A Sea Change in
Scientists launch a new drill ship and ambitious research plans
|Since 1985, the research
vessel JOIDES Resolution has been the workhorse
for scientific ocean drilling. Through 2003, the 470-foot-long
with its 202-foot derrick has drilled more than 1,800
holes in the ocean crust and retrieved samples at some
670 sites. Photo courtesy Ocean Drilling Program. Enlarge »
In the early 1960s,
geologists took their first shot at drilling all the way
through Earth’s crust and into its mantle with the
Mohole Project. It turned out to be a disaster. Named for
the Mohorovicic discontinuity, the boundary between
the crust and mantle, the ambitious attempt to penetrate
6 kilometers of crustal rock was sunk by cost overruns and
management problems and scrapped after a few test holes.
But out of that debacle came a highly successful international
scientific endeavor. The decision to drill Mohole from a
barge—to take advantage of the fact that the oceanic
crust is much thinner than the continental crust—laid
the foundation for modern-day scientific ocean drilling.
And researchers have exploited the world it opened up to
make seminal discoveries about the planet. Now, those efforts
are about to enter a new era.
Over the past 40 years, researchers have drilled more than
2,900 holes in the ocean floor, retrieved 319 kilometers
of mud and rock core, and studied 35,000 samples. The legacy
of ocean drilling includes validating the theory of plate
tectonics and tracing Earth’s changing climate back
100 million years, as well as inventing the field of paleoceanography.
Since 1984, that work has been carried out under the 22-country
Ocean Drilling Program (ODP), a unique effort that ended
in September, 2003. But it will be replaced by something
even more ambitious: In October 2003, Japan and the United
States inked an agreement formally creating the Integrated
Ocean Drilling Program (IODP). It will eventually include
20 or so other countries, cost twice as much to operate as
its forerunner, and use two, and at times three, ships rather
Initially, IODP will rely on an upgraded U.S. drill ship,
either a revamped version of ODP’s workhorse, the JOIDES
Resolution, or a new vessel with similar capabilities. By
it will be joined by a brand-new ocean drilling vessel, Japan’s
Chikyu, equipped with technology that will allow
it to literally break new ground.
Together, the two ships will enable earth scientists to bore
more and much deeper holes than is currently possible and
in locations that are now inaccessible. There are even going
to be “mission-specific platforms” that will
drill niche locations such as the icy Arctic Ocean and shallow
|The Integrated Ocean Drilling
Program’s new drill ship Chikyu (“Earth” in
Japanese) is launched in Tamano-shi, Japan, in January
2002. The 57,500-ton, 210-meter (689-foot)-long ship
will be capable of drilling 7 kilometers (4.35 miles)
below the seafloor—sufficient to reach the mantle.
Its derrick was installed in September 2003 and after
sea trials, Chikyu should be ready by late 2006.
Photo courtesy Japan Marine Science and Technology Center
and the Integrated Ocean Drilling Program. Enlarge»
|Drilling the Seafloor. Interactive »
|Rig floor personnel aboard JOIDES
Resolution work round the clock recovering rock
and sediments from the seafloor. Cruises usually last
two months, with 50 scientists and technicians and
65 crew members aboard, including rig operators, catering
crew, and merchant seamen. Photo courtesy Ocean Drilling
|Teams of scientists
study seafloor core samples in sequence to reconstruct
events and phenomena over millions of years of Earth
history. Photo courtesy Ocean Drilling Program. Enlarge»
A new drillship for a new era
The biggest change in operational capabilities will come
when the 210-meter, 57,500-ton, $475 million Chikyu starts
drilling. For all its achievements, the Resolution has serious
limitations. It can’t drill in shallow water or farther
down than 2 kilometers. Nor can it tolerate the icy conditions
of the Arctic Ocean. What’s more, sedimentary basins
have been largely off-limits because oil and gas deposits
have posed safety and environmental hazards.
The Chikyu will overcome some of these constraints. It will
have a second pipe, called a riser, that will enclose the
drill pipe and allow circulation of a heavy but fluid drilling
mud that will flush debris from deep holes and shore up unstable
sediments. The arrangement will also protect against blowouts
when the bit penetrates pressurized oil or gas deposits.
Attempts at drilling very deep holes using the Resolution were frustrated by the friction and by debris piled up in
“Because of the capabilities of the riser vessel, [all sorts
of drilling] projects will be more viable,” said Hisatake
Okada, a paleoceanographer at Hokkaido University in Sapporo.
But all of this comes at a steep price. The annual budget
of ODP ran about $80 million, with 60 percent of that sum
put up by the U.S. National Science Foundation (NSF) and
the rest split among the other member countries. Countries
additional funds to support scientists analyzing drilling
samples and data.
In comparison, IODP’s annual operating budget is expected
to start at $160 million and rise depending on the amount
and nature of drilling carried out. Japan and the United
States will split at least two-thirds of the operating costs
equally, with other countries providing the rest—and
also funding mission-specific platforms.
Researchers are arguing that the scientific advances will
be worth the price, from a better understanding of earthquake
mechanisms and the history of global climate change to the
discovery of new energy sources and unusual microbes for
use in biotechnology. And governments so far seem convinced.
Exploring large igneous provinces
Ocean drilling’s first significant achievement came
in geophysics. “Past successes have changed our understanding
of how Earth works,” said oceanographer Larry A. Mayer
of the University of New Hampshire, Durham. By dating rock
recovered from numerous seafloor locations, researchers in
the early 1970s confirmed the basic cycle of plate tectonics:
New ocean crust forms at mid-ocean ridges and spreads outward
toward deep-sea trench subduction zones. Crustal drilling
also showed how great upwellings of hot rock, called plumes,
could create chains of islands and seamounts such as Hawaii.
