The Puerto Rico Trench is located on the boundary between the Caribbean Sea and the Atlantic Ocean, roughly parallel to the northern coast of Puerto Rico. The deepest point in the Atlantic Ocean is the Milwaukee Depth at the western end of the trench.
Puerto Rico Trench
The Puerto Rico Trench is located on the boundary between the Caribbean Sea and the Atlantic Ocean. The submarine depression is located roughly parallel to the island of Puerto Rico's northern coast and about 75 mi (120 km) to the north.
The Puerto Rico Trench is about 1,090 mi (1,750 km) long and 60 mi (100 km) wide. The deepest point in the Atlantic Ocean, the Milwaukee Depth, lies at a depth of 27,493 ft (8,380 m) at the western end of the trench, about 100 mi (160 km) northwest of Puerto Rico.
Location map of the Puerto Rico trench (USGS)
On December 19, 2018, its deepest point was identified by the DSSV Pressure Drop using a state-of-the-art Kongsberg EM124 multibeam sonar and then directly visited. Its depth was verified by the manned submersible Deep-Submergence Vehicle DSV Limiting Factor (a Triton 36000/2 model submersible).
The oceanic trench is associated with a complex transition between the Lesser Antilles subduction zone to the south and the major transform fault zone or plate boundary, which extends west between Cuba and Hispaniola through the Cayman Trough to the coast of Central America.
The Puerto Rico Trench is a geologically complex site. The ocean trench is located at a boundary between two plates that pass each other along a transform boundary with only a small component of subduction. The Caribbean Plate is shifting east, while the North American Plate is shifting west.
The North American Plate is being subducted by the Caribbean Plate obliquely at the trench, while to the southeast, the South American Plate is being more directly subducted along the Lesser Antilles subduction zone. This subduction zone explains the presence of active volcanoes over the southeastern part of the Caribbean Sea. Volcanic activity is frequent along the island arc southeast from Puerto Rico to the coast of South America.
Puerto Rico, the United States Virgin Islands, the British Virgin Islands and the Dominican Republic do not have active volcanoes; however, they are at risk from earthquakes and tsunamis. The Puerto Rico Trench is capable of producing earthquakes greater than magnitude 8.0.
According to NASA, beneath the trench is a dense mass that has a gravitational pull on the ocean's surface, causing it to dip somewhat. It also has a negative effect on the accuracy of navigational instruments.
Map of the Caribbean, depicting the location of the Puerto Rico Trench