, we learn about separating our plastics from the biodegradable trash, what kind of footwear is required outside living quarters and on deck, and how to properly return movies into the collection once we are finished with them.
We also learn about more serious things, such as where to muster and what to do in case of fire, if someone falls overboard, or in case we need to abandon ship. For all who’ve never done it, this training includes donning an immersion suit, also known as a “gumby suit”. This is usually a pretty fun exercise because the suits are somewhat difficult to put on so, and everyone seems to have their own favorite technique. Once they are on it is hard not to laugh at how silly the outfit looks. All kidding aside though, these suits save lives, and although I hope I never need to use one, it’s good to know there is one onboard for every member of the science party and crew.
Yesterday we set sail from Manzanillo, Mexico, bound for a hydrothermal vent system on the East Pacific Rise (EPR) near 10 degrees North. The EPR is part of the world’s mid-ocean ridge system where new crust is formed as Earth’s plates spread apart. Many of the most exciting Earth processes occur at mid-ocean ridges, including volcanic eruptions, earthquake swarms, deep circulation of ocean water into the crust and the ejection of that water back into the ocean at the site of high-temperature hydrothermal vents. These vent sites are also home to exotic and strange life forms that make their living from chemicals in the warm fluids, and may hold important secrets about how life on this planet originated and evolved, and how life in other parts of the universe might survive. Our mission on this cruise will be to learn more about how these intriguing environments work.
We are headed to the EPR aboard the R/V Atlantis, a 274-foot research vessel and the tender to the human occupied submersible Alvin. This is a large and capable world-traveling vessel that was built specifically for the kind of research that we do. Atlantis has an extensive suite of scientific instrumentation including multibeam sonar systems, winches and cranes for launching buoys and sensor packages, dynamic positioning, and of course Alvin, the deep-diving submersible that will take us to the seafloor to do our research.
There are approximately 20 scientists onboard this cruise, including a few graduate students and a few technicians. We comprise four different teams, each with a primary mission for the cruise. A group led by Dr. Monika Bright will be gathering biological samples for a variety of analyses, a group led by Dr. Spahr Webb will be recovering a set of bottom pressure recorders that have been collecting data on the seafloor for a couple of years. A group led by Chief Scientist Dr. Scott Nooner will be making pressure recordings at a number of benchmarks along and away from the ridge axis to measure how the shape of the seafloor changes over time. And my group (really just me and my engineer) will be deploying a prototype seafloor camera system capable of measuring flow through black smoker hydrothermal vents over long periods of time.
We will be arriving on station early tomorrow morning, and soon thereafter we will launch the sub for the first of about 10 total dives. In this space over the coming two weeks or so, I’ll try to keep a log of some of the interesting things we see and do during this cruise. Please let me know what you think or if you have any questions. I’ll try to answer anything that comes up in the comments. Cheers!