West Coast Expedition
July 20 - August 30, 2002
West Coast of North America

August 6, 2002: Day #18

Diffuse flow vent.jpg
Diffuse flow vent

Ed Delong writes: What brings together a group of ocean geologists, chemists, and microbiologists in the same place at the same time, to combine their skills and perspectives 6000 feet under the sea surface? The answer, it turns out, is that many ocean processes can’t be studied well by any one individual or discipline. Physics links to geology, geology links to chemistry, and chemistry links to biology (and vice-versa, for all the above!). "It takes a village" to completely understand complex, real-world ocean processes. Scientists are only now fully recognizing that many (perhaps most) ocean features, first thought to be solely geological or biological phenomena, actually represent complex, interrelated physical, chemical, and biological oceanographic processes all working together. Today, MBARI’s Western Flyer and tethered undersea vehicle (the ROV Tiburon) visited "off axis" hydrothermal vents, that flank volcanically active spreading centers off the coast of North America. The geologists, chemists, and biologists on board were focused on answering questions that will help explain a number of intriguing puzzles about how geothermally and biologically active areas actually work. The scientists got a fairly easy trip to view these submarine areas today, thanks in part to the advanced MBARI engineering on board the Western Flyer/ROV Tiburon. Additional credit goes to the skilled captain and crew of the Western Flyer, and the pilots who "fly" the ROV Tiburon. These MBARI staff dealt easily with the few minor snags that are bound to pop up on complex operations at sea. Of course, sunny skies and pancake FLAT seas didn’t hurt either (knock on wood!).

Diffuse flow vent.jpg
Lobate flow

Submarine geologists onboard are now working on how submarine regions around geothermal areas form and evolve, and how and where the great amounts of heat produced in these regions are dissipated. Ocean chemists are working to understand the diverse chemical makeup of rocks and vent water, and their relation to the surrounding geological and biological processes. And biologists are trying to puzzle out how microbial populations vary and adapt to diverse subsea environments, and how subsurface chemistry fosters blooms of microbes, and how they in turn can alter ocean chemistry and geology itself. And all these are not studies in isolation, since the information gathered by each scientist has direct bearing on the studies of the others. A unifying principle that brings diverse ocean scientists together is the realization that nature of rocks, water, and "bugs" (microbes) is all interrelated. Chemical changes in underwater rocks are catalyzed by microbial processes, and likely cause much underwater ‘weathering’ (rock breakdown). Microbes themselves can be fueled by the minerals that make up submarine geological formations. Some of these rock-eating bugs can form the basis for underwater food chains, and may change deep ocean chemistry and geological formations in the bargain. Scientists onboard the Western Flyer today saw abundant evidence for this complex interplay of geology, chemistry, and biology. With a little luck and calm seas, more discoveries await underwater explorers charting one of the least understood and largest remaining frontier on our planet.

Cruise Summary: Dive 457

The dive plan for today was to explore a region of extensive low-temperature hydrothermal fluid flow discovered by us in July 2000. The area is about 2 km east of the Juan de Fuca spreading axis and contains hillocks and mounds of broken basalt cemented together by Fe-rich precipitates. Most of these mounds are covered with fluffy green and yellow precipitates that have proven quite difficult to sample.

For today’s dive we carried down quite an arsenal of tools, determined to bring back samples of rocks, mud, precipitates, microbial debris and water. The mounds are more extensive than we thought from our last visit but we had to search a while to find venting that could be sampled. Fluids are seeping from all the cracks in the mounds evidenced by shimmering water that was a few degrees above ambient. The colorful precipitates (orange, yellow, green) are likely rich in Fe and Mn but an unanswered question is the role that microbes play in their formation.

We had to excavate into one of the mounds and place a bucket over the top to focus these fluids enough for the samplers. Finding the site and collecting the fluid and rock samples took several hours. We sent as much as possible back to the surface using an elevator (that got lost for a while but we found it...)

After we finally finished working at the mound, we set off to the east to explore the volcanic terrain and look for more evidence of off-axis eruptions. At the end of the day each of the scientists had to sort out their samples and begin the descriptions.

-- Debra Stakes

Diffuse flow vent.jpg
ROV Tiburon with the toolsled filled with three different types of fluid samplers: two Ti-syringe samplers for major element analyses, two small gas-tight samples for methane and other gasses, two large gas-tight samplers that can be subsampled for both fluids and gases. We also have a modified low-temperature manifold sampler (LTMS) that can collect fluids into plastic tubing that can be filtered for particulates. The basket has a thermocouple tube for measuring temperature and push cores on the side for sediments and glass collection.

The flow rates are so low that we had to make a funnel out of a plastic bucket and then sample the fluids through the hole.

Placing water samplers and rocks into the elevator to send them back to the ship.

Sorting samples from the Tiburon basket


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