A team of scientists from the Geological Survey of Canada and NEPTUNE- Canada have recently returned from a successful research expedition in the northeast Pacific, where they installed an observatory in the ocean floor about 75 km (about 50 miles) west of Vancouver Island, British Columbia.
Victoria, Canada — The goal of the Integrated Ocean Drilling Program (IODP) “Cascadia ACORK” Expedition was to deploy an instrument, known as an “ACORK” (Advanced Circulation Obviation Retrofit Kit), into a new borehole drilled 330 meters (over 1000 feet) into the seafloor, at a water depth of 1300 meters (about 4300 feet). The ACORK is equipped with ultra sensitive instruments designed to detect changes in pressure and temperature within the ocean floor.
“We want to monitor changes in seafloor pressure and temperature to improve our understanding of plate motions in this seismically active region, known as the Cascadia Subduction Zone,” remarked Dr. Earl Davis, who led the expedition.
“The installation of borehole observatories in the seafloor is one of the best ways to do this – data from these instruments may help us refine our estimates of when the next earthquake and tsunami will impact the Northwest, and more importantly what the distribution of slip and seafloor deformation will be.”
Davis and his colleagues selected the Cascadia Subduction Zone for this work because of its unique tectonic setting- the borehole was drilled into soft seafloor sediments that directly overlay a fault zone. As the plates move past one another along the fault, the sediments are compressed –the compression squeezes fluids in the pore spaces of the sediments like a sponge, producing detectable changes in pressure and temperature.
Subduction zone earthquakes are known to be devastating and can cause widespread destruction in coastal communities, and the tsunamis that they spawn propagate the full breadth of ocean basins. Examples of subduction zone quakes include the Sumatra quake of 2004 and the earthquake in Chile this past February. In the Pacific Northwest, scientists predict that the next “big one” will occur sometime in the next few hundred years – but no one knows when it will strike. Instruments like the CORK observatories provide a new tool for monitoring signs of seismic activity.
In addition to seismic hazards, the ACORK data will be used to elucidate the formation and behavior of gas hydrates – frozen methane deposits – on and beneath the seafloor. Gas hydrates are found along most continental margins at about 600 meters (2000 feet) of water depth and in areas of low temperature (less than 20°C) and high pressure. Gas hydrates are common in subduction zone settings. Methane hydrates may be a source of alternative energy in the future – but have also been blamed as a possible cause for dramatic shifts in Earth’s climate in the past. ACORK data will be used to understand the formation of gas hydrates in the Cascadia region and around the world.
Davis and his colleagues will return to the Cascadia ACORK site next summer to download data from the pressure and temperature sensors. At that time, they plan to connect the borehole observatory to the NEPTUNE Canada cabled seafloor observatory system; this will provide power to the instruments and transmit data to shore in real time. Data from the ACORK (and other instruments already installed on the NEPTUNE cabled seafloor observatory network) will be freely available online at www.neptunecanada.ca.
The ten day IODP Cascadia ACORK expedition took place onboard the scientific research vessel JOIDES Resolution, which departed Ogden Point, Victoria on September 9 and returned to Esquimalt Graving Dock, Victoria on September 18, 2010.
The Integrated Ocean Drilling Program (IODP) is an international research program dedicated to advancing scientific understanding of the Earth through drilling, coring, and monitoring the subseafloor. The JOIDES Resolution is a scientific research vessel managed by the U.S. Implementing Organization of IODP (USIO). Together, Texas A&M University, Lamont-Doherty Earth Observatory of Columbia University, and the Consortium for Ocean Leadership comprise the USIO. IODP is supported by two lead agencies: the U.S. National Science Foundation (NSF) and Japan’s Ministry of Education, Culture, Sports, Science, and Technology. Additional program support comes from the European Consortium for Ocean Research Drilling (ECORD), the Australian-New Zealand IODP Consortium (ANZIC), India’s Ministry of Earth Sciences, the People’s Republic of China (Ministry of Science and Technology), and the Korea Institute of Geoscience and Mineral Resources.
For more information about the IODP Cascadia ACORK Expedition, visit http://iodp.tamu.edu/scienceops/expeditions/cascadia.html
For more information about the JOIDES Resolution, visit www.joidesresolution.org.
For more information about the Integrated Ocean Drilling Program, visit www.iodp.org.
Consortium for Ocean Leadership
Integrated Ocean Drilling Program Management International, Inc. (IODP-MI)