Editor's Note: Peggy Delaney is sailing on a newly refurbished research vessel, the JOIDES Resolution, that left Honolulu on March 10 with an international group of researchers on board. The ship, supported by the U.S. National Science Foundation, conducts scientific investigations beneath the seafloor by drilling the ocean floor and retrieving long “cores” of mud for testing and data collection. This is her ninth blog post. To see all her posts, see "60 Seconds in the Mid-Pacific."
SOMEWHERE IN THE EQUATORIAL PACIFIC (April 18, 2009)—I am definitely at the "Will it never end?" stage of the cruise. I have been studiously ignoring the count of days that many folks keep, and that I have kept on other cruises. Counting forwards or backwards from the trip's 56 days, or so, just seems long, no matter which way you go. We are at our last site, nearly finished with the first hole. I let down my guard and let someone tell me how many days are left—16, plus a wake-up. This seems achievable, but still long.
We are at the last site of the five for this expedition, and we are nearly finished with the first of three holes at this site. Each location that we drill is called a "site". Basic data characterizing each site—the seismic profiles used to image material below the seafloor at this site and its surroundings, a short core of the kind that can be taken by other ships—were all collected much earlier. These were carefully scrutinized as they were used to justify "Why drill there for that set of scientific objectives?"
Once we get to a site, we start coring in a particular hole at that site, lettering these with alphabetic numbers. And by this time in the cruise, every snicker and joke to be had in any discussion of the "A-hole" characteristics has long ago lost its charm for anyone! We proceed taking one approximately 9.5-meter (30-foot) core at a time down the depth of the hole. Our favorite words—the best words in scientific ocean drilling—are the two pages from the driller: "core on deck in five minutes," and "core on deck," signaling the arrival of our next increment of ocean history on the rig floor.
Ocean sediments arrive in the clear plastic liner tubes extracted from the core barrel—handed over from the rig floor crew to the technical science crew—being carried by five or six of the technical staff high above their shoulders, near ear height, in a repeated ritual. The core is laid out in special holders on the core-receiving catwalk. Each 9.5-meter core is split into 1.5-meter (five-foot) sections there, after any special sampling, to work its way through the labs and into boxes to be shipped home eventually.
After each core in a hole is taken, the drill string is advanced by that length and the next core is taken. Core by core, we build a stratigraphic section for this site. We know, well-demonstrated by past experience, that the coring process itself misses out some material in the spaces between the cores—the core gaps. After we core to the defined depth objective at the site in the first hole, the ship moves position a few tens of kilometers to the next hole at this site. Same site, different hole—the second one at a site is the B-hole. We typically core at least three holes at each site when we are really interested in building a complete sedimentary section. Through the use of shipboard, rapidly made, [and] nondestructive measurements on the sediment cores, we can align the coring on the second and third holes to just fill the gaps created in the intervals between cores.
We are at the start of this process for the last site, just about to finish the first hole. This will start the downhill run of this expedition. We are finishing up revisions of the site reports for the earlier sites, and we are writing the site report for the last site, all while we collect the data and make the necessary interpretations for this site. Lots to finish, [and] a finite amount of time to do it in.
Soon, we will face shore and our lives at home. We will have been gone a long time and we have been a long way from anywhere. Right now, we are [about] 1,700 kilometers (1,000 miles) from San Diego and [around] 1,900 kilometers (1,200 miles) from Tahiti. I can't remember how far we are from Honolulu, but I know it will take about nine days of steaming to get there. So, with all the "Will it never end?" it also makes me think, "The end is too near," in terms of finishing all the science, and in terms of leaving this mobile home behind.
Paleomagnetist Yuhji Yamamoto (Kochi University, Japan) collects a cube sample from the working-half section of a core to study its magnetic properties, courtesy IODP