Wed, May 31, 2023 page4

• Australian volcano spewing lava

  • The Guardian
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  One of Australia’s two active volcanoes on an island near Antarctica — known as Big Ben — has been spotted by satellite spewing lava.

  The lava flow on the uninhabited Heard Island, about 4,100km southwest of Perth and 1,500km north of Antarctica, is part of an ongoing eruption that was first noted more than a decade ago.

  The image was caught by the European Space Agency’s Copernicus Sentinel-2 satellite on Thursday, and is a composite of an optical picture and an infrared image.

  

  A composite of visible and infrared satellite images shows lava spilling down the side of Big Ben, a 20km-wide volcano, on Heard Island near Antarctica.

  Photo courtesy of Sentinel-2 via The Guardian

  The lava is seen flowing down the side of Big Ben from near the summit, known as Mawson Peak. Australia’s other active volcano is on the nearby McDonald Islands.

  Reports collated by the Global Volcanism Program at the Smithsonian Institution, before the image was shared, suggest the current lava flow is part of an “eruption episode” that has been ongoing since September 2012.

  The program has records of eruptions at Heard Island going back to 1910.

  Teresa Ubide, a volcanologist and associate professor at the University of Queensland, said: “This volcano has been erupting since the beginning of the 20th century. What’s happening is quite normal and is generating lava flows.”

  The Global Volcanism Program records about 20 “lava flow” incidents since September 2012.

  Ubide said Heard Island was known as an intraplate volcano, because it was in the middle of a tectonic plate rather than being on their margins.

  She said these types of volcanoes were caused by a “hotspot” inside the Earth and were typically not very explosive and so emitted little ash.

  “Many eruptions are composed of smaller events. This [most recent lava flow] seems to be following what’s been happening there since 2012,” she said.

  Jodi Fox, an adjunct researcher at the University of Tasmania, is an Antarctic volcanologist working at the National Museum for Nature and Science in Japan.

  She said Heard Island was likely between 750,000 and 500,000 years old.

  Evidence suggested the source of the magma was the Earth’s upper mantle, which was about 45km below the surface.

  Commenting on the latest lava flows, she said: “This is really pretty typical of how it behaves. It produces these relatively slow-moving flows with few, if any, explosions. Sometimes there’s a plume of vapor and gas at the same time.”

  Big Ben was unusual for an interplate volcano, she said, because it appeared to be lifting higher when other similar ocean volcanoes had tended to eventually collapse into the Earth’s crust under their own weight.

  The Big Ben volcano and Heard Island sit on the Antarctic plate. There are more than 100 volcanoes on Antarctica, including about 90 that are hidden below the ice.

  Heard Island and McDonald Islands sit on the Kerguelen Plateau that is elevated about 3,000m above the surrounding sea floor.

  Heard Island covers 368km2 and is about 40km long and 20km wide.

  Mawson Peak at the top of Big Ben is 2,745m above sea level — 517m higher than the biggest peak on Australia’s mainland, Mount Kosciuszko in New South Wales.
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