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To the north of the island, a portion of the North American plate subducts obliquely beneath the Caribbean plate along the 1,090 kilometer-long Puerto Rico Trench.

In 1964, a French submersible descended 8385 meters to what was then thought to be the deepest part of the Puerto Rico Trench.

This week, Vescovo was set to complete the first dive in the yearlong Five Deeps Expedition, piloting a titanium-alloy, 12.5-ton submersible down 8408 meters to the deepest part of the Atlantic Ocean, in the Puerto Rico Trench.

Another series of faults lie north of Hispaniola, Puerto Rico and the Virgin Islands, and includes the 8,400m-deep Puerto Rico Trench.

The huge collier, Barrash figures, eludes explorers because it sank into the Puerto Rico Trench, the deepest part of the Atlantic.