Gas Hydrates and Marine Geohazards.
Scientists have long postulated a connection between seafloor failures and dissociation of gas hydrate. In deepwater marine settings where warm fluids are pumped from great depths below the seafloor for extraction of conventional oil and gas, heating of sediments near a well could lead to breakdown of gas hydrate and release of gas and water. Intact gas hydrate generally strengthens marine sediments, and dissociation of gas hydrate could lead to subsidence or collapse of the seafloor near the well.
Gas Hydrates Project Home Page
The USGS Gas Hydrates Project focuses on the study of natural gas hydrates in deepwater marine systems and permafrost areas.
Gas Hydrates Research Themes
Features associated with natural failure of the seafloor have also been linked to gas hydrates in some cases. USGS scientists have long studied submarine landslides on marine continental margins and were among the first to note a spatial link between slope failures and hydrate-bearing and/or gas-charged sediments in the 1990s. USGS Gas Hydrates Project scientists support the submarine geohazards research of the USGS Natural Hazards Mission Area through field-based surveys that refine understanding of the hydrates-slope failure association and through geotechnical studies that evaluate the response of sediments to dissociation or dissolution of gas hydrate. In recent years, USGS Gas Hydrates Project scientists have studied the Cape Fear and Currituck Slides on the U.S. Atlantic margin and continental slope slides on the Vancouver and U.S. Beaufort Sea margins.
In the 1990s, USGS scientists Richard Kayen and Homa Lee were among the first to develop a quantitative framework to link submarine slope failures to the presence of gas hydrates in sediments, using the U.S. Beaufort Sea margin as an example (Kayen and Lee, 1991). In the intervening years, the gas hydrates community has recognized that slope failures are indeed spatially linked to the presence of hydrate- or gas-charged sediments, but also that gas hydrates are so ubiquitous in continental margin settings that a causal relationship between the presence of gas hydrates and the development of submarine slope failures cannot be readily established. Some authors have also examined the correlation between submarine landslide evolution in gas hydrate bearing sediments and such climate change events as sea level fluctuations or periods of frequent iceberg rafting.
Without clear spatial or temporal data that could establish a causal relationship between gas hydrate distributions and submarine slope failures, researchers have considered a different causality. Does the presence of gas hydrate and/or gas-charged sediments pre-condition submarine slopes for failure when an external trigger is applied? Such triggers could include earthquakes, rapid sedimentation, oversteepening of slopes, and other factors.
Several types of studies are required to clarify the relationships among slope failures, gas hydrates, and climate change. One of the key needs is determining whether currently-observed charging of sediments with methane gas and/or hydrate leads or lags the timing of slope failures.
- Overview
Gas Hydrates and Marine Geohazards.
Scientists have long postulated a connection between seafloor failures and dissociation of gas hydrate. In deepwater marine settings where warm fluids are pumped from great depths below the seafloor for extraction of conventional oil and gas, heating of sediments near a well could lead to breakdown of gas hydrate and release of gas and water. Intact gas hydrate generally strengthens marine sediments, and dissociation of gas hydrate could lead to subsidence or collapse of the seafloor near the well.
Gas Hydrates Project Home Page
The USGS Gas Hydrates Project focuses on the study of natural gas hydrates in deepwater marine systems and permafrost areas.
Gas Hydrates Research Themes
Sources/Usage: Public Domain.Researchers have postulated that seafloor collapse or sediment failure could occur when certain drilling and extraction activities are conducted in deepwater marine environments where gas hydrates exist in the shallow sediments. This schematic diagram, modified from Ruppel, Boswell, and Jones (2008), shows a compilation of other researchers’ ideas about potential manmade hazards related to gas hydrates. Features associated with natural failure of the seafloor have also been linked to gas hydrates in some cases. USGS scientists have long studied submarine landslides on marine continental margins and were among the first to note a spatial link between slope failures and hydrate-bearing and/or gas-charged sediments in the 1990s. USGS Gas Hydrates Project scientists support the submarine geohazards research of the USGS Natural Hazards Mission Area through field-based surveys that refine understanding of the hydrates-slope failure association and through geotechnical studies that evaluate the response of sediments to dissociation or dissolution of gas hydrate. In recent years, USGS Gas Hydrates Project scientists have studied the Cape Fear and Currituck Slides on the U.S. Atlantic margin and continental slope slides on the Vancouver and U.S. Beaufort Sea margins.
Sources/Usage: Public Domain.1977 USGS multichannel seismic line showing slope failures on the US Beaufort Margin, the location that Kayen and Lee (1991) analyzed in their initial paper on submarine slides and gas hydrates. In the 1990s, USGS scientists Richard Kayen and Homa Lee were among the first to develop a quantitative framework to link submarine slope failures to the presence of gas hydrates in sediments, using the U.S. Beaufort Sea margin as an example (Kayen and Lee, 1991). In the intervening years, the gas hydrates community has recognized that slope failures are indeed spatially linked to the presence of hydrate- or gas-charged sediments, but also that gas hydrates are so ubiquitous in continental margin settings that a causal relationship between the presence of gas hydrates and the development of submarine slope failures cannot be readily established. Some authors have also examined the correlation between submarine landslide evolution in gas hydrate bearing sediments and such climate change events as sea level fluctuations or periods of frequent iceberg rafting.
Without clear spatial or temporal data that could establish a causal relationship between gas hydrate distributions and submarine slope failures, researchers have considered a different causality. Does the presence of gas hydrate and/or gas-charged sediments pre-condition submarine slopes for failure when an external trigger is applied? Such triggers could include earthquakes, rapid sedimentation, oversteepening of slopes, and other factors.
Several types of studies are required to clarify the relationships among slope failures, gas hydrates, and climate change. One of the key needs is determining whether currently-observed charging of sediments with methane gas and/or hydrate leads or lags the timing of slope failures.
Sources/Usage: Public Domain.Swath bathymetric map of the Cape Fear submarine slide, the largest slide on the US Atlantic coast. Data were collected on the R/V Atlantis in 2003. - Publications