Richard B. Coffin

Complex gas hydrate from the Cascadia margin

Natural gas hydrates are a potential source of energy and may play a role in climate change and geological hazards. Most natural gas hydrate appears to be in the form of ‘structure I’, with methane as the trapped guest molecule, although ‘structure II’ hydrate has also been identified, with guest molecules such as isobutane and propane, as well as lighter hydrocarbons. A third hydrate structure, ‘structure H’, which is capable of trapping larger guest molecules, has been produced in the laboratory, but it has not been confirmed that it occurs in the natural environment. Here we characterize the structure, gas content and composition, and distribution of guest molecules in a complex natural hydrate sample recovered from Barkley canyon, on the northern Cascadia margin. We show that the sample contains structure H hydrate, and thus provides direct evidence for the natural occurrence of this hydrate structure. The structure H hydrate is intimately associated with structure II hydrate, and the two structures contain more than 13 different hydrocarbon guest molecules. We also demonstrate that the stability field of the complex gas hydrate lies between those of structure II and structure H hydrates, indicating that this form of hydrate is more stable than structure I and may thus potentially be found in a wider pressure–temperature regime than can methane hydrate deposits.

NATURAL CO2 FLOW FROM THE LOIHI VENT: IMPACT ON MICROBIAL PRODUCTION AND FATE OF THE CO2

The program for International Collaboration on CO{sub 2} Ocean Sequestration was initiated December 1997. Preliminary steps involved surveying a suite of biogeochemical parameters off the coast of Kona on the Big Island of Hawaii. The preliminary survey was conducted twice, in 1999 and 2000, to obtain a thorough data set including measurements of pH, current profiles, CO{sub 2} concentrations, microbial activities, and water and sediment chemistries. These data were collected in order to interpret a planned CO{sub 2} injection experiment. After these preliminary surveys were completed, local environment regulation forced moving the project to the coast north east of Bergen, Norway. The preliminary survey along the Norwegian Coast was conducted during 2002. However, Norwegian government revoked a permit, approved by the Norwegian State Pollution Control Authority, for policy reasons regarding the CO{sub 2} injection experiment. As a result the research team decided to monitor the natural CO{sub 2} flow off the southern coast of the Big Island. From December 3rd-13th 2002 scientists from four countries representing the Technical Committee of the International Carbon Dioxide Sequestration Experiment examined the hydrothermal venting at Loihi Seamount (Hawaiian Islands, USA). Work focused on tracing the venting gases, the impacts of the vent fluids on marine organisms, and CO{sub 2} influence on biogeochemical cycles. The cruise on the R/V Kaimikai-O-Kanaloa (KOK) included 8 dives by the PISCES V submarine, 6 at Loihi and 2 at a nearby site in the lee of the Big Island. Data for this final report is from the last 2 dives on Loihi.