These discoveries have raised new questions about solid earth
cycles and geodynamics, one of three broad themes in IODP’s
initial science plan. Earlier drilling showed that large
parts of the crust were formed by anomalous volcanic events
separate from plate tectonics.
Oceanic plateaus, so-called large igneous provinces, mostly
formed during the mid-Cretaceous period 100 million to 140
million years ago when massive amounts of material burst
through tectonic plates, venting heat and magmatic gases
from Earth’s interior. These features have as yet been
barely sampled by drilling. Researchers hope that data from
a combination of numerous shallow holes drilled by a riserless
ship and deep holes drilled later by Chikyu may
relate these events to Earth’s evolution and reveal
whether or not they triggered climactic changes that led
to mass extinctions.
Another major geophysical target will be subduction zones,
where the clash of sinking and overriding plates generates
90 percent of the world’s earthquakes. Chikyu’s
first target, reached by consensus, will be the Nankai Trough
subduction zone offshore of Honshu, Japan’s main island.
Chikyu’s riser will allow boring through the
deep sedimentary deposits atop overriding plates. Those deposits
to the Resolution because of the danger of a blowout caused
by inadvertently tapping into oil and gas deposits and by
the depth of the fault target.
Gaku Kimura, a geologist at University of Tokyo, says Chikyu
will also be able to install a new generation of instruments
in the bore hole to monitor fault zone temperatures, stresses,
deformation, and fluid pressures.
“This is a completely different scientific approach” to
studying rock samples, said Kimura. “It’s like
the difference between studying a live human being and dissecting
a corpse.” An improved understanding of earthquake
mechanisms could help Japan and other onshore communities
assess the risk of future earthquakes.
IODP may even take another shot at penetrating the Mohorovicic
discontinuity. With the lubricating drilling mud circulating
riser, Chikyu should be able to reach 6 kilometers and into
the upper mantle. Such a hole would help refine knowledge
of the structure, composition, and physical properties of
the oceanic crust.
Probing climate changes on Earth
Although geophysics was the prime motivation for the first
ocean drilling cruises, scientists in other disciplines soon
capitalized on the data obtained from the cores. “Paleoceanography
is one of the strong successes of ocean drilling,” said
Jerry McManus, a paleoceanographer at the Woods Hole Oceanographic
Institution in Massachusetts.
Paleoceanographers recognized that cores recovered from layered
sediments provided clues to a variety of climatic phenomena,
sometimes going back 120 million years. McManus credits ocean
drilling with clinching the orbital theory of climate change
over millions of years, when Earth’s wobbling drove
climate oscillations. It also documented extreme climates
such as the thermal maximum of the late Eocene (55 million
years ago) and rapid climate change.
But the use of drilling for paleoceanographic studies has
been held back by the limitations of the Resolution. It cannot
drill in water much shallower than 100 meters, ruling out
the inner continental shelves and coral reefs that hold long
records of climate and sea-level change. And it can’t
handle more than the passing bit of sea ice, which has kept
it entirely out of the Arctic Ocean.
“You could lay out all the existing Arctic cores in
my office,” said
oceanographer Theodore Moore of the University of Michigan,
Ann Arbor. A successful mission to the deep Arctic, he said,
would provide “an entire history from 50 million years
ago to the present.”
Under IODP’s initial science vision, mission-specific
platforms capable of drilling in niche locations would play
a major role in studying environmental change, processes,
and effects. European scientists, for example, have obtained
sufficient funding to send a drill ship to retrieve long
sediment cores from the Arctic Ocean in the summer of 2004.
Seafloor fuel, sub-seafloor life
The third leg of the IODP scientific tripod, studying the
deep biosphere and the sub-seafloor ocean, is also the newest.
The original ocean drillers never imagined there could be
life within the extreme temperatures, pressures, and chemical
environments of the ocean floor. But reports of microbial
colonies at seafloor vents and volcanic rifts demonstrated
otherwise. Now some experts in extremophiles, as these microbes
are called, believe that as much as two-thirds of Earth’s
microbial population may be buried in oceanic sediment and
One major challenge will be to define the range of temperatures,
pressures, chemistry, and other conditions under which these
seafloor communities thrive and to map their geographical
distribution. Researchers would also like to clarify whether
these microbes get their nutrients from material that filters
down from the surface or from updrafts of fluids flowing
through the interface between sediments and hard rock.
The findings “could revolutionize ideas about the origins
of life,” said Asahiko Taira, director-general of the
Center for Deep Earth Exploration at the Japan Marine Science
and Technology Center. Researchers also hope to add to the
handful of industrially useful microbes already isolated
from deep-sea regions.
Another underresearched area of inquiry is gas hydrates,
deposits of ice-encapsulated methane. Although a potential
new source of clean energy, they also could release a significant
amount of greenhouse gases into the atmosphere if thawed
as a result of global warming. Scientists want to learn how
microbes generate the methane, how hydrates form, and whether
methane can be produced at prices competitive with those
of other fuels.
These intriguing questions weren’t even on the radar
screen of those working on the ill-fated Mohole Project.
But if IODP comes up with some answers, its scientists will
owe a debt of gratitude to those who conceived and carried
out the first scientific attempt to probe what lies beneath
Earth’s oceanic crust.
Reprinted and adapted with permission
from “A Sea Change
in Ocean Drilling,” Science 300:410-412 © 2003,
American Association for the Advancement of Science.
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Posted: Mar. 31, 2004