November 7, 2005

from ScienceDaily Website

When brought to the surface in a core, gas hydrate is no longer

in its stable pressure and temperature field and decomposes (see fizzing and bubbling).

(Image courtesy of Integrated Ocean Drilling Program Management International)

An international team of scientists supported by the Integrated Ocean Drilling Program (IODP) has completed a unique research expedition aimed at recovering samples of gas hydrate, an ice-like substance hidden beneath the seafloor off Canada's western coast.

Gas hydrate, a mixture of water and mostly methane, is believed to occur under the world's oceans in great abundance, but it quickly "melts" once removed from the high pressure and cold temperatures of its natural environment, making it very challenging to recover and analyze.

"We're interested in gas hydrate because we believe these deposits have played an important role in ancient global climate change," explains Michael Riedel of Natural Resources Canada's Geological Survey of Canada, IODP Expedition 311's co-chief scientist.

 

"This expedition is the first to explore a transect of deep drilling research sites across the Cascadia Continental Margin and will yield new data that will help us understand the deep origin of the methane that composes the gas hydrate, how the methane is transported into the sediments where gas hydrate exists, and how methane is eventually released into the ocean, and possibly, into the atmosphere where it could impact climate."

 

"What we've found will fundamentally change how we investigate the impact of gas hydrate deposits," confirms IODP co-chief scientist Timothy S. Collett of the U.S. Geological Survey, Denver, Colo. "Expedition 311 has shown that the occurrence of gas hydrate is much more complex than predicted. Instead of finding gas hydrate concentrated in one layer," he explains, "near the base of the zone where it is stable, higher concentrations of gas hydrate were found within coarse-grained sand layers throughout core samples from most of the sites drilled."

Scientists and engineers aboard IODP's U.S.-sponsored research drilling vessel, the JOIDES Resolution, drilled hundreds of meters below the seafloor and successfully retrieved gas hydrate in long sediment cores.

More than 1,200 meters of sediment core samples were recovered from beneath the seafloor during this 37-day expedition. Once core samples are brought onto the ship, marine laboratory specialists work quickly to scan them using various sensors and computers to find the gas hydrate, which is unstable at the surface.

Most previous research on the Cascadia Continental Margin has focused on conducting detailed, remote sensing studies to image gas hydrate in the oceanic sediments. In past research efforts, gas hydrate has been recovered from the Cascadia Margin area using shallow sediment coring systems that allowed only the upper few meters of sediment to be sampled.

Among the discoveries of Expedition 311 was a thick section of gas hydrate lying near the seafloor surface beneath an active vent site, known as the 'bull's-eye vent,' where methane gas naturally seeps from the seafloor.

This vent site is one of many similar sites observed along the Cascadia Margin and scientists are just starting to understand their role in the overall history of the margin. The episodic nature of the venting and the potential link to earthquake activity, as well as the possible impact on gas release into the ocean and atmosphere, will be researched for many years to come, when future drill site observatories will be linked with the NEPTUNE cable observatory system.

Scientists first became interested in gas hydrate in 1982, when it was discovered during a research leg of the Deep Sea Drilling Project, one of two U.S.-sponsored scientific drilling programs that predate IODP.

The samples were retrieved from the Middle American Trench region, off the Pacific coast of Guatemala.

Since then, gas hydrate has been the focus of numerous studies.

'Frozen' Natural Gas

...Discovered At Unexpectedly Shallow Depths Below Seafloor
August 22, 2006
from ScienceDaily Website

An international team of research scientists has reported greater knowledge of how gas hydrate deposits form in nature, subsequent to a scientific ocean-drilling expedition off Canada’s western coast.

A natural geologic hazard, gas hydrate is largely natural gas, and thus, may significantly impact global climate change. The research team, supported by the Integrated Ocean Drilling Program (IODP), published their peer-reviewed findings, "Gas Hydrate Transect Across Northern Cascadia Margin," in the Aug. 15, 2006, edition of EOS, published by the American Geophysical Union.

Contrary to established expectations of how gas hydrate deposits form, IODP expedition co-chief Michael Riedel, of McGill University, Montreal, confirms,

“We found anomalous occurrences of high concentrations of gas hydrate at relatively shallow depths, 50-120 meters below the seafloor.”

The science party used the drilling facility and laboratories of the U.S. research vessel, JOIDES Resolution, on a 43-day expedition in Fall 2005 during which they retrieved core samples from a geological area known as the (northern) Cascadia Margin.

Gas hydrate deposits are typically found below the seafloor in offshore locations where water depths exceed 500 meters, and in Arctic permafrost regions. Gas hydrate remains stable only under low temperature and relatively high pressure.

IODP co-chief scientist Timothy S. Collett of the U.S. Geological Survey states,

“After repeatedly recovering high concentrations of gas hydrate in sand-rich layers of sediment, we’re reporting strong support for sediment grain size as a controlling factor in gas hydrate formation.”

Prior to drilling, the scientists anticipated that gas hydrate would be more concentrated at deeper levels below the seafloor and more evenly distributed among the various grain sizes comprising the sediments.

The Integrated Ocean Drilling Program (IODP) is an international marine research program dedicated to advancing scientific understanding of the Earth, the deep biosphere, climate change, and Earth processes by sampling and monitoring sub-seafloor environments.

IODP is supported by two lead agencies:

• the U.S. National Science Foundation

• Japan’s Ministry of Education, Culture, Sports, Science, and Technology

Additional support comes from a European consortium of 17 countries, the People’s Republic of China, and South Korea.

U.S.-sponsored IODP drilling operations are conducted by the JOI Alliance, comprised of,

• the Joint Oceanographic Institutions

• Texas A & M University Research Foundation

• Lamont-Doherty Earth Observatory of Columbia University