‘For decades, there has been a big debate as to where the lavas from this massive outpouring came from,’ said Tyrone Rooney, who led the study. ‘Did they emit from deep within Earth or was there some contribution from shallower sources?’
Rooney and his team studied an ancient outpouring in the Great Rift Valley. About 30 million years ago, some 350,000 cubic kilometres of lava poured out across the region as the African tectonic plate broke apart. Using mass spectrometry, they determined the rocks’ chemical signatures, which allowed them to trace their origin.
The results indicated that an unusual group of lavas in Ethiopia was formed when part of the tectonic plate itself melted. These rocks had chemical signatures of materials found in the lithosphere and were distinctly different from most of the other rocks in Ethiopia.
They also found that the samples matched rocks collected from so-called basalt floods elsewhere, suggesting that these may also have a shallow source.
‘We’re interested in this because these massive outpourings happen around the same time continents break apart, create new oceans and affect the planet and the environment on a global scale,’ Rooney said. ‘So knowing the source of the lava gives us insights into a process that we still know little about.’
This story was published in the June 2014 edition of Geographical Magazine