The deepest part of the Atlantic Ocean basin is the Puerto Rico Trench, which runs east from the north coast of Hispaniola to a point beyond the Lesser Antilles. This trench reaches a maximum depth of 28,374 feet, which is around 8,000 feet shallower than the Pacific's Marianas Trench.
The Puerto Rico Trench formed along the boundary between the Caribbean Plate and the North American Plate. Very little subduction takes place at the transform fault between these plates, and most of the movement is lateral. This reduces volcanic activity in the area, but it greatly increases the risk of earthquakes.