In 2002 and 2003, the U.S. Geological Survey (USGS), Woods Hole Coastal and Marine Science Center (WHCMSC), in cooperation with the National Oceanic and Atmospheric Administration (NOAA), conducted three exploration cruises (USGS Cruise 02051, NOAA RB0208, September 24 to 30, 2002; USGS Cruise 03008, NOAA RB0303, February 18 to March 7, 2003 and USGS Cruise 03032, NOAA RB0305, August 28 to September 4, 2003). These cruises mapped for the first time the morphology of this entire tectonic plate boundary stretching from the Dominican Republic in the west to the Lesser Antilles in the east, a distance of approximately 700 kilometers (430 miles). Observations from these three exploration cruises, coupled with computer modeling and published Global Positioning System (GPS) results and earthquake focal mechanisms have provided new information that is changing the evaluation of the seismic and tsunami hazard from this plate boundary. The observations collected during these cruises also contributed to the basic understanding of the mechanisms that govern plate tectonics, in this case, the creation of the island of Puerto Rico and the deep trench north of it. Results of the sea floor mapping have been an important component of the study of tsunami and earthquake hazards to the northeastern Caribbean and the U.S. Atlantic coast off the United States. For additional information on the cruises see: http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2002-051-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2002-051-FA http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2002-051-FA