How a plume of magma threatens to one day rip east Africa apart
A new ocean basin will gradually form in a low-lying region of Ethiopia and, in several million years' time, scientists believe this will develop into a vast crack running from northern Ethiopia down to the middle of Mozambique.
This could result in a 3,200-mile stretch of the east African coast, extending several hundred miles inland, splitting from the rest of the continent as the tectonic plate stretches, thins and eventually ruptures 'almost like soft plasticine'.
This would leave a narrow ocean between continental Africa and a vast new island made up of present-day Somalia and large parts of what are now Ethiopia, Kenya, Tanzania and Mozambique.
The Afar region of Ethiopia is a rare area where three tectonic rifts converge: the Main Ethiopian, Red Sea and Gulf of Aden rifts.
Geologists had suspected that a 'hot upwelling' of molten mantle, often known as a plume, was rising up from between 620 and 1,700 miles deep, shooting upwards and melting the continental crust, weakening and thinning it.
Researchers from the University of Southampton collected more than 130 samples of volcanic rock from the Afar region and Main Ethiopian Rift. They used modelling to understand the structure of the crust and mantle in the area.
They found that beneath the Afar region there was an asymmetrical plume coming up out of the mantle, with patterns that differed in each of the three rifts.
'We found that the mantle beneath Afar is not uniform or stationary — it pulses, and these pulses carry distinct chemical signatures,' said Dr Emma Watts, lead author of the study who is now at Swansea University. 'These ascending pulses of partially molten mantle are channelled by the rifting plates above.'
The results suggest the plume is 'pulsing like a heartbeat', said Tom Gernon, a professor of Earth science at Southampton. 'These pulses appear to behave differently depending on the thickness of the plate, and how fast it's pulling apart. In faster-spreading rifts like the Red Sea, the pulses travel more efficiently and regularly like a pulse through a narrow artery.'
When a hot plume of magma rises from deep within the Earth it flows beneath the base of the tectonic plates and helps to 'focus volcanic activity to where the tectonic plate is thinnest'.
'This has profound implications for how we interpret surface volcanism, earthquake activity and the process of continental break up,' said Dr Derek Keir, a co-author of the study, which is published in the journal Nature Geoscience.
Gernon said that part of the Afar region was about 120 metres below sea level and had been flooded by the sea several times in the past, including 80,000 years ago, as shown by salt deposits in the area.
'The formation of a fully developed ocean and mid-ocean ridge — that is, a plate tectonic feature where new ocean crust is created — in this region is likely to take several million years,' he said.
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