The Mississippi Canyon, a geological formation in the Gulf of Mexico, is located in an area which is part of the territorial waters of the United States. Petroleum companies, searching for oil, have had successful "finds" here.
How did this area of the Gulf form? The abstract of an article (by J.M. Coleman and D.B. Prior) provides technical background information:
It is highly probable, therefore, that the canyon originated from massive shelf-edge slope failure on an unstable continental margin. A series of successive failures, each one creating an upslope instability that triggered the next failure, caused an elongated trough to form that excavated the canyon to a depth of 1,220 m. below present sea level.
Once the canyon formed, its steep side walls continued to be unstable and sediments slumped into the canyon axis, forming the initial canyon fill. This phase is well documented: the lowermost sediment fill is composed of displaced material similar to that now found on the canyon rim. Large scars from side-wall failures can also be easily mapped on the seismic data.
From 20,000 years to approximately 5,000 years B.P., a series of late Wisconsin and Holocene delta lobes formed and were responsible for the remainder of the fill of the canyon. During the past 5,000 years only a thin deep-water pelagic drape has been deposited within the canyon.
Maps have been constructed that depict the various horizons, and the geometry of these horizons verify this mode of formation. (From an abstract - GCAGS Transactions, Volume 32 (1982) - by Coleman, J.M., Prior, D.B.)
It was in this area of the Gulf that Deepwater Horizon was located on April 20, 2010.
Image online, courtesy NOAA.
Abstract online, GCAGS Transactions, Volume 32 (1982), courtesy Google Books.