By Edwin Schiele
October 19, 1998. Two nights ago just before my watch began, Debbie Smith announced that there was no more to see on this line, so the flyer should pull up ARGO II and we should prepare to motor down the ridge to the next site. So I spent my watch in the lab, typed a little, played a little ping-pong, and watched Debbie and Frank Trusdell plot the course for the next line.
The target they were plotting was a point along the ridge where the slope suddenly steepens. By examining the features on either side of that point, we hope to learn what is behind that change in slope. A possible explanation is that the dikes dont extend much beyond that point. As lava from multiple eruptions piles up, the slopes tend to become more gradual. Areas where there are fewer eruptions tend to be steeper.
Yesterday morning, ARGO II toured the upslope side, explored a pit, and discovered some possible remnants of lava tubes. Thirty minutes into my watch, Debbie announced that there was no more to see on this line, so Will Sellers should pull ARGO II part way up and we should motor down the ridge to the next site. Matt Naiman continued to monitor the ships position. Will and I fetched our books from our rooms. Frank passed around a bag of weird dried fruits that actually tasted pretty good even though they still had pits inside of them. ARGO II reached the next line 30 minutes before our watch ended.
Other watches have collected tons of dataso much that organizing it all will be a daunting task. Once the cruise finishes, each investigator will want to analyze various aspects of the data and will need easy access. Dave DuBois (pronounced DuBoyz, not DuBwa) is the man in charge of organizing and archiving the massive amounts of data we are generating. He is also the man to see if you want to know what experiments are going on, when they started and stopped, and what other activities, both scientific and otherwise, are happening aboard the ship. He always responds with raised eyebrows and a careful but confident answer. Part of it is his job. Part of it is his experience as a veteran cruise participant.
Dave has lost count of how many research cruises he has been on, although he estimates that the number is over 20. After finishing his masters degree at the University of Delaware, Dave landed a job at Woods Hole Oceanographic Institution. That was in 1984.
Until this voyage, Dave has participated exclusively on marine seismology cruises. Marine seismologists also use sound to study the composition of the ocean floor, but they do so on a much larger scale. Instead of studying features on the surface of the ocean floor like we are doing, seismologists characterize features as far as 20 kilometers below the surface. The instruments are also different. Instead of towing a sophisticated sonar 125 meters above the ocean floor, they fire an array of 20 air guns that dangle into the water from two booms. Some of the sound waves that the air guns generate penetrate the ocean floor. Just as a prism refracts (bends) light, the layers of rocks in the ocean floor refract the sound waves. The angles that the sound waves bend depend on both the frequencies (pitch) of the sound waves, and on the thickness and density of the layers of rock in the ocean floor. An array of sensors anchored to the bottom receives the signals that refract back towards the surface. By measuring the time it takes for the different frequencies to reach the sensors, the scientists determine the nature and even the shape of the structures within the ocean floor. Other sensors, called ocean bottom seismometers, detect vibrations in the ocean floor. The sound waves from the air guns shake the ocean floor in much the same way that sound waves from the bow thruster shake my bunk while I am trying to sleep. One of Daves jobs is programming the computers on the ocean bottom sensors and then processing the data they collect.
It is hard, especially as a first time participant on a five-week cruise, not to be impressed with Daves record. He has been on cruises with graduate students who became principle investigators on subsequent cruises. (Laura Kong, for example.) Many of the cruises have taken Dave to exciting locations such as the Aleutian Islands, the East Coast of Greenland, and New Zealands South Island. Other voyages, however, have taken him to the middle of the Atlantic or Pacific to study mid-ocean ridges. It often takes one week to get there and one week to get back. Sandwiched in between are four to five weeks of research far from land. That can get pretty old.
Still there are many reasons that propel him out on the next cruise. There is the pride he takes in the data he collects and the desire to collect better data on each voyage. He also sees each trip as a "voyage of discovery," a chance to learn something new, meet new people, see new places, "and live to tell about it." And of course there are the T-shirts. Dave has perhaps the finest collection of cruise T-shirts in the known universe.
Dave is also a master of the country-western dance step and competes up and down the East Coast as a member of the Diamond Jacks dance team. There have also been rumors, perpetuated mostly by the chief scientist, that Dave moonlights as the NutterButter Elf. Dave categorically denies any association with or even the existence of this sprite.