Methane exploded from Arctic sea-floor as Ice Age ended

Huge ocean-floor craters were caused by the expulsion of pressurized greenhouse gas thousands of years ago.


Huge craters in the floor of the Arctic Ocean are the collapsed remains of methane domes which exploded after the last Ice Age as the glaciers above them retreated, research suggests. Even now, some 11,600 years after the last gas domes burst, methane is still seeping out of the sea floor.

The methane explosions, which created craters up to 1 kilometre wide in an area that was once solid ice, but is now the northern Barents Sea off the coast of Norway, are not merely a geological curiosity. “These are processes that could take place in front of contemporary ice sheets,” says Karin Andreassen, a marine geologist and geophysicist at the Centre for Arctic Gas Hydrate, Environment and Climate in Tromsø, Norway, who led the study, published in Science1. Methane is a potent greenhouse gas, so it is tempting to speculate that large seafloor explosions might contribute to global warming. But so far there is little evidence for this, as it is not clear if the gas reaches the atmosphere.

Craters and smaller pockmarks have been spotted on sea floors around the world, but it’s not always clear what causes them. To investigate, Andreassen and her team revisited a cluster of craters discovered in the 1990s, which researchers had already suggested may have been created by the retreat of glaciers2, 3. Using high-resolution sonar surveys, the team identified around 100 craters that were at least 300 metres wide, as well as hundreds of smaller ones, in the space of 440 square kilometres.

Under the ice

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