Charleston Bump

July 22, 2018
By Damond Benningfield
Episode:

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The Charleston bump tops out at about 1200 feet and is home to deep-sea coral reefs and wreckfish. Credit: NOAA

In July of 1969, a small submarine and its six-man crew got stuck. They didn’t run aground, though. Instead, they were caught in a swirling eddy in the Gulf Stream, the current of warm water that flows along the East Coast. The sub needed to surface so it could be towed back into the flow of the Gulf Stream.

Later, scientists discovered what caused the eddy: an underwater mound known as the Charleston Bump. It’s about a hundred miles off the coast of Charleston, South Carolina, on the edge of the continental shelf.

The bump is about 2300 feet deep at its base, but tops out at about 1200 feet, at its northern edge. It’s paved with a thick layer of rock that formed millions of years ago. Later, that part of the ocean floor was pushed upward by motions in Earth’s crust.

The bump deflects the Gulf Stream away from the coastline. That creates a big whirlpool known as the Charleston Gyre. It also creates smaller whirlpools, like the eddy that trapped the submarine.

The bump is home to abundant life. Deep-sea reefs inhabit the flat, rocky regions. And many fish inhabit caves and depressions carved by the Gulf Stream, including marlin and other sport fish. They’re also the spawning grounds for the wreckfish, a commercial fish that can reach up to a hundred pounds. The fish feed on squid that ride the Gulf Stream. In fact, the region is the only known spawning ground for wreckfish on the western side of the North Atlantic -- a nursery made possible by a bump on the ocean floor.