Puerto Rico Trench

The Puerto Rico Trench is located on the boundary between the North Atlantic Ocean and Caribbean Sea, parallel to and north of Puerto Rico, where the oceanic trench reaches the deepest points in the Atlantic Ocean. The trench is associated with a complex transition from the Lesser Antilles frontal subduction zone between the South American plate and Caribbean plate to the oblique subduction zone and the strike-slip transform fault zone between the North American plate and Caribbean plate, which extends from the Puerto Rico Trench at the Puerto Rico–Virgin Islands microplate through the Cayman Trough at the Gonâve microplate to the Middle America Trench at the Cocos plate.

Constituting the deepest points in the Atlantic Ocean, the trench is 810 kilometres (503 mi) long and has a maximum documented depth between 8,376 metres (27,480 ft) and 8,740 metres (28,675 ft). The deepest point is commonly referred to as the Milwaukee Deep, with the Brownson Deep naming the seabed surrounding it. However, more recently, the latter term has also been used interchangeably with the former to refer to this point. The exact point was identified by the DSSV Pressure Drop using a state-of-the-art Kongsberg EM124 multibeam sonar in 2018, and then directly visited and its depth verified by the crewed submersible Deep-Submergence Vehicle DSV Limiting Factor (a Triton 36000/2 model submersible) piloted by Victor Vescovo.

Scientific studies have concluded that an earthquake occurring along this fault zone could generate a significant tsunami. The island of Puerto Rico, which lies immediately to the south of the fault zone and the trench, suffered a destructive tsunami soon after the 1918 San Fermín earthquake.