DSDP Phase: Glomar Challenger
The Deep Sea Drilling Project (DSDP) was the first of three international scientific drilling programs that have operated over more than 40 years.
It was on June 24, 1966, that the Prime Contract between the National Science Foundation (NSF) and The Regents, University of California was signed. This contract began Phase I of the Deep Sea Drilling Project (DSDP), which was based out of Scripps Institution of Oceanography at the University of California, San Diego. Global Marine, Inc. conducted the drilling operations.
The Levingston Shipbuilding Company laid the keel of the D/V Glomar Challenger on October 18, 1967, in Orange, Texas. The ship was launched on March 23, 1968, from that city. It sailed down the Sabine River to the Gulf of Mexico, and after a period of testing, the Deep Sea Drilling Project accepted the ship on August 11, 1968.
Through contracts with Joint Oceanographic Institutions, Inc. (JOI), NSF supported the scientific advisory structure for the project and funded predrilling geophysical site surveys. Scientific planning was conducted under the auspices of the Joint Oceanographic Institutions for Deep Earth Sampling (JOIDES). The JOIDES advisory group consisted of over 250 distinguished scientists from academic institutions, government agencies, and private industry from all over the world.
Over the next 30 months, Phase II consisted of drilling and coring in the Atlantic, Pacific, and Indian oceans as well as the Mediterranean and Red Seas. Technical and scientific reports followed during a ten month period. Phase II ended on August 11, 1972.
The success of the Glomar Challenger was almost immediate. On Leg 1 Site 2 under a water depth of 1067 m (3500 ft), core samples revealed the existence of salt domes. Oil companies received samples after an agreement to publish their analyses. The potential of oil beneath deep ocean salt domes remains an important avenue for commercial development today.
But the purpose of the Glomar Challenger was scientific exploration. One of the most important discoveries was made during Leg 3. The crew drilled 17 holes at 10 different sites along a oceanic ridge between South America and Africa. The core samples retrieved provided definitive proof for continental drift and seafloor renewal at rift zones. This confirmation of Alfred Wegener's theory of continental drift strengthened the proposal of a single, ancient land mass, which is called Pangaea. The samples gave further evidence to support the plate tectonics theory of W. Jason Morgan and Xavier Le Pichon, which at the time attempted to explain the formation of mountain ranges, earthquakes, and deep sea trenches.
Another discovery was how youthful the ocean floor is in comparison to Earth's geologic history. After analysis of samples, scientists concluded that the ocean floor is probably no older than 200 million years. This is in comparison with the 4.5 billion years of our Earth. As the seafloor spreads from the rifts, it descends again beneath tectonic plates or is pushed upwards to form mountain ranges.
The International Phase of Ocean Drilling (IPOD) began in 1975 with the Federal Republic pf Germany, Japan, the United Kingdom, the Soviet Union, and France joining the United States in field work aboard the Glomar Challenger and in postcruise scientific research.
The Glomar Challenger docked for the last time with the Deep Sea Drilling Project in November 1983. Parts of the ship, such as its dynamic positioning system, engine telegraph, and thruster console, are stored at the Smithsonian Institution in Washington, DC. With the advent of larger and more advanced drilling ships, the JOIDES Resolution replaced the Glomar Challenger in January 1985. The new program, called the Ocean Drilling Program (ODP), continued exploration from 1985 to 2003, at which point it was replaced by the Integrated Ocean Drilling Program (IODP).
Core Samples, Publications, and Data
The ship retrieved core samples in 30 ft long cores with a diameter of 2.5 in. These cores are currently stored at three IODP repositories in the USA, Germany, and Japan. One half of the cores is called the archive half and is preserved for future scientists. The working half of the cores is used to provide samples for ongoing scientific research.
The scientific results from DSDP Legs 1-96 were published in the Initial Reports of the Deep Sea Drilling Project. These reports describe the core materials and scientific data obtained at sea and in shore-based laboratories postcruise. These volumes were originally prepared for NSF, National Ocean Sediment Coring Program, under Contract C-482, by the University of California, Scripps Institution of Oceanography. The printed books were scanned by the Texas A&M University Digital Library and prepared for electronic presentation by the Ocean Drilling Program Science Operator, Texas A&M University College of Geosciences, with funding from NSF in 2007.
Although itself a remarkable engineering feat, the Glomar Challenger was the site of many advances in deep ocean drilling. One problem solved was the replacement of worn drill bits. A length of pipe suspended from the ship down to the bottom of the sea might have been as long as 20,483 ft (6243 m) (as was done on Leg 23 Site 222). The maximum depth penetrated through the ocean bottom could have been as great as 4,262 ft (1299 m) (as at Site 222). To replace the bit, the drill string must be raised, a new bit attached, and the string remade down to the bottom. However, the crew must thread this string back into the same drill hole. The technique for this formidable task was accomplished on June 14, 1970, in the Atlantic Ocean in 10,000 ft (3048 m) of water off the coast of New York. This re-entry was accomplished with the use of sonar scanning equipment and a re-entry cone that had a diameter of 16 ft (4.88 m) and height of 14 ft (4.27 m).
One major technological advance was the introduction of the hydraulic piston corer in 1979, which permitted virtually undisturbed cores of sediment to be recovered. This greatly enhanced the ability of scientists to study ancient ocean environments.
Another technological advance was the extended use of the holes after drilling. Geophysical and geochemical measurements were made during and after drilling, and occasionally long-term seismic monitoring devices were installed in the holes. This extended our understanding of the dynamic processes involved in plate tectonics.
From August 11, 1968, to November 11, 1983 the Glomar Challenger achieved the following impressive drilling accomplishments:
|Total distance penetrated below the seafloor||325,548 meters|
|Total interval cored||170,043 meters|
|Total core recovered and stored||97,056 meters|
|Overall core recovery||57%|
|Number of cores recovered||19,119|
|Number of sites investigated||624|
|Number of holes drilled||1,053|
|Number of expeditions completed||96|
|Deepest penetration beneath the ocean floor||1,741 meters|
|Maximum penetration into basaltic crust||1,080 meters|
|Deepest water (Leg 60 Site 461A)||7,044 meters|
|Total distance traveled||375,632 nautical miles|