What's Happening Today - Nov. 11

I thought it might be instructive to provide a bit of background on the research that has been done in this area of the East Pacific Rise (EPR) crest between the Clipperton and Siqueiros transforms. The EPR was first mapped back in the 1960s by Prof. Henry Menard of Scripps Institution of Oceanography. Since that time this part of the mid-ocean ridge (MOR) has been surveyed extensively with standard 12 kHz echosounders and, since the early 1980s, using multibeam sonar. For over two decades, numerous investigators from a wide range of universities around the US and the world have worked in this area mapping the bathymetry and shape of the ridge axis and flanks using various sonar systems, and sampling the seafloor with various devices.

In 1989, Prof. Rachel Haymon (of Univ. of Calif.-Santa Barbara) and I carried out the first detailed survey of the EPR axis from about 9° 08'N to 9° 55'N using WHOI's ARGO towed mapping system. We mapped the seafloor using a 100 kHz sidescan sonar, video cameras and digital electronic still photographs. Based on our analysis of those data, Rachel and I returned to the EPR in 1991 and carried out the first Alvin diving program on the ridge axis in this area. Our intention was to map the volcanic geology and hydrothermal vents along the ridge crest that we surveyed in 1989. We did that and more. What we did in April of 1991 was serendipitously encounter, during our Alvin dives, the first deep sea volcanic eruption along a mid-ocean ridge. This was the first time anyone had witnessed the effects of lava erupting at 2500 m on the MOR axis. Since that ground- breaking expedition there have been hundreds of submersible dives and dozens of research cruises to this site. These have been dedicated to understanding how the seafloor is created at the ridge crest, the types of volcanic rocks erupted there, and the chemical and biological processes associated with hydrothermal venting along the ridge axis. We're glad to have the opportunity to be back at this site to further our knowledge and test our hypotheses about how the ocean crust is created at a fast-spreading MOR. More about our particular research problems in the coming days.

Today we finished Line #3 of our sonar survey and recovered the sonar fish. During the day ABE was readied for it's test dive. As I type ABE is being launched for a pre-programmed track that will take it on an approximately 8 kilometer survey of the seafloor near the EPR crest at 9° 50'N. We'll let you know tomorrow how it all worked out.

I thought it would be fitting to have Brooke Stembridge, a student of Rachel Haymon's at the Univ. of California-Santa Barbara, write about her first few days of this research expedition.

Best Regards,
Dan

My experience at sea so far has been amazing. I love the wildlife that surrounds us from the dolphins and pilot whales, to the booby birds out in the ocean that are making the ship their temporary home. Watching the moon rise and the stars come out at night is absolutely incredible when you are at sea. It gives me a sense of freedom to see nothing but the Pacific surrounding us, and at the same time it is humbling to realize exactly how much ocean is between our ship and the nearest land! I feel that I have already learned so much from the scientists on board because we are living together in such a unique environment. It is wonderful how eager everyone is to answer my questions whether it is over dinner or a 4am shift when most of us would rather be in bed. Sleep here becomes very precious and you get it whenever and wherever you can. Even then, it can be challenging to fall asleep, like the other night when the ship was driving backwards for the DSL-120 surveying and I was airborne each time a wave blasted the stern! This is definitely an
experience I will never forget!

-Brooke Stembridge

A location map showing the eastern Pacific and the East Pacific Rise - the plate boundary between three plates - Pacific, Cocos and Nazca. In the area where we are working, between 9°N and 10°N, the EPR separates the Pacific and Cocos Plates. This section of the EPR axis is between two transform faults, the Clipperton (Clip. on the map) and Siqueiros (Siq. on the map) and is spreading at a full rate of about 11 cm/yr. The arrow points to the area along the ridge crest where we are surveying.

Brooke Stembridge taking a break on the rowing maching in the excercise room on R/V Atlantis.

The depressor weight of the DSL-120A sonar being lifted on board. The depressor, also nicknamed the "batfish", is used to help dampen the effect of the waves and swell on the motion of the sonar fish at depth. The fiber optic cable runs from the ship to the depressor, and then the sonar fish - which is neutrally buoyant - is towed behind it. Gary Austin is directing the recovery operation with Patrick Hennesy, the Bosun (far right).

The depressor "batfish" being secured on deck.

After the depressor is on board, the DSL-120A sonar fish is raised to the surface and the small crane on the port aft quarter of Atlantis is used to bring it on board.

The DSL-120A sonar fish being landed on deck. Thanks to the DSOG and deck crew for doing such a great job.

Gary Austin (right), Ed Popowitz (left) and Dave Sims (background) were part of the team that recovered the sonar fish today.

The Galley Crew on R/V Atlantis. Carl Wood (left) is the Steward, Linda Bartholomee is the Mess Attendant, and Jay Grant is the Cook. These folks do a terrific job keeping us well fed, healthy, and in good spirits during the cruise.

ABE getting some last-minute adjustments by Rod Catanach (left) and Andy Billings, both underneath the lower pod.

Al Bradley 'speaking in tones' to ABE. He and Dana Yoerger tested ABE's acoustic links today by tapping on the tuning chimes which produce tones at the specific frequencies that ABE communicates on.

Al Duester helping out with preparing ABE for its test dive.

Patrick Hennesy, the Bosun, and Christina Courcier, one of the SSSG techs. relaxing with a game of ping-pong in the Main Lab.

Margo Edwards boxing with Alvin's port (left) manipulator. The boxing gloves are put on the claws of each manipulator so no one bashes their heads on them as they are working around Alvin's basket.

Bob Waters working in the Main Lab. He is figuring out the wiring for a deep sea camera that we hope to use during the cruise.

ABE headed for the seafloor this evening.