A groundbreaking discovery in South Africa challenges recent theories that large magma chambers may not occur near the Earth’s surface
Researchers at the University of the Witwatersrand have finally found evidence that large, long-lived, molten magma chambers may exist in the shallow Earth’s crust. The discovery was made at the South African Bushveld Complex, a massive area of layered igneous rocks that were formed by volcanic activity. It’s the largest body of solidified molten magma (known as an intrusion) in the world and covers an area the size of Ireland.
Rais Latypov, a professor of igneous petrology and lead author of the new study, says that the amount of magma in the chamber of the Bushveld igneous rock complex was, at one stage, ‘really staggering – more than five kilometres thick with a volume of more than 380,000 cubic kilometres. This amount of magma is several orders of magnitude larger than any known super-eruptions in the Earth’s history.’
The idea of huge, molten magma chambers, thought to be key to volcanic activity, is a long-held hypothesis, but a lack of compelling evidence has led to doubts in recent years. Thermal modelling also seems to indicate that the formation of a large magma body within the upper crust is unlikely. However, Latypov argues that evidence from the Bushveld complex suggests it is quite conceivable that such magma chambers have developed throughout the Earth’s history and that even if some regions of the Earth’s crust are lacking such chambers, this does not automatically mean that ‘big tank’ magma chambers are absent from other regions. ‘Although, modern geophysical surveys are indeed unable to conclusively identify any present-day magma chambers with a large volume of eruptible melt, it is too early to discard the existence of such chambers in Earth’s crust.’
