seismic and geodetic data continuously real time from
boreholes (e.g., DONET (www.jamstec.go.jp/donet/e/),
NEPTUNE Canada (www.neptunecanada.com)).
The main objectives of developing CORK (Circulation
Obviation Retrofit Kit) technologies for enabling time
series observations have been to identify and quantify
sub-seafloor fluid flows and associated processes where
physically focused flows may be expected such as in the
vicinities of ocean ridges (thermally driven flows) and
plate subduction zones (tectonic compaction).
In order to observe in situ fluid flow and estimate flow
rates and permeability with minimum disruption, CORK
design is intended to seal holes and control perturbation
originally at the seafloor and subsequently evolved to
enable multilevel isolated zones inside the borehole.
The observation parameters expanded from original pressure and temperature to chemical and biological sampling.
It has been proven that these borehole observations not
only provide permeability to be estimated from tidal
responses but also function as volumetric strainmeters at
a microstrain level (Davis et al., 2001). Transients such
as associated with seismic events can be registered (Sites
1173, 1255). Furthermore, the temperature and pressure
series from multiple CORK observatories where observations can be correlated, combined with the subsurface heterogeneous structure, can provide 4-D flow pattern (Holes
1026B, 1027C).
Conclusions
The ocean floor constitutes the top of the oceanic plates
created by seafloor spreading and destroyed by plate subduction as part of the mantle convection. At the same time,
the ocean floor is the bottom of the water column that
hosts the thermohaline “conveyor belt” ocean circulation
system and ocean currents. The chronological records of
these processes are kept in the sediments and crust to be
explored by ocean drilling. Ocean drilling provides ways
to retrieve such information from sub-seafloor core samples and data to better understand how these systems operate and interact with each other.
Ocean drilling has evolved from the early days of
exploratory stage to the more recent idea-testing stage
over half a century backed with technological advancements for better core recovery and deeper penetration
and higher-resolution downhole measurements. Paleoceanography is an Earth science field borne from ocean drilling. Recent new field is the biosphere beneath the oceans.
Ocean drilling boreholes can also be utilized as monitoring observatories for active processes in situ or for
remote sensing for hydrology, geophysics, and biology.
The framework of conducting ocean drilling has evolved
over the last 50 years, but currently the sampling density
in space is quite undersampled particularly in high latitudes, deeper crusts, or high-temperature environments.
Operating drilling platforms year-round requires international coordination of funding agencies, scientists, engineers, and platform operators. It has grown from a single
non-riser drilling vessel era (DSDP-ODP) to a multiple
platform era (IODP) that enables very deep penetrations
or drilling in very shallow waters or ice-covered seas.
The history of ocean drilling has been to advance for
recovery of high-resolution and high-quality samples with
long history in all oceans as well as deeper penetrations
into igneous rocks and developing capabilities to monitor
ongoing geophysical, geochemical, and biological processes. It should be recognized that much of the ocean
floor remains undersampled considering the heterogeneous nature of the processes in the oceans and beneath.
Ocean drilling is emphasizing its utility to predictions of
climate, geohazards, and ecosystem through new discoveries in basic science.
Ocean drilling complements continental scientific drilling and ice core drilling.
Bibliography
Bach, W., and Edwards, K. J., 2003. Iron and sulfide oxidation
within basalt ocean crust: implications for chemolithoautotrophic microbial biomass production. Geochimica et
Cosmochimica Acta, 67, 3871–3887.
Bascom, W., 1961. A Hole in the Bottom of the Sea: The Story of the
Mohole Project. Garden City: Doubleday & Co., p. 352.
Becker, K., and Davis, E. E., 2005. A review of CORK designs and
operations during the Ocean Drilling Program. In Fisher, A. T.,
Urabe, T., Klaus, A., and The Expedition 301 Scientists (eds.),
Proceeding of the Integrated Ocean Drilling Program. College
Station, Integrated Ocean Drilling Program Management International, Washington, DC, Vol. 301, doi:10.2204/iodp.
proc.301.104.2005.
Byrne, D. A., Harris, D., Duennebier, F. K., and Cessaro, R., 1987.
