A rather sizeable coral reef has been found hiding 260 kilometers (160 miles) offshore from South Carolina. Although it's discontinuous along its expanse, according to preliminary mapping reports it’s 140 kilometers (85 miles) in length, nearly twice that of the distance between San Francisco and San Jose.

It was discovered during an ongoing underwater expeditionary mission, the Deep Sea Exploration to Advance Research on Coral/Canyon/Cold Seep Habitats, or DEEP SEARCH. It's led by the National Oceanic and Atmospheric Administration (NOAA), and features partners from the Bureau of Ocean Energy Management and the United States Geological Survey (USGS).

Using the Woods Hole Oceanographic Institution (WHOI)-operated Atlantis vessel, the interdisciplinary team had hoped to shed some light on what is frankly a largely mysterious section of the Mid and South Atlantic Ocean. This reef was initially found by a series of dives using the boat’s Alvin submersible just last week, which confirmed the presence of Lophelia pertusa, a deep-water stony coral.

As it so happens, back in May and June of this year, a separate ship – NOAA’s Okeanos Explorer – had detected a rocky feature in the same part of the seafloor, stretching for tens of miles in multiple directions. It’s known that L. pertusa grows atop the skeletal remains of its fallen cousins in a process that takes perhaps hundreds of thousands of years.

With that in mind, the team suspects that “it is highly probable” that those mounds and ridges were formed by corals.

“This is a huge feature,” Erik Cordes, DEEP SEARCH’s chief scientist, told the Huffington Post. “It’s incredible that it stayed hidden off the U.S. East Coast for so long.”

This isn’t a tropical coral, one that lives in relatively warm waters and features polyps living with symbiotic, photosynthesizing algae. Instead, this is a cold-water coral, one that does without the algae and consists instead of larger coral polyps all by their lonesome.

They hang around in the relative darkness, normally at depths of 40 to 2,000 meters (130 to 6,560 feet). Without those algae providing them with a food source, these polyps snatch food particles out of the water column, which is generally fast-moving in their preferred habitat.

The WWF notes that, despite being cognizant of their existence for several centuries, the fact that they live at depths below that of tropical corals means we’ve only recently begun to visit and scientifically probe them. That means, compared to their warm-water compatriots, we know less about them – including, rather importantly, how they respond to environmental stresses, particularly anthropogenic ones.

What is known, however, is that deep-sea reefs are certainly biodiversity hotspots, helping to drive the productivity and to maintain the health of the ecologies down there. They are also an important part of the nutrient cycle, in that they convert organic matter falling from above into an important food source that upwells to the algae-riddled surface.

The discovery of this colossal L. pertusa reef, then, is a rather big deal. Its presence also makes it likely that such reefs can be found in places that researchers haven’t yet thought to look: L. pertusa has been found in somewhat shallower areas closer to the coast, but this example is not only deeper than others like it, it’s also further offshore.

In the near future, additional dives will take place to better constrain the health and extent of the reef. Extra samples will be taken, but this is easier said than done. This coral lives at temperatures of around -13°C (9°F), compared to the surface water temperature of 30°C (86F), which means that samples taken to the surface have to be rushed to a cold-water lab onboard Atlantis before they die of heat shock.