Transfer at Sea

Monday, September 26, 2005

Mary Goff and Will Wilcock

Daily Report

Mary Goff, Science Teacher, Oregon
Today the northerly winds continue to be light at 10-15 kts and both ABE and Jason have been in the water since last evening. There's a mild and slightly balmy feel to the 57° Fahrenheit air. Light rain fell by breakfast time. A crescent moon was spotted through broken clouds at 3:30 AM this morning.

Jason's work continued on Dive #177 during the night, starting first at the KEBB (Keck Endeavor Broad Band) site at 2370 meters where data from one broadband seismometer was retrieved and checked. It was found to be transmitting data inaccurately and Paul McGill, MBARI electrical engineer, was able to make some adjustments on the site. Further refinements will have to wait until next year when the instrument is retrieved. In the meantime, Tony Ramirez, “seismometer repairman”, was awakened from a deep sleep to successfully rig up a new seismonument after one was inadvertently broken. Scientists and ROV crews from Woods Hole and MBARI must anticipate problems like these and bring spare parts along just in case.

Jason carried the pieces of the broken seismonument along in its titanium arms as it transited to another site at KESW (Keck Endeavour South West) site. One exciting event thrilled the Jason II team in the van - they witnessed the actual landing of an elevator. Jason's lights illuminated the platform as it settled firmly on the seafloor. No waiting around for an elevator this time! Afterward the elevator was sent to the surface with the broken seismonument. It was on deck by 11:45 am and we began our transit to Mothra, the southernmost vent site in the Endeavor Segment. At Mothra work began to retrieve Dr. Marv Lilley's two gas tights and one major water sampling bottles. These were waiting from an earlier dive.

This afternoon we turned our attention to the biological world. First a rare white octopus was spotted swimming near Faulty Towers. A little later a special microbial incubator sheath was sent to the bottom where it was used to protect the precious incubator after it was removed from the walls of Roane, an active sulfide chimney. The incubator was inserted in Roane at the beginning of the cruise. The horizontal placement of the insert ensured a wide range of temperatures that might provide differing habitats for hydrothermal microbes. Temperatures can range from almost 300° C water near the inside of the hydrothermal vent to a cool 2° C water toward the outer margins. Co-Chief Scientist Dr. Deb Kelley will use this sample to identify the different populations of microbes that can live in each temperature environment. As we toured Roane and nearby structures within the Faulty Towers complex, Deb noted that Finn had continued to grow. She estimated that Finn had added an additional 5-9 meters since its top was removed in 1998. Finn is also famous for being home to the most heat loving microbe in the world, known to survive in 121° C water!

After Jason was brought on board we rendezvoused with the Arctic fishing research vessel, Frosti, shortly after 7 pm in fading daylight. Conditions were generally calm for the transfer of personnel and equipment at sea. We welcomed several scientists, new ship's crew, and our camera crew. The crew transfer took REVEL leader Véronique Robigou and most of the seismologists back to Victoria on a 30 hour transit. Weather permitting, Véronique will rush onto a seaplane and back to the University of Washington studio in time to narrate the live web cast planned for 2 pm Wednesday. It is a busy time.

Impressions

Dr. William Wilcock, University of Washington School of Oceanography
I am originally from Britain, and one of my family’s stories concerns my grandfather, who spent most of his childhood in Holland, and as a consequence spoke fluent Dutch. During the First World War he was conscripted by the British Admiralty to participate in the naval blockade of Germany. He sailed on a fleet of North Sea fishing boats that intercepted passenger ships from neutral countries. He was part of the boarding party and his job was to interview the passengers and identify Germans who were passing themselves off as Dutch. He was good at his work, but, like me, he had a strong tendency to get seasick. As the story goes, he eventually sailed with one experienced captain who promised to help him overcome this affliction. At the height of a North Sea gale, my grandfather was taken out onto the deck and lashed to the mast. He was horribly sick but after several hours of utter misery the winds abated, and my grandfather recovered and was never seasick again.

I have never been brave enough to attempt this drastic remedy nor, I suspect, would Captain Phil Smith be willing to implement it - for one thing, anyone venturing near the Thompson’s mast would get toasted by ship’s radar unless the ship was willing to sail blind. However, after participating in a dozen research cruises, I have finally reached the point where I am no longer queasy through the whole cruise and I can participate fully in life at sea.

