The Atlantic Ocean is the second largest ocean basin on Earth, covering roughly 20% of the planet’s surface. Its vast waters hold numerous geographic features, ranging from the submerged mountain chain of the Mid-Atlantic Ridge to its deepest abyssal plains. This immense body of water has inspired centuries of seafaring and a continuous drive to map its most extreme depths. Finding the absolute lowest point represents a major achievement in oceanographic exploration.
Identifying the Atlantic’s Deepest Point
The lowest point in the entire Atlantic Ocean is known as the Milwaukee Deep, a specific location within the much larger Puerto Rico Trench. This trench is a colossal submarine depression situated just north of the Caribbean island of Puerto Rico and the Virgin Islands. The deepest measurement confirmed by modern expeditions is 8,376 meters (27,480 feet) below the surface.
This precise depth measurement was verified by the Five Deeps Expedition in December 2018. Explorer Victor Vescovo made the first crewed descent to this Atlantic nadir in the submersible DSV Limiting Factor. The expedition utilized state-of-the-art multi-beam echo sounders and direct pressure measurements to establish the accepted standard for the Milwaukee Deep.
The Geological Origin of the Trench
The existence of the Puerto Rico Trench, and consequently the Milwaukee Deep, is a direct result of the complex dynamics of plate tectonics in the Caribbean region. The trench marks the active boundary where two massive sections of the Earth’s crust meet. The North American Plate, which carries the entire North Atlantic basin, is slowly colliding with and sliding beneath the smaller Caribbean Plate.
This process is known as subduction, which forces the oceanic crust downward into the Earth’s mantle. The downward bend and descent of the North American Plate creates the profound, narrow chasm that defines the trench. While the tectonic interaction involves both convergent and transform (sliding) motion, the subduction component is responsible for the extreme depth of the Milwaukee Deep. The trench has been an area of significant tectonic activity for millions of years.
History of Exploration and Measurement
The first attempts to gauge the deep water north of Puerto Rico date back well over a century, relying on weighted sounding lines lowered from ships. The feature was officially discovered and named in 1939 by the U.S. Navy cruiser USS Milwaukee, which recorded an initial deep reading using early echo sounding technology. This initial discovery gave the deepest point its enduring name.
Throughout the mid-20th century, other vessels like the U.S. Fish and Wildlife Service vessel Theodore N. Gill refined these measurements. In 1964, the French bathyscaphe Archimède explored the trench, though it did not reach the absolute deepest point. The most significant modern effort came with the 2018 Five Deeps Expedition, which used advanced multi-beam sonar mapping to precisely locate the Milwaukee Deep. This expedition, which included the first human descent, finally provided the definitive, highly accurate bathymetric data accepted today, marking a major step in the technological evolution of deep-sea mapping.