What Are Cores Anyway? |
Deep-sea cores are long cylinders of
sediment taken from beneath the surface of the ocean floor. 
The coring apparatus is a long hollow pipe lined with plastic tubing
coupled at the top to a weight. The rig is slowly lowered over the side of a
ship, and when it is about 25 feet from the surface of the ocean floor, it is
allowed to free-fall into the sediment. 
The force of the weight
drives the corer into the sediment while a piston riding up the pipe provides
suction to increase the movement of sediment into the tube. The image to the
right is of a linered core being removed from the core pipe. After the cores are
removed from the pipe, they are split vertically into halves so that the layers
beneath the ocean floor are revealed.
Deep-sea sediments contain microscopic fossils of marine animals, volcanic glass, sands originally from land (terrigenous material), cosmic material (microtektites), and other unusual materials unique to a marine environment (such as manganese nodules). The microfossils -- foraminifera, radiolaria, diatoms, etc. -- are important as time and environmental indicators; they are very sensitive to slight changes in temperature and chemical changes in their environment. Volcanic glass is an important "time marker" and records instantaneous geological events. Sands can indicate the presence of ocean currents, tell of ancient shorelines, reveal a past dust storm, or record submarine slides which might indicate submarine earthquakes. Deep-sea samples hold a permanent record of magnetic history revealing to scientists the ever-changing magnetic orientation of the poles.
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For more information, contact Rusty Lotti Bond (curator@ldeo.columbia.edu). Comments are welcomed. Last update of this page was February 20, 1997.