Sharks in a Volcano: Why You Should Care


Scientists studying the activity of an underwater volcano in the Solomon Islands were shocked when a hammerhead shark emerged from the cloud inside the volcano’s crater. Kavachi, also called Kavachi’s Oven, is one of the world’s most active submarine volcanoes and has risen above the waves eight times since 1939, only to erode back into the sea.

Ocean engineer Brennan Phillips and his team were on a mission to map Kavachi’s peak and gather as much information as they could about the volcano. Because the volcano is underwater, there’s little record of how often it erupts, but Phillips said “it is usually erupting.” When it is erupting, Phillips says, you can hear it: “Anywhere within 10 miles even, you can hear it rumbling in your ears and in your body.”

The water around the volcano is extremely acidic and the heat rises the closer you get. “Divers who have gotten close to the outer edge of the volcano have had to back away because of how hot it is or because they were getting mild skin burns from the acid water,” Phillips said.

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In order to study the volcano, Phillips’ team used robots and cameras. While the volcano was not erupting, the images are blurred by orange plumes and bubbles. Carolyn Barnwell, writing for National Geographic, said that in the video “carbon dioxide and methane gas bubbles” can be seen rising from seafloor vents, and that the color of the water was “due to reduced iron and sulfur.”

Phillips and his team were shocked to find both hammerhead and silky sharks, in addition to stingrays and smaller fish, swimming around inside the volcano:

The idea of there being large animals, like sharks, hanging out and living inside the caldera of this volcano conflicts with what we know about Kavachi, which is that it erupts. But when it’s erupting there’s no way anything could live in there. And so to see large animals like this, that are living, and potentially they could die at any moment brings up lots of questions – do they leave, do they have some sort of sign that it’s about to erupt, do they blow up sky high in little bits?

Kavachi is one of over 400 volcanoes in the Pacific basin, part of what is known as the Ring of Fire. The Pacific plate is the world’s largest tectonic place, a piece of the Earth’s upper crust pulling away from, grinding against, and crashing into other plates in a slow but volatile geologic evolution of the planet. This movement, plate tectonics, is what generates volcanoes and earthquakes along the boundaries between plates — 90 percent of the world’s earthquakes occur along the Ring of Fire.

The presence of large animals inside the crater of the volcano leads to the question of whether they can sense an eruption coming. If so, can scientists figure out how? For the people living through the Pacific it could be a life-saving answer. Many of the volcanoes in the Pacific are underwater or on remote islands, but some are in devastatingly dangerous locations.

Oceania, in particular, trends to the former with volcanoes on remote islands impacting relatively few people. In August 2014 Tavurvur in Papua New Guinea began its eruption with a bang. Communities near the volcano, which is on the island of New Britain, were forced to relocate following the eruption and nearby Rabaul’s 3,000 residents were told to try to stay indoors. By the end of its most recent eruption in March 2015, the Hunga Tonga volcano, less than 20 miles from Fonuafoʻou in Tonga, formed a new island.

Elsewhere in the Pacific, active but quiet volcanoes could threaten millions. Krakatoa, whose most famous eruption in 1883 was heard 3,000 miles away, is about 100 miles from Jakarta. Kilauea on the island of Hawai’i has been erupting continuously since 1983, oozing lava into the ocean. Mount Fuji, which last erupted in 1708 is about 60 miles southwest of Tokyo — which has a metro population of over 35 million.

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