Kathryn Moran of the Bedford Institute of Oceanography in Dartmouth, Nova Scotia, is practically hopping up and down; she has been grinning since the word got out yesterday that the time we had saved at Hole 395A would be devoted to a day of coring. Moran is part of a group of scientists who are on board as advisors to a project, called JANUS, to improve the database that contains the core information. Actually doing it was not part of the plan on this leg.
During the night, we have moved 2.4 nautical miles to a site over what appears to be a small volcano buried beneath the sediment on the seafloor. The area is of particular interest because earlier visits found large amounts of heat flow to the surface. The sediment layer is thin here, so Pollard hopes to be able to drill into the basement rock below, potentially capturing a sediment record of seven million years.
The drill string once grows downward to the bottom, reaching the seafloor in the early morning hours. This time it is headed with an "advanced piston corer." This device is akin to a high-tech cookie cutter. Water pumped down the drill string develops a pressure of 27,000 pounds on a piston that literally shoots the hollow core tube 30 feet into the mud.
Coring does not start immediately, however. The television camera is lowered down to examine the condition of the seafloor. All looks well--the bottom is flat and featureless mud. At 1:30, the site is "spudded"--with a rare bonus. Because the TV camera is dangling off the pipe, we can watch as the bit is rammed deep into the sediment. . This is not a gentle process! Thirty feet of twitching core casing is driven into the mud in three seconds.
After an anxious wait of about an hour as the nearly 3 miles of cable holding the core barrel are reeled in, the core assembly finally reaches the top of the drill string. As the 3-inch diameter plastic tube packed with mud is slid out of the barrel, it is grabbed by eager hands and carried to a long rack that on a balcony a few steps below the drilling floor known as the "core catwalk." It looks like a 30-foot long sausage.
The outside of the tube is quickly wiped down with rags. It is marked off in sections each about five feet long and cut with hacksaws. Brown sticky mud oozes from the ends which are quickly covered with plastic caps. Shorter sections, each about four inches long, are cut from each section--these go to the chemistry lab.
Once the sections have been capped, they are carried into the core lab and placed on racks near the door. They will be allowed to warm from the near-freezing temperature (3 degrees C.) of the seabed before testing begins.
The core lab is the scientific heart of the Resolution. It is not a place to do research, but rather an efficient data gathering operation designed to collect as much information as possible from the fresh cores. Tests are run, samples taken and analyzed in other labs on the decks below, the core characterized. All the data is included in a database for future analysis, linked to the core section, which will be stored in one of four permanent archives on shore. The cores move from station to station and data at each step is entered into the ships computer system.
When the mission is coring, the laboratory becomes a hive of activity, staffed by more than 20 scientists and technicians who process core after core--sometimes miles of it on a leg. Today, however, the crew is made up of whoever is available, including the willing volunteers from the JANUS group. Kate Moran heads the physical testing station. Steve Hurst, a physical geologist from the University of Illinois at Urbana-Champaign stands by to characterize any hard rock. Eve Arnold of Indiana University of Pennsylvania takes over the job of characterizing the sediments.
Mitch Malone, the staff scientist from ODP on board, reverts to being a chemist and backs up the one chemistry technician on board, Chieh Peng. And geologist John Farrell of Joint Oceanographic Institutions in Washington, DC sits in for the paleontologists.
Even with the somewhat impromptu staff, the core sections wend their way steadily from station to station. First Kate Moran inserts a probe that measures the thermal conductivity of the core. Then it is slowly tracked through a series of instruments that record a profile of physical properties. The cores response to magnetic field, gamma radiation, and acoustic signals are mapped.
The core is sliced along its length into two pieces. One half will be used for sampling and testing. The second sealed and placed in an archive. Eve Arnold "reads" the open record of the sediments, entering symbols on an image of a core section in a computer. The type of sediment, presence of inclusions such as pieces of ash or broken rock, are all noted.
A cryogenic magnetometer measures the magnetic field of the core; X-rays and X-ray fluorescence measurements reveal the mineralogy of the sediment. Finally each core section is photographed and sealed for archiving. Until they are unloaded on shore, they will be stored in walk-in coolers in the hold of the ship.
Meanwhile, the paleontologists have washed the silt away from their sample and are making microscope slides of the tiny exoskeletons of ancient diatoms and foraminifera. I look up from a binocular microscope and ask, "How old are these?" "Pleistocene," is the off- handed answer. Well, it is the first core.
The chemists place their samples in a hydraulic press that applies 40,000 pounds of pressure to squeeze out the tiny amounts of water that are trapped in the ancient sediments The chemistry of this water reveals changes that are taking place in the sediments. Water flowing through the sediments also leaves telltale traces.
Before the job is done, seven more cores will be processed, hopefully including one drilled from the hard rock at the bottom of the sediment layer. The core crew will be up most of the night and work into tomorrow. The final core is due on board at about 5 AM.
By Resolution standards, this isn't much. But these scientists are satisfied. Because of an unexpected opportunity they have added a small datapoint to our knowledge of the earth.