Sailing on cruises with John and Deb is always stimulating. I am a seismologist and many of the cruises I have been on have focused entirely on seismology. We will drop a large number of autonomous ocean seismometers that will sink to the seafloor, shoot compressed air guns for a few days, and then send acoustic commands to the seismometers so that they drop their anchor weights and float back to the ship. While such experiments can produce excellent data sets and interesting scientific results, the actual cruise itself is a monotonous experience. In contrast, on this cruise we have at least five different seafloor components all of which are technologically challenging. We are continually juggling our objectives, and pushing the envelope of what can be accomplished in a month at sea.

At present, the funding for oceanographic research in the US is fairly tight, and it increasingly difficult for many scientists to raise funds for their own research endeavors. Some of my colleagues feel that too much money is being spent on supporting seagoing facilities, rather than going towards supporting scientists. This cruise has convinced me otherwise. If our visions of heavily-instrumented permanent seafloor observatories are to come to fruition, we must dedicate some of our large research vessels to hosting robust remotely-operated vehicle systems that are designed to work in rough seas, build fleets of autonomous underwater vehicles to survey the seafloor efficiently and respond to geological events, and provide the people who are developing new instruments with frequent opportunities to test them at sea on multidisciplinary cruises like this one.

Daily Question

  • How far down does the magma lie under the vents?
    Stephanie Poletti     Grade 9, Crater High School, Central Point, OR


    Great question, Stephanie! As you know magma is liquid rock, in this case, under the seafloor. It tends to collect in pockets called magma chambers as it rises upward through the crust. Magma chambers are found in many areas of the world's oceans. Spreading zones occur when hot magma (around 500-700 °C) rises to the surface where the Earth’s plates are moving away from each other. This process isn't a smooth one and numerous earthquakes happen as magma pressure cracks the crust and pushes its way to or near the surface. Geologists estimate that 90% of the world's strongest earthquakes happen underwater, many of them at spreading zones. The cooled material creates new oceanic crust and underwater mountain chains called oceanic ridges.

    Geologists can measure the depth of magma chambers by setting off underwater explosions (after looking out for wandering whales!). They track the path of these sound waves as they bounce off the different layers of material in the seafloor. The picture at the right shows the sonic image of the layers under the Main Endeavour hydrothermal vent field in the Endeavor Segment. The top of the magma chamber is seen as a line below the red dots that indicate the location of earthquakes.

    Your question about the depth of the magma turns out to be a key point. According to Dr. Andrew Barclay, one of our team of ocean-going seismologists, shallower magma chambers tend to be hotter and create more spreading activity, while deeper and cooler chambers are less active. The magma chamber under the Main Endeavor Field is about 2.5 km down and the seafloor above it is spreading apart at about 6 cm per year. This is a medium-deep chamber with a middle range spreading rate. The fastest spreading zone in the world is in the tropical Pacific at a place called the East Pacific Rise where spreading rates are 10-20 cm/year!

  • How do scientists know how to find the same vents again?
    Amy Dundorf     Age 12, East Pennsboro Middle School, PA


    Hi, Amy,
    I'm writing to tell you that I just spoke to your ocean-going REVEL mom, Carol Dundorf, and she's sending salty hugs to you and your family!

    Your question about how we locate underwater sites like vents again starts with an understanding of how we find them in the first place.

    Usually there are clues that first lead scientists to the general vent area. These could be a pattern of earthquakes near an active spreading zone like here on the Juan de Fuca Ridge. When scientists suspect that a vent system may be present, they can send down a manned or robotic sub to take a look at the terrain, mapping the features they see.

    Sometimes a lucky accident can lead scientists to a hydrothermal vent. Dr. Marv Lilley, a geochemist on board the RV Thompson, recounted the exciting discovery of a "mega plume" of vent fluid in 1986 that was located when an oceanographic ship just happened to be sampling water in the area soon after an underwater eruption. Hydrothermal plumes are like underwater smoke stacks rising from a vent source. They contain a special blend of warmer water with dissolved carbon dioxide, helium and hydrogen from the vent below. These days CTD (conductivity, temperature, depth) samplers are routinely used to home in on new vents. (See "Prospecting for Plumes with a CTD" on the REVEL website's "Mapping the Water Column section.")

    However they are located, Amy, you're right, scientists will want to return to the same vent again. They want to study how each vent is different and how a vent may change over time. Whenever a new vent is discovered its location is plotted on an underwater map and notes are made of the recognizable features near by. The vent's depth, its latitude and longitude, and its local X-Y reference coordinates are recorded. Sometimes a reflective sonar marker is left as well.

    In the past few years signaling devices called homers, are becoming more popular as well, according to Jason navigator Dara Scott. When Jason returns to the general area of the vent it receives a special signal from the homer. With the aid of their previous notes, coordinates, and visual markers, the pilot can then guide Jason back to the same vent again.