These 3-billion-year-old crystals deep inside an underwater volcano could be from an ancient continent

January 31, 2017

These 3-billion-year-old crystals deep inside an underwater volcano could be from an ancient continent

tanzania volcano

When the Earth was new, there was one continent called Pangaea. About 175 million years ago this supercontinent started to break apart, and over millions of years the continents we know today were formed.

Scientists are interested in finding out more about these early continental movements, and they've been gathering evidence that old continental crust may be lying beneath some oceanic volcanoes.

A new study, which was published this week in the journal Nature Communications, suggests this crust is contributing parts of itself to some of those volcanoes. The evidence? Zircon crystals — some of the oldest rock fragments ever found on Earth — discovered within lava brought to the surface that are estimated to be between 2.5 and 3 billion years old.

The research took place in Mauritius, where the crust underneath would have been part of the old continent Mauritia that broke away and formed Madagascar and India about 60 million years ago. The new findings could shed new light on the mechanisms of plate tectonics in these underwater hotspots, the researchers say.

"Our findings tell us that rifting and break-up of continental entities, driven by plate tectonic processes, is more complex and messy than we previously thought," Lewis Ashwal, a petrology and geochemistry professor at the University of the Witwatersrand in Johannesberg and lead author of the paper, told Business Insider. "Fragments of continents of many sizes can be left behind in the new ocean basins, and some of them can be blanketed by younger lavas, and thus can be 'hidden' from view."

Still, when it comes to predicting how tectonic plates will behave in the future, it's all pretty speculative, Ashwal added.

"As geologists, we are much better at studying the past than predicting the future," he said. "We can expect that the former pieces of the supercontinent Gondwana, including India, Africa and Madagascar will continue to drift apart from one another, possibly for several tens of million years, but we cannot predict how the Earth will operate too far into the future."

India and Asia will continue to collide, which will ensure the existence of the Himalayan mountains, but just how long for is a mystery, he said. Also, the entire continent of Africa appears to be starting to part, which would produce big volcanoes in Ethiopia, Kenya, and Tanzania.

"We don’t know if this will eventually lead to full-scale continental break-up, with the formation of a new ocean in this region," Ashwal told Business Insider. "But our work implies that if this does happen, the break-up is likely to be messy, with many continental fragments, of variable size, some of which could be scattered across the new ocean."

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