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Ocean drilling program.

THE OCEAN DRILLING PROGRAM (ODP) sponsors an international partnership of scientists and governments to explore Earth's origin and evolution beneath the seafloor. Scientists sail the world's oceans in a continuous series of cruises aboard the drill ship JOlDES Resolution to retrieve long cylinders of sediment and rock samples, called cores, from beneath the seafloor. In addition, an extensive program in downhole measurements obtains geophysical data from the drilled holes.

On each cruise, ODP addresses specific problems concerning how the biosphere, atmosphere, ocean, crust, and mantle interact through time. The program's four broad areas of interest are tectonic evolution of passive and active margins, origin and evolution of oceanic crust, origin and evolution of marine sedimentary sequences, and paleoceanography.

The 143-meter JOIDES Resolution, officially registered as Sedco/BP 471, carries a scientific and technical party of 50 supported by a 68-member crew. The ship is outfitted with the most modern communications, navigation, computer, and geological and geophysical research equipment.

Plans for an ODP cruise begin many years before drilling. During the early stages, scientists from different disciplines meet to discuss both the geological theme of the cruise and the specific geographic area to be drilled. From these meetings, the scientists outline scientific objectives and propose drilling sites. Then they establish a general ship's track and begin formal plans for drilling. A survey is usually conducted by another research vessel to help select sites that are the most valuable scientifically and where no hydrocarbon accumulations will jeopardize the safety of the ship or the environment.

About a year before a cruise, ODP chooses two co-chief scientists, and then other cruise participants are identified based on their expertise and interest in a field important to the scientific objectives of the cruise. Several months after a cruise, a preliminary report is published in Initial Reports of the Proceedings of the Ocean Drilling Program, and some months later the scientific results of the cruise, including shorebased studies of samples and data, are published in ODP Proceedings.

ODP cruises generally last about two months. While on site, drilling continues 24 hours a day. Many lengths of 9.5-meter drill pipe are attached together to lower a large drill bit to the seafloor. This takes about 12 hours in 5,500 meters of water. Core barrels are then lowered through the drill pipe to receive and contain the core material. When a length of about 9.5 meters has been drilled, the core barrel is raised to the ship, where technicians recover the long cylinder of sediment or rock, cut it into 1.5-meter sections, and begin documenting and describing its origin, appearance, and contents. Deep holes may require several changes of drill bits; for each change, the drill string is brought back aboard the ship, pipe by pipe, and then reassembled as the new bit is lowered. A reentry cone facilitates relocation of the hole with a sophisticated system of scanning sonar equipment and an underwater television camera.

Seven laboratory levels occupy 1,115 square meters aboard JOIDES Resolution to provide space and equipment for studies in sedimentology, paleontology, petrology, geochemistry, geophysics, paleomagnetics, and physical properties. Following routine whole-core analysis, each core is split lengthwise and one half becomes the working section, the other the archive section. Small samples of the working half are removed according to the cruise sampling plan and the dictates of direct observation. The archive section is photographed and rigorously described before it is boxed for long-term, refrigerated storage. As technicians complete initial analyses of each core, the data are entered into the central computer for display on terminals throughout the laboratory complex. Scientists working anywhere on the ship can track the arrival of new samples and become immediately involved in their analysis.

Since 1985, ODP has recovered more than 77,500 meters of cores from 683 holes at 279 sites. Nearly 50 cruises have taken JOIDES Resolution to sites in the Atlantic, Pacific, northern and southern polar, and Indian oceans. Thousands of core samples have been distributed to investigators in more than 38 countries. ODP scientific accomplishments include new understanding of the causes and history of ice ages, the evolution of continental margins, Earth's tectonic processes, marine sedimentation, and the origin and evolution of oceanic crust. The US National Science Board recently recommended renewal of the program for another decade.

ODP is funded by the US National Science Foundation and contributions from 18 other ODP member countries. Nationally, 10 major oceanographic institutions comprise Joint Oceanographic Institutions Incorporated, which manages ODP. Internationally, a group of scientists provides overall planning and program guidance through the Joint Oceanographic Institutions for Deep Earth Sampling organization. Texas A&M University (TAMU) is the ODP science operator and ship manager, and the Lamont-Doherty Geological Observatory (L-DGO) maintains all aspects of wire-line logging data from JOIDES Resolution cruises and combines them with the archived data from the Deep Sea Drilling Project, ODP's predecessor. Cores are archived at TAMU, L-DGO, and the Scripps Institution of Oceanography of the University of California, San Diego.
COPYRIGHT 1992 Woods Hole Oceanographic Institution
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Author:Cullen, Vicky
Publication:Oceanus
Date:Dec 22, 1992
Words:834
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