Supervolcanoes are categorised as volcanoes so immense they can erupt with a Volcanic Explosivity Index of eight – the largest recorded value on the index. This means the volume of deposits for such a violent eruption are larger than 240 cubic miles (1,000 cubic km).
An international team led by Curtin University researchers have identified an area in the Indian Ocean as the world’s most continuously-active inter-linked volcanoes, which have been erupting for 30 million years straight.
This has implications for how we understand magmatism on Earth, and on other planets as well
Professor Fred Jourdan
This magma “conveyor belt” has been fuelled by a constantly shifting seabed, creating space for the molten rock to spew for millions of years.
Qiang Jiang, a Curtin School of Earth and Planetary Sciences PhD candidate and the study’s lead author, confirmed the volcanoes were in the Kerguelen Plateau, located approximately 1,860 miles (3,000km) southwest of Western Australia.
He said: ”Extremely large accumulations of volcanic rocks – known as large volcanic provinces – are very interesting to scientists due to their links with mass extinctions, rapid climatic disturbances, and ore deposit formation.
“The Kerguelen Plateau is gigantic, almost the size of Western Australia.
“Now imagine this area of land covered by lava, several kilometres thick, erupting at a rate of about 20cm every year.
“Twenty centimetres of lava a year may not sound like much but, over an area the size of Western Australia, that’s equivalent to filling up 184,000 Olympic-size swimming pools to the brim with lava every single year.
“Over the total eruptive duration, that’s equivalent to 5.5 trillion lava-filled swimming pools.
“This volume of activity continued for 30 million years, making the Kerguelen Plateau home to the longest continuously erupting supervolcanoes on Earth.
“The eruption rates then dropped drastically some 90 million years ago, for reasons that are not yet fully understood.
“From then on, there was a slow but steady outpouring of lava that continued right to this day, including the 2016 eruptions associated with the Big Ben volcano on Heard Island, Australia’s only active volcano.”
The volcanologist’s colleague and co-researcher Dr Hugo Olierook added such long-lasting eruptions require very particular geological conditions.
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He said: ”After the partial breakup of the supercontinent Gondwana, into the pieces now known as Australia, India and Antarctica, the Kerguelen Plateau began forming on top of a mushroom-shaped mantle upwelling, called a mantle plume, as well as along deep sea, mid-oceanic mantle ridges.
“The volcanism lasted for so long because magmas caused by the mantle plume were continuously flowing out through the mid-oceanic ridges, which successively acted as a channel, or a ‘magma conveyor belt’ for more than 30 million years.
“Other volcanoes would stop erupting because, when temperatures cooled, the channels became clogged by ‘frozen’ magmas.
“For the Kerguelen Plateau, the mantle plume acts as a Bunsen burner that kept allowing the mantle to melt, resulting in an extraordinarily long period of eruption activity.”
Professor Fred Jourdan, Curtin’s Director of the Western Australia Argon Isotope Facility, revealed a cutting-edge argon-argon dating technique was used to date the lava flows.
He said: ”Finding this long, continuous eruption activity is important because it helps us to understand what factors can control the start and end of volcanic activity.
“This has implications for how we understand magmatism on Earth, and on other planets as well.”
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