The Case of the Mysterious Holes on the Seafloor
During Dive 04 of the second Voyage to the Ridge 2022 expedition, we observed several sublinear sets of holes in the sediment on the seafloor at a depth of approximately 2,540 meters (1.6 miles). While the holes look almost human made, the little piles of sediment around them suggest they had been excavated. We attempted but were not able to take a peek into the holes and poke them with the tools on the remotely operated vehicle. It was also not apparent as to whether the holes were connected beneath the sediment surface.
During Dive 04 of the second Voyage to the Ridge 2022 expedition, we observed several sublinear sets of holes in the sediment on the seafloor at a depth of approximately 2,540 meters (1.6 miles). We saw the holes again during Dive 09 a total of four times at depths ranging from approximately 1,440 to 1,500 meters (4,724 to 4,921 feet). During Dive 09, the remotely operated vehicle pilots used the suction sampler to collect sediment from fresher holes. A look at the sediment upon recovery revealed no clues as to what formed the holes. A water sample was also collected during the dive for later processing for environmental DNA (eDNA), to learn more about what may be living in or around the holes. Video courtesy of NOAA Ocean Exploration, Voyage to the Ridge 2022. Download largest version (mp4, 165.9 MB)
Scientists are not certain as to the origin of these holes, so we put it out to followers on social media platforms such as Twitter and Facebook , to see what hypotheses members of the public might have as to how these holes formed. We got a variety of responses, from aliens to an unknown crab species to gas rising up from below the seafloor…and more.
This was not, however, the first time that scientists had encountered these mysterious holes. In July 2004, while exploring at a depth of 2,082 meters (6,831 feet) during an expedition along the northern Mid-Atlantic Ridge, scientists discovered several sets of these holes. A paper by scientists Michael Vecchione and Odd Aksel Bergstad highlights how these unusual holes point to gaps that exist in our basic understanding of mid-ocean ridge ecosystems. In the paper, the scientists address some of the hypotheses shared on social media.
A close look at the sublinear sets of holes in the sediment observed during Dive 04 of the second Voyage to the Ridge 2022 expedition. These holes have been previously reported from the region, but their origin remains a mystery. Image courtesy of NOAA Ocean Exploration, Voyage to the Ridge 2022. Download largest version (1.9 MB).
While Vecchione and Bergstad were not able to definitively determine the source of the holes or how they were constructed, they hypothesize that the raised sediment may indicate excavation by an organism living in the sediment or digging and removal, perhaps via a feeding appendage of a large animal on the sediment surface. They used the term “lebensspuren” to describe the holes, which translates to “life traces” and refers to patterns in surface sediments resulting from bioturbation (or the disturbance of sediment by living organisms). These lebensspuren are reminiscent of ichnofossils reported from deep marine rocks.
The ultimate origin of the holes still remains a mystery and indeed the unknowns we encounter are often as deep and mysterious as the ocean itself. With each expedition to map and explore ocean depths, however, we learn more about this ecosystem that is so vital to all of our lives.
These sublinear sets of holes in the sediment were seen during Dive 04 of the second Voyage to the Ridge 2022 expedition. Note the two red dots on the seafloor; these laser points are 10 centimeters (4 inches) apart and give a sense of scale of the size and spacing of the holes. Image courtesy of NOAA Ocean Exploration, Voyage to the Ridge 2022. Download largest version (1.2 MB).
Another perspective of the series of holes observed in the sediment during Dive 04 of the second Voyage to the Ridge 2022 expedition. Image courtesy of NOAA Ocean Exploration, Voyage to the Ridge 2022. Download largest version (1.3 MB).
Published July 27, 2022
Relevant Expedition: Voyage to the Ridge 2022