The Discovery of Sharkcano: An Undersea Batcave for Sharks Within an Acidic Hydrothermal Cauldron

by Carolyn Sotka

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Scalloped hammerheads and silky sharks were swimming inside the Kavachi Volcano’s caldera off the Solomon Islands. Screenshot from NatGeo’s video, Sharks Discovered Inside Underwater Volcano”.

The last few years it has been hard to miss the ‘so bad it’s good’ trilogy ‘Sharknado’; a waterspout that lifts sharks out the ocean, dumps them ashore in Los Angeles, and apocalyptic chaos ensues. What you may not have heard of is the recent discovery of a real ‘SharkCano’, 147 feet deep in an undersea volcano in the Solomon Islands.

The volcano, known as Kavachi, is highly volatile (acidic) and extremely active, thus very hard to study. At an opportune time to collect data between explosions, Brennan Phillips and his National Geographic crew sent a camera into the sunken caldera. What they found there was a complete surprise; two sharks–and a sixgill stingray–seemingly thriving in the plume and a hot acidic environment with carbon dioxide and methane bubbles rising from the seafloor vents. Not exactly hospitable elements for biology, as we know it.

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Video shows the team watching the footage live with excitement seeing the sharks and stingray in their “cave-homey-thingy”.

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Above: The NatGeo team marvels at the discovery. Screenshot from NatGeo’s video, “Sharks Discovered Inside Underwater Volcano”.

According to the National Geographic Society’s article, Phillips described the volcano as frequently spewing hot lava, ash, and steam up into the air. When erupting, divers have not been able to get close to the volcano because the water was too hot and “they were getting mild skin burns from the acid water.”

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Sixgill stingrays also seem to call the caldera home. Screenshot from NatGeo’s video, “Sharks Discovered Inside Underwater Volcano”.

So why can’t humans get close to withstand the conditions, when sharks and rays can? What adaptations allow them to survive in this extreme environment? Are they blown sky high “to bits” during an eruption or is there some kind of cue or early warning that allows them to escape, or hide in nearby caves, and then perhaps return post-explosion?

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Screenshot from NatGeo’s video, “Sharks Discovered Inside Underwater Volcano”.

The team cannot say for sure and this opens a box of many unanswered questions. Not necessarily what they set out to study, but a bonus for any researcher to learn something unexpected during their study.

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So while ‘Sharknado’ is proudly, shamelessly, and gloriously brainless – this expedition could unlock previously unknown mysteries and add to the scientific complexity of the secret world of sharks. As National Geographic Engineer Brad Henning says, “. . . That’s the best project, is to go out with one question, and come back with many, and that’s exactly what happened here.” – CS

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