When a slope fails
Side scan sonar images of the Albemarle-Currituck slide along the edge of the continental shelf on the eastern edge of North America offshore offshore North Carolina.An underwater slide is like a landslide on land, except that it takes place under water. Slides occur when a slope fails to hold itself up.
Image courtesy Neal Driscoll
Side scan sonar images of the Goleta slide along the edge of the continental shelf on the western edge of North America offshore southern California near Goleta, Santa Barbara County.
Image courtesy Neal Driscoll
It seems plausible, but do underwater slides actually cause tsunami? Luckily it doesn't happen every day.
Scientists have found evidence of massive underwater landslides in the past. Geologist Neal Driscoll maps underwater slides using specialized tools such as side scan sonar. This tool allows him to "see" the sea floor in new ways. His images of the Albemarle-Currituck slide show large slides on the edge of the continental shelf. Not only do his images show where the slope has failed, they suggest that these slopes could fail in an even bigger way in the future. Could such slides generate tsunami that head toward cities on the east coast?
Once scientists estimate the volume of sediment and rock that might move, and where it might move to, they can pass the information on to tsunami modelers who try to figure out how tsunami might be generated and where they would go. Then, they would let people in the tsunami's path know, so they can be prepared.
Scientists are interested in understanding more about nearshore slides because they might generate devastating tsunamis close to shore. Beacuse it's such a nice place to live, most coastal areas are densely populated. These areas may be so close to the source of tsunami that there wouldn't be enough time to evacuate everyone. This happened in Papua New Guinea. Unlike tsunamis generated by earthquake, underwater slides generated by tsunami can happen around the Atlantic as well as the Pacific rim.
What causes underwater landslides?
There are several possible triggers for underwater landslides.
At the Ocean Institute
Where to find more information:
"A new USC study shows that tsunamis - triggered by earthquakes and underwater slides - could threaten Southern California’s coast."
By Bob Calverley, USC News
About the risk of tsunami, including the Albemarle-Currituck slide mapped by geologist Neal Driscoll.
North Carolina Museum of Natural Sciences
Potential for Large-scale Submarine Slope Failure and Tsunami Generation along the U.S. Mid-Atlantic Coast
Sample of published scientific article.
Neal Driscoll, Jeffrey Weissel, and John Goff, 2000 in The Geological Society of America Online Journals
Powerpoint presentation: Slope Stability
Example of slides use in presentations given by geologist Neal Driscoll.
Neal Driscoll, Scripps Institution of Oceanogrpahy