What happens when we punch a hole in the seafloor?

Fig 3. Temporal sequence of landscape at/around Hole D/E. From Nakajima et al. 2015.

Fig 3. Temporal sequence of landscape at/around Hole D/E. From Nakajima et al. 2015.

A longtime submariner I know tells the story of a most unusual dive. On this particular plunge, they went down into the briny deep to place what can best be described as a giant manhole cover on the seafloor. There was a hole, and, by all accounts, the sea was draining in to it.

For more than half-a-century, we’ve been drilling holes in the bottom of the sea. Some reveal the buried history of the evolution of our oceans. Others uncover vast wells of crude oil. Science, exploration, and exploitation have all benefited from ocean drilling programs. But what happens to the seafloor when you punch a hole in the ocean? In my friend’s case, the drilling program opened a sub-sea cavern, resulting in changes to local current regimes, potentially disturbing the surrounding benthic community. The most practical solution was to simply plug the hole.

We’ve punched a lot of holes in the seafloor, but despite a few anecdotes and scant research, we know precious little about how these holes actually alter the marine environment. This is particularly worrying, as deep-sea mining at hydrothermal vents, manganese nodule fields, and oceanic crusts are slowly creeping out of the realm of science fiction and into our oceans. Ocean drilling in the deep sea is perhaps the closest analog to industrial-scale deep-sea mining. Understanding the potential impacts is critical to designing management and mitigation regimes that protect the delicate deep seafloor.

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