Keck Expedition 2004
September 2, 2004 Day 4
Update for September 2, 2004—Transit day from Cleft to Endeavour
We spent the day steaming north from the Cleft dive sites to the Endeavour spreading segment—a total of 205 nautical miles with sunny skies and choppy seas. Although we all thought that this would be practically a day off, there were still lots of jobs to do. Deb G., Jim and I debated the pro’s and con’s of different potential tracklines for the five scheduled dives on Endeavour. Although the Endeavour segment have been studied for almost 15 years, most of the work has focused on the voluminous hydrothermal discharge systems spread along the entire axis. Surprisingly, the basic geological mapping and studies of the rock chemistry were never done on a systematic basis. There were few samples recovered by submersible where the detailed age relationships could be observed. We have five ROV dives to understand the geology for this important area and collect the volcanic samples required to constrain our models. With all seagoing programs, the weather is a wild card, but for submersible investigations the health of the vehicle can also bring an early end to a planned dive or even the entire leg. The captain helps by keeping us updated on the weather’s status, the pilots work very hard to keep the vehicle working as long as possible, and we always do the highest priority work first. “Plan each dive like it is the last one” is a mantra among submersible users.
Deb Glickson has contributed her new fine-scale bathymetry of the seafloor around the vents and down the entire axis center. She needs for us to dive across the new data to provide some ground truth. The new data will permit us to map in larger topographic features as we go. Tony puts the new bathymetric data into the ArcNav database and it appears as part of the real-time navigation basemap. With the three of us commenting, Tony then redraws the next day’s dive track on the new combined map. We had promised the captain that the bridge would have the diveplan waypoints by noon and it was delivered with only a few minutes to spare.
Meanwhile in the other lab, the rock team is VERY impatiently waiting for Tony to photograph the rocks so that they could begin. This could be a long process with 43 samples waiting to be done. Tony sets each rock on a clean backdrop for its picture (see image at left), and then breaks a corner off the photographed samples so that the interior of the rock can be examined and described .
I am astonished to find fresh glass under the brown manganese coatings for almost every sample. Frank is equally amazed to find that almost none of the samples contain crystals, one of the enigmas of mid-ocean ridge basalts—moderately evolved rocks with none of the expected crystal formation. Sarah systematically describes each sample for size, shape, and the extent of vesicularity (how many gas bubbles). Sarah is also watching for news of the hurricanes in Florida, where she goes to high school. She recently won the second prize in the International Science Fair working on rocks from the Juan de Ridge collected in earlier expeditions. The next step is for Laurie and George to chip off glass fragments and put them into small plastic bags to hand-carry back to shore. The glass is the most valuable component for modern geochemical analyses as it is taken to represent the composition of the original lava before it cooled, crystallized and interacted with seawater. The complete chemistry can be done with only a few grams of fresh glass. The remaining rock material is packed into buckets and then all the counters are cleaned. Given the small quantities of glass that we work with, it would be too easy to mix up the tiny fragments. So good housekeeping is a requirement, along with good bookkeeping. It takes 8 people until dinnertime to complete all of the rock preparation.
Beginning tomorrow we will have five dive days in a row so it is great that the team is now well-trained and ready to take on all of the control room and post-dive jobs. The evening however is free for music, computer games and watching the beautiful evening sunset on the Pacific.