McDonald Island, an isolated companion to Heard Island — itself a barren outpost — has doubled in size in recent weeks according to satellite photographs.

The chief scientist with the Australian Antarctic program, Professor Michael Stoddart, says it appears the volcanic eruption is not violent. “This is more like a gentle squeezing of the toothpaste tube, where the toothpaste is coming out of the top and running down the side,” he said.

“It’s a slow oozing of a very thick sticky, magma … so we’re not going to see all sorts of pyrotechnics.”

The remoteness of the area usually makes it difficult to study, with scientists relying on satellite images, which was how the recent activity was picked up.

The island is just 44 kilometres from Australia’s only other active volcano, on Heard Island, which has not erupted in recent times.