Magma ‘conveyor belt’ fuelled 30 million year long eruption.
Thu, 19 Nov 2020, 11:2711:27 AM | BY: ELEANOR
Research led by geologists from Curtin University discover that a volcanic province in the Indian Ocean was the world's most continuously active large igneous province (LIP), erupting for 30 million years and was fuelled by a constantly moving 'conveyor belt' of magma.
The Kerguelen Plateau in the Indian Ocean is the world's longest continuously erupting supervolcano dating back into the Cretaceous (Image: National Geophysical Data Center).
LIPs are massive crustal emplacements of volcanic rock and are a dominant form of near-surface magmatism, typically consisting of subaerial basalt flows.
Such long-lasting supervolcano eruptions (capable of producing volume deposits exceeding 1,000 cubic km) require very particular geological conditions. This research, published in Geology, indicates a magma 'conveyor belt' was created by shifts in the seabed thus continuously making space available for the molten rock to flow for millions of years (activity from ca. 122 to 90 Ma).
After the partial breakup of the supercontinent Gondwana, into the land masses now known as Australia, India and Antarctica, the Kerguelen Plateau (Kerguelen LIP) began forming on top of a mushroom-shaped mantle upwelling (mantle plume, the Kerguelen hot-spot) as well as along deep sea, mid-oceanic mantle ridges. The volcanism was prolonged 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'. In other volcanic systems, this channel would become blocked by cooled magma therefore causing activity to cease but in the Kerguelen Plateau, the mantle plume allowed constant melt and an unusually long period of eruptive activity.
The Kerguelen Plateau covers approximately 1,250,000 sq km and rises 2,000 m above the surrounding oceanic basin. Research lead Qiang Jiang contextualises the scale of this long-lasting supervolcanic eruption through helping to visualise the amount of lava output over the 30 million year period… ‘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 0.2 millimetres every year. 0.2 millimetres 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!’
The Kerguelen Plateau records the longest, continuous high-magma-flux emplacement interval of any LIP. Argon-argon dating was used to date the basalts. Intermittent volcanism continues to this day on the Heard and McDonald Islands.
The findings from this study help provide further insight into the factors that may control the start and end of this style of volcanic activity as well as facilitating understandings of general magmatism, both on Earth and other planets.
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