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May 17th, 2003; Leg 6, Day #3

Our geological explorations continued today with two dives in a submarine canyon east of Peninsula Concepcion. The first dive was in 1,500 meters of water. The ROV Tiburon settled on the bottom, and we immediately took a push core (see right). We then proceeded to move toward the southwest up canyon. Brittle stars littered the seafloor in this section of the canyon (see below). The sediment veneer was thin, exposing scoured surfaces of the rock into which the canyon has been cut. Mid-day we recovered Tiburon and moved the ship a few kilometers to the southwest so that we could examine a shallower portion of the canyon. Once on the bottom (about 1,350 meters), we continued to

collect push cores, rock samples, and a few vibracores. Low outcrops of flat, massive rocks poked up through the sediment. Sponges populated some of these rock surfaces (see left). Because sponges are filter feeders, they rely on the local hydrodynamics to deliver food to them. Because sediment will clog their feeding apparatus, they grow preferentially on rock surfaces that are above the seafloor and are often situated where currents accelerate around rock outcrops. Near the end of the dive, we discovered small patches of Calyptogena clams on the seafloor. These clam patches were located on steep, eroded slopes. We collected a few live specimens that confirmed their identity. However, these clam communities did not appear to be robust, and the availability of hydrogen sulfide that fuels their life is probably diminishing. Life is hard for a chemosynthetic clam when the food runs out. 

We recovered Tiburon late in the afternoon so that the pilots had sufficient time to prepare for tomorrow’s dive in the Guaymas Basin to recover instruments that were left by Leg 2 scientists Debra Stakes, Meg Tivey, and Geoff Wheat. The pilots removed the vibracoring system and Niskin bottles, moved the Schilling manipulator arm to the port side (left-hand) of the vehicle and added the Kraft manipulator arm to the starboard side (right-hand) mount point on the vehicle (see right). 

In the laboratory this evening, we examined some of the massive flat rocks we recovered during the second dive today. Testing the rock with dilute phosphoric acid showed that they are comprised of calcium carbonate. The appearance of these rocks is similar to those known to have been formed from methane-derived authigenic carbonate. Further study will be required, but this was a pleasant surprise. 

The misadventures of Pinkie continued today. I spied Pinkie outside the companionway door that leads out to the back deck. I stepped outside, and she was frantic.  

“I want to find Boss, but I’m afraid the dogs will bite me.”  

“What dogs? There aren’t any dogs on this ship!”  


“B-b-b-but, it says ‘Dog Door’.”  

Silly bird. "Dog Door" is a nautical term for latching the door. This notice was placed on the door to remind everyone to dog the door. Pinkie was notably relieved and went inside to search for Boss. But, who is Boss? 

Bill Ussler, reporting


All exterior doors on ships have two dogs (the upper one is shown in this photo). Because minor distortion of doorframes occurs regularly on a rolling ship—especially during storms—ordinary door locks will often fail to keep a door closed. Dogs provide a positive latch that keeps a door secure and watertight under extreme conditions.


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