by Courtney Flanagan
Once the Gravity Corer is pulled up, the long tube is first detached from the weight. It is then cut into 1.5 meter (5 foot) lengths, and then cut horizontally. One half of the cut tube is then photographed and not touched. It is immediately covered in plastic and refrigerated to be saved and taken back to shore where it will be scanned by an XRF machine to determine its chemical composition, which in turn will give an idea of its mineral content. Before doing any process on the remaining half, geologists describe the color, structure, and type of grain (coarse or fine, muddy or clear, etc.). A band is put on the side of the tube to clarify the depth of each part of the sample. Then the core water is removed with syringe. Studying it gives a history of reactions that have taken place between the microbiology and the minerals. Later the sediment itself is studied. In particular the shells of Foraminifera, essentially tiny snails, give great records of the temperature of the surface water at the time of the snails' death. These carbonate shells contain some Carbon 14, which is radiogenic and thus allow scientists to date the part of the core where the shells are found. In addition, the form of the shells has changed over time so that too gives an idea of the age of the sample.
How far down does the Gravity Corer go?
It doesn't go further down than 5 meters (about 15 feet). Therefore it is only bringing back samples of the sediment on the ocean floor, not of the rock beneath it. However, there are much larger drilling projects that do dig below the sediment into the rock beneath. Recently for instance the Japanese have developed a massive drilling project. As a country that often suffers from earthquakes, a hope is to discover what triggers the "unlocking" of the earth plates. As the plates move, at some point they lock into place. It is when they "unlock" that a huge amount of energy is released which results in an earthquake. If scientists could determine what causes the "unlocking," better warning could be given citizens, just as now can be put out for potential volcanoes.