Archive of October 3rd, 2007

Science Update October 3 by Chuck Blay

Reading a Sedimentary Rock

Sample J2-299-15 was picked up by the ROV Jason 2 from the seafloor about 40 kilometers (25 miles) south of Kauai at a depth of 3200 meters (10,500 feet). The small boulder size sample has a length of about 25 centimeters (10 inches), weighs about 8 kilograms (17.5 pounds) and has a black bumpy surface. In order to examine the sample in more detail we cut it open with a rock saw and discovered that it is actually a sedimentary rock with a complex composition.

(Click on images for higher resolution versions.)

The rock is composed of sand to pebble size fragments (clasts) of basalt that are cemented together by a silty and muddy matrix. Such a sedimentary rock is called a conglomerate if the clasts have rounded edges or a breccia if they have sharp corners. This sample has some of both, so it is sort of a transitional breccia to conglomerate.

Sedimentary rocks like these are a result of a long complex history. A possible history for J2-299-15 is as follows: 1) Basalt fragments were broken or eroded off a volcanic island or smaller seamount. The dense and vesicular lava rock fragments may have come from Kauai where such rocks are as much as 5 million years old or from a much younger (1-2 million years old) submarine volcano. 2) The basalt rock fragments were transported and mixed with sand and reddish mud to form a pebble gravel sedimentary deposit, which then hardened to become a basalt pebble breccia, or maybe conglomerate sedimentary rock. 3) That sedimentary rock was then broken up and transported again to form a new rounded sedimentary clast, the boulder-size J2-299-15 sample. 4) As the rock sat on the sea floor it became coated with a thick black layer of manganese-iron oxide, which grows by chemical/biological precipitation from seawater at a rate of about 2.5 millimeters per million years. The coat on J2-299-15 is about 3 millimeters thick, which indicates that it sat around on the sea floor for over a million years before Jason 2 grabbed it.

Well, that's the simple preliminary interpretation. Additional work on the more precise compositions of the pebbles and matrix and the geological age of the pebbles will give us a better idea of its complex origin.

Teacher at Sea log for October 3rd, 2007 by Linda Sciaroni

Working at sea is both physically and mentally challenging. Some are on a regular schedule of work and time off and others have opted to stay out to sea for six months or more, living all of their life aboard the boat. It is odd to spend all your time with fifty of the same people day in and day out without interacting with anyone else. I have had quite a few belly laughs with crewmembers about how working on a ship would be a good place to go if you were in need of a hideout. No one I met is here to hide out, but each has a story about the ebb and flow of work. Some have earned money non-stop to get over a difficult era; other times they have left this work for a long period to immerse themselves in other activities. Being paid a lump sum for several months of good quality work allowed them to afford wonderful adventures. For example, Casey Agee is about to embark on a journey to volunteer at a school in India, and Thomas Perry took time to train as a Kung Fu Sifu in China. This aspect of life at sea makes these people extremely interesting to spend time with. They have chosen a career that has an interesting trade off between work and rest, family and earning, vocation and avocations.

All of the teams, the scientists, the ship's crew and the Jason team, have full-time employees and contract workers. Contract workers are those who are employed for one project at a time, but are often rehired for future jobs. A few of the people I have met have gone years with no house. Going from sea duty to adventure to boarding hotel and then back to work.

All of the careers, with the exception of the academic researchers, have a career path that could include school and/or apprenticeship. Our captain and his mates reflect these options. Second Mate Liz Scanland began as a deck hand and worked her way up through hours of service and passing exams, Chief Mate Brian Wehmeyer attended the California Maritime Academy and Captain Rick Meyer served in the US Navy for four years. We have included some information about the schooling of the Jason team and the scientists in the biographies section.

Presented by the School of Ocean and Earth Science and Technology at the University of Hawaii, with financial support from the National Science Foundation.