The ocean sub-bottom seismometer system installed in Deep Sea
Drilling Project Hole 581C, Leg 88: a technical review. Initial
Reports of the Deep Sea Drilling Project, 88, 65–88,
doi:10.2973/dsdp.proc.88.106. Washington (U. S. Government
Printing Office).
Davis, E. E., Wang, K., Becker, K., and Thomson, R., 2000.
Formation-scale hydraulic and mechanical properties of oceanic
crust inferred from pore-pressure response to periodic seafloor
loading. Journal of Geophysical Research, 105, 13,423–13,435.
Davis, E. E., Wang, K., Thomson, R. E., Becker, K., and Cassidy,
J. F., 2001. An episode of seafloor spreading and associated plate
deformation inferred from crustal fluid pressure transients. Journal of Geophysical Research, 106, 21953–21963.
Davis, E. E., Kinoshita, M., Becker, K., Wang, K., Asano, Y., and
Ito, Y., 2013. Episodic deformation and inferred slow slip at
the Nankai subduction zone during the first decade of CORK
borehole pressure and VLFE monitoring. Earth and Planetary
Science Letters, 368, 110–118.
Detrick, R. S., Collins, J., Stephen, R., and Swift, S., 1994. In situ
evidence for the nature of the seismic layer 2/3 boundary in oceanic crust. Nature, 370, 288–290, doi:10.1038/370288a0.
Fisher, A. T., Wheat, C. G., Becker, K., Davis, E. E., Jannasch, H.,
Schroeder, D., Dixon, R., Pettigrew, T. L., Meldrum, R., MacDonald, R., Nielsen, M., Fisk, M., Cowen, J., Bach, W., and
Edwards, K., 2005. Scientific and technical design and deployment of long-term, subseafloor observatories for hydrogeologic
and related experiments, IODP Expedition 301, eastern flank
of Juan de Fuca Ridge. In Fisher, A. T., Urabe, T., Klaus, A.,
and The Expedition 301 Scientists (eds.), Proceeding of the Integrated Ocean Drilling Program. College Station, Integrated
OCEAN DRILLING
551
boreholes (e.g., DONET (www.jamstec.go.jp/donet/e/),
NEPTUNE Canada (www.neptunecanada.com)).
The main objectives of developing CORK (Circulation
Obviation Retrofit Kit) technologies for enabling time
series observations have been to identify and quantify
sub-seafloor fluid flows and associated processes where
physically focused flows may be expected such as in the
vicinities of ocean ridges (thermally driven flows) and
plate subduction zones (tectonic compaction).
In order to observe in situ fluid flow and estimate flow
rates and permeability with minimum disruption, CORK
design is intended to seal holes and control perturbation
originally at the seafloor and subsequently evolved to
enable multilevel isolated zones inside the borehole.
The observation parameters expanded from original pressure and temperature to chemical and biological sampling.
It has been proven that these borehole observations not
only provide permeability to be estimated from tidal
responses but also function as volumetric strainmeters at
a microstrain level (Davis et al., 2001). Transients such
as associated with seismic events can be registered (Sites
1173, 1255). Furthermore, the temperature and pressure
series from multiple CORK observatories where observations can be correlated, combined with the subsurface heterogeneous structure, can provide 4-D flow pattern (Holes
1026B, 1027C).
Conclusions
The ocean floor constitutes the top of the oceanic plates
created by seafloor spreading and destroyed by plate subduction as part of the mantle convection. At the same time,
the ocean floor is the bottom of the water column that
hosts the thermohaline “conveyor belt” ocean circulation
system and ocean currents. The chronological records of
these processes are kept in the sediments and crust to be
explored by ocean drilling. Ocean drilling provides ways
to retrieve such information from sub-seafloor core samples and data to better understand how these systems operate and interact with each other.
Ocean drilling has evolved from the early days of
exploratory stage to the more recent idea-testing stage
over half a century backed with technological advancements for better core recovery and deeper penetration
and higher-resolution downhole measurements. Paleoceanography is an Earth science field borne from ocean drilling. Recent new field is the biosphere beneath the oceans.
