A sonar mapping cruise taken in June to the Baltimore, Washington and Norfolk Canyons and selected regions of the continental shelf revealed steep escarpments that probably pose no tsunami hazard
?| November 10, 2011?|
High-resolution multibeam bathymetry collected in and between Baltimore and Accomac Canyons during the June 2011 cruise. Color key at left shows depths (in meters).
Image: OurAmazingPlanet.com
The East Coast of the United States isn't the first place that comes to mind as being at risk of tsunamis, but new sonar maps are now helping to show that these risks do exist.
For about the past five years, researchers at the U.S. Geological Survey, along with other governmental and academic partners, have been gauging the potential for tsunamis generated by landslides in submarine canyons in the mid-Atlantic to strike the U.S. Atlantic and Gulf of Mexico coasts. The investigation was requested by the U.S. Nuclear Regulatory Commission, which is concerned about the potential impact tsunamis might have on new and existing nuclear power plants, especially in light of the devastating tsunami in Japan in March that sparked the greatest nuclear disaster in years.
The research identified landslides along the submerged margin of the North American continent as the leading potential source of dangerous tsunamis to the East Coast. These landslides either originate in submarine canyons or on the continental slope.
Mapping mission
Investigators set out to map key areas of the Atlantic continental margin in high resolution, work that could uncover more about these hazards. Although this is one of the best-mapped continental margins in the world, significant gaps still remain along the upper slope and shelf where potentially dangerous submarine landslides might occur. [Natural Disasters: Top 10 U.S. Threats]
"Given the immense size of the regions in which we are working, it has taken many years of data collection and integration of existing data sets in order to produce seafloor maps with the resolution needed to identify all the features we are interested in," said U.S. Geological Survey research marine geologist Jason Chaytor.
A sonar mapping cruise taken in June to the Baltimore, Washington and Norfolk Canyons and selected regions of the continental shelf between the canyons marked the first field effort of the multiyear Deep-Water Mid-Atlantic Canyons Project. Using echosounders installed on the hull of the National Oceanic and Atmospheric Administration (NOAA) ship Nancy Foster, the science team mapped canyons and shelf regions at high resolution over more than 380 square miles (1,000 square kilometers) of seafloor from south of Cape Hatteras to Baltimore Canyon, which runs from offshore North Carolina to the eastern tip of Long Island.
"Probably the biggest challenge we faced was avoiding the ever-present fishing gear deployed around the canyons while still collecting enough data to not leave any gaps in the final maps," Chaytor told OurAmazingPlanet.
Submarine canyons and landslides
The science team's preliminary analysis of these new data revealed the presence of steep, sharp, stepped escarpments, or slopes, rimming the upper parts of each of the mapped canyons. These may be submerged ancient shorelines cut during times of lower sea level, "the most recent of which occurred during the last glacial period, which ended about 19,000 years ago," Chaytor said. Although the researchers do not at this time feel there is any connection between these features and tsunami hazards, "they may provide important insights into the development of the canyons and help us understand the role of changing sea level in the evolution of the Atlantic coast," he said.
Source: http://rss.sciam.com/click.phdo?i=9dc22fd7b661d8515f23f11f8e276302
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