First, the Panama
Isthmus:
It was on June 24,
1966, that the Prime Contract between the National Science Foundation and The
Regents of the University of California was signed. This contract began Phase I
of the Deep Sea Drilling Project, which was based out of Scripps Institution of
Oceanography at the University of California, San Diego. Global Marine, Inc.
performed the actual drilling and coring.
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 and sailed down the Sabine River
to the Gulf of Mexico on its 15-year-long scientific expedition. After a period
of testing, the Deep Sea Drilling Project accepted the ship on August 11, 1968,
and 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 when Phase
II ended on August 11, 1972, and the ship began a successful scientific and
engineering career.
Glolmar
Challenger awaiting the drilling rig installation on its main deck alongside the docks at Orange, Texas
The Glomar Challenger
was given its name as a tribute to the accomplishments of the 1868-era oceanographic
survey vessel HMS Challenger, with Glomar a truncation of Global Marine—and
its success was
almost immediate. Criss-crossing the Mid-Atlantic Ridge between South America and Africa
and drilling core samples at specific locations, the age of the samples was
determined by paleontologic and isotopic dating studies, which provided conclusive evidence for the seafloor spreading hypothesis, and, consequently, for plate tectonics.
Glomar Challenger during completion of its
main deck and building cranes still affixing final touches
Another ambitious
program was probing into the sedimentary layer of the world’s oceans. Their
objective was to seek answers concerning the geological history and past life
of our planet. The first 12 missions were undertaken in various select
locations within the Atlantic and Pacific oceans. By mid-1979, the emphasis
shifted to the Caribbean Sea east of the Isthmus of Panama. There Challenger hove to and scientists aboard
drilled four holes on the seafloor. After retrieving the sediment cored from
these holes, the Challenger sailed
through the canal to the Pacific side and drilled four more holes in the much
softer sediment of the Gulf of Panama. This Joint
Oceanographic Institutions for Deep Earth Sampling—JOIDES, which includes
Woods Hole Oceanographic Institution and Scripps, recovered samples containing a detailed record of
perhaps the greatest change in the earth's internal boundary conditions in
recent geologic history.
Project Map showing Leg 68 of the
Challenger’s mission that drilled on both the east and west sides of Panama’s
coastal waters
The leg 68 measurements of both sides of the Isthmus of Panama
coastal waters discovered a long believed, but until then unproven idea. Using
the technique of hydraulic piston coring, the disciplines of Paleoclimatology,
Paleoceanography, Sedimentology, and Organic Geochemistry, among others, were
able to determine a wealth of new scientific data and information.
Paleoclimatologists specifically were able to model the climate system that
extends very far back in time, and were able to see how events linked to one
another over time. At the same time, Paleoceanographers deciphered the history
of deep-ocean circulation and identified the forces that drive it.
Left: Driven by water
pressure supplied by large pumps on the deck of the Glomar Challenger, the
hydraulic piston corer thrusts rapidly into 15 feet of soft sediment, and the
core is then retrieved intact; Right: Drilled cores on deck awaiting sampling,
measurement and analysis
Using the hydraulic piston corer
allowed scientists to retrieve pristine, high-quality cores of soft Pacific
sediments, unlike conventional hollow rotary drilling equipment which mashes soft sediment
into a murky paste. Study and comparison of samples from both sides of the
Isthmus of Panama made possible a detailed sediment record which showed that
the isthmus was submerged and rose up to join the South American continent
(closing off the Isthmus) in recent geologic time, which diverted warm,
tropical waters into the Gulf Stream. This compaction, the decrease in sediment
volume through water loss, can tell something about the depositional history of
sediment, and like the telescope revolutionized astronomy in the 17th
century, the hydraulic piston corer will join a list of the inventions that
have allowed science to take quantum jumps to new states of knowledge.
As a result of the Glomar Challenger’s drilling on both
sides of the Isthmus of Panama, it is scientifically proven that the closing of the Isthmus of Panama and the
isolation of two great oceans occurred in recent geologic time and that once
separated, the Panama Isthmus rose up to join with South America above the
surface, isolating the Pacific Ocean from the Atlantic Ocean for the first
time.
(La Brecque, “Coring Near the Mudline,” Mosaic,
September/October 1981, pp 3-4(7), in conjunction with The National Science Foundation and the Division of
Ocean Drilling Programs)
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