A volcanic eruption on a remote island in Australian territory outside the Antarctic circle has been filmed by scientists on a research expedition.
The scientists said they were delighted to witness the eruption of Australia's second-tallest mountain on Heard Island, 4,100km south-west of Perth.
Big Ben is known to have erupted at least three times since 2000, but such eruptions are rarely witnessed.
Heard island is dominated by the Big Ben massif and its summit, Mawson Peak.
The scientists on board the research vessel Investigator, who are researching whether active undersea volcanoes support life in the Southern Ocean, said they were thrilled to witness the eruption.
Lava flows beneath ice
Professor Mike Coffin, a geophysicist from the University of Tasmania's Institute for Marine and Antarctic Studies (IMAS), called the experience "an amazing coda to this week's submarine research".
"We saw vapour being emitted from the top of the volcano and we saw lava flows coming down the flank of Big Ben," Prof Coffin, the voyage's chief scientist, said.
Image copyrightPete HarmsenImage captionBig Ben includes Mawson Peak, the highest mountain on Australian territory, which stands at 2,745m (9005ft) tall
"This was a very exciting observation. There are very few ships that come to this part of the world and in fact the last geological expedition that landed on Heard Island was in 1987.
Prof Coffin said the lava flowed over the top of the glacial ice at the top of the mountain before descending beneath the ice further down the volcano's slope.
"So there's a strong interaction between glacial ice and molten lava on the side of Big Ben," he said.
The scientists aboard the Investigator are seeking to prove that iron from underwater volcanoes influences the phytoplankton blooms that fertilise the Southern Ocean.
The 2,745m-tall Mawson Peak is Australia's second-highest mountain, surpassed only by the Mount McClintock range in Australian Antarctic Territory at 3,490m.
Mount Kosciuszko, the tallest mountain on Australia's mainland, is 2,228m tall.
Image copyrightPete HarmsenImage captionThe Big Ben is known to have erupted at least three other times since 2000, scientists say
Image copyrightPete HarmsenImage captionEruptions are usually only recognised from sparse satellite images
Image copyrightPete HarmsenImage captionGeophysicist Mike Coffin described the eruption as an "amazing coda" to the team's research journey.
