EUGENE, Ore. -- (Sept. 22, 2009) -- After 30 days at sea and 16 days of successful seismic surveying of deep-sea hydrothermal ecosystems on the Pacific Ocean floor off British Columbia, researchers from two Northwest institutions have returned to dry land.
Their mission to study the deep crustal structure of the Endeavour segment of the Juan de Fuca ridge had drawn last-minute opposition by environmental groups, who in court filings had sought to stop the seismic surveying because of potential harm to whales and other mammals. A portion of the ridge includes the Endeavour Marine Protected Area that was established to foster conservation and responsible scientific study. Canadian courts rejected the groups' cases.
Prior to sailing, the project -- the Endeavour Seismic Tomography Experiment -- underwent a thorough environmental assessment by Canadian and U.S. regulators. The timing of the expedition was chosen to minimize marine mammal encounters. During the survey, certified marine mammal observers monitored the region on a 24-hour per-day basis.
"Not a single marine mammal was either visually observed or acoustically detected during the seismic survey," said Doug Toomey, professor of geological sciences at the University of Oregon and principal investigator of the National Science Foundation-funded project that was done from the research vessel Marcus G. Langseth.
The ship is the academic community's flagship seismic research vessel and is owned by the NSF. Universities, research institutes and labs use the Langseth to study the earth’s interior below the world’s ocean floors. The Lamont-Doherty Earth Observatory, part of Columbia University, operates the ship on behalf of the NSF.
"Our results will have direct societal benefits, including an improved understanding of the life-cycle of deep-sea vents and on the importance of the Marine Protected Area as a long-term species reservoir for the entire northeast Pacific," Toomey said. "We are learning about and how the structure of ocean crust and the Juan de Fuca plate contributes to earthquakes, tsunamis and volcanic hazards that threaten the Pacific Northwest."
Unlike other marine and terrestrial ecosystems, Toomey said, the hydrothermal vent communities at Endeavour are entirely dependent upon heat from a magma body within the oceanic crust as their primary source of energy. "A primary goal of our study was to image these below-seafloor heat sources, or magma chambers, that fuel and sustain the vent fields and their bottom-dwelling communities," he said.
Scientists from the UO and University of Washington used the ship's extensive air source array to send low-frequency sound waves to image the structure beneath the seafloor of the region, which is a source of numerous earthquakes. Many of these earthquakes generate sound in the same frequency band as the ship's seismic array. Earthquake swarms can continue for several weeks.
Information gathered by researchers will prove useful to a major Canadian project, as well.
“This experiment is particularly timely because it provides subsurface geological information that complements the work of the NEPTUNE Canada project at the University of Victoria to install a long-term cabled hydrothermal observatory in the hydrothermal fields” said William Wilcock, a UW marine geophysicist and a co-principal investigator on the project. He also noted that the seismic work went so smoothly that the Langseth was able to spend the last two days at sea mapping the seafloor in nearby regions that are also of interest to the NEPTUNE Canada team.
“Professor Toomey's project will provide fundamental data complementary to data from NEPTUNE Canada’s cabled ocean observatory, with a node site at Endeavour. Data on 3-D seismic structure of the ocean crust will reveal how magmatic and hydrothermal vent processes sustain the special ecosystems and the relationship between regional plate-tectonic processes and natural hazards such as earthquakes, tsunamis, major slope failures, gas hydrate release,” said Chris Barnes of the University of Victoria in British Columbia and project director of NEPTUNE Canada.
“This project will directly contribute to ecosystem and conservation research at the Endeavour Marine Protected Area,” said Kim Juniper the BC Leadership Chair in Ocean Ecosystems and Global Change at the University of Victoria. Acquiring that information on the sub-surface magma system is essential to determine the stability of hydrothermal vent populations, he added.
Emilie Hooft, a UO professor of geological sciences also participated in the study. She noted: “The academic marine seismic community is one of the most careful communities in the world when it comes to monitoring and mitigating the effects of our seismic sources on marine ecosystems.”
The Langseth operates in accordance with rules and regulations set forth by U.S. governmental entities and laws, and, in this case, Canada’s Department of Fisheries and Oceans.