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Frontiers
Core on deck!
September/October 1998
With that summons, crew,
technicians and scientists rush to the drilling deck of the 469-foot-long research
vessel JOIDES Resolution, the world's largest scientific drillship. JOIDES
Resolution is the flagship of the international Ocean Drilling Program
(ODP), which explores the evolution and structure of Earth. With this ship, scientists
can drill cores--long cylinders of sediment and rock extracted from beneath
the seafloor--in water depths of more than five miles.
"For the past 30 years, scientific ocean drilling has been the inward-looking ‘telescope' by
which we've studied how Earth works as a dynamic planet," explains
Roger Larson, former chairperson of ODP's U.S. Science Advisory Committee
and a geologist at the University of Rhode Island. "ODP research has brought
us many unexpected discoveries, for certainly 30 years ago, no one predicted
ocean drilling's amazing sea stories."
Robert Corell, assistant director for the Geosciences Directorate at NSF, which
funds a majority of the program, adds, "ODP is a beacon of success in
the geosciences. It brings together people from many different cultures, and
from that mix come wonderful results."
"ODP shrinks the world," agrees Bruce
Malfait, director of ODP at NSF. "It's one of the largest
geosciences programs on Earth, and, with many countries participating
in its efforts, it's truly larger than the sum of its parts." Joint
Oceanographic Institutions (JOI) Inc., in Washington, D.C., under contract
to NSF, acts as program manager of ODP, with Texas A&M University
in College Station, Texas, serving as science operator under subcontract
to JOI. The Lamont- Doherty Earth Observatory in Palisades, New York,
is also a subcontractor to JOI; it provides the program with services
such as logging of downhole measurements and management of ODP's
site survey data bank.
Aboard JOIDES Resolution, the "core
on deck!" cry announces that a 31-foot-long section of ocean sediment
or rock is being hoisted from the water. Once the core is safely aboard
ship, scientists carry the plastic-sheathed cylinder to the first of many
laboratories in which it will be studied. Geologists then begin reconstructing
another chapter in Earth's history.
FROM SOLID CORE TO EMPTY TUNNEL
Scientific investigation doesn't stop with the cores themselves.
Once they have been extracted from drill holes, the empty "tunnels" left
behind become laboratories. In a process called downhole logging, scientists
lower instru- ments into drill holes to record the physical and chemical
properties of the surrounding rock. Afterward, some holes may become sites
of long-term observatories. Instruments that measure temperature and pressure,
and that take water samples, remain in the boreholes for several years after JOIDES
Resolution has left the site. Data can be retrieved from these
sub-seafloor observatories using remotely operated vehicles or by submersibles.
It was through results of this type of
research done by scientists affiliated with ODP, and with its
predecessor, the Deep Sea Drilling Program (DSDP), that the
theory of seafloor spreading was proven. Plate tectonics, as
the process of formation and subduction of Earth's crust
is now known, is nearly a household word. "But without
findings derived from core samples taken far beneath the bottom
of the sea," explains Malfait, "it's doubtful
that plate tectonics would be what it is today: the base upon
which the earth sciences are built."
ODP scientists have made a long list of discoveries
in the last three decades: hot springs that bubble up from the center
of Earth's seafloor spreading ridges with deposits of iron, copper
and zinc flows... enormous plumes of rock that rose eons ago from beneath
Earth's surface, triggering volcanoes...a deep biosphere in the
oceanic crust, which may contain most of Earth's biomass...undersea
volcanoes oozing with green mud, instead of molten lava.
"All this would have been considered science
fiction three decades ago," says Larson. After more than 180 DSDP
and ODP expeditions, scientists now believe that these amazing sea stories
are true.
OCEAN DRILLING'S EARLY DAYS
In 1957, two well-known oceanographers--Walter Munk of the Scripps
Institution of Oceanography in California and Harry Hess of Princeton University--proposed
developing a capability to drill deeply into the Earth beneath the seafloor,
allowing oceanographers to sample the material below the boundary of Earth's
crust and mantle, called the Moho. Their efforts eventually led to Project
Mohole, an attempt to acquire a ship that would let researchers drill into
the Moho. Cost escalations eventually killed the project.
