Enormous Underwater Volcanoes Discovered Near Antarctica

By Douglas Main
A thousand miles north of Antarctica, in one of the most remote parts of the world, enormous surprises lurk beneath the surface. Near the South Sandwich Islands, a British territory that straddles the Southern Ocean and the south Atlantic, scientists found more than a dozen huge underwater volcanoes, some of which tower 2 miles above the ocean floor. The expedition's leader, volcanologist Phil Leat, who is working with the British Antarctic Survey, says the volcanic cluster is unusually dense and active. "We weren't expecting to find so many undiscovered volcanoes here," he says. 

To conduct the study, presented last week at the International Symposium on Antarctic Earth Sciences in Edinburgh, the crew used multibeam sonar to map the ocean floor. The sonar bounced sound waves off the bottom and back to measure the depth. Then computers aboard the team's research vessel, the RRS James Clark Ross, assimilated the data to create a 3D image of the terrain in real time. "The map appears onscreen in front of your eyes as you move along," he says. "It's quite exciting." 

The remoteness, freezing cold temperatures and famously bad weather of the region (plus the fact that this multibeam sonar has only been around for about 20 years) helps to explain why the volcanoes remained unmapped until now. (A British naval vessel saw evidence of an undersea eruption in the area in 1962, but lacked the technology to find and map the volcanoes.) With means to produce a 3D map in hand, Leat got the British Antarctic Survey to fund cruises in 2007 and in 2010. The goal was to produce a basic map of a completely unknown area, which will help scientists understand how volcanoes evolve, how ocean currents have changed and what kind of life might exist in the region. 

Leat says the formation's conical shapes and cratered summits are signs of recent eruptions, meaning that almost all of these volcanoes are active. "This is the only place that's this active in the whole of the Antarctic Ocean," Leat says. The tallest of the newly discovered volcanoes has a summit that lies just 160 feet below the surface (less than twice the ship's length). Another eruption might be enough for this volcano to break the surface and become an island, adding to the South Sandwich chain to which the underwater giants belong. 

Only one other volcanic arc in the Atlantic—the Lesser Antilles, the string of Caribbean islands that extends from the Virgin Islands south to Venezuela—was formed by subduction, in which one tectonic plate slides violently beneath another. Pressure creates searing heat, and molten rock bubbles to the surface. This often creates violent eruptions, like the 1995 explosion of Montserrat's Soufriere Hills volcano, which covered the Caribbean island's capitol in 39 feet of mud, causing half of its population to move away. 

Using the same sonar technology, the team also located a number of hot springs, called white smokers, known to be rich in deposits of copper, lead, zinc and gold, Leat says. The South Sandwich region should be home to a wide variety of marine life, too. "There have got to be new species on these volcanoes waiting to be found, and probably a very large number," he says. 

That haul of biodiversity is beginning to be revealed. Leat's team collaborated and shared resources—including the vessel—with a complementary mission led by Paul Tyler, a deep-sea biologist with the National Oceanography Centre in Southampton, England. Exploring a nearby underwater formation called the East Scotia ridge, Tyler's team found four clusters of hydrothermal vents, called black smokers, the first found in the South Ocean. These differ from the hot springs Leat noticed in that they form much deeper in the ocean and contain higher levels of sulfur. Tyler also found high densities of creatures living around the vents, including crabs, snails, anemones and stalked barnacles. At least 10 of them are new species, but Tyler couldn't elaborate on the details because his paper on the subject is in the midst of review. 

Leat plans to return to the area next year to conduct a survey of the life around the volcanoes. "It's very exciting to explore a part of the Earth that we know almost nothing about," Leat says. "There are countless discoveries just waiting to be made." 


Read more: Enormous Underwater Volcanoes Discovered Near Antarctica - Popular Mechanics