Ocean drilling boreholes can also be utilized as monitoring observatories for active processes in situ or for
remote sensing for hydrology, geophysics, and biology.
The framework of conducting ocean drilling has evolved
over the last 50 years, but currently the sampling density
in space is quite undersampled particularly in high latitudes, deeper crusts, or high-temperature environments.
Operating drilling platforms year-round requires international coordination of funding agencies, scientists, engineers, and platform operators. It has grown from a single
non-riser drilling vessel era (DSDP-ODP) to a multiple
platform era (IODP) that enables very deep penetrations
or drilling in very shallow waters or ice-covered seas.
The history of ocean drilling has been to advance for
recovery of high-resolution and high-quality samples with
long history in all oceans as well as deeper penetrations
into igneous rocks and developing capabilities to monitor
ongoing geophysical, geochemical, and biological processes. It should be recognized that much of the ocean
floor remains undersampled considering the heterogeneous nature of the processes in the oceans and beneath.
Ocean drilling is emphasizing its utility to predictions of
climate, geohazards, and ecosystem through new discoveries in basic science.
Ocean drilling complements continental scientific drilling and ice core drilling.
Bibliography
Bach, W., and Edwards, K. J., 2003. Iron and sulfide oxidation
within basalt ocean crust: implications for chemolithoautotrophic microbial biomass production. Geochimica et
Cosmochimica Acta, 67, 3871–3887.
Bascom, W., 1961. A Hole in the Bottom of the Sea: The Story of the
Mohole Project. Garden City: Doubleday & Co., p. 352.
Becker, K., and Davis, E. E., 2005. A review of CORK designs and
operations during the Ocean Drilling Program. In Fisher, A. T.,
Urabe, T., Klaus, A., and The Expedition 301 Scientists (eds.),
Proceeding of the Integrated Ocean Drilling Program. College
Station, Integrated Ocean Drilling Program Management International, Washington, DC, Vol. 301, doi:10.2204/iodp.
proc.301.104.2005.
Byrne, D. A., Harris, D., Duennebier, F. K., and Cessaro, R., 1987.
The ocean sub-bottom seismometer system installed in Deep Sea
Drilling Project Hole 581C, Leg 88: a technical review. Initial
Reports of the Deep Sea Drilling Project, 88, 65–88,
doi:10.2973/dsdp.proc.88.106. Washington (U. S. Government
Printing Office).
Davis, E. E., Wang, K., Becker, K., and Thomson, R., 2000.
Formation-scale hydraulic and mechanical properties of oceanic
crust inferred from pore-pressure response to periodic seafloor
loading. Journal of Geophysical Research, 105, 13,423–13,435.
Davis, E. E., Wang, K., Thomson, R. E., Becker, K., and Cassidy,
J. F., 2001. An episode of seafloor spreading and associated plate
deformation inferred from crustal fluid pressure transients. Journal of Geophysical Research, 106, 21953–21963.
Davis, E. E., Kinoshita, M., Becker, K., Wang, K., Asano, Y., and
Ito, Y., 2013. Episodic deformation and inferred slow slip at
the Nankai subduction zone during the first decade of CORK
borehole pressure and VLFE monitoring. Earth and Planetary
Science Letters, 368, 110–118.
Detrick, R. S., Collins, J., Stephen, R., and Swift, S., 1994. In situ
evidence for the nature of the seismic layer 2/3 boundary in oceanic crust. Nature, 370, 288–290, doi:10.1038/370288a0.
Fisher, A. T., Wheat, C. G., Becker, K., Davis, E. E., Jannasch, H.,
Schroeder, D., Dixon, R., Pettigrew, T. L., Meldrum, R., MacDonald, R., Nielsen, M., Fisk, M., Cowen, J., Bach, W., and
Edwards, K., 2005. Scientific and technical design and deployment of long-term, subseafloor observatories for hydrogeologic
and related experiments, IODP Expedition 301, eastern flank
of Juan de Fuca Ridge. In Fisher, A. T., Urabe, T., Klaus, A.,
and The Expedition 301 Scientists (eds.), Proceeding of the Integrated Ocean Drilling Program. College Station, Integrated
OCEAN DRILLING
551