Shifts in the sea floor led to the formation of channels that allowed magma to flow freely, researchers say. This resulted in an extended eruption period from about 122 million years to 90 million years ago; extraordinary when you consider that these types of currents usually only lasted 1 to 5 million years.
This all took place on the Kerguelen Plateau, which is now under the Indian Ocean. It is a large igneous province, or LIP, a widespread accumulation of magma and lava. Scientists can use these LIPs to trace volcanic activity back through time.
“Extremely large accumulations of volcanic rocks – known as large volcanic provinces – are of great interest to scientists because of their connection with mass extinctions, rapid climatic disturbances and the formation of ore deposits,” says geologist Qiang Jiang of Curtin University in Australia.
Jiang and his colleagues used samples of black basalt rocks taken from the ocean floor, along with an argon isotope dating method, to determine the spread and rise of the LIP, which was on a so-called mantle cloud created by rising magma.
In the roughly 30 years of intense activity, the Kerguelen Plateau rose by around 20 centimeters per year, according to the researchers. In the gigantic size of the LIP – about three times the size of Japan – the pouring out of lava corresponds to 184,000 Olympic swimming pools per year.
The Kerguelen Plateau, because of its unique configuration, recorded such a long and steady course of supervolcanic activity as the study suggests: a mantle cloud that combines with slowly spreading ridges in the mid-ocean that direct the magma upwards.
“Volcanism lasted so long because magmas caused by the mantle cloud flowed continuously through the mid-ocean ridges, which in turn acted as a channel or ‘magma conveyor belt’ for more than 30 million years,” says Hugo Olierook, geologist of from Curtin University.
“Other volcanoes would no longer erupt because the channels were clogged by ‘frozen’ magmas as the temperatures cooled. For the Kerguelen Plateau, the mantle cloud acts as a bunsen burner, which continued to melt the mantle, resulting in an extraordinarily long period of eruptive activity. ”
That’s a lot of volcanic eruption over many millions of years, but the rate dropped significantly about 90 million years ago, and scientists still aren’t sure why. The associated volcanic activity continues to this day to a much lesser extent.
It is a fascinating look at the past of our planet and of course also a reference to our study of volcanic activity in the present – the more we know how such systems can form and remain active, the better we can understand the interactions that are going on take place under the earth’s surface.
“Finding this long, continuous eruptive activity is important as it helps us understand what factors can drive the onset and end of volcanic activity,” says geochronologist Fred Jourdan of Curtin University.
“This has an impact on how we understand magmatism on earth and on other planets.”
The research was published in geology.
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