Expedition to the Mariana forearc

Mar. 23 - May 4, 2003

Day 15, April 6th

(click on any image for the larger version)

Day 15 Yikes! Stripes!! This is so much fun. Put this on your list of things to do at least once during your lifetime (or make a career of it). It’s easy to enjoy research at sea when the seas are calm, the water clear and the sun shining, but I think I’d be having fun even in rough weather. I’d love to be at the heart of this exciting research but just being an observer of cutting edge science is a total thrill.
Pacman Seamount rocks Pacman seamount rocks
 The piston core at the summit of Ms. Pacman Seamount was deployed at 0200. The scientists were watching the tension display as the trigger core hit bottom followed rapidly by the piston core. As the core pipes were lifted, the tension did not increase as expected when the core pipes are full of sediment and stuck in the mud. Back at the surface, the small sample was mostly small rocks and gravel. The trigger core had dents indicating that it had been hit by the piston core weight stand. The rocks, like the mud, have stories to tell the geologists. They are serpentinized mantle rocks with a fine grain size. The surfaces of these rocks have scrape marks indicating they have been dragged against and past each other, probably in a fault zone.

The maps of the Marina forearc show abundant faults along the range of the mud volcanoes. The faults are breaks in the crust. The crust breaks because it is stretched as the Pacific Plate subducts under the Philippine Sea Plate. It is along these breaks that the serpentine mud of the mud volcanoes finds its way to the surface.

By sunrise the piston core was complete and we were off to Pacman Seamount for more sonar surveys with the DSL-120. Everything is running well and we expect to continue throughout the night.
The other day I was talking to Charlie about trash disposal at sea. Then I start thinking about other waste disposal, like flushing the toilets. When Andy gave us a tour of the engine room that was one of the systems he showed us. Andy laughed as he said his job as an engineer was to make sure, “The light glows, The ship goes, And the sewage flows.”
sewage pipe onboard the ship Sewage pipe onboard the ship
The head in one of the bunkrooms Head in one of the bunkrooms

The toilets operate with a vacuum-flush similar to those used on airplanes. The toilets, sinks, and showers drain to the engine room where the water is treated. The system is called the MSD or Marine Sanitation Device. “Orca” grinds the waste into very fine particles. The technical name for Orca is macerator which means chewer, so Orca (killer whale) is an appropriate name. The waste is then treated chemically and sprayed through a screen which breaks it into even finer particles. If it doesn’t pass through the fine mesh of the screen, it won’t be discharged. The final product is held in a storage tank until it is discharged into the ocean. The ship goes well beyond the distance from shore required by law before waste water is discharged, generally more than 15 miles from land.

Don’t flip out here. It’s legal to dump waste water into the ocean. Many places in the world are dumping untreated wastes right offshore into their own oceans. In Guam we discharge raw sewage at a depth of 60 feet, but that is often less than a quarter mile off the beach. The R/V Thomas G. Thompson and its crew are very concerned and very careful to dispose of waste in a conscientious and environmentally friendly manner.

Science Summary - Days 15 and 16, April 6th and 7th

Science Objectives, Day 15 &16:

The fifteenth and sixteenth days of the cruise, Apr. 6 and 7, after finishing deployment of transponders at the site of Cerulean Springs on Pacman Seamount’s southeast arm. We will do a piston core on the seamount immediately to the south (the grad students nicknamed it Ms. Pacman). We will then do a DSL120 survey of the southeast arm of Pacman Seamount. This will take the remainder of the day and part of tomorrow. After the survey we will do a piston core at Cerulean Springs then move to Conical Seamount to set transponders and navigate them in as the Jason2 group switches the control van from DSL120 operations to Jason2/Medea operations.

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