Mysterious Tar Mounds Harbor Deep-Sea Creatures

Mysterious tar mounds have been found off the coast of Angola, and despite being made from the same substance that covers our roads, these structures harbor a wealth of deep-sea creatures, new research describes.

More than 2,000 mounds of asphalt lie just two kilometers (1.2 miles) beneath the ocean's surface, ranging from the size of a football field to small hills just several hundred meters across. Scientists had already known these asphalt mounds existed, as they are found in the Gulf of Mexico and off the coast of California, but this is the first time they were seen on this side of the Atlantic.

The findings are described in the journal Deep Sea Research Part I: Oceanographic Research Papers.

These deep-sea "slow tar volcanoes" are created from oil flowing from within the ocean sediment and hydrocarbons migrating around subsurface salt structures.

They may seem inhabitable, but according to the study, at least 21 types of deep-water creatures call this place home, including large sponges, soft-corals, octopus and fish, along with blobfish and sea cucumbers.

While looking for oil reserves off Angola, the oil company BP - responsible for the infamous 2010 Deepwater Horizon oil spill in the Gulf of Mexico - stumbled upon the asphalt mounds. Their initial surveys of the seafloor revealed some unusual surface features, which were subsequently investigated using underwater robots. They ended up finding a total of 2,254 mounds using side-scan sonar, covering a total area of 3.7 square kilometers (1.4 square miles) of seafloor - that's about the area of a small town.

That's when BP decided to contact scientists at the National Oceanography Centre (NOC).

"By working together as a team, we used the industrial data and expertise to get a much better understanding of these important systems, which will be of great value both to the scientists, but also to the BP environmental management teams," lead author of the study, Daniel Jones from NOC, said in a statement.

Researchers also hope a better understanding of the tar mounds will help with future predictions of seabed patterns, rock types and habitat in similar areas of ocean.

Tags tar mounds, deep sea creatures