How long is the Puerto Rico Trench?

The Puerto Rico Trench is approximately 810 kilometres long. It lies north of Puerto Rico, along a complex plate boundary between the Caribbean Plate and the North American Plate, and forms the deepest part of the Atlantic Ocean.

Unlike a straightforward subduction trench, the boundary around Puerto Rico combines oblique subduction with strike-slip motion. This means the plates move both toward one another and laterally past one another. The same broader fault system continues westward through the Puerto Rico–Virgin Islands region and toward the Cayman Trough.

The trench reaches a maximum depth of roughly 8,376 to 8,740 metres, depending on the survey and measurement used. Its deepest area is commonly called Milwaukee Deep, although Brownson Deep is also used for the surrounding seabed and, in some sources, for the deepest point itself.

Because earthquakes on this boundary can displace the seafloor, scientists consider the region capable of generating significant tsunamis. Modern sonar mapping and crewed submersible dives have refined measurements of its depth and shape.