What is the deepest trench in the Atlantic Ocean?

What is the deepest trench in the Atlantic Ocean? The Puerto Rico Trench is the deepest trench in the Atlantic Ocean, reaching more than 8,300 metres below sea level.

It lies north of Puerto Rico at the boundary between the North American and Caribbean plates. The region is tectonically complicated: it combines subduction, where oceanic crust descends beneath another plate, with sideways transform motion. That combination makes the trench an important source of earthquake and tsunami risk for nearby islands.

The trench's deepest area is commonly called the Milwaukee Deep, although the names Milwaukee Deep and Brownson Deep have sometimes been used inconsistently for the deepest depression and its surrounding seabed. Modern measurements have produced somewhat different figures, including about 8,376 metres from direct pressure measurements during a 2018 crewed descent.

The South Sandwich Trench is another very deep Atlantic-associated feature and is sometimes listed in comparisons involving the Southern Ocean. In standard Atlantic Ocean lists, however, the Puerto Rico Trench is deeper. It is far shallower than the Pacific's Mariana Trench, whose Challenger Deep is the deepest known point in any ocean.