The remnants of Project Mohole became the four-institution-member
Joint Oceanographic Institutions for Deep Earth Sampling (JOIDES), forerunner
of present-day JOI. JOIDES was awarded a contract by NSF to establish
the Deep Sea Drilling Program in 1966. DSDP gave way to ODP in 1983. Since
then, many ODP "legs," as the two-month-long expeditions are
known, have resulted in spectacular scientific revelations.
Leg171B
ODP's leg 171B focused on a location
in the Atlantic Ocean 300 miles off Florida. Scientists sailing on this leg
uncovered dramatic support for the long-standing theory that a large asteroid
slammed into Earth about 65 million years ago, at the Cretaceous/Tertiary
(or "K/T") geologic time boundary. This event, geologists believe,
caused extinctions of some 70 percent of all species on Earth, including the
dinosaurs.
Leg 171B researchers recovered cores that reveal "a
cataclysmic story of destruction and biotic upheaval," says the
leg's co-chief scientist, Richard Norris of the Woods Hole Oceanographic
Institution in Massachusetts. "The story is clearly evident in the
layers of sediment: from before the catastrophe, to debris from the vaporized
meteorite, to the time when survivors of the fireball repopulated the
oceans."
Leg 150
Layers of sediment buried off New Jersey
and retrieved aboard leg 150 tell a tale of another eon long past. Greg
Mountain, geophysicist at Columbia University's Lamont-Doherty Earth
Observatory in New York, was one of several scientists to discover a history
of global sea-level changes ranging back some 35 million years. "This
history holds clues to what might happen to coastal areas if global climate
change continues to result in rising sea levels," says Mountain. "Reading
the sediment layers, we gained clear insights into how large, rapid global
sea-level changes result from waxing and waning of ice sheets. These changes
have occurred over periods that are beyond most people's time-frames,
but we can learn information from them that's important to us today."
Leg 82
Evidence uncovered on leg 82 is perhaps
a look into the future rather than the past, says geologist Martin Fisk
of Oregon State University. Until recently, conventional wisdom held that
Earth's subsurface was sterile, devoid of life. But on leg 82, during
drilling at a location west of the Mid-Atlantic Ridge, scientists found
evidence of organisms living deep beneath the seafloor. Fisk believes that
microbes live on and in volcanic glass, "a material that one would
think would be inhospitable to life. But microbes may well be ‘eating' the
glass, using it as an energy source. Life forms that derive their energy
from inorganic chemical reactions suggest that life may thrive in previously
unsuspected places."
Leg 164
In another amazing discovery, ODP scientists
on leg 164 learned that the world's largest potential source of fossil
fuel remains buried in places like the Blake Ridge off the coast of North
Carolina. Enormous volumes of natural gas are stored in marine sediments
as gas hydrates, explains Charles Paull, a geologist at the University of
North Carolina at Chapel Hill. Gas hydrates are icelike deposits of crystallized
methane and water that form under the high pressures and frigid temperatures
of the deep sea. Large fields of methane hydrates are scattered throughout
the world's oceans, and are thought to contain as much energy as all
other forms of fossil fuel combined. "This unconventional energy source
has remained untapped, however, because traditional sources are still plentiful
and less expensive to develop," says Paull. Based on the 1996 rate
of U.S. energy consumption, Paull and his colleagues estimate that the methane
hydrate field off North Carolina contains enough fuel to meet U.S. energy
needs for 105 years.
DRILLING INTO THE 21ST CENTURY
What's next for ODP? According to Malfait, continued exploration
of the dynamics of Earth's environment, including its changing climate.
Adds Katherine Moran, ODP director at JOI, "We're preparing
for a future that will use several drilling platforms. This new ocean drilling
program will provide us with the technology needed to broaden the scope
of our research, especially in the areas of the deep biosphere, paleoceanography,
and drilling in the arctic region."
No one predicted the current results when the program
began. Larson muses, "The question of what to expect from ODP in
the future is perhaps best answered with a remark made by Wilbur Wright
in 1908: ‘We can see enough now to know that the next century will
be magnificent; only let us be the first to open the roads.'"
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