Marine geologists have returned from two months at sea off British Columbia, Canada, where they installed two observatories in the ocean floor to run innovative experiments at the bottom of the sea.

The Integrated Ocean Drilling Program (IODP) "Juan de Fuca Ridge-Flank Hydrogeology" expedition – Expedition 327 – left Victoria, Canada, on July 9 and returned on Sept. 5.

Using the scientific research vessel JOIDES Resolution, the team drilled boreholes nearly 1,800 feet deep into the ocean floor to install the observatories.

"The ocean crust is the largest aquifer on the planet," says expedition co-chief scientist Andy Fisher of the University of California at Santa Cruz. "We know it's made up of many sections, but we have no idea how these parts connect or how they interact with one another. The observatories will help us find answers."

These observatories, known as "CORKs" (because they are used to seal boreholes), were installed 125 miles west of Vancouver Island, Canada.

Each CORK is packed with scientific instruments that collect samples and data at multiple depths to learn more about the water, pressures, temperatures, chemistry and microbiology within the rocks and sediments of the ocean crust.

"Expedition 327 has completed some of the most complex borehole observatory installations ever attempted," says Jamie Allan, program director in the National Science Foundation's (NSF) Division of Ocean Sciences, which funds IODP.

"These observatories will measure directly, within the oceanic crust, key characteristics that govern an unseen, remote, yet geographically widespread biological world, and will support long-term chemical and biological sampling and environmental monitoring of this exotic habitat."

The CORKs are being used as part of a sampling and monitoring network to allow scientists to determine the properties of the ocean crust, and to better understand how water, heat and chemicals are transported across vast distances below the bottom of the ocean.

The volume of salt water in the ocean crust is comparable to the volume of fresh water in Earth's ice caps and glaciers – about 4.7 million to 7.2 million cubic miles.

For comparison, this is about 2,000 times greater than the global fresh water supply, and about a half million times greater than annual fresh water usage in the United States.

Like fresh water on land, the salt water below the seafloor is in motion, moving rapidly from place to place.

Until now, scientists have never been able to tag water in one place below the seafloor and determine where it flows.

Experiments begun during the expedition will provide the first direct evidence of active flow pathways and rates in the ocean crust.

Researchers used the boreholes to run experiments during the expedition. In one experiment, they injected benign tracers into the ocean floor to track the directions, rates and patterns of fluid flow within the seafloor.

In another experiment, microbiologists placed chips of rocks and minerals in the CORKs to identify microorganisms living in the seafloor.

Fisher and his team will recover CORK samples and data and run additional experiments next summer and in later years.

"Beyond the successes of this expedition," says Rodey Batiza, marine geology and geophysics section head in NSF's Division of Ocean Sciences, "the upcoming ACORK (Advanced Circulation Obviation Retrofit Kit) expedition will instrument the sea-floor with very sophisticated instrumentation to conduct experiments.

"The results will be relayed in real time via cables as part of the Neptune Canada Observatory Network, showing the great scientific overlap between ocean observing and scientific ocean drilling."

Next IODP Expedition

The JOIDES Resolution embarked on its next expedition on Sept. 9. Led by Earl Davis of Canada's Pacific Geoscience Center, the "Cascadia ACORK" expedition will install a new CORK observatory in the Cascadia subduction zone, about 46 miles off the coast of Vancouver Island. The CORK will monitor changes in pressure associated with this seismically active setting, and help scientists understand the formation of gas hydrates – ice-like deposits of gas commonly found below the ocean floor.

In a year, the new CORK will be connected to the NEPTUNE-Canada deep-ocean cable network, which will provide power and real-time data collection over the coming decades. An onboard education program, "School of Rock," will teach 20 educators about marine geoscience. Davis and colleagues return to Victoria on Sept. 19.